Please understand that this is a “primer” so to speak. I cannot take into account all of the various factors that people may encounter.
I did this so people can have an idea of what the baseline looks like. From there people will need to use this information and apply it to their particular situation.
A little of my input and how I “tune” a rifle. I’m lucky enough to have access to the equipment required to do rate of fire (ROF testing) which helps.
In this example the setup I’m discussing is a:
11.5" barrel, carbine gas, 1.74mm gas port, Wolf extra power buffer spring, tungsten granulated buffer, FA carrier.
I build a rifle and take a couple types of ammo from accross the reliability spectrum. M855, M193, American Eagle 50-55gr, Wolf steel, and Ruag Frangible.
I take 3 mags and 3 rounds of each and check lockback. If i can get the brass case to lock back properly, and the steel and frangible to lock back with a step down in buffer weights, I’m good.
From there I do 3-10 round ROF readings with each ammo type. If I’m 700-750 with brass that’s perfect for ME. I can usually get a ~700 RPM with the weak stuff if I step down the buffer weight as well.
Having the multiple buffers on hand is perfectly acceptable to me. The same as requiring a BFA to fire blanks, having a lowered H buffer in the bag allows me to adjust during training and go back to the proper configuration when I’m using “duty ammo” (or whatever the F- that means to a civi/gun-tech/guardsman whos not using his issued M4).
*Side note, for frangible I love Remington Disintegrator as it performs the same to me as brass UMC or American Eagle as oppossed to most frangible which can suffer serious feeding and cycling issues.
Personally I prefer a lower ROF as it keeps the muzzle rise down, and significantly increases the lifespan of the rifle. At the current setup when I throw a can on I’m looking at a ~50 RPM jump which is still well within the acceptable ROF for a STANAG fed stoner design. I’ve found that the Wollf spring can ensure reliable feeding at lower ROF due to the extra boost forward during feeding which may be an issue with a weaker spring.
I don’t look at ejection, other than it be semi-consistent within an ammo type. Inconsistent ejection means more as something is not consistent during extration or ejection which could present a problem at some point.
I also rarely clean my guns, so introducing fouling isn’t going to be a factor while I’m tuning.
Tuning means something different to each end purpose of the rifle. If you want to feed RUAG at 950 RPM, tuning might mean a S/A carrier and carbine buffer with a hogged out gas port. Others may be meaning to fire one ammo type with very specific impulse at the expense of realibility with all other types (like 3-gunners).
My process is for guys with quality guns firing quality ammo looking to lower felt recoil and wear on the gun itself. YMMV. The biggest part is understand exactly what each piece of the puzzle does and understanding that each piece has multiple effects despite a blanket effort to categorically shoehorn that part into a role regardless of the other pieces of the puzzle.
Great thread, thanks.
Great candidate for stickyhood. Recommend all responses commenting but not adding germane info be deleted before we have to slog through 80% fluff to find the good stuff.
Like this one for example.
For the sake of comprehensiveness:
BUFFER WEIGHTS
Standard CAR 2.9 oz.
H buffer is 3.8 oz.
H2 buffer is 4.6 oz.
Rifle buffer is 5.17 oz.
9mm buffer is 5.5 oz.
H3 buffer is 5.6 oz.
This one I picked up from elsewhere, can’t attest to it’s accuracy.
Barrel Length (in) Barrel Diameter (in) Distance from Muzzle (in) Min Port Size (in) Max Port Size (in)
11.5 .625 3.850 .081 .089
11.5 .750 3.850 .086 .094
14.5 .625 8.375 .063 .078
14.5 .750 8.375 .070 .086
16 .625 8.375 .063 .078
16 .750 8.375 .070 .086
20 .625 6.875 .086 .093
20 .750 6.875 .093 .096
24 .825 N/A .089 .089
Great information. thank you. This will be a big help on my build
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IG, thank you for the excellent post. All great things to know- especially with regard to the gas system!
Excellent write up… after doing a couple self builds and tuning etc I am thinking Id like to spend some coin on a SAI or Warsport and see how much better tuned they are.
Very helpful thread, thnx for posting !
Very helpful guide, thanks for posting this up.
Thanks for posting this…
meatservo