This is for an AR chambered in 308.

I have a Criterion AR hybrid barrel with a rifle length gas system. Criterion says on their website it comes with a barrel extension with M4 feedramps.

I am using an Aero M5 upper which also says it has M4 feedramps. I realize 308 stuff there is no real standard so while I was hoping I wouldn't have a problem, I recognize it's an issue.



So my question is anybody run into this and do they think it's a problem? I will try out the rifle before I attemp any fix.

Thanks

That's not a problem. If the receiver is cut with M4 feed ramps and the barrel extension is not, you have a problem. If the barrel extension has M4 feed ramps and the receiver does not, it's not a real problem. If the feedramps are not the same size, and as long as the feedramps in your receiver are not "deeper" than the feedramps in your barrel extension, you're GTG (if they are deeper, the lip created in the barrel extension will make it difficult to reliably load rounds - that's the real issue).

You'll be fine as Snow Monkey said.

As long as you don't have a barrel extension without the cuts and a receiver with the cuts, you'll be ok.

Yeah, I don't think it'll be a problem. I was having trouble with an Aero 308 build from my dad, but it was gas issues. My feed ramps look the same and I don't think that was related to problems I did have.
I've never had any issues with my 556 or even 300 blk ARs, but the 308 sure does seem more finicky.

Came to post the same picture. You good.

Yeah I have seen that picture, but the situation looked in between. I verified both are "M4 feedramps" but looks like the definition of that was different to both companies.

Thanks

They'll still play nicely together. Other combos may be a bit better but you will probably never notice.