M14 Forum

bricktop

Hi Everyone, first-time builder here. I picked up a M25 receiver in the group buy last year, and had it installed with a 22" MMW Wolfe barrel at LRB (had to pick something for them to install their bolt with). Later on the fluted 18.5" barrel came out, and it looked like something I wanted to try. So I picked one of them up and want to install it. I built up a receiver vise fixture and barrel wrench, which ended up working very well. I got the 22" barrel off without much effort, thanks to the 5-foot angle-iron wrench leverage.

The 22" barrel now times at about 20 degrees off center when hand-tight. The 18.5" barrel I want to install times at about 40 degrees. I'm wondering how much shoulder crush to expect, and if I need to have a few thousandths or so taken off the shoulder of the new barrel. What's the proper hand-tight timing for new barrels (with uncrushed shoulders)?

I have the guages for measuring headspace, and am not too concerned with that, cause both barrels are chrome-lined, and my only option then is to lap a bit off the lugs if it needs to be larger (I don't want to have to take much cause I'm sure LRB did some lapping for the 22" barrel - none at all would be ideal). So, it'll either headspace with or without a bit of lapping, or it won't - then I'll decide where to go from there.

Thanks much in advance!

Ted Brown

I'd suggest that this amount of crush would be excessive. You need to lathe off enough of the barrel shoulder to bring it to about 15 to 20 degrees of hand tight index.

bricktop

Thank you very much Ted, it seemed like a bit much to me too. Will report back after I get a little lathe work done.

Gus Fisher

I would add that you keep the 1 degree angle on the shoulder for crushing against the receiver and holding the barrel.

Personally I prefer 20 to 25 degrees from TDC when one hand tightens the barrel. I have seen a VERY few barrels over the years loosen up when they were around 15 degrees.

bricktop

Would that 1 degree be cut so that the most inner part of the barrel shoulder is cut in, forming an acute shoulder, or the other way?

thanks!

Gus Fisher

Good question. Because most of us are not machinists and because at times I get confused between terms like convex and concave, etc., allow me to explain it other than to describe the type of angle which I may unintentionally screw up. Grin.

The one degree angled surface on the barrel shoulder is where the outside of the barrel diameter contacts and crushes first against the shoulder. IOW, like you described in the first part of your question.

You do not need nearly as much "barrel crush" in a bolt action rifle as you do a Garand or M14. In 1974, I saw a shooter with a bolt action target rifle shooting the National Match Course in the "Any rifle, open sight" classification. He shot one barrel in the rifle at 200 and 300 and then went back to his car and pulled out a rudimentary barrel vise and replaced the barrel for 600 yard and later 1,000 yard shooting. I watched him in awe as I had not quite yet graduated the OJT training to become a NM Armorer and I had NEVER seen such a thing done before. His scores at 600 and 1,000 showed the rifle lost nothing by swapping the barrels for the different yard line ranges. Needless to say I was impressed and learned something that day.

Bench rest, Bolt Action rifle shooters usually want the minimal amount of pressure applied by the barrel to the action so as not to upset the harmonics of the barrel any more than is necessary. That's why it is a good thing to only use JUST enough pressure of the barrel to the receiver to have the barrel stay in place. But with all the "other stuff" of the mechanics of an M1 or M14 operating rod and gas system twisting the barrel, you need more pressure of the barrel on the receiver to get it to stay in place than on a bolt action rifle.

Of course, if you have never tried to pull a barrel from a M1917 rifle, you have never SEEN excessive force applied to a bolt action rifle to get the barrel to stay in place. It is a real risk on some of those rifles that you may twist or contort the receiver when pulling original barrels. Still, those rifles shot pretty darn well.

bricktop

Thanks Gus. The outside diameter hitting first makes much more sense than the opposite.

My brother had an old Enfield that had improper timing, the front sight had to be slid all the way to one side to get it zeroed. It was undertimed, so this looked like an excellent way to get a little more value of the barrel wrench I made. Took a more force than I expected, but we got it fixed up right. Must be a thing with the old war rifles.

Major Stuph

Since we have a 10 TPI (the barrel thread) each 3.6 degrees advancement would= .001 off the shoulder. So if you are off 40 degrees you have over .011 crush which is too much to torque. If you take off about .005 off the shoulder, a square cut on the lathe, you'll be within range of a good torque. At first just touch the tool to the shoulder and do a, I call it a nothing cut, to see how out of square you are. When you have a .360 degree clean up cut mind your compound to determine what was removed. Once you have that number factor that into you overall measurement. Done many over the years and I have found most GI barrels not quite square on the shoulder. The commercial barrels are, for the most part, very good.

Major Stuph

Gus,
I had an M1 receiver that was out of spec. and all barrels had no crush. I had a friend make up a fixture to punch out rings to fit over the barrel to make up the difference. I did that one M1 with a .003 SS ring and it shoots great. If you need any give me a ring.
Carl Leisinger

Rojkoh

Good post! Personally I like it at around 7-10 degrees before I tighten it seriously. I've never understood people that want to muscle a barrel on instead of doing it right. First USGI NM barrels I did I had to take back to the milling machine 3 times to get it right, but I'd rather not waste a good barrel. I noted someone here actually called for something like 100 foot pounds of torque and couldn't believe it.

MemphisMachinists

Must have been a lot of work to cut that shoulder in a milling machine. It's much easier in a lathe.

Gus Fisher

Carl,

Thank you for the offer. We had to do that on one or two barrels over the years as well.

Gus Fisher

LOL. I was thinking the EXACT same thing when I read that. Grin.