Any AR builders/tuners — Lapping Q?
- Thread starter Rsadams
- Start date
Rocketvapor
Gold $$ Contributor
@LVLAaron
Post your results as you go along.
(insert popcorn emoji here
)
May I suggest, if you have access to the tools measure Receiver I.D. and Extension O.D.
I read a lot about "Buy this because it's Thermal Fit" but seldom any measurement data.
I slipped one together last night that many would claim to be a Thermal Fit.
Extension was a little small at the tail end, probably made that way on purpose to start into Receiver, but about 0.0006" larger than Receiver bore about half way in, 0.0008" IF I had tapped it all the way in.
I know that's a lot of measurements for a Lego rifle
Post your results as you go along.
(insert popcorn emoji here
)May I suggest, if you have access to the tools measure Receiver I.D. and Extension O.D.
I read a lot about "Buy this because it's Thermal Fit" but seldom any measurement data.
I slipped one together last night that many would claim to be a Thermal Fit.
Extension was a little small at the tail end, probably made that way on purpose to start into Receiver, but about 0.0006" larger than Receiver bore about half way in, 0.0008" IF I had tapped it all the way in.
I know that's a lot of measurements for a Lego rifle
jelenko
Gold $$ Contributor
Very cool!!
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When they first showed the barrel, my first thought was 'That's a barrel?'.
My take was, bedding wouldn't make much difference with that type of barrel. I.e., I would expect the thin barrel they were working with would produce groups somewhere between 1 and 2 MOA. Another 1/4 MOA wouldn't matter much.
They also mentioned the holding force between two flat [ahem] surfaces [the barrel extension flange and the upper receiver] would prevent [it hurts to say it] wiggle in the barrel. But that requires those surfaces to be FLAT and in the same plane and to have a very high clamping force [I actually don't know how high], which, I think leads to the recommendations from some to use 80-100 ftlbs on the barrel nut. Of course, all that can be avoided by simply preventing the barrel extension from moving. Not sure why they want to 'dis' it.
On lapping the receiver face, I've lapped 5 recievers - some that were no name and some that were considered 'top shelf'. Every one of them had a high side.
LVLAaron
Gold $$ Contributor
And they probably all came from the same machine shop.
Rocketvapor
Gold $$ Contributor
The order of machining operations might matter.
If the last operation to the upper is threading the nose then that can leave an edge.
I know folks don't like them but at least LOOK at the BCA side charge upper.
$99 and includes a BCG. While it's only 4 oz or so heavier than a thin upper (without steel port door or FA)
That's about 60% more 7075 Anodized Aluminium Alloy.
If the last operation to the upper is threading the nose then that can leave an edge.
I know folks don't like them but at least LOOK at the BCA side charge upper.
$99 and includes a BCG. While it's only 4 oz or so heavier than a thin upper (without steel port door or FA)
That's about 60% more 7075 Anodized Aluminium Alloy.
I guess that settles it then.
Rocketvapor
Gold $$ Contributor
Being the poor I am,
I bought a Mitutoyo 1 inch 0.00005" digital micrometer off ebay for $10.
Digital display was dead. Checked against a Chinese pin set and an old B grade Jo-block set.
Better than my old mic.
Bought a Chinese 1-2" inside mic with setting ring that I didn't really trust, labelled as 0.99988.
Made an "offer" on ebay and the seller accepted.
I think it was $53, shipped.
Checked against an old 30mm ring I had, then bought a 0.99985" "X" Master ring
Low and behold, the mic is accurate.
I bought a Mitutoyo 1 inch 0.00005" digital micrometer off ebay for $10.
Digital display was dead. Checked against a Chinese pin set and an old B grade Jo-block set.
Better than my old mic.
Bought a Chinese 1-2" inside mic with setting ring that I didn't really trust, labelled as 0.99988.
Made an "offer" on ebay and the seller accepted.
I think it was $53, shipped.
Checked against an old 30mm ring I had, then bought a 0.99985" "X" Master ring
Low and behold, the mic is accurate.
This...so much this.
I had this “discussion” with a guy some years ago. He was insisting that the brand of AR that HE owned was not only the absolute best of them all but was the one you could could stake your life on when the chips are down. All others would leave you hanging.
He was especially down on several brands, saying they were “absolute crap” and anyone who would own one of them was a stupid, cheapskate...what is it called...Live Action Role Player (LARP) who would die first in a real battle.
I told him he’d be surprised to learn that many of the names in the AR world source parts from the same small number of outfits that actually make the parts. I also said a few of the name brands today (the "absolute crap" ones) started out machining parts for other “big name” brands. No Way, said he.
Then on another forum the rep from his absolute-best-of-them-all brand, in a reply, stated they used several suppliers for their parts and listed specifically the company my friend was the most critical of, the “absolute crap’ company. And he refused to believe this, saying it was BS, the post was fake.
Sometimes ya just gotta let things (and people) go.
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Rocketvapor
Gold $$ Contributor
Upper finished out @ 8 pounds
Nap time.
Nap time.
LVLAaron
Gold $$ Contributor
Got a "naked" picture of the mandrel you've got the upper on in the lathe?
I don't have a pic of mine either but just imagine a 1" piece of drill rod about a foot long and that sums it up pretty close. It's a lot straighter than any of the standard uppers and can be tight enough to touch up the front with nothing more than a friction fit on the mandrel. Doesn't get much simpler, I don't think. Works great. That's what I worry about.
skeeljc
Gold $$ Contributor
It is just a piece of 1" diameter TG&P rod. It fit snug enough I did not need a driver.
LVLAaron
Gold $$ Contributor
Cool. I couldn't tell from the photo if it was something "special" or not. I've got a PTG alignment bar that also fits just right.
Heat-to-fit Bravo "blems" fixes sloppy fit.
Just for laughs and giggles. Bore the buffer tube for proper fit and function. Brake cylinder hone works great to polish buffer tube bore
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VA_XTC_Shooter
Silver $$ Contributor
I use the Midwest URR, works great.
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