Lapping the receiver face

[rcoodyar15]

Have any here ever lapped the receiver face to try to improve the accuracy of a gun instead of for getting the timing right on the barrel nut?

If so what were the results?

[T2C]

I am interested in hearing the need to do this as well. Over the years a few of my match rifles would shoot 1/2 MOA at 300 yards without lapping the receiving face.

[C4IGrant]

Have any here ever lapped the receiver face to try to improve the accuracy of a gun instead of for getting the timing right on the barrel nut?

If so what were the results?

I doubt many people (if any). The first question is, are you a good enough shooter to know? Second question is, do you have the proper tools (optics and ammo) to take advantage of this?

For most people, the answer would be no I think.


C4

[Eric D.]

From a theoretical standpoint, I don't think lapping the face will improve accuracy. If the receiver face isn't perpendicular to the receiver's bore axis the barrel is going to be angled in the same direction as the 'low spot' on the receiver face (barring a tight fit of the barrel extension in which case the barrel should be pretty true.). In other words, assuming the barrel extension and everything else is in spec, square, true, etc. the barrel will naturally align perpendicular to the receiver face (unless the barrel extension is a tight fit.).

Lapping the face will change your zero if the face is not already square but I don't think it's going to affect the repeatability of shot placement.

[rcoodyar15]

From a theoretical standpoint, I don't think lapping the face will improve accuracy. If the receiver face isn't perpendicular to the receiver's bore axis the barrel is going to be angled in the same direction as the 'low spot' on the receiver face (barring a tight fit of the barrel extension in which case the barrel should be pretty true.). In other words, assuming the barrel extension and everything else is in spec, square, true, etc. the barrel will naturally align perpendicular to the receiver face (unless the barrel extension is a tight fit.).

Lapping the face will change your zero if the face is not already square but I don't think it's going to affect the repeatability of shot placement.


the picture I have in my head is maybe a slight hump or bump in the receiver face where the barrel would not have full contact across the face of the receiver. seems that might cause the barrel to shift ever so slightly during recoil. Probably not true but just for the hell of it I am going to try it. My project for tommorow.

I have a 20 shilen match barrel, 24x luepold scope and all the other precision rifle stuff. shooting good groups now. consistent .5 to .75 at a hundred yrds.

I would like to see consistent .5 groups

I have worked up loads with several different powders and 69 mk's 77 mk's and 70 berger VLD's

Looking for that magic combination

[Onyx Z]

I would like to see consistent .5 groups

I have worked up loads with several different powders and 69 mk's 77 mk's and 70 berger VLD's

Looking for that magic combination

Try 8208XBR. This stuff has worked wonders for me. Consistently .5moa or better.

[Eric D.]

That's a possibility!


the picture I have in my head is maybe a slight hump or bump in the receiver face where the barrel would not have full contact across the face of the receiver. seems that might cause the barrel to shift ever so slightly during recoil.

[Warg]

I certainly wouldn't lap one using the Brownells tool, a vise and a hand-held drill. I think there is too much opportunity for error due to tolerances between the upper, the lapping tool and the user. I would rather pay a smith to do it than take a risk or utilize another upper.

I had one "premium" upper and barrel that was would not time correctly with the BBL nut (tried several) unless torqued to 80 lb ft. I could have messed with shims or sourcing additional barrel nuts, but it wouldn't shoot all that well either (~.75" groups with a Kreiger BBL), so out of curiosity I sent it to my gunsmith who lapped it on a lathe and checked headspace after lapping. He commented that is was not exactly square, but not terrible either (can't recall the exact dims). I did not shoot any better, however this is a sample size of one. I decided that the tolerances between the barrel extension and upper could have been better, so I installed the barrel in another receiver with a tighter fit. That worked nicely. Funny thing was that the new receiver was a plane Jane, inexpensive piece compared to the fancy high-dollar model many use for precision builds.

Now I tend toward using barrel nuts that do not need to be timed, using uppers that result in tight with the barrel extension (or blue Loctite on the BE if a tad loose) and only moderate torque for accuracy builds.

[jmnielsen]

I've lapped my receivers with the Wheeler tool and my rifles shoot great (.75 MOA consistently). I've never done a before and after comparison so I can't say definitively that the lapping helped, but it makes perfect sense to me why someone would lap their receiver. The more contact with the receiver the better. Same reason people lap scope rings.

[rcoodyar15]

I've lapped my receivers with the Wheeler tool and my rifles shoot great (.75 MOA consistently). I've never done a before and after comparison so I can't say definitively that the lapping helped, but it makes perfect sense to me why someone would lap their receiver. The more contact with the receiver the better. Same reason people lap scope rings.

I am going to try it. If it works great. If it doesn't I will get another upper and a krieger barrel and try that. I am ready for something different anyway. This gun is my toy. It is fun and I have learned a lot playing with it.

can't decide between a mega or mur upper next time though. both are supposed to be stiffer than a regular receiver.

[markm]

We just did this receiver lapping thread a month or so ago. C'MON, Man!

[Warg]

I am going to try it. If it works great. If it doesn't I will get another upper and a krieger barrel and try that. I am ready for something different anyway. This gun is my toy. It is fun and I have learned a lot playing with it.

can't decide between a mega or mur upper next time though. both are supposed to be stiffer than a regular receiver.

I honestly am starting to question the value of these receivers. Yes they are stiffer, but I'm not seeing the benefits compared to a well machined, standard forged upper. I do hear good things about the Rainer Ultramatch upper too, but no experience with those.

Back to Markm's favorite subject...

[markm]

I honestly am starting to question the value of these receivers.


Don't even go there. You'll bring out the VLTOR Stalker. Some lunatic was obsessed with the MUR upper and stalking Vltor with nutbag emails, and posting whacko shit here.

The MURs are quantitatively stiffer. Whether you need that or not is your own call.

[Warg]

Don't even go there. You'll bring out the VLTOR Stalker. Some lunatic was obsessed with the MUR upper and stalking Vltor with nutbag emails, and posting whacko shit here.

The MURs are quantitatively stiffer. Whether you need that or not is your own call.

Ha, ok. I agree RE: MURs stiffness and general build quality/tolerances. I'm also confident that the likelihood of getting a well-made upper from VLTOR is higher than than from most manufactures. Just have not quantitatively observed differences when shooting.

Some of the F-Class TR dudes are shooting a mix of stuff, i.e., standard uppers, thick billet uppers, MURs, etc. There seems to be little correlation between high scores and uppers, but I haven't spent a whole lot of time looking into this. What seems to be consistent are high quality barrels and good hand loads.

Then again, I see KNS pins on some of these rifles.

[IraqVet1982]

I doubt many people (if any). The first question is, are you a good enough shooter to know? Second question is, do you have the proper tools (optics and ammo) to take advantage of this?

For most people, the answer would be no I think.


C4
I agree. Time/money is better spent at the range on ammo practicing.

[rcoodyar15]

We just did this receiver lapping thread a month or so ago. C'MON, Man!


If you don't have something constructive to add why not just move on

[.46caliber]

If you don't have something constructive to add why not just move on

https://www.m4carbine.net/showthread.php?t=154901

Sent from my Nexus 4 using Tapatalk

[markm]

If you don't have something constructive to add why not just move on

This shit was just covered extensively. NO NEED for a NEW THREAD on it. Your inattentiveness is no reason to be a bad person on the inside.

for anyone interested in the topic....

https://www.m4carbine.net/showthread.php?127822-quot-Truing-quot-an-AR-s-receiver-face