How to Lapp an AR Upper Receiver

[@_Delta_P_]

it wont change headspace. the pin on your barrel bottoms out in that grove. you are just smoothing the mating surface. the barrel isnt sitting back any farther.

[@sorryociffer]

DO NOT apply compound to the part, apply it to the tool AFTER it is lubed and inserted into the upper. NOT doing this ends up introducing compound into the interior of the receiver and you end up also lapping the INSIDE. I could literally hear the grit of the compound against the inside of the upper as the tool slid in. 😢

[@shadowironbank5469]

Great! We now are getting there.. and yes if you take the extreme of cutting half the reciever threads you may get extraction and failure to feeds, however this will not affect headspace on an AR. You probably didnt mean headspace issues but rather “other” issues in terms of rifle function. Well my apologies if I didnt expain myself well, but at least now your viewers are more informed about the differences in AR and bolt gun headspace. 👍🏼

[@andycaldwell4828]

Shadow Iron Bank No. My position still is that lapping an upper may affect headspace. Doing so could introduce slop/play to the barrel in relation to the barrel nut and threads by removing too much material. Buffer spring tension could also be altered due to a different load being placed on the bolt carrier group, again due to removing too much material - This all could effect the dimensional tolerances of bolt-face to shoulder centerline within the chamber.

[@tommygunss4576]

@@andycaldwell4828 , thats why you don't use a power drill. And if you do over lap the receiver they do make things called "shims"... ;-)

[@shadowironbank5469]

Andy you are correct removing material from the AR receiver will set back the barrel or set it in more into the reciever, however what you fail to notice is that in an AR the BCG moves according to the placement of the barrel. In a bolt gun the bolt is fixed. It does not move until you unlock it. When you fire it it remains in the locked position. On the other hand an AR moves back by virtue of the gas system. Hence the BCG can lock up in any position the barrel is set back while still maintaining the same headspace. A bolt gun is fixed since the barrel is screwed into the reciever.

[@andycaldwell4828]

Ok, but in altering the barrel position back further as in this example can introduce primer strike issues in relation to the fire control group and BCG. One may also experience failures to feed and failures to extract. There is a specified tolerance of where the barrel should be in relation to the bolt-carrier group. So lapping an upper receiver can impair the function of a rifle that may be at the extreme of tolerances. That is all that I am trying to say in the video.

[@alanmeyers3957]

@@andycaldwell4828 that’s getting better, however your initial statement about it affecting headspace is incorrect, just own it and move on.

[@andycaldwell4828]

@@alanmeyers3957 Well it can effect headspace. So go harass someone else's channel.

[@_Delta_P_]

It ill not make the barrel sit farther back. the pin on the barrel isnt magically going into the groove deeper.

[@_Delta_P_]

@@andycaldwell4828 it is physcally impossible for that to affect headspace unless your barrel pin is not fully seating into the groove in the first place. the barrel nut just holds it down.

[@shadowironbank5469]

Hey Andy, make a video on this!! Diff between AR and bolt gun headspace. Good luck.

[@shadowironbank5469]

Ok one last try, a barrel on a bolt gun screws directly into the reciever. Headspace is adjusted by screwing the barrel in or out of the reciever. If you remove the barrel, you change the headspace. On then other hand, an AR barrel is screwed into a barrel extension not the reciever, and headspace is set by how far you screw the barrel into the barrel extension. Unlike a bolt gun an AR barrel can be removed and not affect its headspace even if you remove material from the receiver. Thats why anyone can buy an AR barrel and replace it with out a gunsmith because the headspace is determined by the barrel extension at the end of an AR barrel. As long as its mil spec. Bolt guns require a gunsmith to set headspace. Is there any gunsmith which can vouch for what im trying to explain or is everyone confused??

[@andycaldwell4828]

Ok. Mill half of the barrel nut threads off of an AR upper. Next try to attach the barrel. Thereafter, try and fire it. Tell me how it works out for you.

[@alanmeyers3957]

This guy doesn’t get it, you could say this 100 times, as you said, it will-click for him someday.

[@shadowironbank5469]

My response was not meant to harass, but to educate you. Im sorry if I have not been clear, taking material off an AR reciever does not affect headspace, this only occurs on a bolt action rifle. If you dont understand its because your assuming an AR at the chamber end is the same as a bolt gun. They are not, the AR bolt only locks with the barrel extension where as the bolt gun locks with the barrel.. i dont know why you cant grasp this idea? Go figure?

[@andycaldwell4828]

You cannot educate anyone when you don't know what you yourself are even talking about. It doesn't matter whether the bolt locks within the barrel or not. In lapping an upper receiver, removing material, you are essentially shifting the entire barrel back in relation to the contact point with the upper receiver. This would in turn effect headspace. Go educate yourself first before you spread your disinformation here.

[@briandavern8741]

@@andycaldwell4828 But the barrel's index pin is not getting closer to the receiver and this determines headspace in the AR platform. Isn't the only issue that excessive lapping shortens the threads on the outside? Or at least that is what I was instructed at Armorer school. I have not tried lapping a upper yet but would appreciate any information you can pass on about the headspace issue as this could change my mind about the plans I have to do so. Also great job on explaining the reason to lap in the first place.

[@andycaldwell4828]

@@briandavern8741 Right. If you remove too much threading there could be excess play between the barrel nut, upper receiver, and the barrel itself. Which I have seen people do - this would adversely effect headspace. Also, you do not want to move the final barrel position/seating of the barrel too far to the rear of the upper receiver, as this could effect proper feeding and ejection.

[@alanmeyers3957]

@@andycaldwell4828 shadow is correct, lapping the receiver will/ does not effect headspace on the AR platform.

[@andycaldwell4828]

@@alanmeyers3957 Do you by chance know what spring tension is?

[@shadowironbank5469]

Andy, in order for the headspace to change on an AR, you would have to loosen or tighten the barrel extension, niether of which you are doing by removing reciever material. Removing reciever material only allows barrel extension to get closer to the BCG as a unit, not the bolt face. Again, the headspace is set by matching the “bolt” to the barrel extension. Please research, gunsmiths Do Not set head space on an AR by trimming the reciever they adjust the “barrel extension to the barrel end.”

[@andycaldwell4828]

The bolt face is part of the bolt carrier group. You are speaking total and complete nonsense. My video is on lapping an upper receiver, not setting headspace. And removing too much material from an upper receiver absolutely can effect headspace. Go harass someone else's channel.

[@shadowironbank5469]

Headspace? This is an AR. Headspace is set when barrel extension is attached. I think you were thinking of a bolt gun.

[@andycaldwell4828]

Headspace, on an AR, is measured from the surface of the boltface to the midpoint of the shoulder contact surface within the chamber. As with a bolt action style rifle, an AR style platform also has both features.

[@shadowironbank5469]

Hmm.. you sound sarcastic. Even if you cut half the threads the bolt will still close since it still has the same headspace in the barrel extension. Although your barrel will be closer into your reciever. I’m getting the feeling you dont know the purpose of a barrel extension? Nor the difference between a bolt gun and AR barrel?

[@shadowironbank5469]

Wow, your feathers got flustered! Lol, you can shoot an AR without the reciever becuz you still have bolt lockup with the barrel extension, not possible on a bolt gun.

[@shadowironbank5469]

Anyway, I give up, your taking it personal. You dont seem to want to learn.. one day you will have an Aha! Moment and say, “ohhh so that was what he was talking about!” Lol til then enjoy life amigo and keep on producing those excellent videos! 😏

[@shadowironbank5469]

You are now bringing up other things I never questioned. I only questioned your original statement that removing material off an AR reciever will “interfere with your headspace”. Sounds like your trying to cover up your false statement. Anyway, good luck with that, the truth always comes out in the long run. One day you will learn, your just trying to save face on what you said.

[@andycaldwell4828]

Shadow Iron Bank Yeah look who's talking. You do not know your head from your ass.

[@glpdrum]

I agree with you on this one, headspace is determined in the barrel extension which is why the wylde barrel was created correct? The only issue I see is the feed ramps cut in the upper and how that could change but it would need to be drastic IMHO. According to the book: "Gunsmithing the AR-15" by Patrick Sweeney, it states the following: "The barrel of the AR is made to be a simple item to replace. Unlike the barrels of earlier rifle designs, the AR/M16 barrel does not require headspace , or "shouldn't."

[@doughammer2161]

The headspace on an AR15 is set when the barrel (assembly) is manufactured,and is set by screwing the barrel extension onto the barrel until the headspace is correct. The barrel extension is then pinned to the barrel, permanently setting the headspace. The AR receiver plays no part in head space.