How Much Can 9mm Bullet Weight Affect POI (S&W 3913)

[AxlMyk]

Stopped by my local gun shop to buy the ammo and was talking with the owner about my problem. He whips out a 3913 from under his shirt and proceeds to tell me

He un-holstered his loaded weapon right there? Is he stupid, ignorant, arrogant, or all 3?

[ShootistPRS]

Walt,
Are you a good enough shot to separate two groups that are a half inch apart or would it look like one group at 25 or 50 yards?

If the barrel of the gun moves .082" it is reasonable the the back end of that gun moves .010"?

You have already said you have good enough eyes to to tell the the gun is not moving AT ALL in the slo-mo videos.

The link in 1911s are all the same. Having a different bullet has nothing to do with the link. "Linkless systems" use a ramp to replace the link. It is cheaper to mill a ramp than it is to make the link. With or without the link the barrel tilts down at the rear (up at the front) before the barrel disengages with the slide.

You are never likely to see the angular change in a semi-auto handgun as it is being fired. Human eyes are not that good. Fire your handgun at a longer distance and the change in point of impact will be more visible.

[Walt Sherrill]

Originally Posted by ShootistPRS

If the barrel of the gun moves .082" it is reasonable the the back end of that gun moves .010"?

If the FRONT of the slide moves .082" inches to the rear, the REAR of the slide will also move .082" to the rear. It's not easy to calculate how far the frame itself will move to the rear due to slide movement, because the slide and barrel are only indirectly connected to the frame at that point in the firing cycle. (As the bullet is about the exit the barrel, slide movement has just started to lightly compress the recoil spring and will only compress it for a that 1/10th of an inch of slide movement before the bullet is gone.) Spring compression will continue, but the bullet is gone so what happens from that point on can not affect the bullet's path.

Before the bullet leaves, the frame is receiving some of the force applied to the recoil spring, but its not immediately obvious how much force is being shifted to the frame. We also don't know how much the front of the barrel, slide and frame will tilt/rise as a result of the barrel and slide's .082 rearward movement, or the frame's .01" rearward (and downward) movement -- if it moves that much, or more.

Can you tell us how you came up with your .01" figure? Did you find a calculation that led you to that result? As I read what you wrote, it seemed more like a "SWAG" figure used to explain how rounds hit a target down range that gave you a way to "back into" a barrel rise calculation. You say .01" is a reasonable assumption. If so, how does that very small frame movement lead to barrel rise? Is the whole frame assembly (including the grip) moving to the rear, or is the grip twisting in the shooter's hand, allowing the barrel to rise while the rear of the frame dips? If the top of the slide is pushing back against the frame we may be talking about a vector force, and there may be a way to calculate it. How do we calculate that force and its effect?

Your claim that a slow-moving heavy bullet will cause more barrel rise in a SRLB semi than a fast-moving light bullet may be correct, but that claim is offered without evidence and with only theoretical justification. You also say that high speed videos are not precise enough enough to show the subtle rise that occurs when heavy, slow-moving bullets are fired. Perhaps, but I'd argue the videos are better evidence than no evidence at all.

Maybe someone else here can give us better explanations and put us (or me) out of our misery.

[lwestatbus]

Well THIS is embarrassing after the doctoral dissertations in physics and the extensive exchanges. It turns out the gun shoots where it is pointed but I don't seem to point (this gun) very well.

As promised, I bought a box of 124 gr and one of 147 gr cartridges and headed to the range. The 124s were shooting right where the 115s were, about 4" low at 20 ft. The 147s were slightly higher but if I were assigning this as a problem to my graduate statistics students I think they would tell me that any difference in the center of the group could not be considered significant due to the dispersion of the two groups (ouch). Regardless, all three cartridges were shooting low.

This range isn't really well set up for bench shooting but I was getting frustrated and worked with the range master to shoot supported from the firing point's table. I had to rest the pistol on the magazine to keep the rounds in the impact area (I know, not preferable, but still better than unsupported).

From the rest I was able to put a full magazine each of all three cartridges into tight groups right at the point of aim (bottom of a 2" Shoot 'n See paster).

Sigh. So that means the issue is with me and the pistol. I shoot multiple other pistols quite competently so I have some learning to do. The 3913 trigger is much heavier than my others so that may take getting used to. After the bench shooting I experimented with some different finger positions on the trigger but nothing conclusive came out of that. I also have the darndest time on just this pistol with focusing on the sights. I get a lot of ghosting on the top edges of both front and rear sights so it may be that I am just not aligning the sights correctly. That is my current front runner theory as I have been able to achieve some acceptable but low groups shooting free hand.

The bottom line is that the pistol definitely shoots well enough for defensive use in a pinch and I would most likely doing point and shoot with it anyway. I may get hits in the gizzard when I was aiming at the 10-ring but enough of them should put someone down regardless. But I also want things to work the way they are supposed to and this is the kind of problem that wears at my craw until I solve it.

Many thanks for all of the responses and activity in the thread. I definitely learned some things about firearm engineering.

AxlMyk: He un-holstered his loaded weapon right there? Is he stupid, ignorant, arrogant, or all 3?

None. I didn't have any problem with his conduct. It was safe in all respects. When I said "whipped out" that was hyperbole. The shop owner then went to the back of the store and came out with a second unloaded 3913 which he proceeded to dissect in considerable detail. It was quite educational, just like this thread has been.

[Walt Sherrill]

Originally Posted by lwestatbus

The 3913 trigger is much heavier than my others so that may take getting used to.

A slightly lighter hammer spring, which you might be able to change yourself, could make a world of difference in that HEAVIER trigger.

[DaleA]

Good on you lwestatbus. Now when anybody talks about 115, 124, 147 grain rounds you'll be able to say I know how the gun shoots with those, I've actually done it.

Shooting a gun from a rest or a supported position is something I always try to do with a new gun as soon as possible. I get to see just how tight a group the gun is capable of and then that shames me when I practice and spurs me to try harder and practice more.

It's all fun!

Good luck and stay safe.

[JohnKSa]

Taking the end product of .082" of movement while the bullet is in the bore Makes it easy to understand why you don't "see" the movement on high speed photography. If the muzzle rises just .010" in the 8 or so inches between the hand and the muzzle at 25 yards the bullet hits 1.125" higher than the actual line of the bore before the trigger was pulled.
When you change the weight of the bullet and slow it down it spends more time in the barrel which can raise the muzzle more.

All this ignores the fact that you can look at the bore line and sight line and tell if the muzzle rises significantly while the bullet is in the bore or not.

If the muzzle rises significantly between the time the trigger is pulled and the bullet leaves the bore then the muzzle will be pointed down in relation to the sight line.

Since it can be clearly seen in the figure I posted that the bore actually points upward relative to the sightline of the autopistols I checked, there's no need to theorize about whether the muzzle rises significantly or not. The measurement shows it doesn't--at least in those pistols.

On the other hand, it clearly does rise significantly in the revolver I measured.

[pete2]

My experience---------------
92FS, had to install higher rear sight
Kimber 1911 45, filed front sight
Ruger CMD 45, filed front sight
Citadel 1911, 9MM, filed front sight.

It doesn't matter a lot, if any, what weight bullet you use in a semi auto.
Ruger told me they don't care where a gun shoots as long as it groups(the wouldn't do anything about the problem) they did put a black sight on it so I could file it down, they replaced the first gun due to a mis machined frame(I returned it because it shot low). Beretta also blew me off when I called them.

Bottom line, replace the sights or file the front. A worse problem is if it shoots high.

[45_auto]

Originally Posted by Walt Sherrill

Perhaps I'm I just the victim of trick photography (or particularly astute videographers) and have fooled myself by my own poor testing techniques. If so, can you, with your (better than my) understanding of physics, explain this apparent lack of barrel rise?

I'm not really sure what you're looking for. Post below is a reply to one of your previous threads on the same subject a couple of years ago.

It should be obvious by the difference between the Point Of Aim (POA) and the barrel axis on a semi vs a revolver.

Front and rear sights on a semi auto are typically almost the same height, which means that the POA is very close to the barrel axis. However, the front sight on a revolver (or fixed barrel like a Contender pistol) of any power will be SIGNIFICANTLY taller than the rear sight. Therefore the barrel axis on a revolver intersects the target MUCH lower than the barrel axis of the semiauto.

What other conclusion can you draw other than semi-autos have reduced or delayed barrel rise during the time that the bullet is in the barrel?

(The difference is that the semi is primarily conserving momentum as linear momentum by using the slide/barrel to compress the recoil spring and hammer spring while the bullet is in the barrel. That momentum is then transferred to the frame and shooter's hand, at which time a significant portion of it is conserved as angular momentum, resulting in barrel rise. Since a revolver has no moving parts with mass to initially conserve the bullet's momentum, the momentum is conserved by the rearward movement of the barrel/frame being turned into angular momentum by the shooters wrist joint while the bullet is in the barrel.)

That's about the simplest way I can think of to put it. A heavier bullet imparts more momentum to the slide/barrel. That momentum is transferred to the shooters grip/wrist through the hammer/striker/recoil spring while the bullet is in the barrel and the slide/barrel starts moving rearward. The linear momentum of the slide is reacted as a torque through the shooter's wrist. Heavier bullet = more momentum = more torque on shooter's wrist.

Whether that additional torque due to the heavier bullet is enough to affect your group would seem to me to be dependent upon the magnitude of the forces, the strength of your grip, and the height of the bore axis.

I've never really cared enough to do any research on it, if you really want to know how much a 9mm bullet weight can affect POI, it seems it would be easy enough to quantify using something like a Ransom Rest to provide a repeatable resistance to the torque and a series of different bullet weights as your variable.

[Walt Sherrill]

Originally Posted by 45-auto

That's about the simplest way I can think of to put it. A heavier bullet imparts more momentum to the slide/barrel. That momentum is transferred to the shooters grip/wrist through the hammer/striker/recoil spring while the bullet is in the barrel and the slide/barrel starts moving rearward. The linear momentum of the slide is reacted as a torque through the shooter's wrist. Heavier bullet = more momentum = more torque on shooter's wrist.

That is a simple way to explain things, but you keep repeating your theoretical understanding of how things work, and you don't offer us any proof that Browning short-recoil locked-breech guns behave that way. Some evidence would make your argument more convincing.

Until the "extra" momentum (of the heavier, slower bullet in teh barrel) in the slide/barrel is passed to frame, it arguably has no effect. Your simple explanation ignores the fact that with a BROWNING SHORT-RECOIL LOCKED-BREECH SEMI-AUTO the relationship of the bullet to the slide and barrel, and the slide and barrel's relationship to the frame IS A FIXED, MECHANICAL/PHYSICAL RELATIONSHIP. That relationship -- how far the the different components move with regard to each other, not how quickly they move -- stays the same regardless of bullet weight or bullet speed.

The only thing really varies with bullet weight and velocity with the Browning SRLB design, is the time it takes for a bullet and barrel/slide to move. The slide will move just as far when a heavy bullet is fired when the bullet leaves the barrel as when a light one is fired. The slide and barrel may move more slowly or more quickly, but the physical distance traveled is based on the physical relationship of the components at any point during the bullet's travel, and it's a fixed, physical relationship until the bullet leaves the barrel.

IF the slide travels the same distance regardless of bullet weight or speed when the bullet leaves the barrel, where is that extra force necessary to make the barrel rise seen and how is it transferred to the frame? Doesn't slide movement drive everything that follows? And how is the extra force that accompanies a heavier, slower bullet transferred to the frame BEFORE the bullet exits the barrel? It has to be done before the bullets exits to have any effect. What makes the barrel rise before BEFORE the slide has begun to move to the rear? That extra force can't come into play until the slide starts to move because there's no real connection (or way to transfer the force in quesiton) to the frame until it does move.

There is only an indirect connection between the barrel/slide and the frame until AFTER the bullet has left the frame and the barrel and slide hit their frame stops. The recoil spring will be only slight compressed by that by initial 1/10th of an inch of slide movement because the spring is not solid. More importantly, only PART of the force at play can be transferred to the frame in that early slide movement, because part of the force passed to (and through) the spring will be stored in the spring for later use. And even then, the force that is transferred is transferred against the frame at a lower point on the frame and that would suggest that the effect of that force transferred to the frame as a vector force is reduced.

High speed videos do not show slide/barrel rise before the slide begins to move. It doesn't appear visible as the slide begins to move. It also doesn't show barrel rise until AFTER the bullet has exited,

Jim Watson says his 200 gr. .45 rounds group with his 230 gr. .45 rounds. Only his 185 gr. .45 rounds hit lower. JohnKsa says that lower impact could be attributed to a barrel link issue. I would expect a 230 gr. .45 bullet that was 15% heavier than a 200 gr. bullet to have a different point of impact if what you say is true.

When I tried the same sort of test using one of my 9mm semi-autos, using a linkless barrel, I found that my 115, 124, and 147 gr. 9mm bullets all grouped about the same, even though the heaviest bullet was 28% heavier than the lightest.

lwestatbus, whose post started this discussion, and someone who is professionally very comfortable dealing with data sampling and statistics, says that any statistical differences in the center of the groups he fired using different bullet weights could not be considered significant.

Your rationale, above, clearly applies to how a fixed-barrel gun works, but may not be a good explanation for Browning design behavior. It seems that the bulk of the recoil from the Browning design doesn't get applied to the frame until AFTER the bullet has left the barrel. While some recoil force does get applied to the frame before the bullet is gone, it does so only indirectly as explained above, through the limber recoil spring -- which is hardly a great transfer medium. That "pre-bullet exit" force appears to have a very minor effect on barrel rise in the Browning design.

What force is at play that causes the barrel to rise as you say it must. And how do you measure (or demonstrate) it, to show that your claim is valid? Slide movement (how much, how far) seems to be the same regardless of bullet weight or bullet velocity until the bullet is gone.

Shots from a single gun in a Ransom Rest,with the sights reset on the point of aim (but not adjusted for the different bullet weights) to the same point of aim with each shot might convince most of us. Loading the different weight bullets in the same magazine (by a different person), so that not even the shooter knows what's coming with each shot, might add more credibility to the results. The mag loader will have to record the bullet weights for later evaluation.

(While I used a sandbag rest rather than a Ransom Rest, that's a bit like the approach I used with my own 9mm test, but it might have worked better if I had used ONE target, and numbered the shots on the target after it hit, so the bullet weight of each shot could be identified, later. I may try that if I do additional tests.)

.

[lwestatbus]

The bore-line vs. sight-line and muzzle rise due to recoil, shooter behavior, or the Will of Thor have become front and center in this thread.

I am still left with a decision about what to do about my connection with this pistol. I have four facts that bear on my decision:

1. Pistol Shoots Low Firing Unsupported: When firing this pistol with a 2-handed grip unsupported I shoot about 4" low at 20 feet. The groups are acceptable if I pay close attention and are definitely groups. This has been consistent through a few hundred rounds now and three different bullet weights (115, 124, 147).
2. Pistol Shoots Right on Point of Aim Firing Supported: 'Nuff said
3. I Have No Trouble With Other Pistols: I regularly shoot multiple other pistols and do NOT have this low grouping with any of the others. The other pistols include Kimber Pro Carry .45 w/ 4" barrel and fixed sights, PPK/S, Kimber Micro 9 w fixed sights, S&W Model 60s with 3" and 5" barrels.
4. The Sights on JUST This Pistol Are Fuzzy to Me: I've mentioned elsewhere that on just this pistol I get ghosting of both the front and rear sights where, if I concentrate, I can make out two distinct edges for each. One is hazy and one is blacker but the overall effect is blurry. I freshened up the white dots in the sights with an oil based paint pen and this helps.

All of this leads me to two questions:

1. Will shooting from a rest affect any designed 'flip' of the gun while the bullet is still in the barrel?
2. What should I do next?

[Walt Sherrill]

Originally Posted by Iwestatbus

... what should I do next?

1. Consider going to (or joining) the S&W forum. Lots of very helpful (and VERY knowledgeable) folks there, and there's an existing topic where participants give recommendations for upgrading the sights for the 3913. I visited there a lot in years past when I had some 3rd Gen S&Ws, and still visit (because I have an M&P Pro. The following is just a link to one area... it a much broader site than that.

http://smith-wessonforum.com/smith-w...-auto-pistols/

Many of us believe that any flip mostly occurs AFTER the bullet is gone, so that shouldn't affect where the bullet goes.

2, See if you (or your gunsmith) can change to a slightly lighter hammer spring.

3. Re-evaluate the gun, shooting from a rest (see POOR-MAN'S REST and BULLSEYE WHEEL OF MISFORTUNE TOOL, below)

4. Get new sights that are more "eye"-friendly. The link above should help with that, and then go to Amazon or EBAY for a good price.

5. If you don't have one, consider getting a reasonably-priced generic sight pusher from the same place... as you'll use it many times over the coming years. You can find good ones for way under $100.)

POOR-MAN'S REST

About the shooting rest: The ideal inexpensive rest for most folks is a bag of rice (not the smallest bag), carried and used inside two plastic bags in case of a break or tear.

Rest your hands (holding the gun). not the gun, on the bag, and very slowly press the trigger. That reduces the "human factor" to a minimum.

Doing this CAN (not WILL) quickly show you whether an accuracy issue is the shooter or the gun.

Start evaluating the gun at about 15' and then move the target back once you start understanding how things are going.

NEW guns can be a challenge, particularly if they feel and fit you differently than other guns you're familiar with -- so some of your gun "issues" may resolve pretty quickly.

BULLSEYE WHEEL OF MISFORTUNE TOOL:

For unsupported shooting, use the Bullseye tools (link below) to examine your results.

While this tool is intended for one-handed fire, most folks don't use both hands properly when shooting, and their strong hand plays a bigger role in the process than they realize, and contributes more to the target results than you'd expect. It can still offer meaningful guidance.

A sight pusher might be helpful at the range. A brass punch [or hardwood dowel] and light hammer will work, too. Move the rear sight in the direction you want the point of impact to move to. If the front sight can be moved, and you choose to move it, you move it in the opposite direction. You may not be able to do anything about elevation without changing the sights (but you want to do that.)

Here's a link to the Bullseye tool. It tells you how to evaluate what you see on the target. (If you're left-handed, you "mirror-flip" the chart.)

http://www.bullseyepistol.com/training.htm

.

[random guy]

Wasn't sure what to think about this. From experience, heavier bullets and slower velocity means a higher POI in handguns, but upon reflection, most of my shooting has been with fixed barrel guns and linked barrel semi autos.

I also thought that loads fired from magnum revolvers can vary far more than in semi autos so I picked two of the most extreme 9mm loads to test. 95gr Sierra was the lightest 9mm bullet on hand and 147gr XTP being the top end. I loaded the 95 to max velocity (1356fps book) and the 147 to the starting charge (857fps book). Both using Longshot powder. Not really ideal for the light load but good enough to see what I assumed would be a major elevation shift. But I didn't really see it.

I fired 5 rounds each at 12.5 yards with the first round slingshot loaded in each group. Pardon the 147gr group (I'm going to blame an inappropriate powder for the scatter) but if you look at the group centers, there is little vertical movement. Even doubling the change at 25 yards wouldn't amount to more than 2" if that. Maybe an inch would be closer.

http://s107.photobucket.com/user/hva...%20gr.jpg.html

Some floating barrel semi autos may behave differently but this one (S&W M&P 9) defied my preconceptions. On the bright side, this indicates that these pistols tend to shoot most loads to virtually the same POI...a very nice thing.

[JohnKSa]

Nice test.

I've got three boxes of 9mm ammo, all from the same manufacturer and all with different bullet weights that are slated for a test like yours.

I'm going to add one wrinkle. In addition to shooting groups from all three weights to see if a POI difference can be seen, I'm going to fix the slide closed and fire the groups again with all three weights. Right now the test is on hold while I come up with a reliable and practical way to fix the slide closed without causing any damage to the pistol.

I know it's possible to hold the slide closed with one's thumb (I've done it) but that will alter how the pistol is held so I don't want to do it that way. I'm thinking that I may have to do something like ziptie the slide closed (large ziptie looped around the back of the slide and front of the triggerguard) for each shot then cut the ziptie off to manually chamber the next round and repeat.

[ShootistPRS]

I fired 5 rounds each at 12.5 yards with the first round slingshot loaded in each group. Pardon the 147gr group (I'm going to blame an inappropriate powder for the scatter) but if you look at the group centers, there is little vertical movement. Even doubling the change at 25 yards wouldn't amount to more than 2" if that. Maybe an inch would be closer.

Fire the same loads from a rest at 25 and 50 yards. At those ranges the difference will show up a lot more.

[PolarFBear]

The 3913 is my favorite fire arm. It was also my first firearm. But, I never could shoot it well. It always shot a little low and a little left. Without adjustable sights (yes I did try drifting the rear sight), I just learned to compensate. Those sights look fuzzy to me as well. As a check, I gave this pistol to my son who also experiences the same sight picture. Perhaps they just don't fit some eyes. Still, I like them. Have 3 of this generation and will buy another when seen. As for a CCW, I have moved on to a Glock 19. Not in love with it but it WORKS.

[random guy]

Fire the same loads from a rest at 25 and 50 yards. At those ranges the difference will show up a lot more.

Well, that's what I thought, that the difference would increase proportionally with range but from what I can tell from my small and sloppy sample (I cannot explain the low flyers in both groups) there is virtually no elevation change to proportionally increase. At least nothing like we are used to seeing in revolvers. 4 X 0 is still zero. 4 X 1/2" would only be 2" at 50 yards. Not much.

I mean this is like comparing 300 gr cast softball .44 mag to sizzling 200 gr max loads. Just about the most extreme ends of the scale. I did not expect this result. Granted, tighter groups (better loads and shooter) would make this more definitive. Another factor may be the simple difference in total recoil between magnum revolvers and a 9mm. It's not like the 9 just lays there though. This really has me wondering.

[JohnKSa]

Are you a good enough shot to separate two groups that are a half inch apart or would it look like one group at 25 or 50 yards?

Fire the same loads from a rest at 25 and 50 yards. At those ranges the difference will show up a lot more.

I submit that if it is necessary to shoot groups, from a rest, and at distances that are 2 to 4 times further than typical handgun ranges, to even see a difference, that it is perfectly accurate to say: "There's very little recoil arc in a locked breech semi-auto while the bullet is in the bore." or to say: "That is because there's very little muzzle rise while the bullet is in the bore."

Just to be clear, I didn't claim that there's NO difference at all in POI due to bullet weight difference. Here's my first response to the OPs question.

Originally Posted by JohnKSa

The muzzle doesn't really begin to rise significantly until the barrel unlocks and, by design, that takes place after the bullet leaves the bore. As such, there's not as much effect on point of impact when changing bullet weights.

[Walt Sherrill]

Originally Posted by random guy

Well, that's what I thought, that the difference would increase proportionally with range but from what I can tell from my small and sloppy sample (I cannot explain the low flyers in both groups) there is virtually no elevation change to proportionally increase. At least nothing like we are used to seeing in revolvers. 4 X 0 is still zero. 4 X 1/2" would only be 2" at 50 yards. Not much.

Something has changed, and I can't post from Photobucket as I used to. I can, presently, only show the targets in question as an attachment. Click on the "attached Images" link at the bottom. I have posted other images here recently, using the [ IMG ] function, but it wouldn't work this time out.

When I look at the target, I shudder, as my personal shooting performance was terrible. But, I was rigorous in doing everything the same. (The target says 50' but it was shot at 30'-35'.) A first shot that was not part of the test was shot off target so that the first TEST ROUND was chambered by the gun cycling, and not done manually.

I shot the first test round on the first target using a 115 gr round, then the second using a 124 gr. round, then the third using a 147 gr. round, and then came back and repeated the process until all 15 rounds were fired. The rounds were loaded in the mag to allow that. I used the same point of aim on each target, and sights were not adjusted. (My eyesight has been adjusted since then, via cataract surgery... That might make a difference if I try it again.)

I don't know why the 147 gr. rounds made bigger holes in the paper, but they did.

Originally Posted by random guy

... Another factor may be the simple difference in total recoil between magnum revolvers and a 9mm. It's not like the 9 just lays there though. This really has me wondering.

I'm not sure the total difference in recoil matters as much as it seems it should.

As I've noted in earlier replies, until the bullet has almost moved out of the barrel, there's not much connection between the slide and barrel and the frame, and until THAT connection becomes more direct and forceful, there's not much way for any recoil (heavy or light) to have an effect on the frame (and barrel rise.)

The relationship of the bullet, barrel and slide, until the bullet leaves, is based on a fixed, physical relationship, and faster, slower, heavier or lighter bullets don't change that fixed physical relationship. The only thing that changes is the speed with which it is all takes place. But when the bullet is moving as part of that relationship, the timing doesn't seem to matter much, either.

Some recoil force may pass to the frame more quickly if the bullet is moving faster, and to the frame more slowly if the bullet is going slower, but the bullet position is always relatively the same with regard to slide movement. I don't see how the barrel can rise differently from one load to the next, as slide and barrel movement is the main transfer agent!

When the bullet is gone and while the recoil spring is still being compressed, the momentum of the slide and barrel moving to the rear continues until they each hit their respective stops in the frame. THEN you really see (and feel) the force of recoil, and that when the force of all of that mass of material moving to the rear directly causes the gun in the hand to tilt upwards.

While weight shift and more recoil spring pressure is also affecting the gun prior to that, almost all of this movement takes place AFTER the bullet is gone.

[random guy]

I wouldn't have believed it if I hadn't seen it. If not a universal rule, it certainly appears to be an unusual tendency of this type of semi-auto pistol. And a good tendency...unless you want to adjust POI by load.

[random guy]

JohnKSa:

I've got three boxes of 9mm ammo, all from the same manufacturer and all with different bullet weights that are slated for a test like yours.

I'm going to add one wrinkle. In addition to shooting groups from all three weights to see if a POI difference can be seen, I'm going to fix the slide closed and fire the groups again with all three weights. Right now the test is on hold while I come up with a reliable and practical way to fix the slide closed without causing any damage to the pistol.

It would be very interesting to also try a 1911 (or similar) with the slide locked, as the theory is that their quicker barrel tilt is part or all of the reason that we see elevation change with bullet weight in them. At least I think we do. Been a while since I shot mine much.

Not sure how you keep the slide locked though.

[45_auto]

Originally Posted by walt sherrill

Some evidence would make your argument more convincing.

What evidence are you looking for? I'm not going to invest in a fixed rest and shoot thousands of rounds of ammo to provide you with statistically meaningful proof that 230 grain ammo shoots .010" higher at 25 yards than 200 grain ammo which shoots .010" higher than 185 grain ammo. Just doesn't mean that much to me.

Originally Posted by walt sherrill

And how is the extra force that accompanies a heavier, slower bullet transferred to the frame BEFORE the bullet exits the barrel?

As previously stated, the momentum in a 1911 is transferred to frame thus to the shooter primarily by the cocking of the hammer (this is why the small radius on the bottom of the firing pin stop is critical and makes such a large difference in felt recoil) and recoil spring BEFORE the bullet exits the barrel.

No one is disputing the fact that the distance the slide moves is fixed by the mechanics of the pistol. I'm having a hard time figuring out why you can't understand that a heavier bullet moving 10% slower will spend 10% more time in the barrel and thus will be more affected by the forces (minimal as they are) transferred to the shooter as described above.

[Walt Sherrill]

Originally Posted by 45_auto

As previously stated, the momentum in a 1911 is transferred to frame thus to the shooter primarily by the cocking of the hammer (this is why the small radius on the bottom of the firing pin stop is critical and makes such a large difference in felt recoil) and recoil spring BEFORE the bullet exits the barrel.

We aren't really talking about how recoil is transferred to the shooter. We're talking about HOW recoil affects barrel rise while the bullet is still in the barrel. That is clearly dependent on the frame being affected by recoil. This is addressed more directly, below.

Originally Posted by 45_auto

No one is disputing the fact that the distance the slide moves is fixed by the mechanics of the pistol. I'm having a hard time figuring out why you can't understand that a heavier bullet moving 10% slower will spend 10% more time in the barrel and thus will be more affected by the forces (minimal as they are) transferred to the shooter as described above.

If the slide movement is fixed by the mechanics of the pistol, why is there more recoil applied to the frame BEFORE the bullet leaves if the the relationship of the components are the same regardless of bullet weight or speed? It's all based on physical movement, isn't it? A fixed-barrel gun seems to behave differently than a Browning Short-Recoil Locked-Breech gun, even though the physical forces affecting their behavior are the same.

A number of us don't understand why you can't (or won't) offer at least some evidence, like targets with holes in them, that show that a heavier, slower bullet's extra time in the barrel makes a difference in a BROWNING SHOT-RECOIL LOCKED-BREECH (SRLB) semi auto. We all agree that bullet weight and bullet speed does affect barrel rise in a fixed-barrel gun. You offer us only a theoretical argument and no proof that physics affects the behavior of the Browning SRLB system in the same way it affects a fixed barrel gun.

A number of folks here have shown the results of their tests or talked about what they've observed.

• lwestatbus is for more experienced in statistical analysis than most of us, and he found no statistically significant differences between bullet weight groups in the test he did.
  
• I was finally able to post images of my targets -- and I certainly sure can't brag about MY accuracy. I was consistent! (I don't remember which gun I used. If I do it again, I'll use my most accurate 9mm.)
  
• Jim Watson could find no difference in the groups of his 200 gr. and 230 gr. bullets fired from his 1911. And that's MORE than a 10% difference in bullet weight. Jim did see a difference with 185 gr. bullets -- but JohnKsa offered an explanation for THAT difference that may have been caused by the barrel link. (My gun was linkless.)
  
• random guy, did as others have, and was surprised that he saw no differences in points of impact.

We've shown you ours, now you need to show us yours.

You don't need a Ransom Rest to offer evidence to prove your claims. You don't need to fire thousands of rounds. You just need the same sort of rest you'd use when sighting in a gun -- a sandbag or bag of beans or rice -- a target, a variety of bullet weights, and a slow, steady press on the trigger as each shot is fired. Firing all of the bullets from the same gun without changes to the sights, and using the same point of aim makes for an easy test. If you use three or four bullet weights -- maybe 5 or 10 rounds each --means you'd shoot less than one box of ammo.

If you push the target out far enough, I'm sure you'll should see some differences, and the farther you go, bullet velocity will play a more-noticeable role in the results -- as because bullets drop at the same rate whether they're heavy or light. That means given the same barrel alignment with a target, a lighter bullet moving faster will hit HIGHER at greater distances than a heavier bullet that moves more slowly -- the lighter bullet it will have gotten there sooner and have dropped less.

If all the components (bullet, barrel, slide, frame AND recoil spring compression) have the same physical position in relationship to each other whether the bullet is heavy and slow, or light and fast until the bullet leaves the barrel how does that (supposedly) extra force cause barrel rise when a heavier/slower bullet is fired transferred to the frame before the bullet leaves the gun?

Where does that extra force come from and how is it transferred to the frame? The only direct contact of the slide (prior to bullet exit) with the frame is through the recoil spring. A spring doesn't know that heavier recoil is at play -- it reacts by traveling a given distance when compressed by physical movement. If bullet movement in the barrel is a fixed relationship regardless of bullet weight or speed, the amount of spring compression will also be the same while the bullet is still in the barrel.

That seems to suggest that the force transferred to the frame by the physical movement of the slide will be the same, too, until the bullet is gone, regardless of bullet weight or speed. The time involved for all this to happen is different, but the amount of physical movement is not different. Once the bullet is gone, things change dramatically. The PHYSICAL MOVEMENT OF THE SLIDE and how the force of that movement is transferred to the frame is the critical factor.

You haven't shown us WHY or HOW heavier, slower bullets cause a Browning SRLB barrel to rise higher while the bullet is still in the barrel . You seem to acknowledge that the physical relationship of the components are unchanged by bullet weight or speed while the bullet is in the barrel -- that is, in effect, a fixed relationship. That suggests that the force transferred to the frame -- dependent on slide movement prior to the bullet's exit -- is also the same, regardless of bullet weight or speed.

You could easily offer us you own test results that show different points of impact on a target that vary with bullet weight or speed. Give us more than theory -- which is theory that may be misapplied in this case.

.

[ShootistPRS]

In a self defense situation the change in impact of a slower heavier bullet than that of a faster lighter bullet is insignificant. Whether it is being fired from a locked breach semi-auto or a 6" revolver makes no difference.

What I maintain is that there is a measurable amount of difference between the two regardless of the gun used. I practice shooting at 25 and 50 yards more often than I do at 7 yards and less. I rarely use any rest unless I am testing a load or a gun. Once I am familiar with a handgun the only time I practice at less than 25 yards is in "combat" or defensive training. I train at 25 yards shooting 6 inch falling plates. That is for speed training. I shoot the "El Presidente" at 7 yards with the targets 3 yards apart. I do that for speed training. I don't actually use the sights on those games, I fire instinctive point fire. At less than 7 yards I train to shoot from "the hip" without extending my arms and using one hand hold.

I can see the difference in impact points between heavier and lighter bullets when using my sights. I don't shoot small enough groups with instinctive shooting to tell the difference. You have to be capable of shooting groups to see the difference.

[mavracer]

We aren't really talking about how recoil is transferred to the shooter.

Ultimately yes you are because it get's to the shooter thru the frame.
One of the biggest reasons you see less difference in POI when changing bullet weights in a semi auto is bore axis above the pivot point (web of your hand).

And 45_auto is absolutely correct about the firing pin retainer and it's radius being an important factor.