Question: Nork Barrel On Poly receiver

OneBarfly

OneBarfly

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Has anybody tried to screw on a Norinco barrel on a Poly receiver?

I tried to install my shorty Norinco barrel on a newer Poly receiver yesterday and man was it tight. Still about 10 degrees off. I will try again with a sturdier welding table-mounted vice next weekend. Reminded me of trying to fit a .308 barrel on an M1 Winchester receivers over at Hungry's place.... a real impossible ##### to do.
 
Might be necessary to do a bit of adjustment. The barrel shoulder can be trimmed ever so slightly. With a 10 pitch thread you are looking at only about 28 thou.
Are you using a solid barrel vise, or blocks in a machinist's vise?
Good receiver wrench?
 
Agreed - if it's too tight, you can skim a few thou off the shoulder and try again. Less is more, so go slow and keep re-trying until it *just* indexes.

I'm thinking you likely don't own a suitably large lathe, in which case a trip to the gunsmith may be in order.

On my last M305, the barrel was about 1.5 degrees too loose when they drill and installed the set screw, so these guns can be all over the place in either direction. In my case, the barrel snugged up nicely in a barrel vise using a receiver wrench and the set screw went into the garbage where it should be ;)

Not sure why the Chinese install those set screws. Original M14's, M1's, and 99% of threaded barrel guns don;t have a set screw???
 
Yes, those stupid set screws.
Only rifle I've ever seen with a barrel locking set screw that actually had a funtional purpose is the 1905 Ross.
 
I have proper barrel block and a 5" record vice. The wrench is fine, the problem was that I have the vice mounted on a very light weight bench. I do have a smaller lather that could do the trick; however, the guy that I'm visiting on the weekend has a very large TOS lathe (6 foot bed with about 14" swing) along with a welding table that's about 1000 pounds in weight. So, I will try again and if it doesn't move, we will take a bit off the shoulder. Thanks for the advice.
 
A barrel block in a machinists vise does not have the holding power of a barrel vise with fitted bushings. If the barrel is turning in your blocks, that could be part of the problem. If the bench is moving before the barrel turns, that is another.
Recently viewed a new gunsmithing shop being built. The mount for the barrel vise is a 12" steel plate embedded into the concrete floor, with four 3/4" bolts protruding to mount the vise pedestal. That sucker isn't going to move! Ever!
By the same token, there is a limit on how much torque is a good thing.
No. 4 rifles were designed to pull up to index with 120 ft/lbs. That is more than most others.
If too much torque is applied when turning in a barrel, both the barrel shank and the receiver can be damaged.
 
also remember if setting the torque shoulder back, remember to haveit finished with a 1 degree undercut......
correct draw hand tight should be about 15degrees minimum to 20 degrees maximum in relation to top dead center. Then with 90 ftlbs of torque, approx, the barrel should draw to index. if it doesn't..... set the torque shoulder back.
 
tiriaq said:
Yes, those stupid set screws.
Only rifle I've ever seen with a barrel locking set screw that actually had a funtional purpose is the 1905 Ross.
Click to expand...

...that would be because the barrel is barely more than hand tight and the screw is what keeps it in. :)

Rapid battlefield barrel change I guess was the plan.
 
Claven2 said:
On my last M305, the barrel was about 1.5 degrees too loose when they drill and installed the set screw, so these guns can be all over the place in either direction. In my case, the barrel snugged up nicely in a barrel vise using a receiver wrench and the set screw went into the garbage where it should be ;)

Not sure why the Chinese install those set screws. Original M14's, M1's, and 99% of threaded barrel guns don;t have a set screw???
Click to expand...

Perhaps it's because they sometimes don't screw them up tight ?
 
Well, we got the barrel on. Man was it tight. It was a ##### timing it too, as the barrel was cut. The "flats" on the gas assembly were not so flat (on either side, as it was a rather rough casting)

Mr. 14 Doctor, I was wondering about the maximum torque spec. that you referenced. It that a USGI specification? I could only find a minimum quoted. I recal that at a couple of clinics, it seemed like we were puting on much more than 90 pounds - not every one, but a few we really had to struggle, and I'm no light weight (read fat).

Also, everything else is ligned up fine however, the front "navy" sight seemed to have an ever-so-slight cant to the right - almost undectible and is someting easility lived with (It may be the sight not the timing)

Still need to check the headspace.

Thanks for the advice!

PolyRincoM14.jpg
 
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