Advice needed re: fitting TRW bolt to Norinco receiver

[Rosco7002]

Evening gents,

Despite the morale destroying news that my 2016 Norinco M14 (in .308 Win) has arrived with a cast receiver my build is still moving along.

Some OCW load testing on the weekend demonstrated good accuracy potential, that definitely helped with my "recovery" but the BIG deal went down today when a nice USGI TRW bolt arrived in the mail. That being said, some fitting is going to be required and I'd (once again) like to canvas you all for input how to approach things.

Here's where things are at:

1) There is ample room for the bolt lugs to slide home into the receiver once the action is closed / in battery.

2) My barrel protrudes approximately 0.016 beyond the rear of the receiver (see pic).

3) The bolt will not slide home fully due to a very slight binding between the receiver and the bolt body directly behind the right lug.

4) The relationship between the bolt lugs and the receiver offers plenty of room for them to fully rotate / engage (on both sides).

5) The left side of the bolt body has approximately 0.005 clearance between it and the receiver. Seems there is enough room for it to fully rotate into position once the binding on the opposite side is corrected.

Based on the above it looks like a little polishing / re-profiling is all that's required to get the bolt freed up and ready for headspacing / final fit. That could be accomplished by working on the bolt or working on the receiver but either way, some (slight) amount of metal will have to be removed.

Given that the receiver is cast it has been "devalued" in my eyes, that inclines be towards working on it to get things freed up. On the other hand, the bolt is a highly sought after and increasingly rare USGI one... that makes me reluctant to remove metal there (no matter how slight).

This is where I'd really appreciate some feedback... what would experienced hands advise on the appropriate course to take?

Thanks!

 

[just having some fun]

is the pic with a go/no go gauge ?

 

[Rosco7002]

Negative, no gauges used yet. Have to clearance the binding before the bolt will close on an empty chamber.

 

[morggun]

First of all, remove the scope base, 2nd, I did not realize they were making cast receivers, I would think hard about getting rid of it, how did the original bolt fit.

 

[Rosco7002]

Original bolt fit fine, coulda been some tighter tolerances but but no issues. As to the receiver - it’s what I’ve got for the time being but I’m looking to find a forged one to transfer my build to ASAP. scope mount will need to come off once I got the time to get to working lapping, tonight was just a quick trial fit.

 

[can14]

If you are getting a different receiver, leave the trw bolt as is. The
New receive will be different

 

[m14medic.ca]

The correct way is to alter the barrel.....

John

 

[Claven2]

If it were mine, I'd spray the front of the bolt in prussian blue and repeat to see where it's binding. It's likely the barrel that is the issue.

 

[TacticalTeacher]

I would be reluctant to mess or modify or lap or grind that USGI bolt.....

Cheers, Barney

 

[1-trident-1]

take a red sharpie to the barrel to see the interference . norcs are known to have protruding barrels. the bolt is your best part, don't touch it.

 

[tiriaq]

OK, there appears to be a lateral contact between the bolt body right behind the right locking lug and the receiver, which prevents the bolt from rotating into locked position..
If metal must be removed, alter the receiver to create the necessary clearance. The bolt is worth more than the receiver.
Is the bolt nose making contact with the barrel?
Was the original bolt a machined forging or MIM?
Personally, I would keep the bolt, and start over with a forged receiver.

 

[Tom Morrison]

When I did my NorCal IDF build using a TRW bolt, it was hitting the Norc barrel when I was testing the receiver for suitability. Did not have this problem with the USGI barrel

 

[Rosco7002]

OK, there appears to be a lateral contact between the bolt body right behind the right locking lug and the receiver, which prevents the bolt from rotating into locked position..

This is exactly correct. Last night I was able to run a feeler gauge between the bolt nose and the barrel so I don't believe any contact is being made but will confirm with a red sharpie tonight.

As things stand I think the binding between the bolt body and the receiver will have to be addressed before I can determine if the barrel will accept the bolt nose (i.e. because the current interference stops the bolt from moving forward / rotating far enough to see if there is room).

I'm in agreement that the clearance is best created by modifying the receiver rather than the bolt too. From what I saw last night it looks like that would only need 1 or 2 thousandths so a little polishing may get the job done.

Once that's done I'll be able to see if the bolt nose has room to slide home into the barrel. Hopefully that'll be the case but, if not am I right in thinking that resolving the issue may require a new receiver or barrel install. My indexing is good (so backing that out a little isn't an option) and the Norc chamber can't be reamed.

 

[tiriaq]

Once the bolt closes without interference, confirm that the bolt nose isn't being wedged against the barrel face. Then check headspace.

There may be nothing wrong with a Norinco cast receiver; could well be perfectly serviceable. Too little data at present.

 

[m14medic.ca]

“Generally speaking” the portion of the barrel that protrudes in to the action is the culprit.

Turning 8-10 thousandths of an inch off generally fixes the problem.

The bolt and receiver should be surface hardened in contact areas, I would really reccomend that those bearing surfaces not be touched with anything but a lapping compound....

Personally, I wouldn’t bother building off that cast receiver..... find a used forged rifle and start from there.

John

PS,

About 50% of the “most recent” import recievers, that I have seen, WILL NOT accept a GI Bolt.

 

[Claven2]

To further elaborate, in my experience bare forged receivers take GI bolts. Add in a chinese barrel, and, well, not so much.

A GI spec barrel usually fixes things, moreso if you have a short chamber to work with.

 

[Apple tree]

Is it dangerous to have a receiver break? where would the weak point be structurally on a receiver? Did some forged or cast receiver ever fail? Where?

I feel like if the weak point on those receivers are not really dangerous, like nobody ever got hurt from a failing m14 receiver, OP's build replacing a MIM for a forged on a cast receiver might be a good way to see how those hold up. My opinion is if material is bad damage or excessive wear will appear on the receiver's locking lugs before anything really bad could happen anywhere else...

Even if it miraculously splits in half from the bolt bouncing into the heel, I think it would just crack it, not throw it back or anything...

That being said I am glad I am not the one test firing those receivers, being a dummy for the MIM bolts was enough...

Are you a high volume shooter OP? If so please post how the receiver's holding up often!

 

[maple_leaf_eh]

Is it dangerous to have a receiver break? where would the weak point be structurally on a receiver? Did some forged or cast receiver ever fail? Where?

...

I have a small folder on one file directory for guns that have blown up. The spread of M1A and M305 is simple; they don't often blow up and the design contains the flying parts. One had the barrel sheer off in front of the receiver ring. Several sheered bolt lugs. One blew the end of the receiver heel off (might have been an M1).

There are four voices on experience on here giving advice - Tactical Teacher and his evil henchman tiriaq, Claven2, and M14medic. The four of them have forgotten more about Chinese M14s than all of put together have learned.

 

[Rosco7002]

Made some headway tonight.... slow and careful headway. Polished the receiver where it was binding against the new bolt, couple thou metal removed and it will now go to about 50% lock up. I am being cautious but this is not a normal contact area with the receiver (the only reason I’m encountering it is because of the TRW bolt being dimensionally different to the crappy MIM one) and I’m not going deep enough to remove the case hardening. I haven’t removed any metal from the bolt or receiver lugs.

Also, I give way less f*@ks than I normally would due to the “cast receiver surprise”.

As things stand it LOOKS like the bolt will mate to the barrel well once I’ve freed things up. With any luck I’ll be in position to try my go / no-gauges tomorrow evening.

 

[Claven2]

You can also try the prussian blue or sharpie trick on the area you are relieving to determine when it's no longer making contact. I would not worry about the case hardening in that area, once it clears, it should no longer be an area prone to wear.