Feeding/Cycle Issue
 

I was able to take my new Bison Armory 18" SPR in 6.8. I shot 2 different factory rounds. 110 Hornady Vmax and 85 E tip by SSA. The Hornady feed and cycled with no problem. The SSA did not feed from magazine or even cycle. I would have to pull charging handle to extract round or when I shoot the round ejected but another would not feed and go into chamber. I emailed Bison Armory and called about the issue. From what I could find it could be magazine related or gas related. Just weird how the 110s were fine and the 85s were not.

I would assume that on the shot, it is partially extracting - if so, how far?

What buffer and spring are you using? Adjustable gas block? 18" rifle length or mid-length gas system?

It sounds like they would feed from the magazine well enough to chamber the round, just that they weren't self-cycling properly? Meaning they aren't opening enough to fully extract and eject the fired round and closing back on the empty, so the bolt isn't carrying far enough rearward to have even contacted the next round for feeding. But when you run them manually, they feed ok, correct?

underloaded is my guess or the wrong powder for an auto
RR

The Silver State Armory stuff (made by Nosler) is SUPPOSED to be designed/loaded specifically for autos, about the only thing they make is auto-fodder: 6.8, 223/5.56, 308, 3006, 300 blackout. I suppose it's fair to say that the SSA is the cheap, bulk/surplus ammo line for Nosler. Really only marketed towards ammo burners and preppers though. It was one of the first places that did offer 6.8SPC factory custom ammo though.

I'm not sure if SSA ever updated to the Spec II pressures, I've heard that they are not.

I've also heard that most of the Bison uppers come with adjustable lo-pro blocks, so if it's tuned for the 110 V-max or 120 SST dwell time, it'll just need to be opened up a bit for the smaller pills.

The 6.8 SPC is really finicky in an 18" length, absolutely NEEDS to have a mid-length gas system, otherwise you end up with undergassing with anything but the hottest of loads, and even in a mid-length, they're really sensitive to dwell time - the lighter pills just aren't really happy about life. Learned that one the hard way after being too stubborn to listen to more experienced guys trying to warn me.

For what it's worth, I've had terrible luck with the SSA's for accuracy, and haven't ever cared to run the lighter pills for the 6.8 anyway (bc's are terrible), so I haven't shot them much myself.

I don't know what buffer or spring I am using at this time maybe RRA. I just have a standard low profile gas block made by Bison Armory. They do offer adjustable but they don't come standard. I am not sure what type of gas system, I would have to call ask for specifics. I already called Bison Armory about it, just waiting on the blacksmith to reply back.
When I used the 85s. This is what occurs. Firearm shoots projectile. The bullet would eject but next cartridge from magazine would not chamber. I would have to charge manually to chamber a round.
The 110s were fine

This one merits repeating !!!

"Learned that one the hard way after being too stubborn to listen to more experienced guys trying to warn me." NoMercy


I have fell victim to that as well - Disclosure; I'm Irish (American) though ! LOL

In which direction do your empties eject? If straight out from the port is 3, the muzzle is 12, and the shooter is 6. As in a clock.

I have a brass catcher so I'm not sure. I can let you know about that next Friday when I go shoot again but I might not even try the 85s again. I'm loading Sierra PH 110s since they finally came in. That's the bullet I will be using from here on out.

The gunsmith said it was short stroking the lighter ammo. The gas port needs to be opened up a tad or switch my buffer with something lighter To allow the 85 grains to work. I'll stick with the heavier bullets and not worried about the lighter Ones

So are you running a heavy buffer or extra power spring now? I had issues with an 18" rifle length gassed barrel, but my 16" carbine gas and 18" mid-length gas behave with 90 to 120grn pills with extra strength flat springs, H2 buffers, and M16 BCG's (a touch heavier). My current 6.8 is running 2 turns open from full closed on an adjustable gas block also.

This isn't Bison's first rodeo, I've known enough guys with their kit that runs phenomenally, so I'd be surprised if they'd mess up on something as simple as a gas port diameter. No big deal to open it up anyway. I personally would rather have my port be way too large and have an adjustable block be the gate-keeper than be restricted on what bullet weight I can run.

That said - you'll be just fine running heavier pills anyway.