Archived Posts » 60,595,333
AR-10 Lapping tool
12/7/2011 2:42:29 PM
Hi I was wondering if there is anyone making these a buddy of mine made one at his machine shop to use on a couple of his AR-10 builds and it worked really well. He is tossing around the idea of making some more for some other people here locally but was wondering if there was a lager interest in these. It looks similar to this one that Brownells has for the AR-15.
Thanks.
http://www.brownells.com/.aspx/pid=20220/Product/AR-15-M16-UPPER-RECEIVER-LAPPING-TOOL
Thanks.
http://www.brownells.com/.aspx/pid=20220/Product/AR-15-M16-UPPER-RECEIVER-LAPPING-TOOL
12/7/2011 8:41:38 PM
I cannot see using that on either a AR 15 or 10. Maybe if the barrel extension wouldn't fit into the receiver and I already had one. Otherwise what's the use?
12/8/2011 7:03:42 AM
I could see how it might benefit a precision build. But you won't know if your receiver is square or not till you use it. It might help, it might not.
It's not for fitting the barrel into the receiver, its for squaring the receiver so the barrel extension mates up square with the receiver.
It's not for fitting the barrel into the receiver, its for squaring the receiver so the barrel extension mates up square with the receiver.
12/8/2011 5:02:07 PM
How will you not know it till you use it, explain. If the face was trued up and you had a barrel with the barrel extension off sightly how would you know the difference? You think they indicate each barrel in by it's bore in two spots on every barrel they make?
12/8/2011 9:13:44 PM
A forged upper is made mostly on a lathe. E erything is machined relative from a single lengthwise drilling. How could the upper be crooked?
12/9/2011 6:06:19 AM
Originally Posted By rightwingnut:
A forged upper is made mostly on a lathe. E erything is machined relative from a single lengthwise drilling. How could the upper be crooked?
A forged upper is made mostly on a lathe. E erything is machined relative from a single lengthwise drilling. How could the upper be crooked?
Very easily. Wheys worn, dull tooling, DRO's not reading correctly, multi machine setup, multi fixture setup, worn fixtures, the list can go on and on.
12/9/2011 10:47:49 AM
Truely a solution for a non existant problem when there are so many other places to look for accuracy.
If you need this tool you have bigger problems than it can fix.
FWIW
If you need this tool you have bigger problems than it can fix.
FWIW
12/9/2011 10:55:39 AM
Many custom bolt gun builders do true receivers for custom builds and many people are doing this with the AR15 there are alot of write ups on truing your upper receiver. Several on this site and the snipers hide. A lot of receivers are not truly square where the barrel meets the upper. I have read as many as 80% are slightly off.
12/9/2011 11:08:22 AM
The degree of error that lapping would correct is statistically insignificant, when compared to things such as handguard runout & installation error.
I'd bet that most people who use this don't even take a set of calipers to the end of the handguard & barrel, much less have an idea of how much runout is acceptable.
Snake oil X 10000, the KNS pins of barrel installs.
I'd bet that most people who use this don't even take a set of calipers to the end of the handguard & barrel, much less have an idea of how much runout is acceptable.
Snake oil X 10000, the KNS pins of barrel installs.
12/10/2011 1:03:19 PM
I wasn't a believer at first but after thinking about how it does help with the barrel center line being aligned with the bolt carrier center line, I felt it's worth the effort.. I have lapped all my uppers now. Some were perfect, some required .002-.003 to be squared to the bolt carrier center line.
Most all Grendel builders do this as it appears to reduce bolt breakage. The bolt lugs fit the extension with all lugs equally loaded. There is a lot of info on the Grendel forum about it. Guys with bolt breaking would true the face of the upper and no more bolt breaking.
The tool is easy to fab with drill rod and a lathe.
Most all Grendel builders do this as it appears to reduce bolt breakage. The bolt lugs fit the extension with all lugs equally loaded. There is a lot of info on the Grendel forum about it. Guys with bolt breaking would true the face of the upper and no more bolt breaking.
The tool is easy to fab with drill rod and a lathe.
12/10/2011 9:46:08 PM
Originally Posted By BSWilson:
The degree of error that lapping would correct is statistically insignificant, when compared to things such as handguard runout & installation error.
I'd bet that most people who use this don't even take a set of calipers to the end of the handguard & barrel, much less have an idea of how much runout is acceptable.
Snake oil X 10000, the KNS pins of barrel installs.
The degree of error that lapping would correct is statistically insignificant, when compared to things such as handguard runout & installation error.
I'd bet that most people who use this don't even take a set of calipers to the end of the handguard & barrel, much less have an idea of how much runout is acceptable.
Snake oil X 10000, the KNS pins of barrel installs.
Agreed 1000%
12/12/2011 3:17:54 PM
What is handguard runout?
12/12/2011 11:33:17 PM
It's when your barrel is a full .100" closer to one side of your handguard than the other, either due to installation or because the handguard itself was a little off in one of the fixtures during machining.
If you can get both sides within.010" of each other, you're doing good, which can be accomplished by either by reinstalling the handgaurd or even standing on the barrel to bend them into place.
(Receivers are remarkably flexible)
If you can get both sides within.010" of each other, you're doing good, which can be accomplished by either by reinstalling the handgaurd or even standing on the barrel to bend them into place.
(Receivers are remarkably flexible)
12/14/2011 12:44:42 AM
Originally Posted By BSWilson:
It's when your barrel is a full .100" closer to one side of your handguard than the other, either due to installation or because the handguard itself was a little off in one of the fixtures during machining.
If you can get both sides within.010" of each other, you're doing good, which can be accomplished by either by reinstalling the handgaurd or even standing on the barrel to bend them into place.
(Receivers are remarkably flexible)
It's when your barrel is a full .100" closer to one side of your handguard than the other, either due to installation or because the handguard itself was a little off in one of the fixtures during machining.
If you can get both sides within.010" of each other, you're doing good, which can be accomplished by either by reinstalling the handgaurd or even standing on the barrel to bend them into place.
(Receivers are remarkably flexible)
12/14/2011 1:02:15 AM
Email sent. 
As for standing on it, if you have a 16" bbl in a 12" handguard, you can lay it on it's side and stand on the barrel until it touches the side of the handguard. Do that a couple of times and it'll true up to the handguard to the point that you will have little to no windage correction in the rear sight.
You can get the barrel to deflect just as much when getting a super-tight stance with a vertical grip on a non-floating handguard.
It's harder to kill a receiver than most of you would think.
ETA: It's also a matter of how much you need to move it. Standing on it is generally reserved for when it's waaaaay out there, but getting the barrel to touch the side of most handguards isn't hard at all.
As for standing on it, if you have a 16" bbl in a 12" handguard, you can lay it on it's side and stand on the barrel until it touches the side of the handguard. Do that a couple of times and it'll true up to the handguard to the point that you will have little to no windage correction in the rear sight.
You can get the barrel to deflect just as much when getting a super-tight stance with a vertical grip on a non-floating handguard.
It's harder to kill a receiver than most of you would think.
ETA: It's also a matter of how much you need to move it. Standing on it is generally reserved for when it's waaaaay out there, but getting the barrel to touch the side of most handguards isn't hard at all.
12/17/2011 7:13:42 PM
Originally Posted By BSWilson:
It's when your barrel is a full .100" closer to one side of your handguard than the other, either due to installation or because the handguard itself was a little off in one of the fixtures during machining.
If you can get both sides within.010" of each other, you're doing good, which can be accomplished by either by reinstalling the handgaurd or even standing on the barrel to bend them into place.
(Receivers are remarkably flexible)
It's when your barrel is a full .100" closer to one side of your handguard than the other, either due to installation or because the handguard itself was a little off in one of the fixtures during machining.
If you can get both sides within.010" of each other, you're doing good, which can be accomplished by either by reinstalling the handgaurd or even standing on the barrel to bend them into place.
(Receivers are remarkably flexible)
X 2. Yes, and make sure you take your level and straighten that with a sledge hammer. If you are "flexing" your receiver...You are creating a TON of issues. Why not just squeeze it in a vise and get it over with?
Has anyone ever assembled a rifle and tried to zero the iron sights with slight to drastic left/right & high/low from sight mechanical zero? If so, more than likely the upper is out of square where the barrel connects. This tool just makes everything align...Easy and simple. You are LAPPING the front edge that contacts the barrel extension. It really doesn't make it more accurate from this action alone...It just aligns the upper with the barrel, therefore, the bolt is square to the barrel at that time - That helps accuracy.
Oh yeah, things are never machined improperly...EVER. Even with CNC machines, there are still tolerances. Every engineering drawing has them (1.645" +/-0.002"). Nothing is EXACT unless painstakingly filed to perfection by a gunsmith - Those days are over.
1/2/2012 8:51:51 PM
I do it to every one of my AR15's. I'd like to find the same tool for my AR10's too.
