Group buy build won't cycle bolt.

[stvaughn]

[explorecaves]

Assume you verified gas ports on barrel and gas block are centered on each other?

[cory]

Assume you verified gas ports on barrel and gas block are centered on each other?

Exactly what I was thinking!

The gas block shouldn't butt up against the 0.860" portion of the barrel. There should be a gap.

[TheDroz66]

I had the same problem. Here is the link to that thread and ideas that others had for me. I was able to get mine to cycle after adjusting the gas block out quite a ways. I had originally installed my gas block up against the shoulder not realizing that I needed the space. This link has a couple of pictures showing how far off I was between the gas block and gas port (which I found after taking it apart). Hope this helps!

http://www.65grendel.com/forum/showthread.php?8416-Day-out-shooting-with-new-Grendel-Questions

[rickOshay]

Had the same problem with a previous build. The gas block was pushed against the shoulder.

Pen points to where the hole in the block was positioned relative to the gas port.

[rasp65]

I doubt it is that because it clearly states in the instructions that come with the JP gas block:"If you have installed a free floating
hand guard on a military spec barrel, there will be approximately a .025” gap between the back of the gas block and the
shoulder on the barrel." It could be the gas key has an obstruction. I had a complete BCG that had a gas key was not completely drilled.

[Butterbean]

If the carrier doesn't move AT ALL upon firing, there's a complete gas blockage. A pal had this (no carrier movement) with his fresh build. We troubleshot it & discovered the gas tube was upside down............yeah, I know.

[terrywick4]

hook up a hose to the gas line inside the upper (I used an air line from the fish tank pump) and you should be able to blow air thru it fairly freely, if not your gas tube is not lined up correctly and the bolt will not cycle correctly.

[Drifter]

Does it eject and not pick up (feed) the next round?

Does the BCG move at all upon firing?

What buffer and spring are being used?

What type of bolt carrier?

Have you tried a different gas block? (It seems that an adjustable block is not needed since the upper isn't over-gassed, and in my experience, non-adjustable gas blocks seem more efficient versus most adjustable blocks completely opened up.)

While the properly functioning 24" upper suggests that the lower is working correctly, it doesn't necessarily mean that the lower will also be tuned to a 20" barrel with the same length gas system.

Perhaps the OP can elaborate on "won't cycle".

[terrywick4]

did you figure this one out yet?

[Butterbean]

Pins & needles......

[stvaughn]

[Drifter]

Slower-burning powders are more likely to provide reliable function. As you have found, 8208 can be a little fast-burning on a Grendel with an appropriately-sized gas port. 8208 works reliably for many people because Grendel barrels are often over-gassed (which is why so many people use / need adjustable gas blocks).

If desired, your setup could likely be tuned to run with 8208 by using a lighter-weight bolt carrier, or by enlarging the gas port by a few thousandths. To avoid risk of damage to the barrel, a ligther BC is the safer option (albeit more expensive).

[stvaughn]

Thanks Drifter, I just happen to have a lot of 8208 on hand and access to a mill. How many thousands do you think it would take?

Steve

[dmsims21]

Steve, what size is your has port currently?