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Discussion Starter #1
Been reading here on the forum that either LRB or Bula would be/is offering bolts in various sizes to get the correct headspace with chrome lined barrels that can't have headspace adjusted with a reamer because...well...Chrome lined.

So I was thinking that given the current political situation and the future looking none too bright on the 2A front, it might be a good idea to pick up a couple of those bolts for the Polytech & Norinco M14s that I have, before the opportunity passes by. I'm not exactly sure how the new production bolts would fit to the chinese rifles though ?? I've read several of the discussions on fitting a USGI bolt to the chinese rifles with varying degrees of difficulty...from being a drop-in fit on some, while requiring minor lapping in of the lug surfaces on others, and then some where grinding is involved because the barrel extends too far into the receiver.

My main question is this.....Will LRB or Bula bolts offer a drop in fit to both have a better quality bolt AND adjust headspace where the rifles can safely shoot both .308 & 7.62 NATO M80 ball ammo. ??

The headspace as of right now sits at 1.638 on the Polytech & 1.639 on the Norinco so I'm stocking 7.62 NATO marked ammo to use. I'm not intersted in tossing the original chrome lined barrels just to get a new bolt to fit the rifles. I'm just thinking long term that should there be a problem with the existing bolts it would be better to head that off now while a solution is available rather than wait to see if it becomes an issue down the road when perhaps parts are more strictly controlled or not available. Another benefit would be each rifle being able to shoot either .308 or 7.62 NATO without any issues. Thanks.
 

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With the M14, if it is drop in, question the source 99% of the time. Both LRB and Bula have produced custom bolts. LRB made them for their own builds where Bula does market them to the general community as well as using some on specific builds. Bula makes 7 different bolts going from .006 under to .006 over standard spec in .002 divisions. Photo show their armorer's kit which contains one of each. So nice to have and assortment on hand.

 

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Hi
Did this last year with a poly that had an( 1.642) even greater HS. Problem is, my poly receiver face to bolt face is in the .010 to .015 LESS than usgi meaning a standard usgi bolt will decrease your HS to way under min. In mine, the Bula bolt that would increase HS by .006 (largest) was used. After fitting and lapping for contact, I ended up with 1.632 as HS. I am not sure how consistent poly/ norinco components are so your results may differ.
 

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Discussion Starter #4
Hi
Did this last year with a poly that had an( 1.642) even greater HS. Problem is, my poly receiver face to bolt face is in the .010 to .015 LESS than usgi meaning a standard usgi bolt will decrease your HS to way under min. In mine, the Bula bolt that would increase HS by .006 (largest) was used. After fitting and lapping for contact, I ended up with 1.632 as HS. I am not sure how consistent poly/ norinco components are so your results may differ.
Thanks for the heads up on that. So if I'm understanding your post correctly you had to use a LRB bolt that actually would have INCREASED headspace by 0.006 to account for the shorter receiver-to-bolt face measurement found on the Polytech. So the original Polytech bolt has a shorter bolt face than a standard USGI bolt ??

Reason I'm wanting to make sure I'm clear on this point is so that I get it right the first time. SInce I don't have an original USGI bolt on hand to compare the differences I wanted to make sure I was unnerstanding correctly.
 

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Thanks for the heads up on that. So if I'm understanding your post correctly you had to use a LRB bolt that actually would have INCREASED headspace by 0.006 to account for the shorter receiver-to-bolt face measurement found on the Polytech. So the original Polytech bolt has a shorter bolt face than a standard USGI bolt ??

Reason I'm wanting to make sure I'm clear on this point is so that I get it right the first time. SInce I don't have an original USGI bolt on hand to compare the differences I wanted to make sure I was unnerstanding correctly.
Yes the bolt used was a Bula +6
 

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. . . . to get the correct headspace with chrome lined barrels that can't have headspace adjusted with a reamer because...well...Chrome lined.
What makes you think that the headspace cannot be adjusted just because it is has a chromium plated bore and chamber?

Might I refer you to Springfield Armory Report SA-TR18-1055, "Investigation of Chromium Plating Caliber .30 Barrel Bores and Chambers and Headspacing Caliber .3 Barrels Having Chromium Plated Bores and Chambers" E. F. Koetsh, 16 December 1957.

"Ten barrels, caliber .30, M1, having chromium plated bores and chambers and ten barrels, caliber . 30, M1, chromium plated in the bore only were satisfactorily headspaced by a method developed during the subject investigation.

Just use a carbide chamber reamer and cutting oil.
 

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What makes you think that the headspace cannot be adjusted just because it is has a chromium plated bore and chamber?

Might I refer you to Springfield Armory Report SA-TR18-1055, "Investigation of Chromium Plating Caliber .30 Barrel Bores and Chambers and Headspacing Caliber .3 Barrels Having Chromium Plated Bores and Chambers" E. F. Koetsh, 16 December 1957.

"Ten barrels, caliber .30, M1, having chromium plated bores and chambers and ten barrels, caliber . 30, M1, chromium plated in the bore only were satisfactorily headspaced by a method developed during the subject investigation.

Just use a carbide chamber reamer and cutting oil.
Not sure that it matters but removing .010, in my case, may go thru the chrome. Bolt cost(needed anyway)vs carbide reamer cost may be a factor too.
 

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Discussion Starter #8
What makes you think that the headspace cannot be adjusted just because it is has a chromium plated bore and chamber?

Might I refer you to Springfield Armory Report SA-TR18-1055, "Investigation of Chromium Plating Caliber .30 Barrel Bores and Chambers and Headspacing Caliber .3 Barrels Having Chromium Plated Bores and Chambers" E. F. Koetsh, 16 December 1957.

"Ten barrels, caliber .30, M1, having chromium plated bores and chambers and ten barrels, caliber . 30, M1, chromium plated in the bore only were satisfactorily headspaced by a method developed during the subject investigation.

Just use a carbide chamber reamer and cutting oil.
I'm aware chrome lining can be cut since I've seen quite a few shortened chrome lined barrels on rifles where the muzzle was recrowned. Just wasn't thinking it would be a good idea to reduce or eliminate portions of the chrome lining, might induce flaking, kinda defeats the purpose of having in there IMHO.
 
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