Cycling issues in new Grendel build, please help!

[puncher71]

Ok, finally weighed my buffer and it is 3.0 oz. So, from what Ive seen there isnt a lighter buffer, correct? Can I take some of the weights out of my current buffer? Try a lighter spring? OR, just go with rifle tube, buffer, spring, etc...?

[ricsmall]

If you want to retain the carbine length stock and tube etc., get either an h2 or h3, whichever weighs 5.2 oz. If you're going to change to rifle length setup get rifle buffer and spring. At .109" your gas port is too large and you're over gassed. It acts under gassed but your BCG is moving so fast it doesn't pick up next round or lock back on empty mag. PM LRRPF52 and get his take on it. He's pretty sharp on the platform.

Richard

[puncher71]

OK, so yall think it is overgassed with the .109 gas port? I beleive the port measurement is correct. With light finger pressure i can twist a 7/64(.109 if my math is correct) drill bit to the bore. My barrel manufacturer has offered to send me an adjustable gas block. If overgassed, that should fix, correct?

I understand what you say about overgassed bolt moving too fast, but wouldnt it at least eject the spent casing? Sometimes the bolt is still in battery with casing still in chamber after the shot. I assume it blowed back, but cant watch and shoot????

[Rickc]

Ok, finally weighed my buffer and it is 3.0 oz. So, from what Ive seen there isnt a lighter buffer, correct? Can I take some of the weights out of my current buffer? Try a lighter spring? OR, just go with rifle tube, buffer, spring, etc...?

I would go heavier. For a grendel most recommend an h2. Keep your carbine stock if that is what you want. No reason you can't get the rifle to function with it. Maybe someone you know has different buffers you can try.

I have an H2 SCS and a JP adjustable gas block. Mine runs like a.top.

An adjustable gas block will solve your problem.

[ricsmall]

The bolt is unlocking too early it seems, while case is still expanded. sometimes this will leave case in chamber, and when it does extract it will sometimes partially extract or fully extract, but BCG is moving so fast it slams back shut before case clears ejection port. i honestly think it's overgassed but I have been wrong before. Hope u get it running.

Richard

[puncher71]

It was my understanding that an over gassed system that is trying to extract while brass is still under pressure will leave violent extractor marks on case rim. My brass is clean and pretty.

I'm not trying to argue, just trying to wrap my mind around what's going on.

On a side note, when I pulled the gas block off, besides the nice symmetrical carbon "tattoo" around the gas port on barrel, I noticed some faint powder/carbon residue in a about a 1 square inch area around port. My first thought was gas leakage. My barrel is FDE cerakote so it showed up well. I was wondering if this was normal and I had just never noticed it as much on the "black" barrels of my other rifles.

[IceAxe]

Might try locktite around the gas block, its what I use.

[Sticks]

It's possible that you are venting too much gas around your block, but I would think you would notice that when shooting.

Time to take a good look at your BCG.

Gas key (obstructed, or loose?), gas rings on the bolt, bore of the carrier scored?

Can you extend the bolt, set it down on a table bolt face down and it stays extended?

Do you have another carrier you can swap out with?

Look for any excessive wear on the carrier and in the receiver.

With the upper separated and upside down, can you easily slide the bolt forward into battery on an empty chamber?

Gas tube alignment in the receiver - centered? Still round or is it nicked? Sticking out into the receiver far enough?

[puncher71]

I have done all of the BCG tests and everything looks good. Gas tube also looks good. My barrel maker is sending me an adjustable gas block and I ordered a H3 buffer(5.4oz) so maybe this will fix things.

[rabiddawg]

I'm betting it's gonna be that gas leakage.

I had one giving me fits. Started a thread did everything I was told. Took it to a lgs and they said the leakage looked normal

I changed the gas block and used blue loctite under it. Problem solved.

[puncher71]

When yall say use loctite on the gas block, how do you apply it so it doesn't get in the port or smear everywhere when sliding the gas block in place?

[Texas]

Have you checked the gas rings on the bolt to make sure they are functioning correctly? Look at the carbon deposits both sides of the rings.

What ammunition are you shooting? If reloads please provide the powder, bullet, charge, COL.

[puncher71]

Brand new bolt, gas rings appear to be fine, no carbon build up, made sure they are evenly spaced, etc...

Shooting Hornady factory ammo, 123 SST

[VASCAR2]

I use blue loctite on my gas blocks and apply the loctite to the barrel. I put a pencil marks on the barrel showing the location of the gas port. I leave the loctite off the area around the gas block in a straight line so I can slide the gas block onto the barrel without getting loctite into the gas port.

[puncher71]

I received the H3 buffer which weighs 5.4 oz and installed it and did some test firing. The rifle was at least ejecting the spent casings more reliably and consistently and feeding next round sometimes, however it still is not feeding reliably and locking back on last shot. The fact that the heavier buffer improved things makes me believe I do have an over gas issue as opposed to under gassed?? The barrel maker is sending an adjustable gas block but it has not arrived. Hope it takes care of the issue.