Chamber size?

[Mike38]

I was watching You Tube videos by FortuneCookie45LC and ran across one where he explains that the chamber opening (exit) should be .001 to .0015 smaller than the bullet diameter, and the forcing cone should swage the bullet another .001 to .0015, for a total of .002 to .003. This confused me, but I don't know that much about revolvers. He showed measuring the chamber with digital calipers. So out of curiosity I measured two of my .38 Spcl revolver chambers. My S&W measured .357 and my Taurus measured .360. So I dropped a .358 lead bullet (bullet, not cartridge) down the chambers of the .360 Taurus and they fell right through. When dropped into the S&W they stopped in the chamber. Both of these revolvers are very accurate as they are. Does FortuneCookie45LC know what he's talking about here? None of it makes any sense to me! I should be shooting .361 diameter bullets in my Taurus? Does anyone even make .361 bullets?

[Recycled bullet]

Originally Posted by Mike38

I was watching You Tube videos by FortuneCookie45LC and ran across one where he explains that the chamber opening (exit) should be .001 to .0015 smaller than the bullet diameter, and the forcing cone should swage the bullet another .001 to .0015, for a total of .002 to .003. This confused me, but I don't know that much about revolvers. He showed measuring the chamber with digital calipers. So out of curiosity I measured two of my .38 Spcl revolver chambers. My S&W measured .357 and my Taurus measured .360. So I dropped a .358 lead bullet (bullet, not cartridge) down the chambers of the .360 Taurus and they fell right through. When dropped into the S&W they stopped in the chamber. Both of these revolvers are very accurate as they are. Does FortuneCookie45LC know what he's talking about here? None of it makes any sense to me! I should be shooting .361 diameter bullets in my Taurus? Does anyone even make .361 bullets?

Preferably you want a light press fit through the cylinder. The slightest resistance that can be overcome with one fingertips force to push the lead bullet through the cylinder.

Then cross your fingers and hope that the barrel diameter is polished smooth and sized smaller than whatever that cylinder or throat measurement is, and if all the stars line up you hit that paper plate at 50 yards like you're trying to. This is what happens when I shoot my CZP09 or my Ruger Blackhawk. In the Blackhawk 357 bullets offer the slightest resistance and 358 bullets are snug passing through two of the chamber holes.

If the cylinder throats are severely undersized or if the barrel lands and grooves are severely oversized then what will start as ferocious leading will transform into the worst accuracy ever. You will not be able to have a piece of printer paper from 5 yards aiming at the center of it. That's what happens when I shoot lead bullets through my Ruger SP101. It's not possible to push through a 357 soft powder coated slug through this cylinder without using a hammer and a punch.

[The Happy kaboomer]

Believe nothing you read and ONLY half of what you see.

[Jim Watson]

Both of these revolvers are very accurate as they are.

Sounds like your diameters are close enough.

[rclark]

Lets just say Ruger .45 barrels normally have a .451 hole down the middle. The cylinder throats then should be .001 larger, so .452. Therefore the bullet used should be .452 bullets also. The lead bullet then should pass the cylinder throats with finger pressure. If the throats are larger then .452, that is ok too, but then the bullet used still should 'fit' the throat. None of my .45s have that condition. Only one had 'really' tight throats. The rest were slightly small. I reamed them all anyway to .4525 and all is well. After reaming the 'really tight' throats on the original Vaquero, the group size was cut in half, and no longer leaded.

[44 AMP]

Does FortuneCookie45LC know what he's talking about here?

Based only on my personal experience of over 50 years shooting revolvers, mostly S&W and Ruger, shooting cast and jacketed bullets, my considered opinion is he doesn't know jack...squat.

On the other hand, I could be completely wrong, and his ideas might be just the ticket for a match revolver, or something like that, I don't know. What I do know is I've owned regular factory production revolvers that don't do what he says needs done, and they have shot somewhere between fine and outstanding by my standards.

I've read a lot about chamber throat sizes, forcing cone and bullet sizes, and what combinations were "best" long before the Internet and U tube existed. I find the information and the discussion interesting but largely irrelevant to me.

I don't know what my revolvers chamber throats measure, I've never measured them, and I feel no need to do so. I don't care if they meet some self appointed expert's idea of what is right, or best, I care about what they DO in my hands with the bullets I shoot, and so far all have been acceptably accurate for me.

he explains that the chamber opening (exit) should be .001 to .0015 smaller than the bullet diameter, and the forcing cone should swage the bullet another .001 to .0015, for a total of .002 to .003

I don't get this, either. By his standards, the cylinder should squeeze the bullet down and then the forcing cone do the same for a total of .002-003" smaller than original bullet diamter. SO, by his standards the .452" slug I'm shooting in my .45 Colt should be .450" or even .449" when it enters the barrel. Otherwise, my gun won't be accurate???

Against this (for one example) I've got a Ruger .45 Colt Blackhawk I just dropped a .452" 200gr JHP slug into each of the chambers and one chamber it falls straight through, and the other 5 it doesn't fall straight through but if you shake the cylinder a little bit, it falls right out. SO, no squeezing the bullet there.

Yet that same gun, in my hands will shoot a 2-2.5in group at 25yds and ring the 2ooyd gong on the rifle range regularly if I do my part correctly.

I would recommend not paying a who lot of attention to U Tube experts and focus on what the gun(s) and ammo in your hands does. IF yours does what the U Tube guy said it does, fine, he got it right. But if it doesn't?? Draw your own conclusions.

[RickB]

I'd like the chamber mouth to be the same size as the bullet, or .001" larger, and the bore no larger than that; just not a bore larger than the chamber mouth.
Don't know that squeezing the bullet is better than not distorting the bullet at all?

[Skippy]

Originally Posted by RickB

Don't know that squeezing the bullet is better than not distorting the bullet at all?

Doesn't the rifling distort the bullet? Isn't that the point of rifling?

_______________
*I'd give right arm to be ambidextrous*

[reddog81]

Large cylinder throats will cause accuracy issues with lead bullets depending on your standards. Your bullets don’t need to be .003 over size to work well however. .358 bullets will work great with .357 throats as long as the barrel groove diameter is .357 or smaller.

If your lead bullets just drop through the cylinder throats you will probably be better off trying to find a larger diameter bullet if the best accuracy is your goal. Most swaged HBWC bullets are in the .359/.360 range. You could try those in your Taurus.

Jacketed bullets don’t seem to as effected by a larger throat. Many people are fine with shooting 6” groups at 10 yards and probably wouldn’t notice any difference using whatever size available.

[44 AMP]

Many people are fine with shooting 6” groups at 10 yards

If there are "many" people who are fine shooting 6" groups at 10 yards, either they live somewhere else, or like elephants in cherry trees, they hide really, really well....

I don't know any. My personal standard is that a 6" group at 25 yards means either the gun, or the shooter, or both, needs work.

[JohnKSa]

Doesn't the rifling distort the bullet? Isn't that the point of rifling?

It does distort the bullet, but that is a side effect, not a desired result. If there were a way to spin the bullet without distorting it at all, that would actually provide better results. Although, to be fair, the improvement in a handgun probably wouldn't be sufficient to worry about.

...he explains that the chamber opening (exit) should be .001 to .0015 smaller than the bullet diameter, and the forcing cone should swage the bullet another .001 to .0015, for a total of .002 to .003.

This is my view of requirements for the bullet.

1. It should remain centered. No wandering off to one side or the other.
2. It should remain aligned with the bore. No tipping or tilting.
3. It should seal the bore and engage the rifling positively.
4. It should be minimally distorted.


Because of 1 and 2, you don't ever want the bullet to have significant room to move sideways or tilt. On the way from the cartridge to the muzzle, at every step along the way, everything should fit the bullet reasonably tightly, as much as is possible. So the chamber mouths at the barrel/cylinder gap shouldn't be a lot larger than the bullet or the bullet can get misaligned or off center.

Because of 1, 2, 3 and 4 you'd rather not have the bullet swaged down smaller than it needs to be at any point along the journey before it gets to the bore. That would mean that at some future point in the travel it will have extra room to tilt, get off center and it may not seal the bore well or engage the rifling properly. So chamber mouths shouldn't be too small--certainly not significantly smaller than bore diameter or bullet diameter.

Ideally, the bullet should be just a tiny bit oversize for the bore. Maybe 0.001" oversized in diameter (compared to the bore diameter) at the point it hits the rifling. The bullet will generally expand a bit from the tremendous force of the expanding gases behind it. If it's just a little too small, that expansion/upset can take up a little bit of the mismatch, but it's not going to be able to deal with anything other than a very small mismatch.

[reddog81]

Originally Posted by 44 AMP

If there are "many" people who are fine shooting 6" groups at 10 yards, either they live somewhere else, or like elephants in cherry trees, they hide really, really well.....

You must not visit public ranges very often. 6” at 10 yards is about par for the course. If someone is shooting at that level they won’t notice if a bullet is undersized a bit.

[44 AMP]

You must not visit public ranges very often.

I do not. Though I can see the logic that someone who is shooting 6" groups at 30 feet should be at the range, and more often than they are.

[JohnKSa]

A consistent 6" at 10 yards is better than average at the indoor ranges I visit.

I've seen shooters that could barely keep all their shots on human-sized silhouette targets at 5 yards. And the inevitable holes in ceilings, and walls let you know that some are worse than that.

However, true that may be, I would say 6" @ 10 yards is not very good shooting unless the person is shooting for speed.

[Recycled bullet]

Why would somebody practice marksmanship at the astronomical distance of ten yards, we all know self-defense happens at seven yards and closer

The mental gymnastics that is required to justify the continued lack of competence as instead a demonstration of skill would be so much better used instead as fuel to increase skill and ability but then I would repeat myself and be growing unnecessary gray hair so I let them be if they are not dangerous to themself or the rest of us around them who share the public range.

[reddog81]

OP was asking about undersized bullets. If someone is shooting 6” groups at 10 yards they won’t notice their bullets are a bit small. Is someone is going for groups at 50 yards they need to make sure their bullets are sized correctly. It all depends on your standards.

[Mike38]

Thanks for all the replies, and please continue the conversation, I find it interesting. I'm going to leave well enough alone on bullet size. You Tubers like FortuneCookie has his way, and I have mine. If it ain't broke, don't fix it I guess.

The comment about 6 inch groups at 10 yards is very true at the range I shoot at. On a normal day I get disappointed with greater than 2 inch groups at 10 yards, but I've seen many many people that struggle to hit a life sized silhouette at that distance. Actually kind of scary some days.

[rclark]

The comment about 6 inch groups at 10 yards is very true at the range I shoot at.

Yikes! Might as well shoot smooth bore if that is the norm (or just give it up and throw rocks)! As someone said above, if I shot greater than 2" groups (slow fire, off hand), I'd be highly disappointed in myself. That said though, if you are very new to the skill, there is lots to learn about accurate shooting before settling down to consistently shooting decent groups.

[jetinteriorguy]

I shoot pistols for one reason only, self defense. I used to shoot for accuracy and was fairly proficient at it, then I realized that for me it served no useful function. Now I can empty any pistol I own as fast as I can pull the trigger and keep all my shots in a 5” circle at ten yards. This is much harder and takes more practice than slow aimed fire for smaller groups. This is especially true shooting my revolvers DA. Every time I go shooting with someone who shoots slow aimed fire and have them try their hand at rapid fire, they get very disappointed in their performance.

[RoyceP]

It's important to note that 45 Colt ammunition before maybe 1990 was based on a .454" bullet diameter. Someone in the firearms industry wanted the barrel and bullet diameters to be matching for 45 ACP and 45 Colt. So starting some time in the early 1990's SAAMI chamber specifications were modified to show .452".

This is important because older revolvers - all of the ones I own - are intended to use .454" bullet diameter.

Latest revision SAAMI specs see page 59 for 45 Colt:

https://saami.org/wp-content/uploads...12-13-2022.pdf

[44 AMP]

Someone in the firearms industry wanted the barrel and bullet diameters to be matching for 45 ACP and 45 Colt.

Yes, and many if not most of them were called "customers"....

The original .45 Colt bullet size was .454". ALL the bullets were lead. Jacketed .45 bullets don't show up until nearly 40 years later with the .45acp with their size of .451/.452".

After WWII, as the popularity of the Single Action revolver started going back up, (due mostly to Hollywood & tv Westerns) and other makers making and selling SA revolves, Colt got back into the market.

During this era, .45 Colt barrel size was reduced to .452" (generally, not everyone did, or did it at the same time), I think, primarily, because more people shooting .45 pistols were using (and able to get) .45acp size slugs.
The "acp" size barrels gave better accuracy with the smaller diameter bullets (and particularly jacketed ones) and the .454" bullets simply didn't care. They squeeze down just fine, and do not create dangerously high pressure doing so.

Eventually, the smaller bore diameter became the defacto industry standard, and still is today.

[Jim Watson]

.45 LC chamber is still pretty sloppy. Throat .452" -0 + .0075" so anything up to .4595" is technically in spec. Most SAAMI diameters are -0 +.004".

Undersize is worse and not unknown, there are shops doing a good business reaming to .4525".

[rclark]

shops... reaming to .4525".

Or just buy the tool and do yourself.

I shoot pistols for one reason only, self defense.

Each to their own . Rat-a-tat-tat is no fun in my books ... accurate shooting with a revolver out to 100 yards (and beyond) is a lot more fun. Guns aren't 'just' for sub 10 yards. That would get boring real fast. Can be used for bottle busting, gopher/rabbit/varmint shooting and much more 'recreational' uses ... Need to go on the 'offensive' once in awhile on a tin can at 75 yards, or a steel pig out there even further... Or learn the art of waiting for a gopher to pop it's head out.... .

[44 AMP]

Now I can empty any pistol I own as fast as I can pull the trigger and keep all my shots in a 5” circle at ten yards.

And does that skill actually serve a useful function in your life? OR is it just practice for a function you've never needed and hope never to need??

Also, its quite clear you don't own some of the guns I own, and I'd be willing to bet you couldn't empty some of them as fast as you could pull the trigger and put all shots into a 5" circle at ten yards. (I will stipulate a basic requirement that the 5" circle be ON the target, and roughly centered )

You do you, focus on what interests you and what you feel important. In my life there is much more to handgunning than defensive shooting practice, and it forms a very tiny percentage of my shooting.

Also, as to this.

there are shops doing a good business reaming to .4525".

They aren't doing any business with my guns. Nor am I doing any reaming of them myself. I am very much a "if it ain't broke don't fix it", kind of guy, and none of mine are "broke".

[Jim Watson]

I am very much a "if it ain't broke don't fix it", kind of guy, and none of mine are "broke".

A lot of people have trouble figuring that out, but if you had .450" throats, that might qualify as broke.