M5E1 308 ZQI Cycling Problems

[DutchTerror]

OK, so I finally got a chance to run the Aero M5E1 build yesterday. Just for parts reference:

M5E1 Upper and Lower
Geissele SSA-E Trigger
Ballistic Advantage 18" Mid-Length
Syrac Gen 1 Adjustable Gas Block
DPMS 308 Rifle Buffer and Rifle Spring
VG6 Gamma Brake
New 20 rd. PMAG

I was trying to run some of the ZQI 7.62x51 ammo from Walmart as for break in, function test, rough zero, etc. I also started with the gas block fairly closed down. Shot several rounds, all of which failed to pick up a second round. It was ejecting the empty case. Even with the gas block opened all the way up, it would not pick up a second round from the magazine. I switched over to my handloads, which consists of Hornady 168HPBT in LC brass over 42.0gr of IMR-4064 and a CCI-200 primer seated to 2.800". These cycled perfectly, picked up a second round properly, and locked back on an empty magazine. Out of 50 rounds of that load fired, there were zero function issues.

So, should I be worried that my rifle won't run properly on ZQI? I've found some other users that have had issues with this ammo doing basically the same thing. It's certainly not an ammo I would be using on a regular basis, but I think I'd feel better if I new the rifle would eat anything.

Here's my buddy on the left shooting his SR-25 and my FIL on the right shooting my M5E1 at 200 yards. Sorry about the wind, it was blowing 30mph and gusting over 40mph.

[SINNER]

One thing I can say with certainty is that the Syrac gas blocks still flow less gas wide open than a non adjustable gas block. I took a junk piston system off a Blackout with a 16" barrel due to intermittent function issues. Put on a regular gas block and it functioned flawlessly, although over gassed with supers. Swapped in a Syrac block and even with the block wide open the rifle would no longer cycle subs with the can off. Reinstalled the standard block and the rifle functioned perfectly again.

[DutchTerror]

This is the first build that I've used an adjustable gas block and the first build that I've had gassing issues. Half tempted just to put on a standard gas block... Thanks for the info.

[Brahmzy]

Sounds like you might have a smaller gas port to begin with, in addition to the Syrac slightly restricting gas flow. Try a new block as mentioned, and as you're disassembling, make sure you didn't cover up part of the hole forward/rearward-wise. This is often missed as blocks are supposed to sit 1mm or so off the shoulder.

[DutchTerror]

Sounds like you might have a smaller gas port to begin with, in addition to the Syrac slightly restricting gas flow. Try a new block as mentioned, and as you're disassembling, make sure you didn't cover up part of the hole forward/rearward-wise. This is often missed as blocks are supposed to sit 1mm or so off the shoulder.

I did set the block off of the shoulder, and I used the set screw hole for alignment to create an index mark. I don't think alignment is my issue, but I'll definitely be checking it. I'm wondering if it is a combination of the Syrac and a slightly smaller gas port in the barrel. I also emailed Ballistic Advantage to see if they have an opinion on adjustable gas blocks. I doubt I'll hear anything useful back, but it can't hurt to ask.

At this point, I think I'll take the Syrac off, check the current alignment (it should be quite visible after 50 rounds, right?), measure the gas port, and swap in a fixed gas block. It definitely felt softer shooting than my buddy's SR-25. Probably a combination of factors, but it might be as simple as using a rifle buffer and spring vs carbine (or whatever is in the SR-25 by default).

[DutchTerror]

Pulled off the Syrac gas block. It looks as though it was properly aligned. I've swapped in a standard gas block. We'll see if ir makes any difference.

[nijikon84]

I've had issues cycling the ZQI stuff out of my 16" LaRue 762 PredatOBR. After 50-100 rounds of that stuff, the BCG/Chamber seems to get a bit more dirty also.

Someone else was also having issues with that stuff with their SR-25 APC, their quick fix was running the Tubbs Flat Wire Buffer Spring. I tried it and it actually made it worse.

My fix was mostly lube related, running either Weapon Shield or Machine Gunner's Lube.

[DutchTerror]

Thanks for the info. I'm thinking there may be a chance that the rifle needs some break in. I ran it very wet, so that should have helped. I won't cry if it doesn't run the stuff, but it would be nice to know the rifle could eat anything.

[nijikon84]

I feel you, bud.

I just wanted my gun to be able to eat everything also. However, I should take some consolation that it shoots .3-.5 MOA 5 round groups @ 100 yards with off the shelf FGMM.

If you still have issues, you could always try a Tubbs Flatwire spring.

[DutchTerror]

Ran the rifle again today with a standard gas block. The ZQI ammo ran fine, picked up the next round, and locked back on an empty mag. I did not test for groups, only function.

I also got to stretch out a bit. MIL checked a 24" target at 1 MIL. MilDot Master told me that was 670 yards. Verified afterwards with GPS at 676 yards. Dialed in elevation and was on steel on the first shot.

[SINNER]

Same as a non adjustable block when it's wide open my ass. That is at least the fifth time I've heard of this issue with adjustable blocks. And not just the Syrac blocks.

And you still hear people claim adjustable blocks are fine on a duty gun.

[DutchTerror]

Yeah, I won't be going back. I've run at least 10 builds now with a standard block. I thought I was doing the right thing by trying to turn the gas down to soften the cycle. I'm convinced now that adjustable gas blocks only belong on race guns.