What makes a revolver accurate?

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  • Last Post 21 December 2015
tomme boy posted this 09 January 2015

I am new to revolvers. I have been doing some reading on what to make a revolver to shoot. But a lot of information is left out. So lets hear what it takes.

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onondaga posted this 10 January 2015

http://www.castbulletassoc.org/view_user.php?id=6494>tomme boy

 Revolvers generally shoot cast bullets that fit correctly better than jacketed bullets. An important factor is being able to detect problems that make a revolver terrible with cast bullets. Some of the common problems you should be aware of that make revolvers hopeless or very expensive to get ready for cast bullet shooting are:

1, Excessive gap between cylinder and barrel. 2. A barrel with tight spots anywhere. 3. Chamber constriction equal to or larger than groove to groove  bore diameter. 4, rough or out of round cylinder constriction 5, rough, chattered or out of round barrel throat. 6, rough chattered or eroded bore.

These things are repairable to a degree by a competent pistol-smith. Some revolvers are out of the range of being able to be repaired or even be made suitable for cast bullet shooting.

No modern revolvers are specifically designed for cast bullet shooting. Many older revolvers are designed for cast bullet shooting. The biggest problem with modern revolvers and cast bullets is cylinder throats equal to G to G bore diameter. That equity is fine for jacketed bullets but is marginal to horrible for cast bullets. That equity problem to cast bullet shooting is common to some modern revolver makers. When the Cylinder throats are worse than equity and larger than G to G bore diameter, the particular revolver will likely never be a good cast bullet shooter.

A set of pin gauges is a common and effective tool set to detect revolvers that are not suitable for cast bullets.

It is very wise to find an excellent pistol smith that is very familiar and experienced with the needs for a revolver to shoot cast bullets well before purchasing a revolver that will be used with cast bullets.  Do not make your revolver purchase final without the revolver being checked and found to be suitable for cast bullet shooting..

Gary

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RicinYakima posted this 10 January 2015

I can only add to Gary's list: timing is poor, i.e. the cylinder does not lock up in line with the bore; the locking mechanism is poor, i.e. does not lock up in the same relationship to the frame when the cylinder is closed every time. But remember, I am old and don't know much about revolver made in the last 25 years. I only own two revolver made since 1970, and there is reason for that. HTH Ric

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tomme boy posted this 10 January 2015

What I was looking for is like the diameters of the throats, forcing cone, barrel, alloys.

Basically how is each one tied to each other. And if one is off, how would it effect the others.

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onondaga posted this 10 January 2015

http://castbulletassoc.org/view_user.php?id=6494>tomme boy

You are asking for numerous books of knowledge. That won't happen on an internet  forum. Pick a caliber first, study industry standard drawings. The manufacturers sell their revolvers with their sales efforts pointing out how well the tolerance standards are met and what materials are used.

Again, I will repeat: It is very wise to find an excellent pistol smith that is very familiar and experienced with the needs for a revolver to shoot cast bullets well before purchasing a revolver that will be used with cast bullets.  Do not make your revolver purchase final without the revolver being checked and found to be suitable for cast bullet shooting..

Gary

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OU812 posted this 10 January 2015

Inspect pistol before buying (check forcing cone of barrel for smoothness). Use pin gauge to check cylinder forcing cone hole diameters, all should be same diameter . A jacketed .3570” diameter bullet is snug, but easy slip fit thru all my 686 charge holes. Use a bore scope  to check alignment of each charge hole with forcing cone of barrel during lock up. Let hammer fall slowly and check for a tight cylinder lockup while hammer falls. Check gap between cylinder and barrel, usually factory tolerances are wider than optimum.   Size your cast bullets .001-.002” larger than cylinder forcing cone diameter to reduce “not eliminate" gas cutting. Gas check will help reduce leading until barrel is broken in. I remove slight leading and lap my barrel with 0000 steel wool wrapped around bronze bore brush soaked in Hoppes solvent.

  I cut my barrel forcing cone from factory 8 degrees to 5 degrees included to reduce lead splatter on face of cylinder. The Ruger GP 100 is already cut to 5 degrees, so just lapping may be needed.

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JSH posted this 10 January 2015

Some of the replies to the OP really have me scratching my head. The comments on a “new” gun not being made for cast? You going back to the 1800's? Some of the finest handguns are being made today. Along with maybe close to some of the worst. I didn't see him specify full blown custom or factory, so as many of us I have to let my hard earned dollar do my talking. I have revolvers that are still in the works of getting to what I expect. Just have to build as I go. As to doing a bunch of measuring, I totally agree. But there are very few shops that are going to let it leave and come back. I have about 8-10 shops I frequent maybe two of them I could do that.

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mulespurs posted this 24 February 2015

I think you could buy one and shoot it a while. It might just be alright. Fix as you go if you need to, or trade. I don't want to worry so much as some. I would rather shoot more.

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wv109323 posted this 08 December 2015

The basics are: The bore needs to be a consistent size all along it's length. Some claim that the bore can be reduced where the barrel threads into the frame. After the constriction the bore is larger. The forcing cone in the barrel can not be abrupt. There needs to be a taper on the rifling. The cylinder throats need to be consistent at .001 over the bore size. Things like egg shaped throats,poor lock up,barrel constriction are accuracy killers that need to be assumed. The rate of twist needs to be appropiate for the bullet configuration,velocity and range it is going to be used.

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Dale53 posted this 09 December 2015

The biggest single problem that CAN happen with revolvers is a throat size not proper for the barrel groove diameter.

In older .45 Colt's for example (both Colt and Rugers) the cylinder throat was often as large as .458". The early Colt SAA's had bore diameters of .454". Using black powder and soft bullets, the bullets often “bumped up” in size to work well. When the transition was made to smokeless, “not so much".

Later Rugers often had cylinder throats undersize for the barrel (.449"- .450” for a groove diameter of .452"). These would put an undersize bullet (no matter it's original size) into the barrel causing gas cutting and severe leading in just a few shots, ruining all hope of accuracy. As an example, my recently purchased SS Ruger Bisley .45 Colt had throats of .449-450". Inside of thirty shots, you could literally watch the accuracy leave. An examination of the barrel showed it was leaded from end to end.

I borrowed a Manson Reamer Kit (complete with pilots) from a good friend, and reamed the cylinder throats to .4525". Fresh off the tools, the revolver shot like an NRA Bullseye pistol. Repeatable accuracy of well under an inch at 25 yards. This revolver was a convertible (.45 ACP/.45 Colt) and until the ACP cylinder was reamed would not even allow me to load my standard .45 ACP with a .452” cast bullet. Now, it too shoots extremely well.

While I had the kit (and with my friends blessing that owned the kit) I reamed two other friends revolvers and they all turned out extremely well.

You COULD slam Ruger, but actually, as it turned out, I am MORE than happy with the end results and now I have a “custom” revolver and a large smile on my face for just a bit of effort.

Smith & Wesson is not without their problems in the recent past, either. The 1917 revolvers had large throats (some as large as .458") and accuracy was not good with standard ammunition. The 1950 Target .45 ACP revolver as well as the 1955 (heavy barrel “N” frame target .45 ACP) often suffered the same maladies.

On the other hand, my S&W Model 625-6 (Model of 1989) with 5” barrel and my 625-8 JM Special (both .45 ACP's) have PERFECT throat dimensions and shoot well under 1” at 25 yards right out of the box.

So, the answer is, “it just depends". Carefully measuring critical dimensions before buying (if the buyer will permit) can save you some grief along the way.

FWIW Dale53

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Eutectic posted this 18 December 2015

First you need an understanding seller or gun shop owner. I once checked out the entire stock, 6 revolvers to find the one I wanted.

You need to know what you are doing, the shop owner does not want his new guns scratched up. If you are ham handed, take a gunsmith or machinist with you, and expect to pay him!

You need to know the standard SAMMI dimensions, have them with you!

Required tools. You can use a caliper to measure cylinder dimensions, however it is difficult to get good measurements without removing the cylinder. For measuring chambers and cylinder leads,I take jacketed bullets under the desired diameter and squeeze them in a vise until they measure what I want. I have a set of different widths with screws in the hollow points. Range rods are available from Brownell's. Read the instructions on using them. Sized fired cases and a set of feeler gages complete the set.

Tolerances listed in approximate order of cost to correct.

1.The alignment of the chamber throats with the barrel 2.The cylinder throat diameters and barrel groove diameter 3.The chamber diameters 4.The cylinder gap/headspace 5.The angle and smoothness of the cylinder leade 6.The choke in the barrel 7.The angle and smoothness of the barrel forcing cone

Numbers one to four are costly to fix. Undersize may require precision machining. Oversize can require a new cylinder. They may not be correctable on an old gun where parts are not available.

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Pigslayer posted this 21 December 2015

I own a Ruger New Model Blackhawk in .45 Colt that I bought in like new condition as part of an estate sale. I don't think that it was ever fired. I bought that well over ten years ago (maybe 15). The tolerances on that revolver were excellent with the groove dia. being at .451 & the cylinder throats being at .454". This revolver was made in 1979 according to Ruger. It shoots cast extremely well. Recently I bought a new Ruger New Model Blackhawk in .44 Special. Tolerances not so good on this one. I've had to lap the barrel due to thread choke. Seems a lot smoother now & without that restriction as I approach the throat with a patch & jag. The cylinder has been sent to Cylinderhone.net to have the throats reamed as they were about the same diameter as the groove diameter. Reaming them to .432". Doug Phillips at Cylinderhone.net says that he can get all of the throats to .0002” of each other. The throats in my Ruger .45 Colt are really good & it shoots very well but if he can get them to within .0002” of each other I'll be sending that cylinder to him too. Pat

If someone else had of done to me what I did to myself . . . I'd have killed him. Humility is an asset. Heh - heh.

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