Barreling a forged 762 receiver.. ?? - M14 Forum

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Barreling a forged 762 receiver.. ??

This is a discussion on Barreling a forged 762 receiver.. ?? within the Ted Brown forums, part of the Gun Professionals category; Quick question I've got the 762MM fogged receiver.. and a new Chrome 18.5 barrel.. from M-14 parts.. my question is.. seems really tight, to me. ...


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Old November 17th, 2011, 10:03 PM   #1
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Barreling a forged 762 receiver.. ??

Quick question I've got the 762MM fogged receiver.. and a new Chrome 18.5 barrel.. from M-14 parts.. my question is.. seems really tight, to me. Now I've built/barreled a few M-14's before about eight of them to be exact.. it was about 7 or 8 years ago.. all USGI parts and barrels..but I don't remember them being this tight or indexing out that far, These parts are expensive and I don't want to screw them up..by forcing anything.. it appears like I've got a long want to go.. the million dollar question? how tight it too tight? and does one machine off the barrel shoulder to get a bit more space to run that barrel farther in..? B2B

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Old November 18th, 2011, 12:06 AM   #2
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Originally Posted by Bolt2bounce View Post
Quick question I've got the 762MM fogged receiver.. and a new Chrome 18.5 barrel.. from M-14 parts.. my question is.. seems really tight, to me. Now I've built/barreled a few M-14's before about eight of them to be exact.. it was about 7 or 8 years ago.. all USGI parts and barrels..but I don't remember them being this tight or indexing out that far, These parts are expensive and I don't want to screw them up..by forcing anything.. it appears like I've got a long want to go.. the million dollar question? how tight it too tight? and does one machine off the barrel shoulder to get a bit more space to run that barrel farther in..? B2B
The thread interference should allow hand installation, it should not be beyond "hand tight", they should just spin together.
If the fit of the thread male to female is not correct it can damage the receiver, the "tight" fit can split the receiver. It is very important that the threads match correctly.
The timing is different, it would help this discussion if the thread hand tightened properly and you could tell what the head space is, yes if the barrel screws on properly and the headspace is short, and the bolt fits in the hand tight condition, the barrel shank face is trimmed off, the chamber is cut to proper headspace and all is good.
If the barrel hand tightens but seems rough to install, I have used layout blue die, screwed the receiver and barrel together and apart, inspected the wear on the layout die and if it looked correct but tight used lapping compound to the loosen the fit.
I see you are on the "west coast" I am in Portland, what I would do is test the barrel against a known good female thread like a USGI receiver thread (demilled receiver front half) and figure out if the barrel is correct, I would use a known good male thread like a USGI barrel shank and see if the receiver threads are correct. Once you know which one is the problem you can determine if you want to fix it or send it back for a new one.
If you are near Portland let me know I have both parts available to test gauge against as well as a complete set of headspace gauges 1.630-1.644 in .001 increments.


Jim

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Old November 18th, 2011, 05:55 AM   #3
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I'm no expert, only built one with a Lot of help from Ripsaw and Tony(read they installed the barrel and bolt), but it was with a 7.62 receiver and it went on slick and hand tight before final torque. Barrel was a medium weight chrome lined Criterion if I remember rite. We did have to turn the shoulder of the barrel down just a bit to get it indexed rite.

Jake2far has a good suggestion to seeing which threads are out. I'd be kinda of interested in which threads are bad. Could it just be a bur, or maybe some park in the threads?

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Old November 18th, 2011, 09:26 AM   #4
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Your exactly right when you say you have to remove material off the shoulder of the barrel. I think it is a little uncommon with a criterion barrel, I am pretty sure they set there barrels up to hand index around 16-18 degrees. Krieger sets theres up to index at 20-22 degrees. All the receivers I have barreled with krieger barrels I had to send the barrals and receivers off to get some material removed from the end of the shoulder except one and that receiver had already been barreled. I have heard people install the barrel tight then back off and do it again until it indexes correct. That works ok with a krieger barrel because they dont cut a bevel into the shoulder, a criterion has a 1 degree bevel for crush but that will be eaten up fast. Best bet is to sent it to someone with a lathe and has done this before. Or you can do it the dipsaw way and get a piece of sandpaper out which o dont recommend.

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Old November 18th, 2011, 10:06 AM   #5
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Funny thing about the Ripsaw method, it sounds funny, but I've miked the results and they are as close as you can get with a lathe. Have you examined a barrel he did? I have. As someone who is used to working to high tolerance with hand tools don't tell me it can't be done, I've done it too many times, if not on an M14. Time was a good machinist could go to a higher degree of finish and more accurate than a machine, he'd use the machine to get close, then take it the rest of the way by hand. Yes it takes skill and practice, but to say it's wrong or impossible is just muddy thinking.

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Old November 18th, 2011, 11:13 AM   #6
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ok Ill retract that statement I do not want to undermine anyones abilities. I have since heard about machinist having to turn a square into a ball and then back into a square again. I gent I know used the method on an fal barrel. If you are going to do it set up a hole in a block of wood or steel the size of the barrel thread diameter and place the emery cloth on top and work it that way. Just don't think its a good idea is all. WHen you think about it don't you think there is the outside chance that it could be off and add stress to one side or another? Not happening on my rifles, not when its easy enough to find a good smith to do it at a nominal cost.

My concern would be whats out of spec the receiver face or the barrel? If its the receiver face its going to need to be done at each barrel change. Not a big deal. This is the first time I ever heard of it happening to a criterion barrel. I have friends that have torqued barrels on that indexed at 830 or so. Do you think that is advisable? Over torquing a barrel would be a interesting new thread and I would like to see what everyone else has to say on the subject.

PS I would like to edit the post and say I did not say it can't be done but I simply was considering the source. I know how it was done, I used to be friends with the guy, used to. He did it with a file and nobody is going to tell me he did it 100% of the ability of a lathe

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Old November 18th, 2011, 01:42 PM   #7
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Thank you guys for your help and input.. Jim thanks for the offer of help.. but you are too far away to help me.. I haven't built a M14 (clone) in a long time about 6-7 years, and my brain doesn't work as well as it use to..(not that it ever did work that well.) The other guns I've built. I used surplus military barrels so they were already barreled..in the past, so of course they would go on easier.. except two guns which were not SIA chrome lined barrels and were short chambered.. so I had to use a pull through reamer.. on those guns to headspace them.. This one was the first time I've used a Forged receiver..and chrome lined aftermarket barrel.. Thank you M-14 (Jywolf) parts for that 18.5 fluted barrel it is beautiful...and the price was VERY reasonable.( with a discount) The threads were just a touch tight, maybe park on the receiver threads.. barrel would go on by hand, it just required a little bit of effort.. so the threads on both receiver and barrel were just fine..I got it barreled, but If I had to guess I'd say the barrel shank needed a few thousands taken off, I didn't have access to a lathe although I do own one..so I just got a cheater bar and disrupted some metal on the barrel shank (not recommended but I did it anyway.. it's mine and I took the risk.. it may be a bit over torked..but I think it will not be an issue..as standard tork is over 100 pounds..it may be 150pounds..let me say hats off to both receiver and barrel manufacture.. head spaced was dam near perfect using a SA USGI bolt.. I'm very pleased at the result.. a pic for ya.. B2B




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Old November 18th, 2011, 02:04 PM   #8
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Glad to here you got it worked out. If you got it by slightly over torque it I doubt the barrel needed even a thou taken off. Now get it mounted in a stock and let us know how it shoots.

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Old November 18th, 2011, 02:41 PM   #9
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What exactly do you mean about the cheater bar and "disrupting" the metal? That sounds very scary.

Did you have a way of rotating the barrel? I am confused.

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Old November 21st, 2011, 09:17 PM   #10
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(not really scary) I just put a longer pipe on my wrench handle.. the metal is pushed back some by the receiver when it is screwed together.. I test fired it this weekend... it shot very accurate but it need to be broken in, some.. I have some tight spots on the op rod tab..slot.. B2B


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Old November 22nd, 2011, 02:06 AM   #11
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Sounds like you improvised and overcame an obstacle. I have found over the years that your "cheater bar", is really a shop requirement.
Good shooting.
Semper Fi
Art

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Old November 26th, 2011, 03:44 PM   #12
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I agree Art.. I believe the receiver wrench needs extending.. to do the job.. I thought the barrel was a touch tight on the receiver but better it be a little tight than loose.. it Head Spaced perfect with the SA bolt, I used so I can't be happier.. the POA/POI was dead on during my first test firing.. I'll re work the tab with a stone and see if I can smooth up the action a little bit.. B2B

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Old January 26th, 2012, 11:55 AM   #13
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I'm sure most every armorer out there uses a cheater bar when installing barrels. I use the Brownell's barrel vise and receiver wrench along with a 32 inch piece of pipe as a wrench handle. You probably won't over toque the receiver enough to damage it with this set up, but keep in mind that the minimum military spec for barrel torque is 80 foot pounds. Many builders prefer to keep the torque much lower, around 55 to 65 pounds as it has less stress on the barrel. Much of what is required is determined by the hand tight barrel index on the receiver. It should be about 15 degrees or slightly over. 30 degrees or more will require excessive torque.

Thanks from Seventh Fleet and tonyben
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Old February 5th, 2012, 10:51 PM   #14
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Forgive me for hijacking a thread. I finally got a chance to... attempt to dial in my 7.62 group buy build. LSS, it is shooting 2'+ left poa. Ejection is at about 5 o clock, I'm a lefty, whizzing past my cheek. My others drop em at 2- 3, at me feet. Can only guess barrel is not properly indexed. This will be the 3rd time this thing has had to go back. Never expected a match grade, but cannot even find a hole in a 4x4 sheet at 100yds. Drifted windage all the way, to no avail. Bummed out and losing faith, cost me time and $ every time I send it in. How tough is it for a well staffed shop to get a barrel on straight? I'll be taking this up with 762. Again.

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Old February 6th, 2012, 04:08 AM   #15
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Originally Posted by Bolt2bounce View Post
Quick question I've got the 762MM fogged receiver.. and a new Chrome 18.5 barrel.. from M-14 parts.. my question is.. seems really tight, to me. Now I've built/barreled a few M-14's before about eight of them to be exact.. it was about 7 or 8 years ago.. all USGI parts and barrels..but I don't remember them being this tight or indexing out that far, These parts are expensive and I don't want to screw them up..by forcing anything.. it appears like I've got a long want to go.. the million dollar question? how tight it too tight? and does one machine off the barrel shoulder to get a bit more space to run that barrel farther in..? B2B
For one thing, they should index about 4-5 degrees clockwise (looking from the receiver towards the muzzle) so that when you tighten them, they index right into place. When I first started doing it, I was using a hand made action wrench and barrel vise which are easy to buy these days if anyone wants the Brownells part number since I have them in the shop right now. I used to have one heck of a LARGE rawhide mallet and I'd give the action wrench a healthy whack to index it where I wanted it. BUT, also understand that even in the days of USGI parts, I never found a barrel that didn't need to have it's shoulder dressed for proper indexing. The old USGI light NM barrels were the worst. I've got two Kreigers in the shop and both index nicely. In June or July I'll be tearing down a Springfield to mount one of the Kreiger's for ammo testing.

A friend and I are going to be doing .308 and 06 for his Garand once I go through the rifle. Have several boxes of 155 and 175 grain Sierra Match Kings.

I've already done "How to's" in PDF format for them to make available for download on their web site. If they don't, I will. Sad but in all the documentation that did for the M14, not one real reference about rebarreling the rifle. First serious PS pub on the M16, listed the proper torque settings for changing the barrels. Yes, I loved Connie Rod and Will Eisner (the artist).

PS is your 762 receiver dropped forged and what is "Fogged"?

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