Bore Size vs. Cylinder Mouths

[insanelupus]

Okay, I know that ideally the groove diameter will be approximately .001" smaller than the cylinder mouths on a revolver. But what about less than ideal situations?

I have slugged two different .44 Specials. One had a groove diameter of .429" and cylinder mouths of .433". The other had a groove diameter which was .4268" and cylinder mouths of .4305-.4308".

I know common wisdom now days says to shoot a bullet the same size as or slightly larger than (.001" or so) than your cylinder mouths. But could those two revolvers with cylinder mouths so much larger (.004" or so) be made to shoot lead bullets with any accuracy or without a lot of lead build up at the forcing cone, or should they just be relegated to jacketed bullets only and life goes on?

I've actually contemplated recommending the owners try a Keith style bullet and size them the same diameter as the cylinder mouths and give them a try. Possibly even trying to size them .001" under the cylinder mouth size, just to see what they end up with.

In those situations where a person wants to shoot cast, I'd think the accuracy of the load would be more important than how much clean up of lead there is at the end of the day, but I figured maybe some of those more experienced than I have already tried this out and could help me out before I try to reinvent the wheel.

[Bass Ackward]

I know common wisdom now days says to shoot a bullet the same size as or slightly larger than (.001" or so) than your cylinder mouths. But could those two revolvers with cylinder mouths so much larger (.004" or so) be made to shoot lead bullets with any accuracy or without a lot of lead build up at the forcing cone, or should they just be relegated to jacketed bullets only and life goes on?

In those situations where a person wants to shoot cast, I'd think the accuracy of the load would be more important than how much clean up of lead there is at the end of the day, but I figured maybe some of those more experienced than I have already tried this out and could help me out before I try to reinvent the wheel.


I can't sleep so you get the unabridged addition. :grin:

The whole key is the alignment and uniformity. NOT the size relationship. In fact, different designs will perform better if you let Professor Gun tell you what size IS needed and NOT go by conventional wisdom.

As a result, I have sizers in .0005 increments from .429 to .434. I shoot cast from .001 below bore to .002 over chamber throat. Depending on the design. Another guy who does very well uses .439 because that is what will just chamber. But his alignment is good. So there are the extremes and in the end it just depends. And that changes over the life of the gun.

My original dimensions on a 44 Special were .4295 X .416. 700 rounds later found .4302 X .420. So as it cleans up dimensions will move. Since each chamber gets one for every 6 up the pipe, the pipe will move towards the chamber mouths. (more important that they are the same to me than size)(another statement that sounds so simple, but OFTEN a problem)

Then there is the goal. Is no leading more important than accuracy? The answer seems so simple, but we get kinda freaky around here about leading. Everything will foul eventually regardless of bullet material to where accuracy is affected. Until accuracy is, then it ain't fouled. What is needed is a worn or smoothed bore that seals and will clean out with minimal effort.

So will they build up lead? Maybe or maybe not.
Will the gun be accurate? Maybe or maybe not.
How can you tell? Trial and error.

My advice would be a GC design .001 under throat for 2000 rounds to start them out. Then try PB if that is their goal. If the gun won't shoot a GC like that then the choices are copper only or fire lap with no guarantees either way. There is nothing wrong with hot copper for those 2000 rounds either. Many fear copper for lead, but the odds are it makes a better lead gun.

What expectation "THEY" have is MORE the key to success with that gun. Read that again.

If they can see accuracy with cast as equal to jacketed of the same weight at first, then they will tend to be happy. If they expect one hole, then can this project and let them stay with copper. If they expect zero leading, have them take up golf.

[44man]

I ain't touching this one! Bass mentioned GOLF somewhere in there! :groner:

[HeavyMetal]

I hate trying to make someone elses gun shoot for them.

I will assist in loading, I will assist in casting but if the shooter is not a reloader it can be a waste of time.

Most of the time the shooter just has unrealistic expectations, usually of his skill level.

Now if you know and shoot with this guy on a regular basis thats a bit different.

Bass has it right select a load and write it down on paper. Then go shoot it.

Then, and this is very important, make only one change at a time and shoot each load change before you decide to change something else.

You also have another stumbling block to deal with: two different guns with different sets of diamensions.

Beaware one load will not work equally in both guns!

Now what I would do is load a .433 for gun A and .431 for gun B as a starting point!

You might get lucky and hit both right off the bat, other wise make notes and proceed slowly.

[9.3X62AL]

An adjunct to Bass' text--which is EXCELLENT--is to never say "never", and to never say "always".

I was the unhappy owner of a mid-90s Ruger Bishawk in 45 Colt with the infamous .449" throats and .452" grooves. Far from ideal, certainly. But even in that condition, it still shot one boolit VERY DARN WELL, and at velocities from 900-1200 FPS in WW alloy or 92/6/2. That design was Lyman #454490, a SWC/GC with rebated gas check shank. After honing the throats to .453", this same boolit still performs wonderfully--and was joined by a bevy of other designs after the surgery.

Some of the conventional responses to wide throat/narrow groove sitches is to do Taylor Throating/11* forcing cone work, or to use shoulderless boolit designs in hopes that they do a better job of centering themselves in the forcing cone than sharp-shouldered boolits. I chickened out of a pretty good deal or three concerning S&W Model 29s a few weeks ago--these had the typical 1980s-vintage .433" throats into .429" grooves, and already having a Redhawk in that caliber with very good dimensions--I passed on all of them in toto. Life is getting too short to mess around with factory-induced complications that involve extensive mods.

[S.R.Custom]

I can't sleep so you get the unabridged addition. :grin:

For those of you in a hurry, here's the Cliff Notes version...

Having dealt with the same situation many times over the years, I can offer this: A lead Boolit several thousandths larger than the groove diameter does not seem to materially affect accuracy. Does not seem to materially affect leading. And does not seem to adversely affect pressure, either.

Revolver accuracy --and to a certain extent, leading-- is contingent on three things:

(1) Bore/Chamber alignment. The better, the more accurate.

(2) Boolit needs to be at least the same diameter as the groove diameter of the barrel. This will be determined by your chamber throat diameter. Any less, and you have a gas "leak," and accuracy suffers. How much bigger the boolit can be before accuracy starts to suffer is anyone's guess, but suffice it to say, the larger the caliber the more leeway you have.

(3) Boolit has to be at least as big as the chamber throats. This will be determined by how fat a round you can stick in the chamber. Any less, and you have a gas "leak," and accuracy suffers. How much bigger the boolit can be before accuracy starts to suffer is anyone's guess, but suffice it to say, the larger the caliber the more leeway you have.

[Bass Ackward]

I was the unhappy owner of a mid-90s Ruger Bishawk in 45 Colt with the infamous .449" throats and .452" grooves. Far from ideal, certainly. But even in that condition, it still shot one boolit VERY DARN WELL, and at velocities from 900-1200 FPS in WW alloy or 92/6/2. That design was Lyman #454490, a SWC/GC with rebated gas check shank. After honing the throats to .453", this same boolit still performs wonderfully--and was joined by a bevy of other designs after the surgery.



I bought 2, 629-8s about 2 years ago when I quit posting for awhile. These had .428 throats and roughly the same .429 bores. I knew this to be the case ahead of time. So I did before and after comparisons on these reaming cylinders out to .4305. Which should have been ideal.

On both, the throats have opened to .4315 now after cleaning up the tool marks. So this means that I went from ideal conditions to slightly larger which should have improved things along current lines of thought.

Gun "A" shoots better with the throats opened using larger bullets.
Gun "B" shoots notably worse when you go above bore diameter. Hold bore diameter and accuracy and velocity are roughly identical with the same loads before the throats were opened.

The only limitation that I found with the small throats was that I had to shoot higher end loads that would obturate the slug after clearing the throats. From your figures, it seems that you had to do the same.

[Char-Gar]

Until a few years ago, it was common for 44 Smith and Wesson Cylinder throats to run .432-.433. I have a 1931 2nd. H.E. and a 1969 Model 29 that have throats like that. The bores will run from .429 to .430. My solution was to have RCBS made me a .432 sizing die and all is well. Both revolvers shoot very, very well with .432 cast bullets.

I also have an OM Ruger SBH that runs .432 in the throats and .431 in the barrel grooves. My .432 bullet also do very well in that sixgun.

My last 44 is a 1992 vintage 5" Smith 629 that runs .430 in both the throats and the barrel groove. That sizguns get .430 bullet and is the most accuracte sixgun I have owned out of several hundred that have passed through my hands over the decades.

I use ACWW for 44 Special and Mag loads up to 1.1 K fps. For full snort Magnum loads I use No. 2 alloy.

[MtGun44]

Boy do I agree with Al about life being too short to fiddle around with non-std dimensions
any more. I used to think that this was a lot of fun. Seems like nowdays I don't have the
time to deal with all the projects! Moving to the country was great, but added a bunch of
time for mowing and other maintenance issues that don't happen so much in suburbia.

I have enough std .44s with good dimensions that shoot well and I have at least
one or two good loads for each, noted in the files and now I just shoot the known good loads.

I also have a bunch of milsurps that need to teach me about casting for rifles. . . . .

Bill

[Changeling]

Boy do I agree with Al about life being too short to fiddle around with non-std dimensions
any more. I used to think that this was a lot of fun. Seems like nowdays I don't have the
time to deal with all the projects! Moving to the country was great, but added a bunch of
time for mowing and other maintenance issues that don't happen so much in suburbia.

I have enough std .44s with good dimensions that shoot well and I have at least
one or two good loads for each, noted in the files and now I just shoot the known good loads.

I also have a bunch of milsurps that need to teach me about casting for rifles. . . . .

Bill

Bill you have found NIRVANA, now cut the dam grass, trim the hedges, trim the walk/grass line, put down the weed killer, apply fertilizer, spruce up the trees and BTW forget about going over to 44mans shootout !! You have to baby sit your daughters twins, plant my tulips, dig up the crab grass and tonight "Service me"! Now for tomorrow , AAAAHHHHHHH!

[9.3X62AL]

Bass--

I think the whole saving grace for the Ruger 45 was that it "clocked" well--both side-to-side and vertically. It sure wouldn't shoot plain-based boolits very well, though--just that GC SWC. After the throat surgery, everything runs at least decently--sometimes BRILLIANTLY.

I like happy endings. Bottom line was yours, though--shoot the gun, and let its results make the decisions for you.

[Bass Ackward]

I have spent countless hours (and $) not only trying to identify what makes a good gun, but which ones can be made good by some minor work. I am getting tired of the 2000 rounds blown away. Figure that at today's prices and you will soon see that it more than doubles the price of the gun. It is cheaper to pay to have work done. If it can be. Or to spend more upfront and go for better statistics.

I feel that I have made a lot of headway in this regard, but it in the end, it is still a **** shoot for what you can not see or measure. While a slug will pick up a high or tight spot, it will miss low ones. While a Hawkeye will allow you to see defects, some of these defects matter not. And some of this is myth too where conclusions drawn about undersized throats is ALWAYS bad.

In actuality, undersized throats are better in cases of misalignment than over sized throats where you have to try and seal. The BIGGER the bullet diameter, the more steel that must wear OUT of the way. Another way to say this is that the closer to bore you can shoot (GC), the less wear needs to occur to the gun.

And there are different approaches. You can work endlessly with bullet designs and loads too. I find that doing this may mean that you pass the load / design / powder of a lifetime in the guns early stages and these decisions bias you for later when it does correct enough to shoot well. So I have decided to bypass this and just take a control load and shoot that until the gun cleans up. That little GC is worth it's weight in gold unless you have a broken in gun.

So the only REAL way to know IS to shoot it. And shoot it some more. Then when you get a good one, commit yourself to hanging on to it.

Chargar, don't let this 44 pass.

[Bret4207]

As usual, Bass has got me thinking again. Good posts guys, all of you. Fit is an ambiguous term, and it seems the guns think so too!

[felix]

Fit remains king, and that definition includes dynamic fit as well as static fit. More moving parts, more demanding is the total fit throughout the system. Also, as the parts wear, so does the fit wear. Especially springs. I can remember the in-the-know guys at the Colt range in Hartford changing the springs in the 41,52,1911 guns seemingly once a month to keep them shooting perfectly. Service was free of charge. It was an eye opener for me. A brand new spring was almost never used unless others were already taken. The rate of wear is far too fast for the first several 100 shots. ... felix

[Bret4207]

"Fit remains king, and that definition includes dynamic fit as well as static fit." YES! Uncle Felx comes through for me again! Thank you sir for giving me the terms I needed! I've been calling it primary fit and ultimate fit. Your terms are both more descriptive and accurate.

[Char-Gar]

"Chargar, don't let this 44 pass." Bass

Bass, I guess I am a little slow, but I don't get your meaning.

I am a half century deep into this cast bullet in sixguns thing and have found only three or four that can't be made to shoot cast with decent results with enough time and effort. The few that were just *** were sold down river in short order.

In the process I have found some shortcuts and can quickly form an opinion if a sixgun is worth the effort keeping or passing on.

While the vast majority of sixguns can be made to shoot cast bullets "decently", only a small percentage can be truly wonderful sixguns. Truly wonderful sixguns for the most part are born that way. Some fiddlin and fixin can help a mite, but if the basics are not there, they just are not there.

I am in total agreement that the only true way to know what a sixgun will do, is to shoot it. At times I get amused and other times irritated by folks who take a few measurments and want to know how they pistols will shoot. Still others want to start working on them before the first primer is poped. Specs can give some preliminary indication, but all to often that preliminary indication goes out the window when the holes are in the paper.

Felix has more science in his toe nail clippings than I have in my entire body. I am pretty much a hands on dunce who learns the hard way. But, I have found that when a previously wonderful pistol goes South, a change of springs most often restores the luster. We are talking sixguns here..right? Autopistols are a different breed of cat. They have all sorts of moving parts and them whole gizmo disassembles and reassembles in your hand every time you pull the trigger on a loaded round.

I It has been along time since I have done an inventory, but I have probably 40 sixguns that are keepers. Most are wonderful, but others have historical or sentimental value. Many times that number have come and gone. Why keep a lame mule in the barn? He may not be totaly useless someday, but consumes more than he is worth during the wait.

[insanelupus]

Thanks for the information guys.

The first revolver with a .429" groove diameter and the .433" groove diameter is an Uberti. The .44-40 WCF cylinder with it specs out at .431". The second cylinder was added as an after market from VTI and the owner wasn't aware of the significance of chamber mouths at the time he had it fitted. I'm convinced that's the better bet with that handgun or at least the one I would personally try first, even though the .44-40 is a little more difficult to reload due to the bottleneck design. But because it is an Uberti, some fiddling could be done with it with no issues.

The second revolver (.427" groove diameter and .4305-.4308" cylinders) is a 2nd generation .44 Special with the 7 1/2" barrel made in 1959 and I would hesitate to recommend ANY work be done on it as there were only about 830 made in that configuration (according to Taffin's numbers). But this revolver has some muzzle wear and other blue wear and is wearing aftermarket Stag grips, so shooting it is not a problem. I'll suggest a gas check design in the revolver and they can go from there.

Thank you very much.