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Polytech resurrection and headspace

This is a discussion on Polytech resurrection and headspace within the Gunsmithing forums, part of the M14 M1A Forum category; Wanting another M-14, I recently picked up a Polytech at the LGS since that's all we can buy now in MD. Even though the previous ...


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Old June 28th, 2016, 10:57 AM   #1
Grunt
 
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Polytech resurrection and headspace

Wanting another M-14, I recently picked up a Polytech at the LGS since that's all we can buy now in MD. Even though the previous owner replaced the trigger group, sights and stock with GI and added an aftermarket flash suppressor it needs lots of TLC.

The crux of my question for everyone is what to do about the headspacing. Using the Chinese bolt, it closes with NO resistance on a field reject gauge. I have a HRT bolt that won't completely close on a Go gauge and using the light test it looks like there is minimal contact on the left lug. Here are my questions for everyone along with some commentary:

- Lap the HRT bolt? I'm concerned that I would have to take off too much material
- Keep trying different GI bolts? That can get really expensive, really fast unless you have someone willing to keep shipping you bolts to try.
- Fulton or other commercial bolt?
- Some combination of the above along with reaming the chamber?

Suggestions are appreciated, especially from those that have dealt with this before.

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Old June 28th, 2016, 02:20 PM   #2
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Why can't you own another brand of rifle there? Does Maryland own stock in Polytech or something?

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Old June 28th, 2016, 02:42 PM   #3
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was it a 308 field gauge or 7.62 nato gauge?

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Old June 28th, 2016, 03:15 PM   #4
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7.62 NATO, PTG to be specific

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Old June 28th, 2016, 03:49 PM   #5
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not sure where your located but I would look for someone close by that has a box of bolts to try, or send it out to one of the gun professionals on the forum.. I believe there is a gunsmith list somewhere

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Old June 28th, 2016, 04:01 PM   #6
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Check out this link. When I checked my polytech head space it was 1.638. I haven't had any problems shooting reloads. I don't bump the shoulder back all the way to fit a case gauge. Just enough to chamber in my rifle.
Bob

M14 headspacing: quick, simple, cheap, and pretty darned accurate

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Old June 28th, 2016, 04:12 PM   #7
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1.638 HS will work fine. The Field Reject is 1.6455. I wouldn't worry unless it stretches so keep an eye on the length.

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Old July 13th, 2016, 05:22 PM   #8
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I wouldn't be overly concerned about it. If you are gonna do a gi conversion, there're a couple places to look for hang ups. Left inside of receiver in front of lug some material may have to be removed for clearance. Next, sometimes the barrel sticks too far into receiver interfering with fitment. Warbird, and John Wolfe come highly recommended.

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Old July 17th, 2016, 05:08 PM   #9
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When you tried the GO gauge on the H&R bolt did you have the bolt stripped? [no ejector/extractor] It will make a difference. If the bolt is starting to close it should not take lapping to get it close.

Casey

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Old July 17th, 2016, 06:19 PM   #10
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The Chinese Receivers and bolts also probably their chambers are a slightly different dimensions than USGI. Both Poly's I have after screwing on a USGI barrel needed the GI bolt lapped in.
One Poly I built from a stripped receiver, installed a TRW bolt, SAK barrel and an SAK op rod along with all USGI parts and GI fiberglass stock with an ARMS-18 mount.
It turned out to be one of the most accurate and reliable M14s I ever owned.

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Old July 17th, 2016, 06:50 PM   #11
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I picked up a Polytech about a month ago and have ordered a 7.62 Field gage and a go gauge. I might be in the same boat as you soon.

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Old July 18th, 2016, 10:06 PM   #12
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Poly and headspace....


308 Win reloads and my Polytech KABOOM!....

JWB

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Old July 19th, 2016, 11:07 AM   #13
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I spent hours reading everything I could find on the Polys in regards to headspace and bolt fit. Somewhere in there I read someone's claim that Winchester bolts seemed to fit the best. I had a Winchester bolt that I had specifically not tried because it was slated for a build, but it turns out that it was an almost perfect fit. A little lapping and it should good to go.

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Old July 20th, 2016, 04:00 AM   #14
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That's good to know. I have a polytech I'm starting to build, and I was wondering what bolt I should swap in. Guess I'll give a winchester a try.

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Old July 20th, 2016, 06:12 PM   #15
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Hi,
I'm a big fan of the Chi Com M-14's!

This book takes a Poly Reciever and shows how to build using USGI Parts on it!

Very nice book and well worth the money! (my opinion!)
Attached Images
File Type: jpg Book117CoverStroked400_50.jpg (9.1 KB, 3 views)

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