cycling Issues

[Cottobe]

I have a 6.5 grendel PSA 18 inch Rifle length gas upper on a mil spec standard carbine lower. Gas block is adjusted to 'full gas' and the block has not been canted to one side. I have already sent the upper back once to PSA and they installed new gas block and said they fired 25 rounds of 123 grain and everything ran fine.

Since then I have taken to the range and fired 20 rounds of federal fusion 120 grain. The first 10 rounds cycled correctly. Then, I started having issues with failure to feed. Gas Block is full open and all screws are tight the entire time. The last 10 rounds were either problems in feeding the next round or failure for the BCG to be pushed all the way back locking on an empty mag. Rifle was cleaned and oiled before these 20 rounds were fired. And the rifle now how 100 rounds through it so it should be 'loosened up.' Mags are E-lander 17 round and 10 round.

I spoke to a Gunsmith and he wants to test my upper on a lower with a rifle buffer. I will be doing that in a few days. Any thoughts on a different length buffer fixing the problem?

This rifle is extremely accurate and want to keep it. These cycling/Short stroke issues are maddening especially because they don't seem to happen until after 10 rounds are fired.

Any other ideas are greatly appreciated.

[A5BLASTER]

Try a diffrent mag other then the elanders you have. Also open up the gun and inspect it for unusual wear markings.

Could be one part of the reciver set is out of spec.

Testing it on a diffrent lower is a good cheap way of testing as well.

[A5BLASTER]

Forgot too ask. Do you have one of those fancy do hicky extended bolt release things installed on the rifle?

If yes. Take it off and install the standard bolt release and see what it does.

[VASCAR2]

Are you running your BCG well lubed? Curious what buffer your using in your lower. If it is the factory supplied buffer then I’d suspect the gas port is to small. There have been a few post where people had to open the gas port to get reliable function with their PSA. If your using a heavier buffer like H2 or H3 I’d try a carbine weight buffer before checking the gas port size.

The issues I read where PSA gas ports were to small was on rifle length gas 18” barrel 6.5 Grendel barrels.

Here is a link discussing the issue with PSA.

http://www.65grendel.com/forum/showthread.php?19155-PSA-18-quot-upper-short-stroking-Anyone-else

[Cottobe]

My lower is a standard M and P 15 for a 16 inch 223/556. The bolt release is standard. My next step is to try it on a different lower and then try different mags if I dont get better results.

[A5BLASTER]

My lower is a standard M and P 15 for a 16 inch 223/556. The bolt release is standard. My next step is to try it on a different lower and then try different mags if I dont get better results.

So standard buffer and spring.

I think Vascar2 might be correct. Your gas port might be too small.

[Cottobe]

I read that as well about the gas port being too small. BCG is coated with either Hoppes #9 or EWL. PSA said they fired 25 rounds of 123 grain hornady with no issues after they put a new gas block on it about 2 weeks ago. I didnt have those results after taking it to the range myself. The gas is adjusted for full gas. My buffer is whatever comes in a standard carbine collapsable stock. Gunsmith is recommending to try a lower with a rifle stock with longer buffer. I'm trying that in a few days.

[BCHunter]

Ask PSA what lower configuration they ran the upper on? Buffer weight and spring? Would help answer if it is your lower?

[Cottobe]

Ask PSA what lower configuration they ran the upper on? Buffer weight and spring? Would help answer if it is your lower?

BCHunter, the lower they used for 25 rounds of succesful test fire was their standard Carbine Mil Spec Lower, should be identical to what I have as M and P 15 lower.

I did ask about what Mags they used and they said it was standard 30 round pmag used for 223/556 and they loaded 10 rounds of Hornady 123 grain black in it. I found that interesting that they did not use a mag designed for 6.5 grendel round like elander.

My upper is currently with a gunsmith trying to figure out buffer spring weights. If he cannot figure it out then I think I m going to ask PSA to drill the gas port to make larger like some folks have mentioned in the message board here.

[Cottobe]

Update: took my lower and upper to a local gunsmith. He found that the current buffer in my mil spec lower was loose inside the spring. He put a new H buffer and spring in and fired 25 rounds without any malfunctions. Im taking it to the range soon to confirm.

[A5BLASTER]

Update: took my lower and upper to a local gunsmith. He found that the current buffer in my mil spec lower was loose inside the spring. He put a new H buffer and spring in and fired 25 rounds without any malfunctions. Im taking it to the range soon to confirm.

Wait what?

[bbqncigars]

I suppose that a buffer that was too small in diameter could lead to misalignment inside the tube with associated increase in friction. That's just my $.02 worth.