"Truing" an AR's receiver face?

[C4IGrant]

Wait lowest torque? I'm no sniper, but it seems whenever these sort of topics come up (generall talking bolt guns) I've always seen higher torque numbers. Can you explain/help me understand here?

If we are talking about the barrel nut, it depends. For instance, if the rail system has an anti-rotational system (like the Noveske NSR MUR and Rail), I might be in the 40ft LBS range.

If we are talking about FH/MB's, I like to keep these as light as possible. For instance, if you are mounting an A2 birdcage with a crush washer and it is all the way around the other side, that is just too much torque IMHO. I will shim it so that I only need to go about 1/4-1/2 an inch before it is lined up.


C4

[GLShooter]

My feeling is anything that will keep the bolt and barrel as aligned as possible cannot hurt. I have had more than a few uppers built and all have been squared or at least checked. Most have needed virtually no cutting. Others took some but not excessive IMHO.

Greg

[mic2377]

If I were you I would just find a good quality upper and barrel and not worry about this. I also have an SI Defense 308 upper/lower and am very happy with the finish quality and fitment. As for barrels, why not save the $$$ from this arguably unnecessary step and spend the $$$ on a nice Shilen or Krieger blank?

[Robb Jensen]

In my experience where I've done it and it may work for better consistent accuracy maybe 50% of the time.
FWIW the most accurate AR upper I've ever assembled shot a 0.26" 5 shot @ 100yd group when new. On that upper I didn't lap/true the upper receiver.
Where using the tool to make a difference is when installing LaRue or Noveske NSR rails and you need that .003" more rotation for proper alignment of the rail to the receiver under while staying under 80ft lbs of bbl nut torque.

[0reo]

∧This. Facing the receiver extension is only necessary if you can't time the barrel nut for the gas tube without going over 80ft-lbs of torque.

[hk_shootr]

Then that is a whole different ball of wax as opposed to the OP's question.
Material removal from the receiver for timing is not the same as simply squaring the receiver end.

[bp7178]

I wouldn't expect truing the face to effect the accuracy of the rifle at all. Just that the optics and bore will be in better alignment. This isn't so much an accuracy, as to group size, as people are thinking about.

I think there is merit to the process, but IMO you are better off with a better solution up front. Who is to say after truing the face that the top rail is even in alignment with the bore?

I would rather have a tight fit to the barrel extension, and that's second to headspace. If you're on the large end of headspace you won't see good groups unless you are shoulder bumping once fired from that particular rifle.

I agree with Grant, that in the order of priority when building an upper, truing is pretty low.

[az doug]

Sorry for the late reply.

Truing the front of the receiver where it contacts the barrel nut is only one small part of the equation. The barrel nut, receiver extension, locking lugs on the receiver extension and bolt... would all have to be trued. That is if you are going to do this like a precision bolt gun.

ETA: In my opinion the your gain, if any, would be so insignificant that it is not worth it. As someone else pointed out it does have a use in clocking/indexing barrel nuts of some rail systems.

[Clint]

My two cents is: squaring may not help, but it can't hurt unless you over do it.

My two free floated scoped hunting uppers are squared.

My two handguarded iron sighted fighting uppers are stock BCM builds.

If you remove too much material from the receiver, the barrel sits too deep into the receiver and the feed ramps on the extension can form a catch point.

IMO, the transition from the upper receiver feed ramps to the barrel extension feed ramps should have a very slight waterfall or shingle between them.

[SteveS]

What do the people who shoot the space guns do?