What's your thoughts on continuing this build?
- Thread starter Knight
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para5063
Member
Depends on what you're going to build. a standard pressure 5.56 NATO upper, You should be okay.
But if you're going with a high-pressure / magnum upper, get another upper.
But if you're going with a high-pressure / magnum upper, get another upper.
You will be fine. I have never put a lot of value in lapping that surface as that dimension isn't that critical if the upper is in spec. The more important fit is the barrel extension to upper fit on the inside of that bore. I usually bed mine with loctite.
Knight
Well-Known Member
My build is a 22 ARC. It concerns me what would happen under continues recoil in the future, I sent this upper back to the manufacture and waiting to hear what they say...
my thinking, as long as you have 2/3 to 3/4 of the receiver face lapped, that's GTG, you're not going to get the barrel extension flange to rock when it's clamped down, it's securely locked in solid.
if you have 1/2 or less, then you can get a teeter-totter rocking when clamped, depending on how tight the barrel extension fits in the receiver bore.
just my 2 cents.
if you have 1/2 or less, then you can get a teeter-totter rocking when clamped, depending on how tight the barrel extension fits in the receiver bore.
just my 2 cents.
Knight
Well-Known Member
I guess I'll have to wait until I hear from the company that manufactured this upper and hopefully they'll send me a replacement based on this finding. I appreciate other opinions.
ntsqd
Well-Known Member
They may be upset at the lapping. It will be interesting to see how they respond.
I agree with rpol98, the little bit of discontinuity in contact surface should not be a problem. I wouldn't use that upper to build an NRA High Power or other competition rifle, just because, but for a varmint or hunting rifle I don't see any reason not to use it.
If you need that thin section of aluminum to be perfect in order for it to be strong enough for any specific chamber you're in trouble before you started.
I agree with rpol98, the little bit of discontinuity in contact surface should not be a problem. I wouldn't use that upper to build an NRA High Power or other competition rifle, just because, but for a varmint or hunting rifle I don't see any reason not to use it.
If you need that thin section of aluminum to be perfect in order for it to be strong enough for any specific chamber you're in trouble before you started.
Not knowing the structural integrity, it is NOT worth the risk to me, but that's just me. Hopefully, the manufacturer do an NDI for you and end up replacing it for safety/liability reasons. Good luck!
Hope they don't tell you no because you altered it by lapping it.
sneedb82
Well-Known Member
That coating is from the anodizing, and if a chunk of the aluminum is what came off, then there was a weak spot in the forging. Not from the lapping necessarily, but exaggerated by the lapping process.
The whole point of lapping an upper is to attempt to bring the face of the mating material into perfect contact with that of the extension on the barrel. That void may create some harmonics concerns for your barrel, but if torqued to manuf. specification for your handguard, assuming not using a milspec barrel nut that is, you should be good to go.
Hopefully they'll get back to you with a reasonable replacement. Depending on the source of the upper receiver, you may not even have to do such a thing. It can ultimately adversely effect your headspace no-go gauge if you do too much lapping, just food for thought. Good luck.
I would not have sent it back. It represents about 1% of the total surface area of the upper to barrel mating surface. Having a good modern M-Lok style longer non timed barrel nut for free floating hand guard is what really holds the upper and barrel as one piece. The lapping just makes sure that they are true in alignment.
Does anyone know why you can't run the 60,000 psi bolt gun loads through an AR? It seems to me that going with rifle length or even better rifle length + 2 inches on the gas tube, heavy full auto type BCG, correct spring and light weight buffer weight. My AR;s run 60,000 psi with rifle and +2 inch gas tubes length. I use the 5.56 reloading tables as a guide and then determine case life by how flat the primer is.
It appears that the 22ARC holds @ 5 more grains of powder compared to the .223/556 case and it gets say 300 fps higher velocity on all the lighter bullets. When compared to my 5.56 full 60,000 psi rounds
shootersreference.com
It appears that the 22ARC holds @ 5 more grains of powder compared to the .223/556 case and it gets say 300 fps higher velocity on all the lighter bullets. When compared to my 5.56 full 60,000 psi rounds
Shooter's Reference Load Data for .22 ARC (Advanced Rifle Cartridge)
Bolt face being really big for the overall bolt diameter and cracking boltsDoes anyone know why you can't run the 60,000 psi bolt gun loads through an AR? It seems to me that going with rifle length or even better rifle length + 2 inches on the gas tube, heavy full auto type BCG, correct spring and light weight buffer weight. My AR;s run 60,000 psi with rifle and +2 inch gas tubes length. I use the 5.56 reloading tables as a guide and then determine case life by how flat the primer is.
It appears that the 22ARC holds @ 5 more grains of powder compared to the .223/556 case and it gets say 300 fps higher velocity on all the lighter bullets. When compared to my 5.56 full 60,000 psi rounds
Shooter's Reference Load Data for .22 ARC (Advanced Rifle Cartridge)
Statement from white oak
"…We have built many rifles in various wildcat cartridges on the .440 head size case, as well as the .264 LBC. What we found is that they just do not give the reliability and longevity that we as target shooters need at the pressures that we typically shoot. In the crucible of competitive highpower shooting, where we tend to tip the powder can to the limit of what the case will hold, they did just not hold up. Other gunsmiths built them and had success with them, but lug set-back and breakage was at a level that I was personally uncomfortable with. At that time I made the decision to not chamber for the .440 head size cartridges.
….
Hornady confirmed by my feelings by limiting the new cartridge to 52,000 PSI max pressure.At that pressure bolts and barrel extensions should last a long time. Start tipping the powder can and all bets are off. If you are one to add powder until primers fall out then back off slightly, don't expect to keep all the lugs on your bolt if you shoot a lot."
