Reaming chambers a little

[zaitcev]

I have a revolver where the chambers are a little too narrow where the bullet goes through. Note that the chambers are of a perfect size where the case is, the problem is only with the bullets. As a result, the cartridges of certain brands do not seat well enough, their bottoms stick out and jam the cylinder.

The picture shows the bullet inserted from the opposite side, purely to demonstrate that it's the bullet that is a problem, and not the cases.

I'm thinking about finding a gunsmith who can make the bullet passes a little wider. My measurements suggest that 0.0065 of an inch is needed. The allowable error is only 0.0008 or so! This is very little, so I don't think drilling is going to do uniform enough holes. Sounds about the amount of material usually removed with sanding, but then it's even riskier to make holes egg-shaped. But I know nothing about metalwork at this level of precision. The question is, if it's something that can be done.

 

[BobWright]

Your gunsmith can do that fairly easily and economically. Its' not too unusual to find undersized throats.

Bob Wright

 

[Jim Watson]

.0065" is a huge amount to be cutting out of a cylinder throat. Double check before you start tinkering.

There are shops that will ream them to a uniform .4525" for a moderate price. One guy on Castboolits.com shows on FB
https://www.facebook.com/Cylinderhone-756429174391912/

CAVEAT: I know of him only by googling and favorable references on Castboolits, I have not dealt with him myself.

I am sure there are other places, it is not a hard job, but the tools are not cheap and it would not pay to set up for it unless you had the business. So YOUR gunsmith might or might not be ready.

 

[243winxb]

Pitnbull 45 acp revolver? Edit- Nope. Looks like a Taurus 380 revolver

 

[243winxb]

cartridges of certain brands do not seat well enough,

Bullet diameter should be the same . More a OAL problem?

 

[zaitcev]

Bullet diameter should be the same . More a OAL problem?

I took that picture precisely in order to preclude the OAL question from arising. I knew that if I took picture of rounds loaded into the cylinder from the rear, someone would claim that brass was too long.

Measured diameters:
Blazer Brass - 0.3550 - 0.3555 -- does not fit (pictured)
Hornady Crit. Def. - 0.3530 -- can be pressed in with thumb pressure
WWB - 0.3490 -- fits easily (pictured)
PDX1 - 0.3475

SAAMI spec for .380 is 0.3565 +- .0030, or noticeably larger than the largest bullet that actually exists. But it's possible that measuring with my calipers produces a systematic error.

 

[243winxb]

Could be a chamber problem or more likely an ammo problem.

When taking measurements on the bullet, right in front of the case mouth, the diameter will becomes less the deeper the bullet is seated.



This is because of the rounded bullet ogive.

All factory ammo should chamber without problems. Adjusting the chamber or throat may help.

 

[Jim Watson]

I think I'd just be selective on ammo.

 

[243winxb]

Moon clips? Another possibility?

their bottoms stick out and jam the cylinder.

 

[Mizar]

Zaitcev, this is a 9mm Luger revolver, right? Because that "SAAMI spec for .380" you quote makes no sense - neither the caliber, or the throat dimension.

 

[243winxb]

Its a .380 Note difference of bullet design the op is using. Very different ogives.

 

[reddog81]

I've used the guy linked to Jim Watson's post. The work was quality and a reasonable price. I'd prefer to use someone who has all the tools and has done this same thing 100's of times over a local gunsmith who's done it a couple of times.

Do you have access to pin guages? Those would be the best tool to use to determine the throat size. Pushing an oversized lead bullet through each throat will also work assuming you have calipers to measure the bullet afterwards.

I wonder what the factory tolerances are supposed to be? Another option would be to contact the manufacturer and see what they say. IMO any factory ammo in the correct caliber should chamber in the gun without issue, if not it's a gun issue. Maybe they'll take care of you for free.

 

[Mizar]

I stand corrected.

 

[Driftwood Johnson]

But it's possible that measuring with my calipers produces a systematic error.

Howdy

Not sure if you're saying you measured the chamber openings with a calipers or not. If so, that is the wrong tool. The flats on the inside measuring jaws will introduce an error in the measurement. As stated, pin gauges are the proper tool, but not everybody has a set. The idea of pushing a soft lead slug or bullet through the chamber will also work, you can use a standard caliper to measure the diameter of the slug.

I don't have a set of pin gauges, I use a set of hole gauges to determine chamber diameters. You put the gauge in the hole, expand the gauge, then measure across the diameter of the gauge.

https://www.grainger.com/product/STARRETT-Hole-Gage-Set-2ZVC4


Yes, .0065 would be a huge amount to remove.

 

[BobWright]

Undersized cylinder throats have been a problem with many revolvers. If the cylinder throat is less than bore size, there is hardly any way to expect accuracy. If the cylinder throat is oversized, bullets, even jacketed bullets, slug up to seal the throat.

Most gunsmiths are equipped to take care of your situation. If he can't, time to find a new 'smith.

Bob Wright

 

[Milt1]

.0065" is a huge amount to be cutting out of a cylinder throat. Double check before you start tinkering.

There are shops that will ream them to a uniform .4525" for a moderate price. One guy on Castboolits.com shows on FB
https://www.facebook.com/Cylinderhone-756429174391912/

CAVEAT: I know of him only by googling and favorable references on Castboolits, I have not dealt with him myself.

I am sure there are other places, it is not a hard job, but the tools are not cheap and it would not pay to set up for it unless you had the business. So YOUR gunsmith might or might not be ready.

This guy (Cylinderhone) worked on my Ruger .45 Colt and did an excellent job. He was living in Wake Forest when he worked on my revolver. I know it's the sane guy because he has a Sunnen hone and only the most dedicated have this type of equipment. I recommend him highly!

 

[shoobe01]

I'd contact the manufacturer. Maybe it's supposed to be like this, there's an obscure issue with ammo you are running into or: it's broken and they will fix it for free or a nominal cost.

 

[Mizar]

Actually, Zaitsev's calculations for +0.0065" are not far off. He has at least one chamber throat of .353" diameter, while it should be at least .3565" with max. diameter +0.004", or 0.3605" *
*Since SAAMI does not have a revolver chamber spec sheet for .380 ACP, we can extrapolate from the .38Spl/357 Magnum chamber drawing.
But those chamber throats and the bore should definitely be measured correctly and proceed from there. By the way, since the throats are of 0.353" diameter they can be measured accurately enough with a caliper for preliminary (rough) calculations - the error from the caliper jaws is not that big for such diameter. But having said all of that, I too believe that a gunsmith should examine the revolver.

 

[Varminterror]

Have the throats reamed. Life is way more simple than this thread makes it seem. The job isn’t hard to do yourself, but the reamer, pilots, and consumables cost enough to be prohibitive for the average joe to do his own one off job. Any Smith should be able to take on the job, but there are a few non-FFL places which take on the throat Work as the only thing they do.

Reaming throats is one of, if not the most basic and most common jobs in revolversmithing.

 

[BobWright]

I think I'd just be selective on ammo.

If those cylinder throats are indeed undersized, that means a bullet that fits will be undersized. This leads to a loss of accuracy. Bullets need to "slug up" in the cylinder before entering the forcing cone of the barrel.

Bob Wright

 

[BobWright]

Have the throats reamed. Life is way more simple than this thread makes it seem. The job isn’t hard to do yourself, but the reamer, pilots, and consumables cost enough to be prohibitive for the average joe to do his own one off job. Any Smith should be able to take on the job, but there are a few non-FFL places which take on the throat Work as the only thing they do.

Reaming throats is one of, if not the most basic and most common jobs in revolversmithing.

Well said.

Bob Wright