M25 and Cylinder Drag

[GPerry]

I recently inherited a 1960 M25 from a dear friend, and am having to sort some things out. My first two cylinders were some 230-grain Speer hardball followed by Federal 45D 230-grain JHP. I was shooting at some 50-yard plates, which they clanged satisfactorily, but I noted that the Speers seemed fine while the case heads on the Federals seemed to drag a little bit on the recoil plate as I cocked them. I hadn't had time to look for my moon clips, so I just shot them and plucked them out with my fingertips.

Next I found 6 Starline .45 AR cases loaded with some Speer 250-grain LSWC I'd made for my M22-4 Thunder Ranch revolver, and they shot fine. I figured that the OAL on the Federal 45D might be a little long for the M25's chambers.

Last year I bought several hundred brand new .45 AR Remington cases, and loaded them with some newly cast Lyman 452454 bullets, sized to .452. They mostly shot into a ragged hole at 20 yards, but again with some slight cylinder drag. I tried my best to measure the rims, and came out at 90 thousandths for the Remington and 84 thousandths for the Starline. What's more, empty Remington AR brass will rub the recoil plate upon cocking, but Starline does not.

So, I loaded the Starline with the Lyman 454's. I had to push some of them to seat fully, and still got some rubbing on the recoil plate. I tried seating them so the shoulder was flush with the case to reduce OAL, and they still rub.

I've checked they cylinder for end shake, and don't believe that is the issue. This gun has spent its entire life in a box in a safe and would bet it hasn't shot more than a box or two of ammo in 60+ years. It definitely had only been shot with .45 ACP factory ammo, never handloads.

I do not have a set of pin gauges, but I can slug the ball end diameter with oversize lead round balls. I do know that the Lyman 454's, sized to .452, are a slip fit in the chamber mouth at the ball end, but will hang up on the chamber rim if dropped in from the rear of the cylinder.

My next plan is to load Starline brass with some Zero 185-grain JHP, which measure .4515 and have a much shorter length and see how that works.

Of course, all of the above-mentioned variables load and shoot fine from my 22-4. I'm starting to think that this revolver, made during the bullseye era, has chambers and headspace cut to minimum specs.

Any thoughts?

 

[WR Moore]

Maximum OAL for the the 45 ACP/AR case is given as 0.898 in. Book value on the AR rim thickness is 0.090 in. You may want to check the rear gauge/headspace. You should have 0.090 to 0.098 in between rear of the cylinder and the breech face. Somewhere around 0.094-0.096 would be ideal. Feeler gauges from the local auto parts for measurement.

 

[Hondo44]

The only times I've seen the problem you describe, it was a firing pin bushing in the recoil shield that was not flush or had burrs around the firing pin hole.

 

[Muley Gil]

Make sure the ejector rod is tight.

 

[ken158]

A high primer can cause the issue you describe - also try some different moon clips for the acp rounds

 

[DukeSoprano]

TK Custom sells some thinner moon clips for 45 acp

 

[GPerry]

I've checked the ejector rod; it's tight. No burrs that I can feel on the firing pin bushing either. I'll try to find a feeler gauge.

 

[GPerry]

Primers have all been countersunk, so that's not the issue.

 

[6string]

What you are describing is a good thing!

The 1950 and 1955 .45 Target revolver was originally built to be just that, a target revolver! Since the .45 ACP is a rimless cartridge, it MUST headspace off of the casemouth for match grade accuracy!!
Moon clips are for extraction only!
I dress down moon clips on a surfacing plate to accomplish two things:
1) make them thinner so they don’t press against the cylinder breechface.
2) they are more or less dead flat. You’d be surprised how bad they can be!
(It’s better to modify a bunch of cheap moon clips than be tempted to modify the revolver!)

Smith & Wesson cut the chamber depths precisely to work with match grade military hardball ammo. Any case that is too long, be it an ACP case or a Auto-Rim case will cause that drag.
The solution is to trim your brass precisely for handloads, or stick to known, consistent factory ammo.

Unfortunately, many of S&W customers were neither target shooters nor meticulous handloaders who understood this.
So, S&W seemingly felt the easiest thing was to cut deeper chambers.
The result?
The mediocre accuracy that tends to typify most later M25-2 revolvers (although a few good ones are out there!)

Similarly, with chamber throats. Since the chamber is cut without a leade ( the funnel-like taper from the chamber to the throat as is typical for rimmed cartridge chambers) a loaded cartridge sits with the bullet partially seated into the throat.
Again, this is a good thing. At least it is when their sizes match up! Typically, in the good old ones, the throats will generally run 0.452-.453”. With target grade ammo, this works well.
In poorly made handloads, exhibiting things like run-out or perhaps little bits of bullet lube or lead shavings, the cartridge won’t fully seat.
Again, some folks complained.
The “solution” was for S&W to revert to “service revolver” throats measuring .455”-458”. Any hope of real precision accuracy is gone!
The worst combination is oversized throats and overly deep chambers. The bullet gets shaved by the sharp chamber mouth then cants off-center due to the big throats. Some of the late M25-2s are notoriously inaccurate, at least for real match-trget shooting.

If your revolver has the correct “tight and short” chambers, be grateful. And, feed it the best ammo you can, factory or handload.
I personally prep ACP brass lots specifically to match one revolver or another, and I don’t mix them.
It really is worth it!


(I wonder…has anybody ever built a custom benchrest target rifle and then complained that it’s too tight to easily chamber factory hunting ammo? )

 

[GPerry]

Thanks 6string. I am very willing to give this revolver and steady diet of match-grade ammo. I thought about trimming a few cases a couple thousandths and see if that made a difference. Based on what you're describing I'll bet it does.

I'll keep you posted.