Assembling Grendel upper, would love any tips/tricks/info to help accuracy

[AskDrTodd]

So... wanted to build an AR from scratch and loved the ballistics of the 6.5G so went that route. Lower is AA Grendel with LMT LPK, Magpul trigger guard, Timney 3lb trigger, overmolded grip, and Mako SR-25 stock with adjustable cheek weld and built-in monopod.

Upper is AA Beefy Squared side-charging receiver, 20" Satern fluted barrel, EGW gas block (clamp-on), Midwest Industries lightweight quad rail 15" hand guard

I've heard a couple tips for assembling the upper, that I should first use loc-tite primer on the inside of receiver and barrel shank, then a very thin coat of loc-tite blue when assembling to bed the barrel, and clean out any residual with more primer.

When assembling, clean the threads, then a bit of moly grease, then torque to 60, back off, torque to 60, back off, torque to 60 and then turn to next available port so gas tube aligns properly

I don't plan to bed the gas block.

Anyone have a tip how to keep the upper receiver secure in a vise? it doesn't fit in a standard upper-receiver block...

Thanks!

Here's a mock-up (lower assembled, upper gently screwed together to see what it'll look like)

[Hooz]

Sounds like you're on the right track. As for the receiver block, you'll need a DPMS Panther Claw type block...

http://www.bravocompanyusa.com/AR15-DPMS-Panther-Claw-p/panther%20claw%20ar15.htm

You can find them cheaper other places, but that's what you need to look for.

[pappy42]

Brownell's offers a tool that fits into the locking lugs of the barrel extension.

[AskDrTodd]

Brownell's offers a tool that fits into the locking lugs of the barrel extension.

?? Do you have a linky?

[AskDrTodd]

Sounds like you're on the right track. As for the receiver block, you'll need a DPMS Panther Claw type block...

http://www.bravocompanyusa.com/AR15-DPMS-Panther-Claw-p/panther%20claw%20ar15.htm

You can find them cheaper other places, but that's what you need to look for.

Thanks!! Yeah $50 is more than I'd like to spend for something I'm going to use once. Think someone here would be interested in "renting" me one for like $10?

[MikeinGa]

So... wanted to build an AR from scratch and loved the ballistics of the 6.5G so went that route. Lower is AA Grendel with LMT LPK, Magpul trigger guard, Timney 3lb trigger, overmolded grip, and Mako SR-25 stock with adjustable cheek weld and built-in monopod.

Upper is AA Beefy Squared side-charging receiver, 20" Satern fluted barrel, EGW gas block (clamp-on), Midwest Industries lightweight quad rail 15" hand guard

I've heard a couple tips for assembling the upper, that I should first use loc-tite primer on the inside of receiver and barrel shank, then a very thin coat of loc-tite blue when assembling to bed the barrel, and clean out any residual with more primer.

When assembling, clean the threads, then a bit of moly grease, then torque to 60, back off, torque to 60, back off, torque to 60 and then turn to next available port so gas tube aligns properly

I don't plan to bed the gas block.

Anyone have a tip how to keep the upper receiver secure in a vise? it doesn't fit in a standard upper-receiver block...

Thanks!

Here's a mock-up (lower assembled, upper gently screwed together to see what it'll look like)

First I would not use loc-tite primer or blue on a AR barrel due to the high heat. I use loc-tite C5-A anti-seize on all threaded parts. To get the barrel to fit tight and line up with upper, you must lap the upper square to carrier bore. I have found that this helps to get lower sub-moa's. I also use adjustable gas blocks to control the bolt opening and carrier weight system to control the cycling. If yuo have any questions e-mail me. That's IMHO.

Mike

[pinzgauer]

I have also heard not to use loc-tite on the barrel extension to upper interface as it's not needed and can create problems later. I have heard to use a hi-temp "locker" on the barrel to barrel extension interface, but that's something most of us will not have to deal with.

[pinzgauer]

Yeah $50 is more than I'd like to spend for something I'm going to use once.

Unlike the other forms of upper clamps you will use this more often than you think. It's very handy for holding uppers to work on sights, etc.

The internal tool mentioned from Brownells appears to be a very slick method of torquing the barrel nut properly. But from memory it's not any cheaper and does not do anything else.

[pinzgauer]

When assembling, clean the threads, then a bit of moly grease, then torque to 60, back off, torque to 60, back off, torque to 60 and then turn to next available port so gas tube aligns properly

Your torque values are also much higher than most recommend for the initial torque (30 ftlbs).... I'd be worried I could not get to the next gas tube hole without exceeding the 80 ftlb max. My experience has been that to index just a hair to align the gas tube holes can be a 5-10ftlb torque increase.

Maybe this is a secret accuracy thing, but not something I heard or read about either as a solution nor a problem area. I have heard/read of folks overtorqueing and destroying the upper receiver threads. No fix other than to toss it, and buy another.

[noone]

Common sense usually tells me that if the torque wrench is nearly maxed out, and the holes still don't line up, to look for another solution rather than continuing to wrench the barrel nut and end up destroying the receiver. So far, the combination of common sense, and paying careful attention to the torque wench settings has paid off. All the rifles I have built work great, are accurate, and I have yet to destroy an upper.

The process I use, is grease the threads well, tighten, loosen, repeat 3 more times (3x is recommended, I go one more), then do your final tightening.

[AskDrTodd]

k then I'll torque to 30, 30, and then next hole. no biggie.

[pinzgauer]

k then I'll torque to 30, 30, and then next hole. no biggie.

Actually, was more wondering if you had secret info that led to the higher torque values! Most accuracy recommendations have you torquing the minimum above 30, and there have been specific cases of heavy torque leading to accuracy problems. Apparently the norm for mfg's was a much heavier torque than required or specified by Colt and the GI armorer manuals.

Here's the link for the brownell's tool. LR1995 on this forum has used it and recommended it. The idea looks sound, largely removes the upper receiver from the equation.

http://www.brownells.com/1/1/19342-ar-15-m16-barrel-extension-torque-tool-ar-15-m16-barrel-extension-torque-tool-brownells.html

[madcratebuilder]

I'm not a fan of high barrel nut torque numbers. If I have to go over 60-70 Ft Lbs to get the gas tube aligned I try a different barrel nut. I the case of a proprietary nut, I see several manufacturers are saying just machine the nut for gas tube fit.

80 Ft lbs is a lot of load on the aluminum threads of the upper, there has to be some distortion from that.

[noone]

As the original posting was basically asking for accuracy tips if they are building a rifle, here is what I would do:
1. Insure that the face of the upper receiver where the barrel extension meets it is square.

2. Invest in one of the good barrels...it truly is worth the extra money. Trying to build an accurate rifle with a mediocre barrel is similar to building a sword with mediocre steel having a mediocre heat treat. It will fail to do what you want.

3. Make sure the gas block is bedded tight, and the gas tube extension mates up properly with the bolt carrier gas key.

4. Use a free float tube.

5. Install a really good trigger.

6. Make sure that any muzzle devices are mounted square to the bore, not just to the outside of the barrel. Insure there is adequate clearance for the bullet to pass through the muzzle device, but not so much that it negates the device's purpose.

7. Insure that you have proper cheek weld when using the sights, and that the stock fits you properly. If either of these is off, your accuracy will suffer far more than you think it would. If you don't believe me, try shooting decent groups with your scope .25 of an inch too high, or too low...or with a stock that is 1 inch too long or too short.

8. Insure that when testing for accuracy, you aren't having a bad day. Be strong enough to admit it when you are having an off day, and come back when you can do better. It is far better than frustrating yourself, and blaming the rifle.

9. Use good ammo. If your reloads have more than .0025 runout, your groups will really suffer. .0015 and less is much better. Pay attention to your reloading technique, keep copious notes on what you use, and how it works.

10. Practice.

11. If you can afford one of the stiffer upper/lower receivers, stiffer is better, but not so much that it would be the first thing on my list. Barrel, trigger, ammo, fit of rifle are my top ones.

12. If your upper and lower have play when the push pins are inserted, try using a quarter inch shoulder bolt to replace the front pivot pin. If you get the correct length precision ground shoulder bolt, when you tighten it up, it completely eliminates play between the upper and lower receiver. The bolt, washer, and a nice brass acorn nut costs about $3.00 at most large hardware stores. I thought about marketing these, but decided AR people get hosed enough on accessories that are called "tactical". Buy one yourself, so I don't wind up buying them wholesale for $1.00 each, parkerizing them, call them tactical and sell them for $5.00 each, plus $3.00 shipping and handling...there is already enough of that.

[Hoot]

Number 8 gets me every time. There are days I'd be better off writing off the first group and going home. Worst is when I'm trying to get in my groove and a garrulous person sits next to me. I don't mind talking when I'm done, but unless you observe me doing something counter-productive and you know the fix,or dangerous, leave me the heck alone. I try to go on a work day to avoid the crowds or if the weekend is all I have, I get there a half hour before shooting time, set up everything, shoot as soon as the hour chimes and get out of there before the rest of humanity arrives. I actually will take vacation on a particularly nice work day to increase my odds of having the range to myself. For me, this sport is a lot like bowling, golf, billiards, darts, etc. in that your only opponent is yourself.

Hoot