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Model 25-5 oversize cylinder throats???

skeezix

skeezix

SWCA Member, Absent Comrade
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I've read here about the oversize cylinder throats on the early model 25-5s. I have a couple of questions:

1) Why/how does the oversize throat affect the bullet's accuracy?

2) Generally speaking, how inaccurate are these guns with the oversize throats?
 
I traded for a 25-5 (made in 1979) a couple of months ago and with a calipers (not the best way to measure but that is all I have) the throats measure about .454. when I find a set of plug gages (not a high priority) I will get a little better measurement. the cast bullets I shoot are .452 and they seem to to just fine. I shoot mostly off hand so whether it shoots 1 inch groups or 3 inch groups at 25 yards probably won't make much difference. I'm not sure it is anything to get excited about. I might buy some .454 bullets (not a high priority either) sometime to see if it makes a difference that I can. it sure seems to shoot good just that way it is.
 
An oversize cylinder throat and a nominal size barrel creates a mismatch. If using lead bullets, they can expand up and when they hit the barrel, they get swaged back down to the barrel size. Could affect accuracy. Larger throats may allow the bullet to hit the barrel forcing cone off center, casing some deformation. I would guess that shooting jacketed bullets through an oversize throat may not cause too much inaccuracy. The real rub is when the throats are too small and swage the bullet to a smaller size than the barrel size, so the bullet is too small and does not take the rifling well. From what I have read, I think that is worse than oversise. Undersize throats can be corrected by reaming, oversize has no cure other than replace the cylinder. This is from what I have read, and stand to be corrected by more knowledgeable folks here.
 
Idealy for good accuracy the cylinder throats should be bullet diameter. Such as a modren .45 Colt should be .452, but as in most all things this is not an absolute. For instance I have a brace of Uberti Thunderer's in .45 Colt. They both have a throat size of .455, they both shoot .452's very well. And then are my 3rd gen Colt SAA's, they have a throat size of .456 and will not shoot a smaller bullet well at all. A quick and easy way to gauge the cylinder is to take a correct diameter for caliber bullet and drop them into a chamber, if it fall's thru and bounces off your toe its too big. They should stop in the cylinder with the nose just sticking out a bit, then take a rod and try to push it the rest of the way through, if its hard to push thru its a bit tight. I think that about the time the 25-5 came along S&W got it's act together as far cylinder dia. is concerned.
 
Thanks!

Thanks for the responses, guys. You've covered what I wanted to know.

"Won" an early '80s 25-5 on GB last night. :D I'll just have to wait 'til I get it to see what the throats measure and how it shoots -- assuming I can find a some affordable ammo to shoot in it.
 
Any model 25 that has the three letter, four number serial system will have correct thoats. If it is an N prefix, it might. As already mentioned, take a .452 bulllet (preferrably jacketed) and drop it into the chamber from the rear. Lead bullets will stick in the throats much more readily than jacketed due to their lube, so they can give a false impression. It should hang up as already described.

S&W fixed thoat diameter at about the same time that they dropped the pinned barrels, so to me, ny non-pinned model 25 is more desirable than a pinned one. I know lots of guys have posted here that their pinned guns shoot tiny groups, but they don't mention what range or size groups they get. It's just common sense that any variable that causes a problem for the bullet upon entry of the forcing cone/barrel will hurt accuracy.

An oversized throat will affect jacketed and lead bullets alike. The bullet passes through the throat tilted and engages the barrel forcing cone off center, which ruins accuracy at the worst, and doesn't do any good at the best. Using bullets that match throats size regardless of bore diameter (unless the thoats are too small, which is an easy fix) will almost always produce the best accuracy.;)
 
Some good info here....just what I was looking for.

One question.....is the oversize throat issue limited to the 45 Colt guns or also the ACP versions, such as a 25-2??

Tom
 
My 25-5 had .457" throats and it was not accurate unless I shot like size bullets. My 25-2 has .454" throats. I replaced the cylinder on the 25-5 with one having .452" throats. I shoot .452" in the 25-5 and .454" in the 25-2. Both are very accurate.
 
Replacement cylinder?

Has anyone had S&W replace their cylinder because of this issue?
I wonder if they did it early on when these guns were first produced?

Tom
 
My 25-3 throats measured .455 +/-.0005. 3-4" groups 25yds off a bag were the norm. Luckily, with it's pres. case, coin, book... it had interest to someone other than making tight groups. Picked up a -5 & haven't had it to the range yet to compare.
 
Not S&W's but I have two SAA's, one a new Colt and the other a USFA, the Colt's chambers are .457, which is common, the USFA is much better built and it has correct chambers. I use cast loads and see very little difference in accuracy which surprised me.

I also have a 25-2 and the throats are .452.
 
THREEDFLYER said:
Has anyone had S&W replace their cylinder because of this issue?
I wonder if they did it early on when these guns were first produced?

Tom
Click to expand...

Yes I have. My throats were 457". Cost was ~$200 IIRC about two years ago or so. The gun with new cylinder followed by the old cylinder.

Knife375348fire004.jpg


FN_Wisner_PenHolder029.jpg
 
Cylinder replacement

With mine being a blued gun, I would think that the color of a new cylinder would not match the finish of the gun.

However, as long as I had the original cylinder, I suppose it would not be such a big deal.

At least the gun would have the correct throat and I could get the best possible accuracy out of it.

I need to call S&W and see what can be done.

Tom
 
Something best avoided, for sure.
Back in the day, I purchased a new 44 Special Colt SAA that was horribly inaccurate.
It went into storage when i went overseas.
Years later, I found it to have a .427 bore combined with cylinder throats of about .435, IIRC.
 
Range test

I decided to take the 25-5 back to the range for some bench testing.

With various target loads and cast bullets, it was grouping under 4" at 25 yards.

As mentioned, these were various loads shot at the same target. I am sure the groups would have been tighter had I shot the same load.

The barrel does not appear heavily leaded.

Therefore, I think for what I will doing, this gun is just fine.

Tom
 
Iknow that a number of individuals are concerned about the oversized throats in 25-5's. I have one S#823xxx shipped April 1985 which will clean plate racks at 35 yards using a 245 gr .LSWC sized 0.452".
When I attempt to measure the cylinder throat with calipers I get anywhere from 0.453 to 0.455 depending on how much pressure I apply to the calipers.
I am more concerend about performance than measurements and my 25-5 is an excellent shooter
Forgot to mention my 25-5 has the 8 3/8 inch barrel which helps with the 35 yard targets.
 
S&W generally ran out of the replacement Model 25-5 cylinders in the early 1990's. I don't know what they have in stock now.

I have not seen a Model 25-2 or 25-5 that could not be made to shoot very well regardless of the throats being oversize, about .457" or less. It is generally a manner of finding the right bullet.

I have had about 6 Model 25-2's. Three had proper throats, three were oversize, generally .456"-ish. They all shot Winchester's 185 grain Super Match Full Metal Case target loading (X45AWCP) very well, under 2 inch for 6 shots at 25 yards from a well mounted Ransom Rest. They also liked Speer swaged lead 200 grain SWC bullets fired over a faster powder like Bullseye. 25-2's with smaller throats shot the same bullets well, plus other hardcast lead and jacketed 230 grain ball that did less well through bigger throats.

The oversize 25-5's in .45 Colt also shot handloads with R-P and W-W's swaged lead conical flat tip bullets, which weigh 250 and 255 grains respectively. 8.5 grains of Unique or an equivalent load of W-231 got me about factory ammo velocities with those bullets; and pretty much duplicated both companies' traditional .45 Colt factory load. I think a factor that helped was that the big swaged soft lead bullets had a concave base and probably sealed the bore and chamber by bumping up slightly under pressures of firing.

Another bullet that worked great in both 25-2 .45 ACP and 25-5 .45 Colt guns with bigger throats was my home-cast Lyman 454424 sized to .454" or just lubed if they weren't much bigger. They went into .45 Colt cases for the 25-5 and .45 Auto Rim cases for the 25-2.

The gun owner wanting to replace his ylinder with something with smaller, proper throats will be spending some serious coin. I suggest that the gun owner tries some of the above loadings and lead bullets before they give up on the gun's original cylinder. I always found some W-W or R-P load that would work great and bullets I could then reload the cases with that shot just as well.
 
skeezix said:
Thanks for the responses, guys. You've covered what I wanted to know.

"Won" an early '80s 25-5 on GB last night. :D I'll just have to wait 'til I get it to see what the throats measure and how it shoots -- assuming I can find a some affordable ammo to shoot in it.
Click to expand...

If you have a 25-5 without the pinned bbl. The chamber throats will be. 453 it's a keeper.
 
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