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custom build shooting large groups

G

GumBeau

Private
Minuteman
Jan 11, 2023
10
7
Louisiana
Hello, I need some advise. I built an AR-308 and my 100 yd groups are horrible, at first I thought it was just me but I put that one down grabbed one of my AR-15's ad shot around 1" groups. I have tried 150gr match ammo and 165gr hunting ammo and it is shooting around 4 to 5 inch groups. The funny thing is the 165gr was shooting 8" high and 8" left of the 150gr.
the specs are

18" heavy fluted Faxon barrel
muzzle device MWI Mfr Part: MIAR30MB1
Geissele SSA Trigger
BCG Aero Precision

scopes I have used both a Leupold Vari-X 3 and a Primary Arms SLX 4-14x44FFP

The only thing I can come up with is that I need to try a very heavy bullet.
 
If the barrel is a 1:10 twist, I would take the muzzle device off and shoot some 168gr gold medal match and see where you end up. I have not had luck with faxon barrels of any profile.

Shooting a large frame is not the same as shooting an AR15. It took me a while to tighten my groups.
 
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Did you thoroughly clean the barrels bore prior to shooting it ?
QPQ Nitride can leave a bore fuzzy inside. ( Lack of a better term ) and that can't help accuracy.

And what specific brands of ammo ?

​

 
Thanks for the serous help. I would appreciate it if the the rest of you could hold the snide comments.
bfoosh006: I preformed a through cleaning before the last shooting session. The ammo was freedom munitions 150gr match, Winchester 150gr deer season XP, and federal 165gr bonded soft point. I bought 300 rounds of the Freedom munitions on sale during the build the rest is what Academy had on hand.
the monk: I understand what you are saying about the large frame thing but the fundamentals are the same. This gun with the muzzle break barely kicks even my 11yo says so. I started building ARs a few years ago. Prior to that I shot a Remington model 700 mountain in 270 the first 4 ARs I built, I built the lower and slapped a pre-made upper on them for this one I decided to build everything.

next step is to try shooting without the muzzle break with the 150gr and some heaver ammo.
Thanks for the serious comments.
 
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Not all Faxon barrels suck. I have three, an 5.56 pencil, an 6.5 fluted match, and an 16” Gunner 308, and they are all good shooters. Here’s some pictures of the 308 performance at 600 yards as I walked the shots into the center.

694690E9-7B03-40FB-AEB8-3354D5831920.jpeg
64C15023-DA5D-44C7-B755-E8832AE0A277.jpeg
 
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I have one Faxon barrel but it isn't on an accuracy rig but a carbine. I used it for work for quite some time and it does a good job in that role.

There is a reason why you see people bash certain brands when it comes to accuracy. There is also a reason why you see people recommend certain brands when it comes to accuracy too. It's not bashing if they've earned that reputation. While some report acceptable accuracy there seems to be more that report problems or issues when it comes to shooting small groups. But for you guys that want to cheap out when it comes to barrels, go ahead and roll the dice. I hope you get what you expect but I say why gamble? Why not go with a company with a known history for accuracy. To each their own....
 
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I would contact Faxon and let them know the results you got. It's possible you got a bad barrel.

As for "match" ammo, Freedom Munitions doesn't manufacture match ammo and not in 150 gr. They do use some match bullets in some of their rounds but none appear to be listed as match ammo. As previously suggested pick up some Federal Gold Medal Match ammo; 155 gr, 168 gr, or 175 gr as these are considered the GOLD standard that everyone else is measured against.
 
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So to all interested, at the moment I am waiting for some "168gr gold medal match" to come in as-per the monk's suggestion. When that comes in I will remove the muzzle break and see what happens. If the next test does not improve I will reach out to Faxon as suggested previously.

As far as the build I started this when I was unemployed and when the current administration was coming in. I bought most of the parts on sale like the trigger and the Magpul PRS stock. I bought that barrel because Pew Pew Tactical had decent reviews and for my firs build I was not trying to refinance my house to pay for it. I am just building skills. I hadn't thought of removing the break till the people here advised it. This is as much about learning how to troubleshoot as anything else.

Again thanks to all the people helping me on this path.
 
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The only other thing I can think of is if the barrel is not torqued on correctly. I think you are on the right track with the FGGM 168’s and removing the brake. If they won’t shoot and your scope and mounting system is good, it’s time to call Faxon.
 
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I have an 18" Faxon Gunner that shoots in the .7s and a 14.5 that is still getting some rounds through it but it doesn't shoot nearly as good, around 2"

Get some legitimate match ammo, give the barrel a really good cleaning, and see if the groups better. If not, call Faxon.
 
I’m going to throw out another suggestion. While everyone on the internet has rifles that are always sub 1/2 moa guns, evaluate what you really need from this gun. The internet says that 2 moa was sufficient for guys like Hathcock and Mawhinney.

I mean, 4-5 inch groups are pretty trash, but what is acceptable? What is realistic?
 
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Id check the scope/mount first, then barrel to reciever. After that my vote is ammo also.

I have a Palmetto State 20in 308 that shoots 5 moa groups at 100yds with m80 ball, but will shoot 1-1.5moa with 175gr fgmm and 175gr bullets 1st seconds.
 
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I’ve got news for you… if those loads are shooting 4-5” groups FGMM isn’t going to magically make it shoot sub MOA, not going to happen. A barrel that will shoot good with quality match ammo will still shoot decent with other ammo. Everything you listed should be capable of 2MOA at worst. Even the crappiest FMJ shouldn’t do worse than 3MOA.

I didn’t need to read beyond Faxon barrel to know what your problem is. Instead of wasting more time and money on that turd you should just replace it with a good barrel and be done with it.
 
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redneckbmxer24 said:
I’ve got news for you… if those loads are shooting 4-5” groups FGMM isn’t going to magically make it shoot sub MOA, not going to happen. A barrel that will shoot good with quality match ammo will still shoot decent with other ammo. Everything you listed should be capable of 2MOA at worst. Even the crappiest FMJ shouldn’t do worse than 3MOA.
Click to expand...
I would tend to agree, except... I have a LR-308 that shot Federal Fusion 150 gr soft point into a group that maybe could be covered by a basketball. I loaded 5 Hornady Match 168gr Amax cartridges and proceeded to shoot a sub MOA group. It shoots Federal GMM 168 SMK and the Hornady match loads right about MOA, sometimes a bit better. And, it shoots my hand loads a bit better than those factory loadings. So, it CAN happen, but I wouldn't count on it...

www.snipershide.com

Match ammunition. Is it worth it?

I recently bought a new DPMS LR-308. I bought some ammunition to break in the barrel (let's not go down this rabbit hole) and to shoot for groups. I had two boxes of Federal Fusion 165 gr bullets, one box of Federal Gold Medal Match 168 gr Sierra MatchKing, and one box of Hornady Match 168 gr...
www.snipershide.com www.snipershide.com
 
I am not trying to insult anyone.

When I first started shooting my GII, I couldn't get a decent group no matter how hard I tried. After gleening information from Snipers Hide and paying for the ability to watch the Snipers Hide training videos on how to shoot a bigger gasser, I figured out with the help from the Hide, I needed to learn how to properly shoot the GII.

After all is said and done, bigger gassers are hard to shoot. There is a huge difference between shooting a bolt gun and a bigger gasser.

At least for me.
 
GumBeau said:
Hello, I need some advise. I built an AR-308 and my 100 yd groups are horrible, at first I thought it was just me but I put that one down grabbed one of my AR-15's ad shot around 1" groups. I have tried 150gr match ammo and 165gr hunting ammo and it is shooting around 4 to 5 inch groups. The funny thing is the 165gr was shooting 8" high and 8" left of the 150gr.
the specs are

18" heavy fluted Faxon barrel
muzzle device MWI Mfr Part: MIAR30MB1
Geissele SSA Trigger
BCG Aero Precision

scopes I have used both a Leupold Vari-X 3 and a Primary Arms SLX 4-14x44FFP

The only thing I can come up with is that I need to try a very heavy bullet.
Click to expand...
Can you post a pic of the targets? Have you built other ar’s?
 
No offense, but Freedom Munitions isn't very well respected , to many Kabooms from years ago.

Its also very possible your barrel just doesn't like the ammo's you have tried.

Before the ammo shortage, you could easily try 15-20 different brands / loads for a moderate price... and even then you could probably find a surplus'd ammo that shot well.... and was cheap.

Please let us know your results with the 168gr FGMM.

And I have had danged good results with 155gr Hornady American Gunner.

And while the fundamentals are the same... they are and they aren't.
For some reason, I have found , once you are locked into position at the bench, with a LFAR... don't fidget at all, no repositioning your check, no moving an elbow, no adjusting your head to see better through the scope.... nothing.
If you do need to move... start that group over.
The LFAR will exaggerate any flaw, much more than a AR15. I could muscle through typical flaws with my AR15's but the Large Frame AR just exploits them.
So remain locked in position until the action has fully settled.
Another thing that does help me... is hold the trigger "back" well after the bullet and action has settled.

And another stupid thing... but I have seen it happen far to randomly to discount it.. always "season" your bore to the next round to be tested.

I have seen groups slowly shrink after about 4-5 throwaway shoots when changing ammo's... the CMP used to have a what powders not to use after another, and that list was before the internet, so there must be something to say about hands on experience.
 
If you are not already familiar with Litz's (Applied Ballistics) TOP Gun model, buy his book (vol. 3 chapter 3) or subscribe ($9.99) to his podcast and listen to the episode where he discusses specific characteristics of a rifle design and projectile combination as a predictor of accuracy.

If you don't like paywalls, think about how much ammo costs.

If you still don't want to spend the equivalent of 6 rounds of 308 on the podcast... um... you and I have a different understanding of economics.

Regarding this thread:

The above comments seem true:
1. I've personally seen some less-than-stellar QC come out of Faxon.
2. Variable ammo can produce some very interesting mechanical inconsistencies in the AR platform resulting in inconsistent POI. This is even more pronounced in large frames shooting heavier projectiles with higher energies. In short: upper and lower fitment matters for repeatable POI. Variable charge weights in your cartridge will change the way loosely fitting uppers and lowers interact in the same shooting position and can contribute to undesirable dispersal.
3. Shooting lighter-guns-for-caliber is challenging. Suboptimal fitment (i.e. less obvious index points for how you mount the gun), suboptimal connection between the shooter and the stock (i.e. how you pocket the gun) can result in some pretty ugly dispersal pretty quickly.

That said, I think you will find that Litz's TOP Gun model will give you a better understanding of the mechanics associated with your AR-15 1" groups and your AR-10 4" groups and assist you in your future troubleshooting that may not be entirely equipment related.
 
Muzzle devices have an effect on groups, there's lots of good info out there on their effects. One thing you might consider is the crown and possibly having the barrel re-crowned. I've never had to do it so I don't know what it costs. Also, the barrel fit to the reciever is a real big deal, I'd pull it apart and see if there's any slop in the fit up. A shim may go a long way toward helping the problem. I have an Aero Precision with 20" Ballistics Advantage barrel and on my best day with my best handloads I get 1" groups. I'm using the PA M4-72 severe duty brake, it does a great job and keeps my neighbors benches clean. Optic is an Arken SH4, gen 2 6-24x50. This barrel seems to like 175 grain Sierra Match Kings with 42.0 grains of Reloder 15.5. Velocity is not where I want to be though. I've done a ton of ladder testing with a variety of combinations. Still not satisfied. I have a 24" Krieger due to arrive in the next few weeks. To top it off I have a brand new EC-next gen tuner brake going on it when it gets here. I am on a mission to get this rifle down to .5" MOA. You may want to also consider loading your own ammo. Even with powder/primer prices where they are now I'm loading match grade rounds for about $1.50 per round with my own brass on a Lee 4 hole turret press. I think Hornady Match is running about $2.20 per round right now.
Best of luck with it.
 
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KYAggie said:
My guess is, most of the people bashing Faxon have never owned one. Are they up to Krueger/Bart quality, no. But for the money, I’ve found them to be great.
Click to expand...
Nah, I've had two. Faxon replaced the first one, second one was only slightly less terrible. Sent 2k through it and gave it away to someone not expecting to hit anything with it.
 
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OP the federal gold medal 168’s will tell you if that barrel will shoot. Shoot it without any muzzle device to give it a fair shake.
 
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I would suggest you start at the beginning and double check the assembly of the upper. Does the gas tube pass freely through the barrel nut? Has the barrel nut come loose? Does the gas key rub unevenly on the gas tube? Does anything just not fit right or assembled with difficulty? Is the brake torqued too much? Are the projectiles hitting the bore of the brake? No need to answer but these are a couple things to look at. Do take the brake off and try a few rounds. As to the Faxon barrel? I've never heard of them so no comment there. If the FGMM doesn't shoot likely nothing will.
 
One more thing to consider…

I built a large frame AR for my dad, chambered in 6.5 creedmoor. He put a scope on it and took it shooting. He called me up and said it wouldn’t shoot for shit. I was at his place and asked to shoot the rifle. He handed it to me with a box of Hornady black ammo. I put 5 in a sub moa group and handed the rifle, ammo, and target back to him. I’ve never known him to be a poor shot, but it was a shooter problem in that case. Oh, and that rifle has a Ballistic Advantage barrel.
 
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hlee said:
One more thing to consider…

I built a large frame AR for my dad, chambered in 6.5 creedmoor. He put a scope on it and took it shooting. He called me up and said it wouldn’t shoot for shit. I was at his place and asked to shoot the rifle. He handed it to me with a box of Hornady black ammo. I put 5 in a sub moa group and handed the rifle, ammo, and target back to him. I’ve never known him to be a poor shot, but it was a shooter problem in that case. Oh, and that rifle has a Ballistic Advantage barrel.
Click to expand...
my cousin had a rifle he could not hit a 4x8 sheet of ply-wood at 100yds. I took it from him and punched the center of the bullseye out. So I know what you are saying. I may not be a profesional compitetion shooter but I'm not bad.
 
S197 said:
Can you post a pic of the targets? Have you built other ar’s?
Click to expand...
I didn't take pictures of the targets, I was disappointed and just left. As far as building other AR's I have built.
300 BLK Pistol (if the brace thing doesn't work out I will disassemble or convert to 16")
I bought a 5.56 upper for this one
5.56 Rifle
9mm PCC
300 BLK Rifle (my son shot his first deer with this one last season)
308 Rifle (which is the subject of this thread)
AR9 Pistol (If the brace thing doesn't work out in our favor I will disassemble)
300 BLK Rifle (I am planning on putting a thermal scope on this one for hog hunting)
and I have built around 5 polymer 80 pistols

future builds are
8.6 BLK
6.5 Grindel
 
The Federal match ammo came in yesterday. I had planed on shooting yesterday but the wind was a little to high and I want to minimize the variables. I was going to try to beat the rain today but that didn't happen. I am hoping to make it out to my range tomorrow to shoot. I have cleaned the rifle checked for lose parts and removed the muzzle break. I will post back with the results.

Thanks for all the helpful information and the personal experience shared. I am not reinventing the wheel and it is nice to be able to stand on the shoulders of those that have already experienced the things that I am trying to learn.
 
Ok, to anyone still interested in this thread I removed the muzzle break and shot both the 150 gr freedom munitions and the 168 gr FGMM. The point of impact is now at the same place. It puts 3 shots in about 1/2 moa. then the last 2 start to walk to 1 moa and 2 moa respectively. This pattern is consistent. I added a strike industries Jcomp Gen 2 and the pattern stays the same. I believe the big heavy comp I had before was affecting barrel wip. I don't really expect to be shooting more than 3 shots in quick succession so I think this rifle is good.

I want to thank all the people who provided helpful tips and suggestions.

on another note I built a 6.5 Grendel and tested it also and It will drive tacks.
 
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GumBeau said:
Ok, to anyone still interested in this thread I removed the muzzle break and shot both the 150 gr freedom munitions and the 168 gr FGMM. The point of impact is now at the same place. It puts 3 shots in about 1/2 moa. then the last 2 start to walk to 1 moa and 2 moa respectively. This pattern is consistent. I added a strike industries Jcomp Gen 2 and the pattern stays the same. I believe the big heavy comp I had before was affecting barrel wip. I don't really expect to be shooting more than 3 shots in quick succession so I think this rifle is good.

I want to thank all the people who provided helpful tips and suggestions.

on another note I built a 6.5 Grendel and tested it also and It will drive tacks.
Click to expand...

Glad you found a cost-effective remedy. If group suck with a muzzle device on, always try with it off first as it might just be a harmonics issue.

It's harder to determine when you have just put everything together, but starting with the cheapest "fix" first sure can save you a lot of money.
 
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diggler1833 said:
Glad you found a cost-effective remedy. If group suck with a muzzle device on, always try with it off first as it might just be a harmonics issue.

It's harder to determine when you have just put everything together, but starting with the cheapest "fix" first sure can save you a lot of money.
Click to expand...
Part of this journey was to become proficient at diagnosing problems with my builds. The people on this site have helped me grow in this respect.
 
I have a 24" 1-10 Krieger, and my accuracy was total crap when I tried every brand of match ammo I could find. I finally got some fgmm with 168 and 175 smk's, and that finally started to tighten everything up. Now I'm shooting 185 juggernauts, and 200lrht, and it loves them. Just to test my theory 5 years later I bought the new sierra 169's and the shot like crap. Straight back to heavy and tight groups again. My theory is the 10 twist is just too much for lighter 155 grain. And I am only talking about my gun specifically (armalite ar-10t 24" Krieger heavy target barrel), not in general...
 
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