Replacing M305 bolt

[yomomma]

So, What is involved in putting an american made bolt into a norinco. I know I have a large headspace and apparently replacing the bolt can reduce this.

I have seen the odd thread on other forums about this topic but I have not seen any detailed "DIY bolt replacement" posts.

Any input...

 

[Griffin6869]

look up "lapping in a USGI bolt" - in google - lots of info and a few videos will come up

 

[TacticalTeacher]

Most cases, it's a drop in proposition. Sometimes a bit of lapping is needed.

All depends on which high school shop class put yer rifle together. A USGI bolt would not drop into my 2011 shorty. Kept that rifle all Norinco down to the 5 thou headspace merely by swapping, test firing, and then measuring the resultant brass. I kept the bolt that gave me a 0.005" headspace. Nice and tight for a zombie/bear/deer/moose/truck gun.

Cheers,
Barney

 

[Lost...again]

We passed a USGI bolt around at Barneys clinic, and that sucker just dropped right into all the Norcs. What a difference. No more slldey bolt with the action closed.
Just sucked that the bolt cost more than most of the guns in the room LOL

 

[45ACPKING]

The usgi bolts that were coming out of "used" real m14 rifles always seemed to be the best ones for a perfect lapping in. In many cases when I've tried using a new from wrap usgi (or LRB) bolt, too much lapping would have been required to use.

For me, my general practice was to drop in a 1.630 Clymer headspace gauge and see where the bolt ends up when you try and close it on the gauge.
If you get "some" lug engagement, say 10 to 20%.. Yer generally good to continue the lapping process, with the gauge in the chamber.
If you get NO lug engagement (10% or less), a different bolt should be chosen or swap barrel for one you can ream to suit.

There is an M1A bolt lapping tool at brownells for pre lapping bolts into receivers prior to installing a short chambered reamable barrel for those interested.

 

[Ardent]

I wouldn't lap against a headspace gauge personally, you can get a chamfer on your lugs as the early parts of engagement get lapped more than the last parts as it rotates fully into battery. It'll be nice for function but will reduce the bearing area. Even with full engagement you'll have a slight angle on your lugs. It also doesn't let you lap the two surfaces into perfect engagement, as pressure ceases at a certain point when you still have a slight chamfer on the lugs.

Using a tubing cutter cut about 1/8" out of the middle of a case, and put your hammer spring in between the two halves. Have a tap set or broken shell extractor on hand to retrieve the front half from the chamber when done. Chamber with the stripped bolt and a dab of valve grinding compound on each side. Periodically check headspace as you go and you can confirm lug engagement by blacking the bolt's lugs with a Sharpie marker and working it briefly, see where and how much you wear off. This bolt still had a ways to go, the process had just started.

 

[Griffin6869]

That's exactly how I lapped my TRW bolt - i used a bigger diameter spring and it worked like a dream but it does take awhile - slow and steady is the key

 

[yomomma]

Ardent... great minds think alike

 

[Oldsmobiler]

that is unless you need to lap the hell out of it and wear through the hardening....best to leave this to someone with knowledge and tools to do the job

 

[Ardent]

At that point your only options involve another Norc bolt, or pulling the barrel. Norc barrels can't be rechambered, so you'd have to pull the barrel and peen up the shoulder, or replace the barrel entirely with aftermarket or USGI. This is common knowledge but some here won't know so worth mentioning, the risk with too much lapping is wearing right through the extremely thin hardened surface (case) of the parts, to the soft core. There actually isn't a heck of a lot to work with, and lapping is purposefully wearing your parts.

Best case is to find a used USGI like the guys here suggest that drops in and only needs finish lapping for engagement, or rebarrel and set headspace with a reamer (or appropriately headspaced chrome lined like Criterion, but they don't always end up right).

 

[45ACPKING]

Lot's of good info being offered here.
Lapping with a gauge is the down and dirty, get er done approach.
I prefer pulling the barrel and using the prelapping tool but this can be the more complicated approach. If you have the guages and can do the math, it's more work but the finished result is bang on.
I've also used the cut case/spring method and in experienced hands, with a correctly trued "spring assist" lapping tool such as described, the job can also be done to satisfaction.
However, I have also seen guys end up with uneven bolt bearing if that lapping tool was not made "just right"