Help me choose a buffer weight

[DeputyMend]

I have a BCM mid length upper I am building a lower for and I am planning on using a fixed stock. If I use a rifle length spring and a rifle buffer, will that work with a broad range of ammunition? Do I need to use a carbine buffer with carbine spring and one of those spacers? Please help!

[Thomas M-4]

Read gotm4 post it covers it https://www.m4carbine.net/showthread.php?t=23001

[DeputyMend]

I did. I didn't see an exact answer to my question. Maybe I am just stupid.

[Thomas M-4]

The midlength gas system being longer lowers the amount of gas pressure at the gas port thus heavier buffers aren't required. CAR would work fine, H will work but with weaker ammo or a dirtier gun it will likely jam (short stroke, running to slowing to feel as good as a faster cycling gun).

Quoting Gotm4's post

[Thomas M-4]

OH SNAP I just re read it sorry you just use the rifle buffer and standard rifle spring sorry

[DeputyMend]

The rifle buffer isn't too heavy?

[Thomas M-4]

The rifle buffer isn't too heavy?

With the mid-length gas system you will have more gas pressure going to the BCG than with a rifle length gas system.
So the rifle will actually cycle a little faster than it would with a rifle length gas system.
If anything you might try a stiffer rifle spring but I would try the standard one first.

[SWATcop556]

Should run fine with the standard spring and buffer. I run a carbine buffer in my middie and H buffers in my SBR's. Many many rounds down range and so far no snags with either setup.

[kjd2121]

My Larue Stealth midlength uses a H buffer. Works fine with Wolf and Brown Bear ammo.

[Robb Jensen]

I have a BCM mid length upper I am building a lower for and I am planning on using a fixed stock. If I use a rifle length spring and a rifle buffer, will that work with a broad range of ammunition? Do I need to use a carbine buffer with carbine spring and one of those spacers? Please help!

With a fixed length rifle stock the rifle length buffer and spring will work just fine.
If you wanted to you could use a delrin spacer and a CAR or H buffer and spring.