I have seen a few threads on this topic lately, but they have been generally lacking on details of the build. I have ordered a BCM BFH 16" mid length. The lower it will go on is a S&W M&P15 currently with a carbine buffer. The ammo I will use most is XM193. What buffer/spring combo would likley work for me?
What you already have should work fine.
ALWAYS stick to a USGI Stainless steel spring… regardless of buffer.
For your set up and ammo, I’d go with an H buffer at a minimum. I’m running an H2 with a 14.5 middy and I run milder ammo than XM193. We’ve even gone H3 with the middy, but it starts to get a little iffy with wimpier types of ammo.
Why’s that? Not intending sarcasm, but genuinely curious.
You can try the Spikes Tactical T2 buffer
I would use a H or H2 buffer.
I recently purchased a BFH/16" midlength and mounted it on a lower with a carbine extension.
I’m running a Tactical Springs M4 carbine buffer spring. I have tried it with both a carbine buffer and a H buffer, and the gun throws brass far forward. From reading various posts here (please correct me if I’m wrong) I believe this indicates that the gun is over-gassed slightly, and that I could use a heavier buffer. My intent is to try an H2 (and possibly H3) buffer to see if this brings ejection closer to the 3/4 oclock position.
I’m not sure if there are other explanations for why my BFH ejects the way it does.
-Rainman
For range use a H2 would be nice if your rifle will run with it.
Your rifle may run a H2 or even 3 fine but don’t get greedy for low recoil at the cost of being on the edge of reliability.
Your walking a line of bolt bounce, bolt over, high recoil, low recoil, and stuck cases.
I go slight higher in recoil but keeping in mind the chance stuck cases. This seems to work good for me.
If the rifle is not over gassed this is what I see gives the best balance.
Middy semi CAR buffer
Middy select fire CAR buffer
Carbine semi H1 buffer
Carbine select fire H2 buffer
Commando semi H1
Commando select H2 or H3 leaning to H3
I have not played with 18" SRPs much yet or PDW 7" type so IDK on those.
My issue with the M16/4 is the design of the case deflector. Most rifles can be tuned for performance by tuning the ejection this harder to do with the M16/4 because of the case deflector. Instead we have to tune by the o clock patterning instead of the pattern of the cases on the ground.
Based upon my experience with markm’s BCM middy as well as my Noveske I would put an H in there and call it a day.
There’s a lot of aftermarket junk out there. I got sucked into that CS spring horse shit and ended up causing my gun all kinds of malfs.
The SS spring (like the USGI mag spring) is in there because of extensive testing.
I’m running a BCM mid length. I too have been playing with buffer weight. I read somewhere that the test for proper function was to insure that the bolt/carrier would lock back on the last round fired. I put in a H2 buffer w/stock spring and it works fine. I am using a LMT lower. I shoot xm193 and PMC and both work fine. I also shoot some IMI surplus and its ok. I just finished a 2 day rifle class and shot 1300 rounds and never had a failure of any type. There seems to be alot of interest these days with buffers. Seems like it would be a good project for someone to test the various combinations of springs and buffers. I dont know how much bolt/carrier weight varies, but this could also be a factor. Just for the record, i am running the BCM auto carrier…
Is there a target cyclic rate that we should aim for? For example, 750 rpm?
Even if there is, not sure how we’d verify short of lending our uppers out to owners of select fire lowers, getting a stopwatch and timing a 30 round mag dump.
And then it would be cool if someone could create a chart of buffer/spring/gas port diameter combos and plot the cyclic rates so we could just pick off the list and get pretty close rather than blowing a couple of hundred while testing all the latest buffer and spring fad combos.
How I picked by buffer was on the middy threads and Rob_S’s articles about shooting Wolf and PMC.