Barrel/cylinder gap and endshake: M14

[keppelj]

I have a M14 which had too much endshake. I added a .004 washer and now the endshake is .002 (pretty good), but the barrel cylinder gap is .011(not so good?). Seems like I need a longer forcing cone. What's a guy to do? I could split the difference with a .002 washer. Thoughts? There was a helpful section in the FAQs on this but I couldn't seem to find it. Kuhnhausen specs .004-.006 for the barrel/cylinder gap.

 

[keppelj]

I have a M14 which had too much endshake. I added a .004 washer and now the endshake is .002 (pretty good), but the barrel cylinder gap is .011(not so good?). Seems like I need a longer forcing cone. What's a guy to do? I could split the difference with a .002 washer. Thoughts? There was a helpful section in the FAQs on this but I couldn't seem to find it. Kuhnhausen specs .004-.006 for the barrel/cylinder gap.

 

[keppelj]

I should have done a search before I posted my question. I found a fix described by MAGNUMNUT in Nov o7 involving screwing the barrel in a turn and then trimming the forcing cone it to proper b/c gap.

 

[bountyhunter]

Originally posted by keppelj:
I should have done a search before I posted my question. I found a fix described by MAGNUMNUT in Nov o7 involving screwing the barrel in a turn and then trimming the forcing cone it to proper b/c gap.

I would dfinitely not do all that to a gun with a B/C gap of .011". SW ships new guns with gaps wider than that. You won't see much difference in performance by changing the gap from .011" to .006".

 

[bountyhunter]

Originally posted by keppelj:
Kuhnhausen specs .004-.006 for the barrel/cylinder gap.

true, but the range SW specified was .003" - .010" and I have personally seen new guns in the .012" - .014" range. You will lose a bit of muzzle velocity, but not that much.

 

[haggis]

Sounds simple... it's not, at least, not without the right tools.

1. Turn the barrel shoulder back one turn. This takes a lathe, or a special tool from Brownells. It's done in decreasing steps to make sure the barrel crush fits correctly to the frame.

2. Trim off the barrel shank with another special tool from Brownells. Again, this is done carefully in small steps to make sure your B/C gap is correct.

3. Finally, recut the forcing cone with a cone cutter on the barrel facing tool shaft. You'll need a special gauge to determine when it's cut to the proper depth.

These operations are within the capabilities of a careful, capable person. However, the tooling is expensive if you're just going to do a few. For one gun, a gunsmith is a less expensive proposition. However, if this is (or will be) your hobby or avocation, grab your VISA card and have at it.

Buck

 

[keppelj]

Thanks, all. What's made this confusing is that my cylinder is apparently not square to the ejector rod which is straight. No wobble at all. As you rotate the cylinder c/b gap and headspace changes by a couple thousandths, for and aft. Head space can be as small as .004. So I'm going to try a .002 endshake washer and take a look at the whole thing again. I've no hesitation to send it off Clarks or Smith if necessary. I just thought it would be easy so gave it a try. It had 7 or 8 thou of endshake which is how I got started on this.

 

[Texas Roots]

keppelj, that' more endshake and cylinder gap than I could live with too. If it were mine, I'd just send it in and have it fixed by the pro's.

 

[bountyhunter]

Originally posted by Texas Roots:
keppelj, that' more endshake and cylinder gap than I could live with too. If it were mine, I'd just send it in and have it fixed by the pro's.

I would also send any gun needing a barrel removed and replaced to SW. However, according to many posts, they no longer consider a b/c gap of .011" to be out of spec and when people send them in they send them back as is. Don't know if this one would get the same, they may just fix the end shake and send it back with the .011 b/c gap. I would call them and ask before I spent the $80 it costs to overnight a gun these days.

 

[keppelj]

Thanks, Guys. I have some .002 bushings coming from B's and will try one of them. Headspace is now down to .004 and that obviously wont work. So I want .006 there and will see what I have with the other two measurements. I don't know how I can make the endshake right (.001) without making the headspace too small. Seems the barrel, the tube the cylinder turns on needs to be shorter for all to be right.

 

[Texas Roots]

keppelj, I agree with bountyhunter to call before shipping. And then, if S&W won't do it, I'd still find someone else who would; preferably a pistolsmith in the American Pistolsmiths Guild. Those guys are the best.

I prefer a .003" to .006" barrel/cylinder gap and maybe .002" endshake at the most.

However, I have an S&W Model 24-5 Heritage .44 Special that came brand new with the barrel cylinder gap that measures .011" on the left side and .006" on the right side. I've had others too even worse than that one.

It seems sometimes they cut the end of the forcing cone with a chain saw to adjust the barrel/cylinder gap. Everything is so well finished; the timing is right, grips look good, and then they screw it up when they get sloppy with setting the barrel/cylinder gap.

 

[bountyhunter]

Originally posted by keppelj:
Thanks, Guys. I have some .002 bushings coming from B's and will try one of them. Headspace is now down to .004 and that obviously wont work. So I want .006 there and will see what I have with the other two measurements. I don't know how I can make the endshake right (.001) without making the headspace too small. Seems the barrel, the tube the cylinder turns on needs to be shorter for all to be right.

If (and only if) you have a gun where the b/c gap is too wide and the headspace is too small, you can move the cylinder forward by shaving the end of the crane tube and then installing a new ejector with enough pad thickness to take up the added rear distacnce. I have done this, but I don't think SW sells ejectors to the public since they have to be fitted to get proper carry up and lockup. This is way more work than shimming the cylinder.

If you can shim the cylinder to take out the end shake and the b/c gap is still servicable (.011 - .012" is servicable IMHO) but you now are a shade tight on headspace you have one option: if it is only a couple of thousandths, you can shave the breech face to get additional clearance. You can take a couple of thousandths, but not much more. I have also done that, and the upside is most of those faces are not flat and this gives you a chance to square it up.

BTW: check headspace to the cylinder all around the circumference of the breech face since many will not be flat in this area.

 

[bountyhunter]

HEADSPACE: use car feeler gauges to measure the gap between the cylinder and breech face with the cylinder PULLED TO THE REAR as if the end shake was shimmed out. The operating limits for this are .060" - .066". If you are in this range you can shim the endshake and go for it.

With fired cartridegs in the cylinder and cylinder pulled to the rear, check the clearance between the cartridge and breechface and it should be about .004" - .006". This is one I always check all around the circumference of the breech face to catch high spots.

 

[keppelj]

Guys, thank you for your patience! What I get varies by a thou depending on where the cylinders is rotation-wise. But where I chose this morning it's .009 b/c gap, .001 endshake and .004 headspace. Question is, will the gun function with only .004? Not if any primer is a little proud of the case which happens occasionally. If I go to a .002 washer (should come in the mail today), I'll close the b/c gap, pick up the recommended .006 headspace but end up with .002+ endshake. Which is better?

 

[tomcatt51]

There's really nothing wrong with .002" to .003" endshake. The guns I shoot DA all have that much. Less and they tie up.

 

[bountyhunter]

Originally posted by keppelj:
Guys, thank you for your patience! What I get varies by a thou depending on where the cylinders is rotation-wise. But where I chose this morning it's .009 b/c gap, .001 endshake and .004 headspace.

So, with a .004" washer the end shake is .001" and b/c gap is .009"? I think that's a winner.

If you need a shade more clearance at the breechface to increase headspace, you can shave some metal off the surface of the breechface that the rounds ride against. Just go slow and keep it square. Also, measure headspace all around the face not just where the FP comes through.

By an odd coincidence, I had to do the same thing to my M14 when I got it.

 

[keppelj]

Thanks, bountyhunter. I appreciate the advice. I'll take it shooting and see how it seems. If it chokes up warm I'll consider the headspace opening options. I didn't know about the one you mention above shortening the crane tube and getting a new ejector. That appeals to me more than carving away on the recoil shield.

 

[bountyhunter]

Originally posted by keppelj:
Thanks, bountyhunter. I appreciate the advice. I'll take it shooting and see how it seems. If it chokes up warm I'll consider the headspace opening options. I didn't know about the one you mention above shortening the crane tube and getting a new ejector. That appeals to me more than carving away on the recoil shield.

Be advised: assuming you can get a new ejector with enough metal on it, you still have to fit all the ratchets. That's a ton of work and it's gunsmith only. If your headspace is only a couple of thou tight and all the other clearances are OK.... I'd shave the face of the shield. In fact, that's what I did and retouched the bluing on my 14.

Good luck.

 

[keppelj]

Shot the gun last night using my own rounds and it's fine in terms of function. No binding up against the breechface even though the clearance is only .004. I'll run into trouble if I don't completely seat primers. The only odd thing now is that if I tighten the yoke retaining screw so it's snug the yoke binds up noticeably at fully open. Someone seems to have relieved the end of the little screw on one side.