View Full Version : "Precision" Build Questions...
Straight Shooter
02-16-19, 15:37
Gents-
Ive been gathering parts for sometime now to MY version of a 20" precision rifle. It will not be, nor is it intended to be a full blown Navy Seal-USMC Sniper-Ninja rifle...but instead be as accurate a rifle as I can afford, with MY selected parts, for MY shooting ability and AO.
Intends for the gun are: coyotes, crows, chucks, SHTF/Property defense...ect.ect.
Im not wanting some heavy assed rifle, but one easily portable and accurate with good ammo.
Ill be using 69/77 IMI & other quality ammo of that ilk..not gonna be blasting away with range ammo in this one.
So- Ive got questions, as follows-
1. What are the recommended torque specs for barrel & muzzle device?
2. What are the torque specs on a double set screw gas block & what type loc-tite to use there?
3. For THIS rifle..would an adjustable gas block be better or not?
4. About the only part Ive not decided on is the trigger. I was going to get a 3lb. Velocity, as Ive run a 4lb in my LMT for many years now & love it, but Im open to suggestions, especially on Geissele triggers.
5.Thoughts on facing/squaring the upper receiver?
6. ANY other tips/tricks or recommended things I need to know?
Also- are torque specs different for precision guns & fighting guns?
4. About the only part Ive not decided on is the trigger. I was going to get a 3lb. Velocity, as Ive run a 4lb in my LMT for many years now & love it, but Im open to suggestions, especially on Geissele triggers.
I'd take a look at the LaRue MBT.
Do you have the barrel in hand? If not I'd take a look at this one: http://www.gmriflebarrel.com/gm-m20-20-223-wylde-chamber/
223 Wylde Chamber, 1:8 twist, 20" long, 416 stainless steel, weighs 2.20 lbs., Fluted, honed, button rifled, air gauged, stress relieved, passivated, bead blasted matte finish, Nickel Boron extension with M4 feed ramps, and has a rifle length gas block.
I have this barrel and it shoots much better than I do.
I'd take a look at the LaRue MBT.
I’m not knowledgeable enough to add a lot to this conversation, but the above statement is solid. My MBT-2S feels lighter than and at least as smooth as my Geissele SSA. My G2S is actually noticeably less smooth, despite supposedly being “essentially the same thing” as the SSA. This is not criticism of the SSA; it is outstanding. It’s also not a hardcore critique of the G2S, just my experience in the past month.
I have the MBT-2S in my “precision-esque” carbine.
1. A. Depends on guidance from your handguard manufacturer, I believe? Stock barrel nut: 30 ft-lbs B. 15-20 ft-lbs.
2. A. Unsure. B. Red loctite is what I’ve read BCM uses, from ‘those in the know’ on this forum.
3. Not an expert. But...I wouldn’t think so. The 20” rifle length gas system is the basis for the whole system.
4. See above.
5. I looked at doing this with a build I had planned, but it was not going to be practical with the quality tools I would use. Essentially, using the Brownells lapping tool, for instance, didn’t seen to have a proven value and could potentially be detrimental. This was just my conclusion.
6. I’m still a new guy.
Straight Shooter
02-16-19, 19:17
Thank you both for answers thus far. 26 INF..yes, got a barrel already..Criterion 20" Hybrid in Nitride finish. I will investigate that Larue, thank you.
gunnerblue
02-16-19, 20:06
1. Barrel nut and muzzle device should be to manufacturers specs I would think. I was told by a former AMU gunsmith that the muzzle devices they used were threaded until contact and Loctited in place.
2. I only use pinned GB’s but I would just use Rocksett instead of Loctite
3. I’ve never used an adjustable GB, I prefer to tune gas systems accordingly
4. I use a SSA-E and love it. I also have a MBT and it is very nice. Closer in performance to the SSA-E than SSA IMO
5. No idea
Criterion makes a nice barrel. I enjoy mine, it is indeed very accurate. I’m going to replace it with a 20” Bartlein from Compass Lake for the velocity gains for long range predator hunting (currently using a 16”)
Straight Shooter
02-16-19, 20:45
1. Barrel nut and muzzle device should be to manufacturers specs I would think. I was told by a former AMU gunsmith that the muzzle devices they used were threaded until contact and Loctited in place.
2. I only use pinned GB’s but I would just use Rocksett instead of Loctite
3. I’ve never used an adjustable GB, I prefer to tune gas systems accordingly
4. I use a SSA-E and love it. I also have a MBT and it is very nice. Closer in performance to the SSA-E than SSA IMO
5. No idea
Criterion makes a nice barrel. I enjoy mine, it is indeed very accurate. I’m going to replace it with a 20” Bartlein from Compass Lake for the velocity gains for long range predator hunting (currently using a 16”)
You goin with the progressive rifling?
6. ANY other tips/tricks or recommended things I need to know?
There are some tricks used by guys who build match grade service rifle uppers, but they may or may not be worth your time or of interest to you.
Joe Carlos is a retired US Army MSG who served as an armorer for the Army Reserve Marksmanship Team. He claims that in his experience, shimming and gluing a barrel into an upper will reduce group size by as much as 1/3:
https://www.youtube.com/watch?v=pJL-IscH_jo&list=FLXm7aGKTJQAsHVUEvRefHKg&index=35
https://www.youtube.com/watch?v=pJL-IscH_jo&list=FLXm7aGKTJQAsHVUEvRefHKg&index=35
(There are several more videos in that series with him, but the above it the most to-the-point about accurizing an upper by improving the fit between the barrel and receiver extension).
You could probably approach the press fit he talks about by using an upper that in manufactured to have a tighter than normal fit to begin with, as are BCM forged uppers IIRC.
Another short and less helpful video covering the same thing:
https://www.youtube.com/watch?v=y-jKERY7KJE
Criterion also recommends gluing their barrels in during installation:
https://www.youtube.com/watch?v=XHxU8VUAHOY&list=FLXm7aGKTJQAsHVUEvRefHKg&index=28
Again, maybe not for you, but it is something that some folks are doing.
I was going to suggest the MBT as well.
My iPhone XS Max is better than your android!
gunnerblue
02-16-19, 21:35
You goin with the progressive rifling?
Unknown as of now
Several years back, C4IGrant did a rather accurate assembly using a BCM 410 SS barrel and a DD lite rail I believe. He mentioned that 40 ft lbs torque on the barrel nut was preferred for accuracy.
I have one or more Geissele SSA, SSA-E, SD-C, G2S, SSP, Hi Speed National Match DMR and Hi Speed Service Rifle. I like them all in the various rifles I have them in but the Hi Speed National Match triggers are absolutely incredible IMO. They are the only trigger I have that when I dry fire it I smile and say "wow" out loud. I still do it and I've been using them for about 2 years.
ETA: I used an adjustable gas block on my 20" build. I wish I hadn't. It has worked fine but I don't think it was necessary or adds anything.
Straight Shooter
02-17-19, 07:33
There are some tricks used by guys who build match grade service rifle uppers, but they may or may not be worth your time or of interest to you.
Joe Carlos is a retired US Army MSG who served as an armorer for the Army Reserve Marksmanship Team. He claims that in his experience, shimming and gluing a barrel into an upper will reduce group size by as much as 1/3:
https://www.youtube.com/watch?v=pJL-IscH_jo&list=FLXm7aGKTJQAsHVUEvRefHKg&index=35
https://www.youtube.com/watch?v=pJL-IscH_jo&list=FLXm7aGKTJQAsHVUEvRefHKg&index=35
(There are several more videos in that series with him, but the above it the most to-the-point about accurizing an upper by improving the fit between the barrel and receiver extension).
You could probably approach the press fit he talks about by using an upper that in manufactured to have a tighter than normal fit to begin with, as are BCM forged uppers IIRC.
Another short and less helpful video covering the same thing:
https://www.youtube.com/watch?v=y-jKERY7KJE
Criterion also recommends gluing their barrels in during installation:
https://www.youtube.com/watch?v=XHxU8VUAHOY&list=FLXm7aGKTJQAsHVUEvRefHKg&index=28
Again, maybe not for you, but it is something that some folks are doing.
Thanks for that- I have in fact been in touch with MSG Carlos.
everready73
02-17-19, 09:10
For the upper reciever Faxon makes one that is already lapped and trued. VLTOR MUR it the new BCM upper coming out would also be good choices for a precision upper. The MUR is more rigid and can help with accuracy if you do your part
Thanks for that- I have in fact been in touch with MSG Carlos.
No problem. And that's excellent, glad to hear it.
I’m following this thread to learn and I am not qualified to add much.
I do however own a Geissele SD E as well as the G2S E (Brownells exclusive I think) and can say they are phenomenal. I do have a experience with top notch competition grade 1911 and pistol triggers. Both these of these triggers break practically the same in feel though the G2S E is a bit lighter and is measuring at just around or under 3#. I plan to actually swap the springs for SSA spring to add a pound but would have no issue using it as is for a precision rifle.
Considering all the trigger reviews and commentary I have read for the last 10 years, I don’t know why anyone would buy anything but a Geissele made trigger....all things considered
...Considering all the trigger reviews and commentary I have read for the last 10 years, I don’t know why anyone would buy anything but a Geissele made trigger....all things considered
The KAC two stage trigger has a shorter reset, which I much prefer.
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.