Guidance and suggestions appreciated.  If possible... FSC30? Vortex?

I'm not sure what the thread is for a Polytech, but even the standard USGI threads are not 5/8"x24.  Your best bet is to find something that attaches with the Chinese castle nut, as this preserves thread compatibility.  This Vortex would probably be your best bet:

no the threads are metric, retain the chicom castle nut & anything will work, & the gi threads are .595 x 32

Thanks... Who should I send this to if I want to turn it into a Socom and get standard threads for vortex at the same time?

Don't forget to meet the domestication requirement on your Chinese M14 before adding the "evil" flash hider.

Sell or trade for what you really want.  If you really want to keep the forged receiver (and why not?), the only shop with 16" barrels might be Smith Enterprise based on a recent thread.  Anyone else will need to cut down something else and remachine the required features.  That might not be unreasonable if they only thread for a DC Vortex and don't cut the splines for a conventional flash hider.

Springfield Armory, Inc. has M1A SOCOM barrels but I doubt (don't know for sure) they would be willing to install a M1A barrel on a Chinese receiver.  Smith Enterprise, Inc. has a lot of forty 16 " M14 barrels being made presently.

Is this "metric" thread flash a fact or an "I heard it was" ?  I'm going with the latter as I have 2 Polytechs and just bought two of the YHM Phantom (they are on sale http://yankeehillmachine.com/store/product377.html   ) and they both threaded right on, no problem.

You'll need the Socom barrel as it's not possible to shorten a 18-1/2" or 22" to Socom length.
The threads for the gas cylinder lock start at 16-1/4" which also means the barrel would need to be 17" to have threads for a flashider or brake.
You don't gain much going the route of shortening a barrel.



The threads on Chinese receivers are in fact metric, as stated in an earlier post.
If the YHM Phantom screwed right on, I suspect they have a class 1 fit which is very loose.
The USGI castle nuts are typically a class 2 fit as USGI barrels measure .080-.085 diameter on the muzzle threads.
Criterion barrels typically run .085-.090 on the muzzle threads.
Link made hot for the Phantom M14 Flash Hider with Sight Base



Warbird


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Here is a picture.  I took it off and on and the threads are fine.  I was going to use this on my Springfield Scout and swap the brake to the Polytech but didn't notice the part that where it wouldn't fit with the base on a short barrel.  This works for me....twice.

Does the sight base interact with the splines on the barrel or  does it just clamp onto the flash hider? My poly's barrel is over clocked just a hair to make the irons way off. Might be the inexpensive solution I need.

The base does not interact.  You can buy the hider alone.  Mine threaded down and "indexed" with he flats straight on one and top and bottom on the other. There is no "crush washer" as with an AR so I assume it stops where it stops or you blue Loctite it if you want it to be "indexed" .  The base clamps to the flash not the barrel.