How do I know what weight to use? 3 oz, 4oz or 5 oz? I'm using mine in a pistol. — 2 Answers

That depends on a ton of variables including, but not limited to caliber, barrel length, gas system length, gas block style and ammo. It is always best to familiarize yourself with the firearm platform you are putting together and to understand the way an AR or any firearm actually functions. For most AR's an H-weight, which is usually around 3.8 ounces, is generally a good place to start. From there function testing the firearm will tell you whether you need a lighter or heavier buffer depending on the recoil impulse of the firearm, whether the firearm malfunctions and how the firearm is functioning in general.