New 300 Blackout - short stroking

[undeg01]

Tried out my new 300 Blackout today and have a short stroking issue. It is a Spikes upper with a heavy 16" SOCOM barrel and carbine length gas tube, sitting on top of a Black Rain Fallout multi-caliber lower.

I tried two different brands of ammo...both supersonic. The Remington 120 gr wouldn't eject properly. One might eject, the next might stovepipe and another would not clear the ejection port and jam when the bolt carrier stripped the next round from the mag.

I also tried the Hornady 300 Whisper, 110 gr V-Max. These were hotter loads and ejected much better but wouldn't cycle enough to pick up the next round from the mag.

I was running the standard mil spec Black Rain carbine buffer. I came home and gave the BCG a good soaking and swapped the buffer with another carbine buffer. I'm hoping to try this out tomorrow. Fingers crossed that I will have better results.

Has anyone else experienced this problem? Any suggestions to remedie the problem???

 

[Profreedomokie]

You might try changing your buffer spring to a 9mm one or lighten your buffer weight. I had to both to make mine cycle with subsonics.

 

[ASP785]

Your gas block is probably not properly aligned with the barrel. I would look there first. I run an H2 buffer with my noveske short barreled 300 BO and it cycles subs with the can on like a boss.

 

[Shootin 4 Fun]

Short stroking is a common issue with carbine length gas in 300blk. You may need to open up the gas port.

 

[ASP785]

To kind of piggyback on what S4F said, you should be able to run supersonics with a gas port size minimally in the .100" range. If you intend to cycle subsonics WITHOUT a suppressor, you may to want to open your gas port up to the full .125". You'll be overgassed with supersonics, but the 300 BO just is not as violent in an overgas situation as a 5.56 rifle.

I don't really know what the port size would be on your particular barrel but would be worth measuring if you are seeing if your gas block is aligned properly. To not cycle supersonics with a carbine buffer and the factory port size would be kind of shocking assuming everything else in your system is working properly.

 

[aestus]

Sounds like either your gas block is not aligned properly or that your gas port is too small. Also, 300 blackout typically likes pistol gas systems, not carbine length. I have a 10.5" .300 blackout with normal buffer spring, carbine buffer and pistol length gas. It's cycles subsonics and supersonics with no issue.

 

[Super Dave]

My blackout is 16", with a carbine length gas system, and it shoots supersonic all day long. I don't know what size CMMG uses for their gas port (who made my barrel), but it has been my experience that they are super friendly and helpful on the phone. Call them and see what size their gas port is. Could just be misaligned, or a poor sealing block too.

 

[undeg01]

Got the Blackout running today with thanks to Andy at Village Tactical. The gas block wasn't quite lined up and I ended up swapping out the 9 lb buffer spring for a lighter one, just over 7 lbs. it is cycling and feeding a lot better. I was getting a jam about every 3rd round, but figured out that it was a magazine issue. The gun likes pmags but not GI or metal mags much at all. I put a Nikon P-300 on it and after sighting in, got this 5 shot group at 100 yards.

 

[Super Dave]

Excellent!

Glad you found it.