Unreal 300 blk brass ejection distance

[fixit69]

Built a 300 upper with a 9"AAC barrel, CMT bolt, BCM upper and old lower, with carbine spring and h2 buffer.

With AAC 7.62 can on it, I ran a few down the range with 10 123 supers and 10 220 subs. Flawless. Bolt loved back ding the first 1,2,3 round in mag test. BUT, I'm glad no one was standing beside me, it ejected the brass 30 ft on the supers and about 10 15 on subs. Now I had to leave town to go to work the next day and havent trouble shot it yet, but this can't be right. Tried search but could find nothing.

Overgassed, wrong spring and or buffer. What the hell did I do wrong?

[rsilvers]

I guess I don't understand what kind of ammunition you are using.

123 grain? Didn't we not sell that?

You should make sure the spring is in spec and you can always use an H3 buffer.

[fixit69]

I guess I don't understand what kind of ammunition you are using.

123 grain? Didn't we not sell that?

You should make sure the spring is in spec and you can always use an H3 buffer.

Sorry, Remington. I think it was 135's.. What shOuld a standard ejection distance be on average.

[rsilvers]

I don't know of any 135 grain ammunition.

Your choices are 125 or 115.

If it were me I would make sure the spring is in spec, and make sure your H2 buffer really weighs 160 grams. I have read about a lot of buffets marked H2 but not the correct weight. If you buy a new buffer you may just want an H3.

I have never measured ejection distance, and you would have to define if it hit the ground at 30 feet or at 20 but then tumbled 10 more feet.

[Gunut]

Shot mine with and without can
about 10 to 12 supper sonic (feet)
about 6. To 8 sub
Didnt make much dif. With or without can
Also 10.5 upper

[fixit69]

Rsilvers,thanks for the info. Using borrowed ammo and didnt look very closely.

I imagine it's probably the spring, it's got over five through it. Did not know about the out of spec h2. Will check when I get back in a few months.

Gunnut, I have shot friends since. About the same result as you. I didnt take the spring and buffer in to account. That is probably the answers I need.

[SomeOtherGuy]

Replace the spring first.

I run supers only but get about 8-10' ejection distance to first hit (and stop on grass) or add 5' on concrete from bouncing and rolling. This is with two different 16" barrel carbine gas uppers, mostly using an VLTOR A5 system but also some with H or H2 carbine buffers. It has been pretty much the same across 115gr UMC, 155gr PNW and 130gr Gunn loadings.

[fixit69]

I don't know of any 135 grain ammunition.

Your choices are 125 or 115.

If it were me I would make sure the spring is in spec, and make sure your H2 buffer really weighs 160 grams. I have read about a lot of buffets marked H2 but not the correct weight. If you buy a new buffer you may just want an H3.

I have never measured ejection distance, and you would have to define if it hit the ground at 30 feet or at 20 but then tumbled 10 more feet.

The brass was hitting 20+ feet then rolling the rest in sparse grass onto gravel road. We shoot in the sticks, private range. And it was 125 Remington. The 220 subs are AA IIRC.

I'm almost 100% it's spring and or buffer. Will check in September. Thanks for the info.