Chinese bolt question

HILLBILLY7.62 · 07-31-2009, 13:17

Have any of you fellas had a Polytech bolt heat treated? - Can you properly heat treat a Chinese bolt?

Kinslayer · 08-09-2009, 09:47

I was wondering the same thing some time back aways. It would seem easier to reheat treat the Chin bolt than to refit a G.I. bolt.

The Chin bolts are forged after all,and reheating should bring them back to soft. Then the heat treatment should be repeatable.

I have a Springfeild M1A bush, and a Poly M14s. The Poly is in original condition, and head space is fine after a little under a thousand rounds.

Seems to keep up with the Bush as far as reliability, and is more accurate.

V.C. · 08-15-2009, 20:59

I have a Polytech M14s and have put over a thousand rounds through it over the years. My freiend before me probably put at least several hundred through it.

I have never had any issue with it but some would say I haven't shot it enough to wear it out.

My take on bolt hardness would be that the bolt will wear out and not the receiver. You can replace a bolt but the receiver is the heart of the gun. If you use a harder bolt than more wear will take place at the receiver wear the lugs lock up.

I heard that Polytechs are second only to original GI M14s in receiver strength.

Rugerite · 10-25-2009, 00:32

Good to hear, I almost SOLD my polytech M-14 recently and glad I kept it. I haven't its just good to know to have it around still, still trying to decide what sort of 308 win or 7.62 rifle to get next. I want an M-1a or some thing like it, but some people just say get an AR 10...its getting confusing but since I can't afford any yet I still got time to decide. Last gun I got was a Ruger Mini 6.8 for those hunts when I wanted medium range gun, but where even a 308 win is to powerful for safety reasons. IE bullet goes in but not come out.

H2O MAN · 10-26-2009, 06:02

Quote:

Originally Posted by HILLBILLY7.62

Have any of you fellas had a Polytech bolt heat treated? - Can you properly heat treat a Chinese bolt?

All of my Poly Tech and Norinco M14s have USGI TRW bolts that were installed and head spaced by SEI, but Different posted this on another forum:

" As you may be aware, USGI M14 bolts have become scarce and very pricey. For Chinese M14 rifle owners who wish to upgrade the factory Chinese bolt with a USGI bolt, this has become an expensive proposition.

Smith Enterprise, Inc. has done some testing. They have one alternate solution ready to go now. There's a second possible solution still under development. What's the problem? Chinese M14 bolts are hardened clear through to 44 to 47 HRC. They lack the hard surface of USGI bolts that are case hardened. Chinese M14 bolts are made of a steel that doesn't take case hardening, 4135 alloy steel. USGI M14 bolts are made of 8620 steel. Other issues with the factory Chinese M14 bolt is that the locking lugs are narrow and lug contact with the receiver is not always what you would want.

First, no one is saying you have to do anything. The following discusses options for someone who wishes to enhance his Chinese M14.

SEI says this option is good to go. They will cryogenically treat the Chinese M14 bolt. This does add to the tensile strength of the part, 20 % to 100 % depending on the part and its metallurgy. SEI does require that the Chinese (long headspaced) barrel be replaced. They will install and chamber your supplied barrel or one of their own. Headspace will be about 1.633 ".

The second option is still under research. Ron Smith said this may take some time to determine if this is a viable option. It may work, it may not. Anyway, SEI is looking at the possibility of nitrocarburizing the Chinese M14 bolt. Theoretically, this should give the Chinese M14 bolt a wear resistant surface while maintaining an acceptable hardness at the core. This option, if viable, will also require installation and headspacing a short-chambered barrel to around 1.633 ".

X - Man · 10-26-2009, 19:36

As related by H2O MAN, the topic of the bolt used in a Polytech M-14 is still a work in progress. If you have a Polytech, 1; keep it, and 2; have the headspace checked out by a qualified 'smith. Most owners who keep the original bolts are reporting satisfactory performance, but watch for any change in the headspace, or other bolt wear.

If you can find a USGI M-14 bolt - BUY IT! That way you'll have it should the bolt ever needs to be changed.

With the continuing interest in the M-14 and the dwindling supplies of USGI replacement parts several mfg's are starting to make new parts available. Often these new parts are improved over the originals. Once replacements for the old USGI bolts become available, we may also see bolts, and other parts, made expressly for the Polytechs.

IIRC, it's SEI who is already offering some replacement parts for the Polytechs. I've got my TRW bolt just waiting for me to wear out my Poly's original. I've got to get busy and do a lot of shooting!.

Also, any attempt to change the hardness of a bolt should definitely be left to the pros, like SEI.

H2OMAN, a question about having a Poly bolt cryo-treated, does this process change the size of the bolt? If the original headspace was OK is it still necessary to change the barrel? Cryo-treating the bolt sounds like a good option, but I like to learn more.

H2O MAN · 10-27-2009, 07:01

Quote:

Originally Posted by X - Man

H2OMAN, a question about having a Poly bolt cryo-treated, does this process change the size of the bolt?
If the original headspace was OK is it still necessary to change the barrel?
Cryo-treating the bolt sounds like a good option, but I like to learn more.

The size of the bolt is unchanged and I see no reason to swap the barrel out if the head space is correct.

Don't take my word for it though... contact Ron Smith @ SEI.

X - Man · 10-27-2009, 16:54

Thanks, H2O MAN, The headspace on my Polytech is OK. Since it has a chrome lined barrel it can't be reamed out. So, I'm good to go, I'll just go out and have some fun with it!

H2O MAN · 10-27-2009, 17:19

Quote:

Originally Posted by X - Man

Thanks, H2O MAN, The headspace on my Polytech is OK. Since it has a chrome lined barrel it can't be reamed out. So, I'm good to go, I'll just go out and have some fun with it!

For future reference:
SEI can do a USGI bolt conversion on your Poly without replacing or harming your chrome lined barrel.

X - Man · 10-28-2009, 17:47

H2O MAN; You are a wealth of information, thanks again. Also, credit is due to the smithing skills to be found at SEI. It's becoming very tempting to consider having the "operation" performed.

I just install a NM spring guide, from Sadlak Ind., & already replaced the op spring with a GI one. Have a GI fiberglass stock, flash hider/front sight, handguard, and if needed, rear sight assm. Any other suggestions for parts upgrade?