Model 25-2 .45 ACP factory throat diameter questions

[cmansguns]

I think my question belongs in smithing but I'm also in need of a tutorial of how to use the search function of the SWCA Forum.

I've posted my Model 25-2 before and have found out that although I have a Factory Letter decribing how it left the factory, I've since found out (because of the aftermarket double ball detent yoke lock) that it had been setup for competition by the previous owner. Then I was made aware of lightened mainspring, polished internals, shortened rebound slide spring...all resulting in a sweet to shoot light SA & DA trigger pulls.

Anyway....I am going to be selling this one again soon, only this time I will offer with all factory parts, including stocks, as well as all the competition parts. Everything has been posted and commented on by a good number of the knowledgeable experts here on the Forum so the only thing left is the throat diameter. I recall seeing posts (probably years back) about how this Model 25-2 had notoriously large cylinder throat diameters direct from the factory and of course this would affect accuracy.

I cannot find ANY of those old posts and it is probably me not really knowing how the "advanced search" function works. I tried different search terms, different forums, but nothing comes up for me. Is there a sticky for the search option somewhere on the Forum?

For you folks that know this stuff I looked at my copy of SAAMI and for 45ACP FMJ the bullet is .4520" - .0030", and for lead .4530" - .0030".

Next I removed the cylinder and yoke from my gun, aligned cylinder vertically up (throats facing up) and used my Mitutoyo Digital Calipers for measuring each cylinder. With the first throat at 12 o'clock I inserted the zeroed caliper approx 1/4" and thumb wheel expanded till I felt 'mike drag", locked, and removed for reading. Rotate cylinder counterclockwise, repeat all above for "throat 2" through "throat 6.

Results: Throats 1, 3, and 5 measure .4540"; throats 2, 4 and 6 measure .4535. No throats are oblong.

I've also seen an article by Grant Cunningham stating that the only true way to measure throats is with pin gauges, but with this I would need a large set to cover all the possibilities that he mentions being off as much as .003" either way.

In you folks very valued opinion...do I need to worry about oversize throats at .454?? I'm not shooting any competition but I want to list it as fair and as accurate as I can.

Any help is greatly appreciated. Thanks for listening.

 

[H Richard]

The throats of my 25-2 measured "about".455. With my lead target loads it will cut cloverleafs at 25 yards. It does nearly equally with 230 ball rounds. It was the 45 Colt cylinders that seem to have the problems.

 

[series guy]

I have seen throats on these guns as large as .458 and they pattern like a shotgun. Your caliper measurement is most likely off by 1 or 2 thousandths. I have also found that shooting jacketed or plated bullets can give excellent accuracy even with oversized throats.

 

[6string]

Besides pin gauges, you can get accurate readings with an adjustable inside hole gauge. Dial or digital calipers are sometimes jokingly referred to by machinists as "guessing sticks".
It sounds like you did your best with your caliper. But, if you want to be sure of your readings you probably would feel better if you could confirm it with the appropriate tools.
An adjustable inside hole gauge is not expensive. Also, as far as pin gauges go, a full set is quite costly. But, they can be purchased individually.

 

[D Brown]

I agree with the gentleman you referenced in your post. Accurate ball end measurement will require pin gauges.

I find it somewhat curious that you are putting together a package of all the original parts, as there is no way to restore your gun to factory original condition. Seems to me that it would be better to find a buyer that will appreciate your gun with the modifications.

Best of luck with your project.

 

[frankynohankypanky]

In the April edition of Handloader magazine Brian Pearce, in his "Bullets and Brass" column, has written about this. He was answering a question from a reader regarding large throat sizes in 25-2's. It was of interest to me because I also have a 25-2.

Frank.

 

[Krogen]

Besides pin gauges, you can get accurate readings with an adjustable inside hole gauge. Dial or digital calipers are sometimes jokingly referred to by machinists as "guessing sticks".
It sounds like you did your best with your caliper. But, if you want to be sure of your readings you probably would feel better if you could confirm it with the appropriate tools.
An adjustable inside hole gauge is not expensive. Also, as far as pin gauges go, a full set is quite costly. But, they can be purchased individually.

Thanks for the tip! I have debated (with myself) the merits of buying some pin gauges. I just haven't moved on the idea.

I just bought an adjustable gauge from McMaster Carr. Should be here in a few days. I like being able to measure multiple throat sizes with one tool. Buying an assortment of pin gauges for infrequent use sort of bugged me. Also, the accuracy of pin gauges is probably unnecessary for measuring throats.

 

[6string]

Thanks for the tip! I have debated (with myself) the merits of buying some pin gauges. I just haven't moved on the idea.

I just bought an adjustable gauge from McMaster Carr. Should be here in a few days. I like being able to measure multiple throat sizes with one tool. Buying an assortment of pin gauges for infrequent use sort of bugged me. Also, the accuracy of pin gauges is probably unnecessary for measuring throats.

I think you'll appreciate the value of an adjustable inside hole gauge. They bear on the surface with hemisperical jaws. So, unlike with a dial caliper, a slight variation in the perpendicular of the tool to the hole won't skew the reading.
Once you've tried it, you'll soon find yourself measuring the internals of reloading dies, etc.
A very handy tool (or set of tools, if you want to be covered for a large range of holes).

Jim

PS: someone referenced Brian Pearce and Handloader Magazine. Charles Petty was an excellent gun writer and an excellent Bullseye pistol shooter. He wrote a great article on the 25-2 and the 1950 & 1955 Target. It included throat measurements and results of Ransom Rest tests. Some 25-2s have throats as large as .458". They can't be counted on to shoot consistently any better than 12" groups at 50 yds.
But, the good ones are GREAT shooters!

 

[DeplorabusUnum]

This topic has been touched on before. Some people have stated that their chambers measure .454 or .455 and the revolver still shoots good groups with whatever they feed it. I have a 25-2 and the throats all measure .454 with pin gauges. It order to get mine to shoot good groups, I have to size my lead bullets to .454 or .455 or else accuracy suffers.

The takeaway is that you won't really know if the oversized throats are causing a problem with accuracy until you shoot some different rounds from a rest and see. I haven't heard you mention if accuracy with your pistol is a problem. Have you test fired the pistol yet?

 

[6string]

This topic has been touched on before. Some people have stated that their chambers measure .454 or .455 and the revolver still shoots good groups with whatever they feed it. I have a 25-2 and the throats all measure .454 with pin gauges. It order to get mine to shoot good groups, I have to size my lead bullets to .454 or .455 or else accuracy suffers.

The takeaway is that you won't really know if the oversized throats are causing a problem with accuracy until you shoot some different rounds from a rest and see. I haven't heard you mention if accuracy with your pistol is a problem. Have you test fired the pistol yet?

Yes, all good points!

There are additional factors at play, also related to the cylinder.
1) Chamber depth. For best accuracy, the forward edge of the chamber, that is, the part that the case mouth headspaces upon, must be uniform from one chamber to the next, and, must not be cut too deep. Original 1950 and 1955 Targets were scrupulously chambered to fit tight and consistent with match grade ammo. The trade-off is that sloppy handloads will bind up the gun.
2) Headspace. This is intrinsically connected to the above point. Headspace, the gap between the firing pin bushing and the case head must be consistent. So, your chambers need to be consistent as does the OAL of every single case. This is crucial for reloaders.
Some of this can be addressed by using Auto Rim brass. But, not if the cases are a little short! If using ACP brass, for best accuracy, your ammo must headspace off of the case mouth. The use of moon clips should only be to facilitate extraction. If your ammo headspaces off of the moon clip your accuracy might be good, but it will never be to it's full potential. Best bet is to lap moon clips on a very flat stone. You'll be amazed how inconsistent they are in terms of flatness. If your brass is too long for your chambers the cylinder will bind up at the breechface. Same thing if you have little lead shavings built up at the casemouth. (It doesn't take much!!)
If you address these issues, in addition to doing proper load development and alloy/lube testing, you will get much better accuracy out of your .45 Target, even if your throats are .454-455" vs a .452" bore.

My suspicion is that S&W got tired of building nice tight match grade guns only to get complaints from guys whose reloads didn't properly chamber and/or headspace. So, they said, "To heck with it, let's just cut the chambers a couple thousandths deeper and open up the throats. Most guys'll never notice and it'll stop the whining."
But, that's just conjecture on my part...

 

[Krogen]

Thanks again, 6string! As discussed above, I followed your suggestion and bought a Starrett adjustable inside hole gauge. It arrived today.

I wasted no time and got to checking my M25-2's throats. It turns out they're fairly large; ranging 0.455" to 0.456" for all six. It took me a few times to get the hang of things, but the measurements were all repeatable. The tool is physically small for a ham-fisted Krogen and takes a delicate touch, but I prevailed.

As a further validation of my technique, I think I'll grab a 1" micrometer and set it to a known value. Then I'll measure the gap with the inside gauge and a dial caliper to see how well things agree.

The inside gauge is a nifty little tool. I found I could measure groove diameter too. The gauge's measurement faces are radiused enough to drop in between the lands. The M25-2 measured 0.451" just inboard of the muzzle. So, even though the throats are large, at least the groove diameter isn't larger yet!

 

[Housepuss]

25-2

Thanks for the tip! I have debated (with myself) the merits of buying some pin gauges. I just haven't moved on the idea.

I just bought an adjustable gauge from McMaster Carr. Should be here in a few days. I like being able to measure multiple throat sizes with one tool. Buying an assortment of pin gauges for infrequent use sort of bugged me. Also, the accuracy of pin gauges is probably unnecessary for measuring throats.

Been looking for one of those gauges. Can you provide me
with the part number. Not sure exactly how McMaster identifies
that part.

Regards
Dick

 

[Krogen]

Been looking for one of those gauges. Can you provide me
with the part number. Not sure exactly how McMaster identifies
that part.

Regards
Dick

Sure! I bought the Starrett #579A. Here's a link to the McMaster-Carr web page showing the gauge. McMaster-Carr

 

[GBertolet]

My 25-2 cylinders are .456. All .452 cast bullets I tried leaded like crazy. I powder coated some .452 cast bullets, and that fixed the problem, no more leading. The powder coating protects the bullet from the leaking gas through the cylinder throats.

 

[6string]

Thanks again, 6string! As discussed above, I followed your suggestion and bought a Starrett adjustable inside hole gauge. It arrived today.

I wasted no time and got to checking my M25-2's throats. It turns out they're fairly large; ranging 0.455" to 0.456" for all six. It took me a few times to get the hang of things, but the measurements were all repeatable. The tool is physically small for a ham-fisted Krogen and takes a delicate touch, but I prevailed.

As a further validation of my technique, I think I'll grab a 1" micrometer and set it to a known value. Then I'll measure the gap with the inside gauge and a dial caliper to see how well things agree.

The inside gauge is a nifty little tool. I found I could measure groove diameter too. The gauge's measurement faces are radiused enough to drop in between the lands. The M25-2 measured 0.451" just inboard of the muzzle. So, even though the throats are large, at least the groove diameter isn't larger yet!

Hi!
I'm glad it worked out and you're enjoying the tool. (Can't go wrong with Starrett!!) Your description is spot on! A light touch with the adjustment gets you an accurate and repeatable reading.
If you use cast bullets, softer is better for your scenario. The "old school" alloy for your gun would probably be 1:20 ratio of tin to lead. If I need a small quantity of this alloy, an easy way to get it is one pound of 50/50 tin-lead solder with 9.5 pounds of pure lead. I use recycled airgun pellets for the latter.
Lube should be something soft and sticky like Lyman Alox. There's formulas for making your own with beeswax, Johnston's Paste wax, etc. Lee's tumble lube is good right out of the bottle.

If you don't cast, many commercial cast bullet companies let you order by hardness. Go with their softest option.
Some of these same companies will also let you choose "as cast" (unsized) and unlubricated. This puts more options in your hands without having to get into casting.

But, if you do cast bullets (or plan to!) think about ordering a hollow base mold.
Soft bullets with or without a hollow base (but especially the latter) are intended to obturate to fill the cylinder throats yet easily size down in the bore.
Hard bullets don't do this. They often are the worst choice as far as leading goes. Lots of folks think "I tried the hardest bullets and it leads. I guess my gun won't shoot accurately with cast bullets!" Up to 1000-1200 fps, in a revolver, the opposite is true, assuming the fit and lube are correct.

 

[steelslaver]

While I have both pin gauges and a telescoping bore gauge set, you do not need them to check throat dia. Disassemble the cylinder and sit it on a piece of hard wood and tap a soft lead ball part way in the throat and measure the results.

The newer 45 ACP (and colt) cylinders all seem to be .452. The older ones are a bit of a **** shoot. I mostly make my own 45 colts cylinders from 44 mag cylinders even my modified 3 1/4" has a 44mag cylinder reamed to 45 colt and the recessed for ACP in moon clips. Except for a 1917 commercial and a 1937 Brazilian, my only other 45 ACP revolvers are snub 325s with new cylinders.

 

[teletech]

You can usually pick up a pin-gauge set for under $100 on Ebay, it might be a used set with some missing pins, but just make sure it has the sizes you need and you're all-set. I find the small-hole gauges to be useful, particularly for finding oblong holes, but default to the pin gauge fore hole size.
If you just want one cylinder measured, just take it out of the gun and take it to a local machine-shop. A lot of guys in small shops will help you out and drop a pin gauge in your bores for free or lunch-money.

 

[pantannojack]

The possibilities of bbl dia being larger than some cylinder throats in the 45 calibers is why I do not seriously consider a revolver in such. I more favor 44 spcl in my search.

 

[teletech]

The possibilities of bbl dia being larger than some cylinder throats in the 45 calibers is why I do not seriously consider a revolver in such. I more favor 44 spcl in my search.

Sadly, I've had two model model 29s and also a TL with big throats as well, so it being a 44 isn't an automatic defense against large throats.

I should also point out that in at least one of the 44s, there was a very slight ridge at the front of the cylinder on some of the chambers so the pin-gauge wouldn't quite enter from the front but would slide in from the back and with light force elastically displace the ridge, very annoying.

 

[steelslaver]

I have run into .431 44 cylinders and one that was under .428