Handgun bullet seating depths

[cdoc42]

Until recently I only used JHP in revolvers and pistols and never gave thought to seating depth in relation to distance from the rifling as I did with rifles. The distance from the cylinder to the rifling in a revolver prevented any attempt at such measurements.

My guide to seating depths was the manuals from various manufacturers, even though the bullet I was using may not have been the same as that in the reference. I never experienced any problems, so never gave it another thought.

But recently I began to use cast bullets, and when an order of coated bullets from Missouri Bullet Company arrived, I wondered how I should decide on seating depth.

I dismantled my 9mm Walther to get the barrel alone. I dropped a bullet into the barrel, tapped it lightly in place, then inserted a cleaning rod into the muzzle until it gently touched the bullet, and marked a half-circle on the rod at the muzzle. Then I inserted a dummy round of the same bullet I had been using, and made a full circle on the rod. I carefully measured the distance between the marks to obtain the distance of the ogive of that bullet from the rifling.

Here’s what I found with the various 115gr 9mm bullets I have available:

Hornady XTP 115gr JHP: COL= 1.050 Distance from rifling= 0.09”

Precision Delta 115gr JHP: COL=1.055” Distance from rifling = 0.09”

Remington 115gr JHP COL: 1.125” Distance from rifling= 0.066”

Missouri Bullet Co. 115gr Coated “spire”: COL 1.060” Distance = 0.080”

Great. But so what? What SHOULD the distance be in a handgun cartridge?

I then measured each bullet. I can’t make a table here as it never comes out as such, so I’ll have to give you this info per line:

Hornady 115gr XTP JHP .355” diameter; OAL= 0.541” Base to ogive= 0.288”

Precision Delta 115gr JHP .355” diam; OAL 0.551” Base to ogive = 0.273”

Remington 115gr JHP .354” diam; OAL 0.530” Base to ogive= 0.272”

Missouri Bullet Co 115gr coated .356” diam; OAL 0.550” Base to ogive= 0.288”

What have I learned? Even though their base to ogive distance differs by 0.015” I accidently have the distance from the ogive to the rifling the same, at 0.09” for both the Hornady XTP and Precision Delta.

Since the Missouri Bullet has the same base to ogive length as the Hornady XTP (0.288”), it makes sense that I should change the COL to from 1.060” to 1.050.”

I’ll take any recommendations you have to offer regarding the Remington bullet.

Now, having gone through all this, I’m left with a question as to how the various reloading manuals derive their COL data. I’ll just use the 115gr information.

LYMAN- “Universal Receiver”
115gr Hornady XTP COL: 1.090”
115gr Barnes TACXP COL: 1.100”

HODGDON –no gun listed, just barrel length and twist
With Hodgdon powder - 115gr Speer Gold Dot HP COL 1.125”
With IMR Powder- 115gr Rem JHP COL 1.110”
With Alliant powder- 115gr FMJ (No manufacturer) COL: 1.120”
With Winchester powder: ALL BULLET WEIGHTS= COL: “1.169 MAX”

SPEER – Smith & Wesson model 5906
115gr GDHP: COL 1.125”
115gr TMJ: COL 1.135”
115gr JHP: COL 1.125”

So- how do you guys/gals (if any) decide what your COL should be for your revolvers and pistols?

[TJB101]

A lot of research based on bullet profile. The Lee 125gr 2R 9mm profile requires a really short aol due to its bullet profile. 1.06 to 1.08 depending on firearm. Even shorted for my CZ75... a similar plated bullet can be loaded quite long since it has more of a tapered profile. 1.15xx

Tons of reading, research and testing in my barrels led to my determination... but a lot of it is gun specific.

[44 AMP]

So- how do you guys/gals (if any) decide what your COL should be for your revolvers and pistols?

I look in my manuals for max loaded length with bullet. Then I load something less than that.

I set my seater die using a factory round, and if needed, adjust from there. If the bullet has a cannelure or crimp groove, I seat to that. Then check to ensure COL is less than book max.

Final step, ensure they fit the cylinder or cycle all the way through a semi from bottom rnd in the mag up.

I don't think setting (or worrying about a specific distance) of bullet jump to the rifling is particularly beneficial in a repeating handgun. You just don't get the kind of results you can get from doing that in a rifle.

I have a question, what are you calling the "ogive"??

My manuals have the definition of the ogive as the curved or sloped portion of the bullet. The entire part of the bullet from where it becomes smaller than full bore size all the way to the tip.

So, it seems to me that "measuring to the ogive" is actually measuring to a point on the ogive.

And if that's the case, what standard are you using for where that point is?

[Nathan]

Revolvers get loaded to the crimp groove or a manual number.


Semi’s get loaded to the plunk test value....basically, as long as possible without sticking in the rifling. I’m sure I could seat longer to touch the lands, or get close, but then I’m risking a bullet sticking in the rifling while clearing a malfunction or something.

[cdoc42]

44AMP: "My manuals have the definition of the ogive as the curved or sloped portion of the bullet. The entire part of the bullet from where it becomes smaller than full bore size all the way to the tip.

So, it seems to me that "measuring to the ogive" is actually measuring to a point on the ogive.

And if that's the case, what standard are you using for where that point is?"

My view of the "ogive" is that point on the bullet where it will not go any further into the leade; whether it fits the official definition or not, I don't know. But when one drops a bullet into the chamber and gently taps it in place, it has stopped at the ogive or place thereon. Or, measuring with a Hornady or similar "comparator," the tool stops further advancement of the bullet at that portion of the bullet where the curve begins the maximal diameter of the bullet, I've always thought that as the "ogive."

I think correctly saying it as a point on the ogive just uses more words.

Using that as a guide, I can measure that point on every bullet and even within the same caliber that measurement can differ depending on the manufacturer. In fact, I've seen it change in the same .270 spire by the same manufacturer but different lot number. I picked up on it because the position of the cannelure was different.

[Aguila Blanca]

cdoc42 -

I think you are using the term "seating depth" when you are really talking about cartidge overall length. The seating depth is how much of the bullet body is inside the case. I don't know of any loading manual that gives that dimension, and if you load different bullets (say three brands of JHP) to the same COAL, more than likely the seating depth will be different for each of them.

I don't load handgun ammo for bullseye accuracy, I load for combat accuracy with 100 percent reliability. I use the "plunk" test -- if my ammo drops cleanly into all the barrels I'll be shooting it out of, I'm good. If it doesn't "plunk" in some barrel, then I shorten the COAL a little until it does pass the plunk test.

My only concern about bullet jump in a semi-auto handgun is that I have "some" -- which is what the plunk test tells me.

[44 AMP]

My view of the "ogive" is that point on the bullet where it will not go any further into the leade; whether it fits the official definition or not, I don't know.

Your definition does not match the ones found in several dictionaries and tech manuals I've seen. ALL them refer to the entire curved portion as the ogive, and not a specific point.

I think correctly saying it as a point on the ogive just uses more words.

Using more words to precisely convey a specific technical point is something I think matters. You clearly know what point you are measuring to, but no one else does, or can.

Additionally, using he point where the bullet hits the rifling and measuring to the case base for an overall loaded length only works for the specific barrel used. It can be different with each different barrel tested.

As such, the measurement of your barrel has no practical use for the rest of us.

[ghbucky]

I'm glad the OP started this topic, because I've been thinking about this as well.

I'm doing some early research into loading 44 Rem Mag for accuracy to 100 yards, because I want to get into silhouette. Sierra says their 220gr fmj with true blue powder is their 'accuracy load', but I'm wondering if there is anything that can be done (or if it is an exercise in futility) about the jump to the rifling in revolvers as well.

[44 AMP]

One thing to remember about any claimed "accuracy load", all it means is that load was the most accurate of the loads they tested in the test gun they used.

It does NOT mean you will get the same results.

Its a fair place to start, but it is no kind of guarantee that it will be the most accurate load in your gun(s) just because it was in their gun.

[ghbucky]

Well, so much for Sierra's load anyway. Looks like they stopped making the bullet that I was reading about.

[BJung]

Here are two targets set side by side and shot at 20 yards. The only difference is the COL.

[44 AMP]

Unless fired from a machine rest, the human factor is always a possibility.

And, its one the shooter can be entirely unaware of, believing to have fired both groups "identically" when in fact they didn't.

Only a machine rest removes the possibility of human variables.

[BJung]

This is what I shot. The bullets and casings were all weighed. I sat on the ground, rested my handgun on a sandbag, and carefully pulled of the trigger while maintaining sight alignment. I wasn't doing a Dirty Harry type of shooting. The OAL of the longer is the same listed on the Lyman Cast Bullet book. If I repeat the test, I believe the longer COL will be the more accurate.

[cdoc42]

"Additionally, using he point where the bullet hits the rifling and measuring to the case base for an overall loaded length only works for the specific barrel used. It can be different with each different barrel tested."

There is no question about that, and, as I mentioned above, one must repeat the process with every different bullet in the same gun.

"As such, the measurement of your barrel has no practical use for the rest of us."

The practical use for everyone else is the fact that it had to be done in my gun for me to obtain the best accuracy, and requires you to repeat the process for the same result in your gun. I don't believe I've ever read that a suggested COL for any cartridge is related to accuracy rather than function.

"Using more words to precisely convey a specific technical point is something I think matters. You clearly know what point you are measuring to, but no one else does, or can."

How would you describe the procedure for determining optimal seating depth and labeling the final length of the cartridge without using the term, "ogive?"

[cdoc42]

Just for general interest, I have a Browning 1911-380 and my neighbor has a .380 by Sig.
We are reloading 95gr coated bullets made by Missouri Bullet Co. for each gun.

I've already fired mine and the accuracy at 7 yards off hand is acceptable. I dismantled both guns and removed the barrels. A loaded cartridge with a COL of 0.950" plunked into the barrel and compared to just a bullet plunked resulted in a calculation that the bullet was 0.04" from the leade.

Repeating the procedure with my neighbor's Sig showed the same COL placed the bullet right at the leade. This suggests to me that we can expect battery failures to occur if the bullet is seated longer than 0.950".

At 0.950" the case mouth is at the very end of the top of the lube groove, so any further seating would appear to have the bullet seated too deeply, but that's what we'll have to do if he does not obtain the same level of accuracy as I did if we want to duplicate the 0.04" jump that I have. The other concern is deeper seating and reduced powder space but I'm not concerned that 0.04" will produce a significant problem. The other option, of course, is to opine his gun simply does not "like" this bullet from an accuracy standpoint and search for an alternative.

[stinkeypete]

It's something I have wondered about, overall length.

Way back in the day, .38 Special bullseye target accuracy wadcutter loads were just a tad longer than the case. For revolvers. Huh.

For my Ruger Vaqueros, I got better accuracy seating the wadcutters more like a conventional bullet and crimping on one of the lube grooves. The fellas laughed at me for my silly looking wadcutter but they stopped when they saw my target... as that pair of .357s liked the bullets out long.

The S&W Model 52 is reported to be stunningly accurate. It's a semi auto that uses wadcutters seated only just a tad longer than the case.

Is this due to more reliable ignition due to small remaining case volume? But but.. in rifles one likes to seat very close to the rifling for best accuracy...

With my bullseye .45, the thing was very tolerant. Just load the overall length in the manual, double check with a plunk test, and lots of different powders and lots of different cast bullets all made ragged holes from a rest with minor tuning to powder amount.

I've decided that if I really want to understand revolver accuracy I need to number my cylinders and shoot at 6 targets in order to see if the cylinders might not be a part of the inaccuracies I see. If ever I get really bored.

Now.. short answer- how long? Follow the manual when possible. Then plunk test.

When there is no manual, try to estimate as close as possible with a similar bullet. Do a plunk test. Maybe even make a test round you can jam in to the cylinder or throat to seat the bullet.. remove and know that there is TOO LONG and take some off. Then plunk test again!

[44 AMP]

How would you describe the procedure for determining optimal seating depth and labeling the final length of the cartridge without using the term, "ogive?"

This is a reasonable question, and one worthy of a bit of thought. To the best of my knowledge, we do not have a specific term for the point where the bullet contacts the rifling. Perhaps we need one but it could only be generic, such as the "datum line" used on the drawings and specs for bottle necked rifle cases.

SO, we could create a term but its actual location would need to be understood as a different spot on the ogive for each different profile bullet AND each individual barrel used.

To additionally complicate things different bullets seated to the same distance from the rifling can produce rounds with different total over all lengths.

We are reloading 95gr coated bullets made by Missouri Bullet Co. for each gun.

A loaded cartridge with a COL of 0.950" plunked into the barrel and compared to just a bullet plunked resulted in a calculation that the bullet was 0.04" from the leade.

Repeating the procedure with my neighbor's Sig showed the same COL placed the bullet right at the leade. This suggests to me that we can expect battery failures to occur if the bullet is seated longer than 0.950".

This is interesting, considering that the spec for the .380 max COL is 0.984"
However I think it is explainable, and simply, because of the bullet you are using being different from the one used when the OAL standard was adopted.

Generally speaking, the length standards for about all rounds were adopted using the "standard" bullet profiles in use at the time. And using bullets of those profiles, loaded to the max length, should work through the magazines, actions and chambers of all firearms made to "industry specs".

To further muddy the waters, I just measured some RWS 95gr FMJ .380 and they run 0.966"

I think the point here is that while there are max length standards different bullets will be loaded to shorter lengths for reliability of function due to actual bullet profile.

Way back in the day, .38 Special bullseye target accuracy wadcutter loads were just a tad longer than the case. For revolvers. Huh.

Is this due to more reliable ignition due to small remaining case volume?

I don't think it had anything to do with the small difference in case volume. Back in the day, people either seated wadcutters flush or standing about 0.1" proud" beyond the case mouth. Some went with more bullet out of the case but usually not a lot.

While I never had anyone "explain" why, I think it had to do with crimping, and paper target scoring rules.

Being shot from revolvers (mostly) crimping was needed to prevent "bullet jump. Admittedly not a big problem with .38 wadcutter recoil levels so a light crimp was used.

Roll crimping a flush seated bullet "rounds" the sharp square front edge of the wadcuttler bullet and when playing a game where a hole that cuts a scoring line scores the value of that line, doing something that didn't leave the sharpest cleanest hole in the paper could be a disadvantage.

With the wad cutter just a bit beyond the case mouth, a light crimp into the soft lead of the bullet would hold it in place well enough, and didn't "round" the cutting edge of the bullet.

And, lastly (for now) a word about the "plunk test". Removing the barrel and plunking a loaded round into it and using the case base position compared to the barrel hood to determine if the round is too deep or not deep enough simply isn't applicable to all pistols. If you've got a gun you can do that with, great. I have some. I also have several where you can't do that, so assuming everyone can always do a plunk test isn't the case.

[cdoc42]

44AMP, here's what Hornady has to say in their website ad for the comparator (https://www.hornady.com/reloading/pr...d-gauges/loc):

"Measuring cartridge lengths across the bullet tips is not a reliable (or repeatable) method for measuring loaded rounds. Its common for variations of up to .025" to exist from one round to the next. Our Bullet Comparator measures rounds from the ogive to provide consistent, precise measurements. You can also use it to check uniformity of bullets from base to ogive.

The Lock-N-Load® Bullet Comparator Inserts allow the reloader to measure the bullet from the base to a specific point on the ogive, which has little variation, if any."

In the first paragraph, Hornady uses "ogive" as I reported above. In the second paragraph, the casual reader may completely miss Hornady's presentation being in agreement with you.

[cdoc42]

I should add, for the sake of completeness, a question: what is the proper pronunciation of the word, "ogive?"

Is it ogive, as in "live?" (i.e., ogIve)

Or is it ogive, as in I'm giving you a gift?

[Unclenick]

The Hornady measures a somewhat arbitrary location on the ogive. You make that measurement on a cartridge seated to contact the lands and then again with how you are seating it. The difference is the bullet jump. The same comparative method can be done just measuring the difference in COL. The problem is a lot of bullets, particularly match hollow points, don't all have the same length in the box, so the COL method is only exact for the particular bullet you made the measurement with. By measuring further down, you are measuring from a more consistently located dimension.

If you replace your Hornady bullet comparator insert with a stainless steel Sinclair insert, the Sinclair measures lower down on the bullet. It is profiled to come close to matching a typical bore throat, which they can do with steel, but which would harder to do with aluminum. It is a little more exact, though, as you are measuring at the throat contact point you are interested in rather than a bit above it. The only drawback occurs when someone seats the bullet shoulder slightly below the case mouth, as when trying to 80-grain .224 SMK's to feed in an AR magazine, in which case only the Hornady lands high enough to measure a finished cartridge, while the point the Sinclair is looking for is below the case mouth. But that's not too common a situation.

I measured fifteen Sierra .308 150-grain MatchKing bullets with both inserts to compare how long the distance from the base of the bullet to the insert's contact location on the ogive was, and put the following table together with them. You can see the Sinclair hit a spot 0.144" lower on the bullet and that resulted in slightly lower standard deviation, so it was slightly more repeatable. I also measured the total length of the bullets (the base-to-meplat measurement), which you can see varied a good bit more.



As to how you seat handgun bullets, there are two considerations. One is seating depth. The deeper the bullet goes into the case, the smaller it makes the volume the powder ignites in, and that raises peak pressure if the primer doesn't unseat the bullet ahead of the powder burn getting underway. Both happen in some conditions and with some component combinations. So, if you don't want to raise pressure substantially, you don't want to wind up with substantially greater seating depth. One saving grace in the common pistol cartridges is the cases are designed to withstand being fired partially unsupported, so the brass thickens below a point, limiting how deeply you can seat a flat or hollow base bullet (a boattail can go deeper).

To compare seating depths, the general formula is:

Seating Depth = Case Length + Bullet Length - COL

Since you are interested in the combustion space under the bullet, you don't want individual case length variation reflected, since you are using the same COL for all. Just use the SAAMI maximum length to have a consistent reference point.

For bullet jump, my experience matches Burbank_Jung's when soft bullets are involved. I determined in my bull's-eye match 1911's (.45 Auto) that lead bullets were significantly more accurate when they start out in contact with the rifling. This usually called "headspacing on the bullet" as the bullet meets the throat and stops the cartridge from going further forward before the case mouth gets to the end of the chamber. The first time I tried it was with 185-grain swaged LSWC's that were part of a bulk order from Star that a number of us shared in back in the early '80s. It cut the group diameters by 40% at 25 yards. I got the same effect with the more common H&G 68 form cast bullets, too, and they were still more accurate overall. HOWEVER, I never saw any measurable difference doing this with jacketed bullets. They seem to straighten themselves out in firing in that caliber. I've not had occasion to analyze it with other chamberings to see if they are the same or not. The 0.37" CTC group below was fired of a Hoppe's pistol rest with Hornady 200-grain JSWCs over 4.2 grains of Bullseye. The were seated with the shoulder of the bullet the usual 0.020" above the case mouth. The barrel in that gun has been throated, so the jump was probably at least a tenth of an inch.



The same gun with garden variety commercial lead bullets would shoot 5 rounds into about an inch at 25-yards most of the time, but they had to be headspacing on the bullet, and not loaded to standard depth or they would grow.



Another advantage with lead bullets is lead fouling is greatly reduced by headspacing on the bullet. It lines the bullet up to seal the bore better and prevent gas cutting due to gas bypass. It also prevents lead from shaving on the edge of the case mouth step in the chamber as it finds its way into the bore. It also causes start pressure to be more consistent when you shoot mixed cases, which may be part of the accuracy improvement. For reasons of fouling and accuracy, I've been recommending determining COL for lead loads as shown fourth from left below, provided your bullet shape will feed seated as long as this requires.

[Aguila Blanca]

Originally Posted by cdoc42

I've already fired mine and the accuracy at 7 yards off hand is acceptable. I dismantled both guns and removed the barrels. A loaded cartridge with a COL of 0.950" plunked into the barrel and compared to just a bullet plunked resulted in a calculation that the bullet was 0.04" from the leade.

Repeating the procedure with my neighbor's Sig showed the same COL placed the bullet right at the leade. This suggests to me that we can expect battery failures to occur if the bullet is seated longer than 0.950".

At 0.950" the case mouth is at the very end of the top of the lube groove, so any further seating would appear to have the bullet seated too deeply, but that's what we'll have to do if he does not obtain the same level of accuracy as I did if we want to duplicate the 0.04" jump that I have. The other concern is deeper seating and reduced powder space but I'm not concerned that 0.04" will produce a significant problem. The other option, of course, is to opine his gun simply does not "like" this bullet from an accuracy standpoint and search for an alternative.

So your question is about determining the optimum COAL, not about seating depth. Although, as you mention in this post, reducing the COAL also reduces the remaining case volume -- because it increases the seating depth.

That said, your concern about the lube groove is a non-sequitur. You are loading a revolver bullet for use in a semi-auto, and you are loading a coated bullet so (presumably) there is no lube. Even if the groove is lubed ... it's a lube groove, not a crimping groove, and the lube groove in a revolver bullet is intended to be completely within the case, not stop with the edge of the groove aligned with the case mouth.

If you need these loads to work in both guns, you can certainly load that bullet a few thousandths deeper. If you're at the maximum load already, back off the charge a couple of tenths, otherwise I wouldn't worry about it.

[cdoc42]

Thanks to the three experts for this marvelous discussion; it clearly points to the advantage of being a participant in the Firing Line. I've been reloading for rifles and revolvers for over 40 years and only in the last 4 years or so have I gotten into pistols. But for whatever reason, within the last week I happened upon this road to investigating seating bullets in the pistol as I do in the rifle. That's what sparked this conversation and I've now learned that getting that detailed in seating pistol bullets was more intellectual curiosity than useful procedure. The newbies here hopefully will get a take-away that there is always room for new knowledge.

[Aguila Blanca]

That level of detail would likely be of interest to a bullseye competitor. I have a friend who is one of that breed. He weighs all his bullets and sorts them by weight, he separates brass by headstamp, then measures the wall thickness of the case with a tubing micrometer, and he does a number of other things that have no significance for most handgun shooters. That degree of fussiness could well make the difference between a score of 100 - 3X and a score of 100 - 8X, but for plinking or IDPA that level of detail isn't worth the time and effort.

Much depends on how you will use the ammo you load.

[higgite]

Much depends on how you will use the ammo you load.

Or how much time you have to kill.

[cdoc42]

I be loading some .380 auto coated cast bullets tonight for both guns, using the info here, especially that re: best accuracy with flush headspace.

When I started in 1976 I read a book by John Wooters in two nights, which is where I learned the technique for determining the relationship between the rifle bullet and the lede. I dug it out of my library to review what he said about "ogive:"

"Benchrest shooters mostly prefer fairly firm contact between the bullet's ogive and the rifling,......."

and

"....but it isn't the tip of the bullet which contacts the rifling......it's some point on the ogive, well back from the tip and just in front of the full diameter section of the projectile."

44AMP, that was 44 years ago and your discussion above mirrors it. So - what would you like to call that point to settle the quandary for the next 44 years?