S&W 25-2 question for Old Fuff

[jaybar]

Here’s the problem: Shooting a S&W 25-2 .45 ACP full moon clips, 200gr SWC with 4.2gr WST (light target load), Federal primers. The primers are seated flush before firing, after firing the primers are protruding slightly and dragging on the recoil plate causing cylinder drag with commensurate lousy double action pull. Fire the same rounds in different 25-2 and there is no primer backout. I’m guessing that the problem is probably excessive headspace (haven’t measured anything yet). Question is:what is the proper way to measure headspace on the 25-2? With cartridges in or not? What is the proper headspace? If excessive can it be cured using the cylinder/crane shims that Brownells sells or is a new crane in order?

 

[JoeHatley]

Not Old Fluff, but here's how I measure mine. With the cylinder full of spent cases in the moon clip, hammer cocked, measure between the case base and the recoil shield.

IIRC... you should be looking for something around 0.006".

Good Luck...

Joe

 

[kimbernut]

Light loads

Light loads seem to be prone to backing out primers.Why they don't do it in another revolver I can't explain . Same reason ,I guess, that the same load in one gun can show high pressure and in another it won't.

 

[Old Fuff]

Rimless cartridges in a revolver can be … WAIT!!! Is Art’s Grandma around ????

Well anyway. In conventional revolvers using rimed cartridges (.38 Special .45 Colt, etc.) the cartridge is positioned by the rim, and headspace is usually measured with a feeler gauge as rim-thickness + .006â€. A better way of course is to have headspace gauges with appropriate rim thicknesses in each gauge (go or no-go).

In a revolver chambered to use a rimless cartridge (such as .45 ACP) each chamber should be checked using a standard .45 “go†gauge (.898â€) plus feeler gauges between the breech face and the end of the plug gauge. The ideal would be .006â€.

What if you don’t have a gauge? Well it wouldn’t be a bad idea to get some (from Brownells) but you can get by with a go-gauge and a set of feelers (also available from Brownells.) As a temporary alternative take a fired case and measure the overall length. For purposes of illustration lets say it come out to be .900†in length. That’s .002†longer then standard (.898â€) so the headspace with that particular case should be .004†between the case head and breech face when measured with a feeler gauge. However if the chambers check out at between .003†to .006†I would be satisfied. Be sure to check all 6 chambers, and don’t expect they’ll all be the same.

You might try some factory hardball to see if the primers back out, and if you can find some .45 Auto-Rim try it. Also be sure you are not crimping your handloads enough to let the case can drop down lower into the chamber. In a pistol the shoulder on the semi-wadcutter will sometimes headspace the cartridge on the rifling in front of the chamber, but this won’t happen in a revolver.

But... but ... won't the clip (half or full moon, whatever) determine the headspace? Not very well because the extractor groove in the cases may be slightly different. It may be that the clips are all or part of your problem, but I'll go into that after you find out what's going up to this point. Otherwise we won't have a post, but rather a book.

 

[P95Carry]

Fuff - one other thing. I am thinking that with relatively weak rounds, the case being fired will not set back so hard against recoil shield ... in average loads this set back sorta ''puts back'' the primer - which for obvious pressure reasons, would love to pop out!

Is this another possible factor? I am aware that Jay had OK results in another 25 but - that may have had a tighter tolerance on the rear space.

 

[Old Fuff]

Sure it could be possible, even probable - although I would think that 4.2 grains of powder should re-set the primer, all other things being equal. If you are right a heavier load - such as hardball or Auto-Rim - should work fine and provide us with a clue.

Also, commercially loaded ammunition usually has the primer sealed (glued?) in place with a special lacquer where with reloaded ammunitions, most often the primer isn't.

The difficulty here is that I can't actually examine the gun; so therefore have to precede one step at a time, or like I said, write a book.

Rimless cartridges in revolvers are very sensitive to headspace because unlike a Government Model pistol the firing pin can't reach out and touch ... So besides the obvious you get into issues such as firing pin protrusion, mainspring strength, clip binding, and more.

 

[P95Carry]

Thank you for your esteemed opinion Sir!

 

[jaybar]

Thanks for the aggregate knowledge -so far

Fuff et al, Thanks for the feedback. Here's what I gathered so far: Ideal clearance between recoil plate and back of shell (or go-gauge) is .006". I measured that distance with a feeler gauge in the gun that didn't show primer set-back (my gun) and it is a tight .006". Fuff -you state that .006" is "ideal" , what's the acceptable max and min????. I won't be able to measure the gun in question (my buddy's gun) until next Monday I'll let you know what I find then.
BTW the load mentioned (4.2gr WST behind a 200gr LSWC with Federal primers) is very popular target load with Bullseye shooters. It is about equivalent to 4.0 gr Bullseye which gives about 720 fps mv. It never shows primer setback in any other gun semi-auto or revolver except for the particular 25-2 revolver in question.
Thanks again for the input I'll let you know what I find next week.

 

[jaybar]

Headspace not the problem - I think

Hey Fuff - I finally got to measure the 25-2 in question and headspace seems to be in the range you specified. Upon closer inspection I notice the firing pin bushing (actually called the "hammer nose bushing" in S&W terminology) is not flush with the recoil plate. It is about .003"-.004" recessed, which is exactly the amount that the primers are backing out of the fired shells. I'm guessing that what's happening is that the primer sets back like normally expected at firing but its set back is limited by the firng pin bushing. The shell eventually moves back to reseat the primer but the rearward motion of the shell is stopped by the recoil plate which is .004" in front of the bushing, hence the primer is never fully reseated. What do you think - and more importantly how do I cure it?????

 

[Old Fuff]

I think you found the answer. The bushing is smaller then the case head. When the cartridge is fired the case hits the breechface, but the recessed bushing allows the primer to back out. I should have thought to warn you about the possibility.

I would return the revolver to S&W and have the "hammer nose bushing" replaced. An alternative would be to file the whole breechface area flush with the bushing, but I don't like that idea, and it would ruin the blue finish.

Call S&W Customer Service and see what they're opinion is.

 

[PinnedAndRecessed]

I'm not an expert but here's my .02. Years ago I used to clean the primer pockets with an itty bitty metal brush designed for that purpose. I must have cleaned too vigorously because the primers did the same thing you describe. Ultimately the primers flopped around in the primer pocket because I removed too much metal. The problem was severe in my 45 ACP loads and most noticable in my 25-2.

I'm sure that's not your problem but I ended up disposing of the brass and going with a Dillon Square Deal loader which doesn't give you the option of cleaning the primer pockets.

 

[jaybar]

Did it myself

Hey Fuff - Contrary to your well thought out advice to send it back to the factory for nose bushing replacement I opted to try it myself. I ordered a new hammer nose bushing through Brownells (about $4.50). Drove the old bushing out with a narrow punch through the hammer slot. The new bushing measured about .009" thicker than the old one. Lined the new bushing up correctly. The bushing is not symmetrical, there is a slot that captures a high firing pin (oops hammer nose) that must be pointing straight up. Inserted a 3/8 brass rod through the muzzle and placed it on the bushing and proceeded to smack it a few licks with a brass hammer. The bushing seated nicely but stood about .005" proud. (remember the old bushing was about .004" recessed.). I filed the bushing flush with recoil plate, lightly chamfered the nose hole to eliminate any burrs, hit the bushing ( and the recoil plate) with some cold blue and took the gun to the range. Problem solved. No more set back primers, no more lousy double action pull. Thats the good news - bad news is that one of my other shooting buddies was eaves-dropping on my conversation with the gun owner and he produced a nickel-plated model 19 that exhibits the same problem. Sure enough the hammer nose bushing is recessed enough that you can see it. I'm going to guess about .001"-.002". Is this problem more common than we think??

 

[Old Fuff]

No, I wouldn?t say it was a common condition, but now we?ll see if any more reports come in. Usually what happens is that the bushing wasn?t fully seated at the factory so there is enough space behind it to allow the movement you saw. The proper correction is to do what you did and replace the bushing. Given that the hole in the frame has been slightly enlarged when the first bushing was placed, I think a drop of red lok-tite is a good idea when replacing one, but be SURE the new one is lined up and fully seated.

Another thing to look out for is where a loose bushing migrates outward and someone who doesn?t understand what?s going on will notice that it?s high and file it flush with the breechface. The bushing is now too short and can be pushed back into the hole. Then you?ll end up exactly the way the guns you formally described were. Never file on one until you are certain it is fully seated.

Now it will be interesting to see how many more guns show up, and perhaps our fellow member, Jim Keenan might have some informed comments.

Edited to add: If you replace the bushing in a nickel plated model 19 you might consider getting a stainless bushing as used in a model 66.