Posts: 44
Threads: 11
Joined: Oct 2019
I have worked like a Turk to scrape out 11/2- 21/2 inch groups in a 20 inch BA and 20inch Sanders Armory barrels. I knew I was in trouble when my 50 yard breaking in groups struggled to make 1inch. It could be me, the gun, but I dont think the ammunition. I have tried several Hornady black, AA, and others. I am new to the Grendel forum, but my two other builds , my Larue and Odin works will shoot 1moa or better. All my AR and other bolt action rifles in different calibers shoot well. The basic platform performs and cycles fine. Maybe its just me.
Posts: 989
Threads: 64
Joined: Feb 2019
03-22-2020, 11:57 PM
(This post was last modified: 03-23-2020, 12:02 AM by Lemonaid.)
AR, give the Sierra 120's a try (120 match king and 120 pro hunter). Even my BCA barrel would group less than 1 moa with these.
Posts: 4,287
Threads: 156
Joined: Jan 2017
Do you have a chrony so you can track some MV's? wide spreading MV ranges means the load isn't a good tune for your barrel.
My 20" BA shoots the 123 sst custom factory load, and the Federal 90 TNT well (1" or less), the Hdy Black, not so well.
"Down the floor, out the door, Go Brandon Go!!!!!"
Posts: 35
Threads: 5
Joined: Oct 2019
I have a replacement 12.5 barrel on its way from BA. show about 6-7 different factory loads and nothing was within 3. They were pretty easy to deal with. I would call or send them an email and see what they say about it
Posts: 941
Threads: 46
Joined: Sep 2016
true the receiver face, see if the helps, maybe even bed the extension if its loose
Posts: 1,104
Threads: 8
Joined: Nov 2017
Did you get matching bolts . my 18" sanders put them in the same hole at 25 yards and cloverleafs then at 100 yards with their bolt .
Posts: 3,654
Threads: 17
Joined: Aug 2013
sundowner Wrote:Did you get matching bolts . my 18" sanders put them in the same hole at 25 yards and cloverleafs then at 100 yards with their bolt .
That's amazing precision for an AR barrel and rifle. I bet you are pleased with 0.26MOA.
Posts: 44
Threads: 11
Joined: Oct 2019
I am breaking the gun down and have another barrel to try. My gas tube has a lot of play and wobble. Does that mean anything?
Posts: 1,104
Threads: 8
Joined: Nov 2017
Klem Wrote:That's amazing precision for an AR barrel and rifle. I bet you are pleased with 0.26MOA.
I love that barrel , replaced a BCA 18" barrel that had at it's best a 6" plus groups .
Posts: 1,104
Threads: 8
Joined: Nov 2017
Allen Roberts Wrote:I am breaking the gun down and have another barrel to try. My gas tube has a lot of play and wobble. Does that mean anything?
How tight is your gas block .
Posts: 44
Threads: 11
Joined: Oct 2019
Thanks for your input. I am trying to trace accuracy problems on two barrels using the same upper/lower build. Aero precision upper, Anderson lower, nickel bcg, 2-stage RR trigger etc. Reviewing the situation 1) gas block / both barrels dimpled, block itself firm, but block/ tube slack and a lot of play on the receiver end.2) These are 20 inch rifle gas setups, but they would short stroke using rifle length springs. When I relaced the rifle length spring with a carbine length sling, short stroke problem was instantly solved. Any suspect area here? 3) cheap compensator w/ linear noise hood used on both barrels. Any suspect here? Same different ammo, maybe some improvement. I realize I may be the constant suspect culprit creating poor groups. I want to try to find that out.
Posts: 4,287
Threads: 156
Joined: Jan 2017
Is your stock a rifle length stock or carbine, as in adjustable length or etc? If rifle (A2-ish), then first thing, do not use that carbine spring in your rifle length stock. I don't care if it works (for now), it's bad juju safety wise (unless you have one of those "carbine stock inserts" in the tube as well that shortens the stoke).
The compensator is probably not an issue.
You say there is wobble in the gas block to tube fit-up, I wonder if that tube is even pinned? check that out, kind of a long shot but easy to verify. My probable culprits, losing gas or gas port too small.
A properly made gas block will fit tightly onto the GB journal of the barrel, no wobble, just barely slide on.
Case in point on the gas port. I have 2, 223 wylde BA barrels 18" RLGS, shoot really great but little to no lock back and definitely short-stroking. Near as I could measure their port holes they were the std BA diameter of 0.09375. The IMI 77 gr would cycle fine but virtually nothing else.
So after doing lots of search on the web for BA barrels it comes up that enlarging the port to ~0.100-ish solves this... ie, more gas pressure allowed into the DI cycle system. So I ordered a set of wire-gage drill bits and gradually opened the port to 0.1015 -- result, everything now cycles great. Federal 69 & 77 SMKs, cheap AE 193's, 69 gr Black Hills, IMI, Hdy black 75, everything I shot.
So if everything in the build checks out maybe look at enlarging the gas port. One nice thing about that is if you get 'way too large an adjustable GB can mitigate it.
Need to be careful however on drilling it so as to not mar the other side inner surface/land/groove. I put a cheap aluminum cleaning rod inside so I could hit that but not go too deep and hurt the barrel. Do this even if you have a drill press.
"Down the floor, out the door, Go Brandon Go!!!!!"
Posts: 4,287
Threads: 156
Joined: Jan 2017
Footnote to add: the gas tube will and should wiggle at the receiver end, allows for mate-up to the gas key during cycling.
Once you get the rifle to cycle completely and well, then it would be time to look for accurate loads.
"Down the floor, out the door, Go Brandon Go!!!!!"
Posts: 44
Threads: 11
Joined: Oct 2019
Greyfox hang on. When I check the gun again I will be back. I know the stock is a magpul carbine (milspec 368). Also the gas block slides on with ease. So should be able to use a rifle length spring if everything is built correctly or using the carbine spring means Iam compensating something to make it work. Is it ok to replace a rifle length gas system to substitute a carbine length spring as long as everything cycles normal? If I built the gun correctly would t be talking about spring substitutes?
Posts: 6,193
Threads: 170
Joined: Mar 2015
Allen Roberts Wrote:Greyfox hang on. When I check the gun again I will be back. I know the stock is a magpul carbine (milspec 368). Also the gas block slides on with ease. So should be able to use a rifle length spring if everything is built correctly or using the carbine spring means Iam compensating something to make it work. Is it ok to replace a rifle length gas system to substitute a carbine length spring as long as everything cycles normal? If I built the gun correctly would t be talking about spring substitutes?
Ok slow down and stop I mean stop lock the parking break sir.
Take us a pic of your buffer tube and stock. And don't do anything else until you post it here and we reply.
Because from what you just posted you have all kinds of wrong going on with your stock/buffer system and you don't know what's the difference between carbine and rifle length.
Posts: 4,287
Threads: 156
Joined: Jan 2017
A5 Good idea, Allen get us some good pics.
The short version is, with a carbine stock you use a carbine buffer and carbine length spring, and carbine weights. With a rifle stock you use a rifle length buffer and rifle spring, and rifle buffer. (Yes there are ways to use rifle stock otherwise but let's keep it simple for now!)
show us some pics please so we can see what's going on.
"Down the floor, out the door, Go Brandon Go!!!!!"
Posts: 1,691
Threads: 18
Joined: Feb 2013
Klem Wrote:That's amazing precision for an AR barrel and rifle. I bet you are pleased with 0.26MOA.
You pegged out my sarcasm meter 
Posts: 3,654
Threads: 17
Joined: Aug 2013
rabiddawg Wrote:You pegged out my sarcasm meter
What? 
Posts: 44
Threads: 11
Joined: Oct 2019
gray fox, thanks for your help. A friend has help me clear up my confusion and questions. I will tell you that gas block will slip and spin around the barrel with no effort. I will correct the block and tube issues.
|
