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Discussion Starter · #1 ·
I recently picked up a nice heel stamped Kengs Polytech M14S. I want to install a GI TRW bolt. The GI bolt will not close on an empty chamber. From my reading on this and various forums I should grind/file off the portion of the barrel shroud that it is hitting the front of the left bolt lug as shown in the arrow below
I wanted to check with the experts before i get the Dremel out.:)


447741
447742
 

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Very easy undercut the angle on the barrel and she will work like greased lightning.
 
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If it were my rifle, and I wanted to install a USGI bolt, I would remove the barrel properly and dress back the protruding barrel flange to be flush with the receiver breech ring using a bench top belt sander or lathe. That is assuming I intended to re-install the original Chinese barrel.

While the barrel is out, I would confirm bolt & receiver lug contact and lap accordingly. Once the USGI bolt and the receiver lugs have good contact, I would hand tighten the Chinese barrel and see where the headspace is at. You may find that the headspace is too short or too long with the Chinese barrel and you might have to consider alternatives.

My experience with the CAI/Kengs heel stamped import M14's is they can have short headspace with the original Chinese barrel and bolt, unlike later Polytech and Norinco M14's that almost always have headspace out near 7.62 or .308 Field Reject.

Some other things to check is to make sure the shank of the USGI bolt right behind the lugs does not drag on the receiver, lapping compound works there too.
And of course, confirm firing pin / receiver bridge retraction and firing pin tip protrusion.

A Dremel tool may make a mess quickly of what is likely a very good receiver if you are not real careful, and you may end up with headspace issues anyway which would require the barrel and / or the USGI bolt be replaced.
 

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Discussion Starter · #4 · (Edited)
Well yikes. Upon further examination it seems the right bolt lug is too wide for the receiver. I dont want to grind the front of the bolt lug so i wrote to Warbird to see if he is still doing conversions.

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USGI TRW M14 bolts tend to have the largest spec lugs, and yes sometimes the front of the lugs & receiver lug recess face have to be lapped as well.
TRW bolts are typically the most labor intensive of any USGI bolt to fit to a Chinese M14 receiver.

My experience in fitting TRW bolts to Chinese M14 receivers, specifically the CAI/Kengs import receivers is that they will have short headspace
using the original Chinese barrel.
USGI M14 barrels tend to headspace OK, commercial barrels may or may not headspace and may require reaming if the headspace is too short.

Any bolt has to checked and fitting correctly to any M1 Garand or M14 receiver before you start to worry about barrel headspace.
USGI bolts tend to fit with little or no issues to USGI receivers, Commercial / Chinese receivers require the bolt to be fitted properly.
That is why I pull the barrels for USGI bolt conversions. I have never used a Dremel tool on a receiver for a bolt conversion.

I would suggest finding a good USGI SA , Winchester or maybe an HR M14 bolt as they typically have lugs towards the minimum side of specs.
I also understand Bula makes some good aftermarket bolts in various lug sizes that may be ideal for your conversion.
I have no experience with the Bula bolts, but I hear good things about them and their M14 receivers.

If your Chinese bolt's headspace, lug contact and firing pin tip protrusion are are good, it may be cheaper and better in the long run to stick with it.

I do not know what tooling and gauges you have available, but please don't butcher your receiver with a Dremel tool.
 

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Discussion Starter · #6 ·
I am not going to use a dremel on the receiver. Just kidding. I might hit the barrel shroud to loosen it up if necessary.
I see you beat me to the SA bolt on the PX :(

PS Is Warbird still doing conversions?
 

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Just curious..? Did you check headspace on the bolt that came with the rifle..
I have several Polytechs and a couple headspaced well within SAAMI NO GO limits, which is damn near NATO GO, and have shot 1000/s of rds with no measurable change in headspace.
 

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I am not going to use a dremel on the receiver. Just kidding. "I might hit the barrel shroud to loosen it up if necessary."
I have done a few of these conversions. If you think that TRW bolt is going to headspace with that Chinese barrel, you may be disappointed.
The Chinese barrel's chamber may be too short, and your headspace may be too short with that TRW bolt.

Do you have a set of NATO spec 7.62Xx51 and SAAMI spec .308 Headspace gauges? If not you are making a mistake trying this yourself.

Below minimum headspace in a semi auto or selective fire weapon is very, very dangerous. Out of battery detonations maim and kill people.

As someone else suggested what is the headspace with the Chinese bolt? If you have headspace gauges you should be able to answer this question.

"PS Is Warbird still doing conversions?"

I have no ideas at all regarding Warbird.
 

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Easy solution for a short headspace is carbide reamer. Not a big problem at all.
 

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Discussion Starter · #10 · (Edited)
I do have a set of headsapce gauges. 1.635 closes with Polytech bolt, 1.638 doesnt close.
I am planning on sending off for a pro to do it taht has the right equipment.
 

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What ... nf1e says.... little to no benefit by changing bolts..

Don't believe all the rumors about having to swap to USGI bolts cause the " chinee " are junk
 

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I do have a set of headsapce gauges. !.635 closes with Polytech bolt, 1.638 doesnt close.
I am planning on sending off for a pro to do it taht has the right equipment.
It sounds like it is good to go now for NATO spec 7.62 ammo. How does it shoot?

You may be better off investing in a good USGI op rod spring, rear sight assembly, front sight blade, flash hider or commercial muzzle brake and a good tight fitting stock.
Spend the rest of your bolt conversion money on factory made NATO spec 7.62 ammo and have fun!

Early CAI/Kengs import heel stamped Polytech M14's are kind of rare, and IMHO were the best of the Chinese M14's imported into the USA.
They are much better than some of the later Chinese Norinco M14's as far as fit and finish in my experience.

Can you provide good clear photos of your Chinese bolt showing the lugs and their wear pattern?
 

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Discussion Starter · #14 · (Edited)
It sounds like it is good to go now for NATO spec 7.62 ammo. How does it shoot?

You may be better off investing in a good USGI op rod spring, rear sight assembly, front sight blade, flash hider or commercial muzzle brake and a good tight fitting stock.
Spend the rest of your bolt conversion money on factory made NATO spec 7.62 ammo and have fun!

Early CAI/Kengs import heel stamped Polytech M14's are kind of rare, and IMHO were the best of the Chinese M14's imported into the USA.
They are much better than some of the later Chinese Norinco M14's as far as fit and finish in my experience.

Can you provide good clear photos of your Chinese bolt showing the lugs and their wear pattern?
Pictures of the locking lugs attached.
I have blueprints of the M14 receiver but they do not show the dimensions of the locking lugs.
The receiver ring is correctly dimensioned.
I have a SAII and Winchester bolt on the way so i will try them.
 

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Pictures of the locking lugs attached.
I have blueprints of the M14 receiver but they do not show the dimensions of the locking lugs.
The receiver ring is correctly dimensioned.
I have a SAII and Winchester bolt on the way so i will try them.
The images are out of focus and not much can be seen.

Danny

Sent from my SM-N950U using Tapatalk
 

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The bolt lug pictures are pretty blurred. Can you take better photos of the lugs in bright light using the Macro feature of your camera?
 

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448209


It is difficult to tell from your pictures but I do not like the shiny mark I see circled in red. It looks like maybe your right and left bolt lug roots may be contacting the receiver lugs inside leading edge. If they are, you may be getting a false headspace reading with this bolt. It is a very easy fix to put a very, very small (tiny) chamfer or radius on the inside leading edge of the receiver's bolt lugs with a small fine whetstone (DO NOT TOUCH THE LUG FACE WITH THE WHETSTONE!!!). I usually very slightly chamfer the inside leading edge of the receivers lugs to prevent bolt lug root contact and help keep the center face of the bolt lugs engaged with the center face of the receivers lugs.

When I say very slightly chamfer, I mean very, very, very slightly, really I just very slightly deburr the inside edge of the lugs with a couple of swipes with a oiled fine whetstone. I do this before lapping. You do not want your bolt to headspace off the root of the bolt lugs because when firing that will cause the bolt lugs to flex excessively and could break them. Those marks could also be a impact marks if the bolt has a lot of side to side play when in battery. Either way it is typical wear associated with Chinese M14 receivers and bolts and the way the Chinese built their rifles. Which is why properly done USGI bolt conversions are so popular with the Chinese M14's.

As I said your pictures are not real clear. If this was my rifle, I would chamfer the receiver lugs leading edge very, very lightly as mentioned above, lap the bolt very, very lightly with fine valve grinding compound and recheck the lug contact pattern with a Sharpie marker or Dykem and recheck headspace after I knew I had good lug contact. If it all came out good I would run a hundred rounds of 7.62 NATO through it, clean it up and examine the bolt lugs, receiver lugs, recheck the contact pattern and headspace.
 

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Discussion Starter · #19 ·
Well I decided to send the rifle off to tim Strait, Warbirds custom Guns, who claims he has done over 1,000 Chinese to GI bolt conversions. I will post results in a couple weeks when i get it back, with pictures.
After that I will sell my Chinese bolt.
 

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Well I decided to send the rifle off to tim Strait, Warbirds custom Guns, who claims he has done over 1,000 Chinese to GI bolt conversions. I will post results in a couple weeks when i get it back, with pictures.
After that I will sell my Chinese bolt.
Please show good close up and in focus pictures of Mr. Strait's workmanship. I am interested in his technique. Did he say he could use your existing barrel?
You may want to photograph and record your USGI bolt's lug dimensions and your receiver bolt lug recesses before shipping your rifle off for the conversion.
 
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