Tuesday, January 25, 2011
PRI Adjustable Gas Block Review - 308AR
I recently tested a PRI Adjustable Gas block on a DPMS LR.308 w/ a 16" Kaiser Military Technologies Barrel w/ mid-length gas system. The main goal was to see how the recoil was affected by metering the gas adjustment down to where it was just enough to engage the BHO (Bolt Hold Open). For set up, I turned the set screw all the way in, loaded one round in the magazine and fired. The bolt short stroked (as expected). I adjusted the screw out (1/4" at a time) until the BHO was engaged, and then added an additional 1/4 for any ammunition variation. The test was using some cheap (and relatively weak) golden bear, that way anything more powerful would have no problem engaging the bolt (I tested a few different Surplus rounds with great results).
I was curious as to how much the set screw was covering the gas block, so I pulled it off to take a look:
I was amazed at how much of the gas hole was covered up, but it still cycles perfectly. Makes me think that the 308's are greatly over-gassed, especially in the carbine length gas system rifles. The recoil was considerably less (purely subjective) with the gas block metered down.
There are many reasons to buy an adjustable gas block. Having a fine tuned rifle, at least only having enough gas needed to cycle the rifle, while also reducing perceived recoil is a good reason in my book.
I just changed out the barrel for an 18.5" Fulton Lightweight/chrome lined barrel. The gas block required no adjustment. It's amazing how small the gas port really needs to be.