Help new build gas adjustment problem

[Heshin]

Glad to hear!

Lube, well that should get this thread rolling! I now use mobile1 synthetic 5w30, CLP cooked off a bit too fast for me.

[Steve RA]

Shell Rotella T - full synth - 5W/40

[EkuJustice]

Slide glide light

[CraigS.]

Does the rifle cycle properly, but won't lock back on the last round?

if so take a close look at the bolt catch to make sure it moves freely.

[TitoR]

Craig, the rifle is cycling and locking back correctly with brass case ammo. With tulammo, the casing does not release from the chamber (Wylde) and the cycle stops and I have to extract the spent casing with the charging handle. This means I have to stick with brass cased ammo for now.

[TitoR]

OK, I finally got around to do some additional testing and I would like to validate my conclusions. I have three buffer springs, CAR, Rifle and JP Rifle; and two buffers: JP and STD Rifle.

I measured the start and final force of the spring in the buffer tube to come up with the spring rate. I used a travel distance of about 1.6 in.

Here is the data:

CAR. 5.125 lb and 7.75 lb for a spring rate of 1.68 lb/in

RIFLE. 6.25 lb and 8.438 lb for a, pring rate of 1.4 lb/in

JP. 7.25 lb and 9.813 lb for a spring rate of 1.64 lb/in

The JP buffer weights 3.25 oz., while the rifle buffer 5.125 oz.

Next, I went to the range to adjust the gas block with all the combinatioms of springs and buffer for reliable lock back with empty mag.

For the JP and STD springs I had to open the gas block 4 turns for the JP buffer and 4.5 turns for the Rifle buffer. I was surprised about this since the Rifle spring rate is lower than JP's as well as having a lower starting force, which should have allowed the BCG to cycle with less gas.

With the CAR spring I had to open the gas block 3.5 turns for the JP buffer and 4 turns for the Rifle buffer. This makes sense, since the starting force is much less than the JP and Rifle springs, althought the spring rate is higher of the three.

My conclusion was that the gas block was only slightly throttling down the gas volume that the barrel gas port was allowing to operate the system, but mainly the barrel port is controlling the rifle cycling.

Is my conclusion correct?

Thanks in advance for the feedback.