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Discussion Starter · #1 ·
I finally finished assembling my new 6.8 and breaking in the barrel, an 18” SPR profile from Bison Armory. I’m not set up for reloading yet, so I took it to the range to see what the barrel could do with 5 different factory loads—3 with bullets good for hunting and 2 with “match” bullets. Sorry, text came out tiny in the photos, but I thought a side by side view would be best. The ammo was:
  • SSA Custom Competition 115 grain (yellow circle)
  • Wilson Combat BTHP 110 grain (pink)
  • SSA w/Nosler Accubond 110 grain (green)
  • Cavity Back Bullets MKZ 105 (blue)
  • Wilson Combat w/Barnes TSX 110 grain (orange)
Day 1: I left the silencer on for all shots. The front rifle rest was decent but not ideal, and I used a shooting bag for the rear rest. All shots at 100 yards. I was limited on time and ammo so just did 4 shot groups. I measured shot spread from center to center of holes farthest apart.

Day 2: Much better front bench rest and same rear shooting bag. 100 yards. I was time limited, so I didn’t shoot the SSA custom competition. Silencer off this time for comparison’s sake for all shots except the WC TSX because those were looking like the best for this barrel, I intend to use the silencer while hunting, and I only had one box of that ammo so needed to conserve. That’s also why I only shot three of that load. The first two WC TSX shots are the two stacked on the right, then I adjusted the scope 1 click left before the third shot, so that group could have been even smaller. Not the most scientific comparison but still useful.

I was really hoping the CBB would be best because I bought a few boxes of that and other folks’ results with those bullets look great. Alas. I look forward to getting set up for reloading and giving the CBB bullets another go. Worse news for me—Wilson Combat switched to Lehigh right after this, so I can’t get any more of the TSX rounds. I haven’t tried the new WC 6.8 112 grain Lehigh rounds. If any of you have spare WC TSX rounds, please let me know. I’d like to purchase outright or trade with CBB I have.


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If you didnt clean the barrel between the other bullets and the CBB the can cause bigger groups.
CCB copper is softer than any other copper from those other bullets.
They copper foul less because of this but can also be more effected by copper deposits from other bullets.
ymmv
 

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Discussion Starter · #3 ·
If you didnt clean the barrel between the other bullets and the CBB the can cause bigger groups.
CCB copper is softer than any other copper from those other bullets.
They copper foul less because of this but can also be more effected by copper deposits from other bullets.
ymmv
Good to know. On day 2, I shot CBB first. I don't recall the order on day 1. I'm not intending to knock CBB ammo at all here. Just showing what this barrel seems to like and my experience with what a Bison Armory barrel can do when the load is right. Given what I saw with the CBB 105 grain, do you think the 120 grain ammo would perform much differently in this barrel?
 

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Good to know. On day 2, I shot CBB first. I don't recall the order on day 1. I'm not intending to knock CBB ammo at all here. Just showing what this barrel seems to like and my experience with what a Bison Armory barrel can do when the load is right. Given what I saw with the CBB 105 grain, do you think the 120 grain ammo would perform much differently in this barrel?
Depending on the twist. My 16" loves anything up to 115 gr. It didn't perform that good with the 120s, course I could have had an off day.
 

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Good to know. On day 2, I shot CBB first. I don't recall the order on day 1. I'm not intending to knock CBB ammo at all here. Just showing what this barrel seems to like and my experience with what a Bison Armory barrel can do when the load is right. Given what I saw with the CBB 105 grain, do you think the 120 grain ammo would perform much differently in this barrel?
Yes the 120 could perform different in your barrel.
At the end of the day some barrels just dont like some bullets.
That said my Bison 16in Recon likes anything I feed it. It is the least picky barrel of any gun I own.
 

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I couldn't get the 120 CBB to shoot very well but the 105 performed great. I did get some OK groups with the 120's with 27 grains of A2200, not sure why I was using that powder, but it gave me 2575 fps from an 18" barrel. The 105 loads were 28 to 28.8 grains of H335, all loaded to 2.280" with no crimp. This was back in 2018 and I didn't write any other notes or muzzle velocity down.

I need to give them another shot, so to speak. Been too focused on service rifle match shooting with .223 and long range .224 Valkyrie, and have been letting the 6.8 languish except for hunting. I'll make sure I start with a clean bore next time out before shooting any CBB bullets. Yamaraja, do you have a load that you like for the 120 from a 16" barrel?

Anyway, it looks like you're off to a good start.
 

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I don't even really test for accuracy till I have done a proper break-in on a barrel. Own three of the fast twist Bison barrels along with two (18" and 20") that while sold and stamped Bison know for a fact were spun by White Oak Armament. Your day one and two variations are probably more affected by barrel not being seasoned than ammo brands.

If your barrel is factory lapped would reccomend following these instructions before testing ammo for accuracy.


If it's not factory lapped would consider lapping first if know how. If not experienced lapping you can cause more harm than good so just extending the break in period will suffice for most. While I do record group sizes once get past the single round and clean phase, mostly its just to help gauge how well the break in is progressing. Generally I begin accuracy testing after my borescope and examining patches tells me barrel is broken in. YMMV
 

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Discussion Starter · #9 ·
Thanks, huey. My understanding is my barrel was not lapped at the factory so I completed the conventional break-in Bison recommended. Similar to what Krieger recommended at that link. That was before doing this pair of range days. Still, I should do another ammo accuracy test after a few hundred more rounds to see if anything changed. Although hopefully by then I will be handloading. :)
 

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As another personal opinion I almost never run copper solid projectiles in first few hundred rounds. In 0.224" and many other bore sizes do my break-in with SMKs. 5.56 I use Tubbs loaded 69 grain DTAC and 308 use Tubbs 168 grain DTAC. Tubbs uses SMKs for these two cartridges. For 6.8 I generally use 90 grain Speer TNT handloads for break-in.

Have found ammo and methods I prefer that seem to usually do well so stick to them. Once barrel seems happy then begin testing factory loadings and handloads. Have seat covers on my truck seats that hold ballistic panels and rear is molle from top to bottom. One seat has a dozen 5.56 mags and other has a dozen 6.8 mags so whatever rifle I put in lock has its load out and can add a bandoleer if needed.

My truck loadout for 6.8 spc II is six mags of 110 grain Accubonds and six mags of Barnes 90 grain copper solids. Will usually add a six mag bandoleer of 90 grain Speer Gold Dots if its a tactical rifle or six mags of Speer TNTs if its more of a varmint build. Between a pile of Accubonds, Gold Dots and TNTs have not found much I can't do with a 6.8.
 
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