I recently acquired a used Burris 1-8 scope. I set it up on a 11.5 Sionics barrel with AAC can and it was pretty sweet. But I really wanted to run the scope out at distance and 11.5 is not ideal.
Therefore, I bought a new Faxon 16 inch 1/8 barrel new in wrapper off EE. Upon delivery, the fit and finish was very nice and the profile was super thin. I bought an SLR GAS block, geissele 15 rail and had a spare LMT MARS lower with SSA Trigger.
I took my new beloved rig out and drove the time proven load of 77 grain SMK and TMK. Well well well,
With the suppressor it offered up 5 inch groups, without 4 inch groups. We shot multiple groups thinking no way. But it was consistent.
I contacted Faxon and they suggested 60-70 grain bullets. The following week, with little hope any barrel is going to shoot lighter bullets to any satisfaction, the gun grouped 1.5 and one moa group. The 62grain BTHP shot 1.5 and some other load I had shot MOA. Mark may remember the load.
I forgot to take 69 grain SMK’s. Range report to follow from this Sunday shoot.
Very strange, I wish it shot 77’s well, it was built for distance.
Is this faxon 1/8 twist?
I’ve had similar issues with another 1/8 twist
Any heavier than 62g the group opens up
I’ve heard of folks who have around moa
Group with 1/7 twist 11.5 barrels using 77smk
I have every possible size barrel in 1:7 , 10.3, 11.5, 14.5, 16 all group moa with 77’s. I was shocked when this 16 inch barrel shot atrocious with SMK 77’s.
I am hopeful to get SMK 69’s to cruise with this barrel. That would suffice me. I’ve never seen any barrel close up groups THAT MUCH by dropping a few grains off the BULLET.
Just to reduce any wild cards, Got any factory ammo to run through it? I am assuming you are using custom loads since you referred to “proven loads”
I would be interested to hear how faxon treats you on this
I am looking at a pencil or gunner for my next build…
I’ve read that when manufacturers label a barrel twist, there can be a fudge factor one way or the other. Don’t remember where I saw that or what the reason is. Perhaps your 1/8 is actually 1/9; you could measure it with a twisty cleaning rod and jag.
When we took the barrel out on week two, all groups were better. The best was a hot 55 gr game king load that I’d put together last year some time.
It also shot the 77 gr house load MUCH better, but not quite sub MOA. The barrel is spaghetti strap thin, and we have a Sig can hanging on the front of it, so harmonics may be super sensitive.
Faxon, so I assume it’s nitrided/QPQ? The twist rate theory and your harmonics theory have merit, but it is possible the barrel may just need several hundred rounds to settle in. I have seen and experienced this several times with nitrided barrels. The surface is so hard that the imperfections take many rounds to smooth out. For this reason, it’s common for precision barrels to be hand-lapped or fired a few times before being nitrided.
You’re likely aware of all this… Send another couple hundred rounds through it and test again? Curious minds want to know.
I am curious: wouldn’t barrel length and resulting velocity interact with twist to produce rpms necessary to stabilize a bullet? Faster bullet as it leaves barrel = higher rpm?
Recognize gun to gun, barrel to barrel diffs and admit I have no experience with short barrels. Little experience with ar…
This is correct. The stability is a primary function of the bullet rotational RPM, and that results from a combination of both twist rate and muzzle velocity. However, the difference is not that large even for significant changes in MV. You can play with the calculator here: http://www.bergerbullets.com/twist-rate-calculator/
And get a good sense of it. Berger’s 77gr OTM was still stable in a 1:8 at just 2200fps MV, per this calculator.
I suspect that the new barrel and pencil profile are the main issues.
We are hopeful that the barrel needs to settle in with more round count. We brought this up as a potential causative factor. It would be truly stunning if this barrel goes from 5 MOA to MOA with round count. I bought some premium ammo from Bonefrog, we have some 69 SMK’s to try and we have Black Hills 77 and 69’s to try. Very excited to try the BH fodder.
Barrel twist is but one factor in stabilizing bullets. I have a 1/9 Rem 700 5R bolt gun that shoots 80 grain SMK’s light out. It is the most accurate gun that Mark or I have ever shot. There is a great sticky on this about barrels if i’m not mistaken.
I am committed to make this barrel work, I have too much $$ in the gun and SLR gas block that won’t fit any other barrel I own. This is the skinniest pencil I have ever seen. The gun handles very nicely. I’ll get Mark to post some pics since I’m Photo challenged on M4.