Lapped a TRW bolt to a 2009 Polytech yesterday.

[Claven2]

Well, my last TRW bolt is now mated to a 2009 ployech shorty barelled receiver. What a big job this time! the Poly lugs were so tight, the TRW would not even rotate closed - not even close - with no gauge in the chamber at all!

So here we go, lapping at home on the cheap for dummies.

1) You need to put even back pressure on the bolt so that the lugs lap evenly. There are plenty of expensive jigs you can buy, or you can do like I do and cut a casing in half and chop a 1911 recoil spring in half to make a back force tool.



2) You need lapping compound. Brownells sells some fancy stuff, of for under $5, you can get valve grinding compound at Cambodian Tire.



3) You need GO and NOGO gauges. I use Clymer .308 SAAMI, but any will do so long as they are for the type of ammo you plan to use. I plan to shoot SAAMI match ammo, so...



4) This is the setup you need to duplicate. Put compound ONLy on the lug faces. Nowhere else. Minimum every 100 laps or so, you need to clean everything off and check your headspace with the GO gauge. If you want a match chamber you stop lapping JUST as the bolt will close on a GO.




5) I use a punch through the extractor hole to rotate the lugs up and down on the lug seats - only about 10 degrees of rotation back and forth.



6) In this photo you can see it's getting close. You want to stop when the bottom of this lug flat rests on the op rod guide ledge with the GO gauge in the chamber.



7) This is what the seats look like as they are lapped.



8) Done! Lapped and right at minimum SAAMI.



Now one final issue I had is that this bolt, for some reason would not fully open. I traced it to the rear left lug being too thick on the bottom. Odd because on my other USGI bolts, this was not an issue and they dropped right into this receiver, but this TRW bolt had to have a few thou skimmed off the bottom of that lug so that it would not bind in this receiver. It *JUST* fit in my other receivers, so I imagine it's an issue of this one receiver being slightly too narrowly inletted at the heel. Of well, it works great now.

The bright area is where I had to grind off about 5 thou to make the receiver and bolt work so that the bolt would fully open without binding:



And there you have it...

Information

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[Claven2]

Oh yeah.... my two most recent builds are both completely finished as of today. Finally got around to re-parkerizing the parts on the MCS rifle that were used and had some finish wear and swapping out the crush washer from a stainless one to a blued one, and the old-school looking rifle got a freshly parkerized GI flash hider to finish her off (along with an ARMS mount, ARMS rings and a 10X target scope).

The old-school is nearly all GI apart from the leather goods, and the Douglass/Barnett NM barrel and of course, the 2005 Norinco receiver. Stock is bedded with USGI Bisonite.

The MCS is mostly GI, remaining chinese parts include:
- Receiver (2009 Polytech)
- Trigger housing (internals are all GI)
- Barrel
- Gas system

I think they both look nice and provide a rather interesting contrast to one another.



Funnily enough, the wood stocked rifle is significantly lighter.

I don't imagine I will ever sell the Wood stocked M14S as I just like it too damn much - it oozes "early vietnam". The other one is a fun rifle - not sure yet if it will stay in the stable though as I'm usually not a very racy guy. WAY too much money into it though! LOL.

Funniest thing of all? Both of these rifles, together, cost about what an M1A Supermatch retails for. Scary stuff what they want for those cast boomsticks these days...

[ballbags]

Thank you for the Tutorial. Now I understand what is meant by Lapping the Bolt

[Thaine]

Thanks for posting this. I haven't seen anything that showed this in such easy to understand terms.

[Bill Hollinger]

Again, very good information! Thanks so much.

[Rotor]

Yes. This is an awesome photo tutorial.

Whats next? How about a trigger job?

JR

[Claven2]

A trigger job huh? Not a bad idea except that I've already done all my M14 trigger groups! A great suggestion though - hopefully someone else here with the skills and a virgin trigger group will take up the challenge?

[Roadawg]

Claven2
Thanks for the time and effort to share this process with us, I've often thought about lapping my HRA M14 bolt into my Norinco receiver but have been a little gun shy about trying it. That may change now. Good Work! Bob B.

[CZM]

I've got a Fulton armory and a polytech. the fulton could use a trigger job, but the polytech is good like it came. I prefer the polytech over the fulton(both have wood stocks,and they both look like what i carried about forty five years ago. USMC airdail(MACS-5)
Pat