Here are OP's pics.

OP, any updates.i just got your PM. Like a month after the fact. Your barrel is adjustable, not self regulating.
Mines been running great with the exception of breaking a disconnecter. Which was strange.

I hope everything well. You never  said what you paid for the unit, but if you haven't smashed it or sold it..i got a line on good used ones.. also if you haven't molested it yet i might make an offer or trade, contingent on inspection.


Edit..
Use code "LD2017" through 9/5 for 20% off and free shipping


Just got emailed the promotion.

MCR-036S

Short heavy adjustable barrel, good feed tray no sites....3,057.60 shipped

hammer slap from piston guns does this. I haven't broken one but I've have them damaged badly from it.

Damn where was that code from MG noob?

I got mine back last week. Just looking it at, it doesn't really look like they fixed much of anything. Appears to be the same gas block and barrel. I suppose they just beat the pins in with an extra big hammer and called it good. {it looks like it leaks gas between the block and barrel}

But it does function from that aspect of it now. So that seems ok i suppose. Interested to see if the gas block shoots loose again. {i have my suspicions}

Delinking is maybe a bit better. But it still stops trying to delink. you can reach in and push the bolt forward with the slightest of effort to get it home. So i figured its just ever so slightly under sprung still.

I pulled the buffer spring and spacer, and started tossing quarters in the buffer tube.  Im up to 7 quarters, the gun pretty much functions flawlessly by hand. The bolt catch is catching on the carrier not the bolt at this point.  

Ive ordered an MG34 spring and hope thats what I'm looking for. The Springco Orange and Fight Lite aren't quite cutting it.

So with some more spring tuning i hope to have a 100% runner. Will keep y'all posted on the progress.

p.s. the feed tray is eroding at an alarming rate.

The factory spring is designed to be used in a collapsible stock.  If you are using it in an A2 stock you need to use the factory spacer or an equivalent one to compress the spring more.  The factory A2 spacer is 2.7" long, so you are going to need quite a few quarters.

Needless to say, you won't be able to use a full-length buffer if you do this.  If you are currently using a carbine buffer in your A2 stock, you are risking damage to the lower receiver as the roller assembly will hit it as the gun cycles.

If you want to use the full-length buffer in the A2 stock, you will need the MG34 spring, clipped to give proper functioning.  I was using one for a while with an LMG buffer for a nice slow cyclic rate and it was working well cut to 34 coils.  FWIW

it sounds like you dont have enough space in the tube. That will slow it down which will cause FTfeed

Ironically 7 quarters is my preferred amount of shim for alot of my hosts .
I cant say in recommend it for the mcr though...you want maximum travel while avoiding contact with the receiver.
Verify your buffer tube is in spec, ive seen this issue before.


Im glad to see you sent it back and they did something..
Now that you've gone through the motions if it comes loose again i would like to think theyll fix it replace it.

I wish i used that discount code, but i dont have endless money maybe soon a  sale will be below 3k.
At some point ill need another.

Strech your links and spray them with silicone spray... i run mine almost too loose... its the way to go.

I have both the spacers for both length tubes, so thats not the issue.

The fight lite spring is just a hair too soft for my setup.

I looked at what they did to it a bit closer today and noticed they did polish the upper feed ramp a bit, where it drops the belted round down. There are actually two sort of horns formed by where the lug notch and barrel detent hole bisect. I kind of wish they didnt do any grinding, as it looks like there will be failure area there in the future.

I got a new contract mg34 spring from RTG Parts. Its a bit looser wind and heavier rate than the fight lite. I clipped it to about 32 coils. Real close in length to the fight lite spring. Maybe a hair longer.

Now when i row the bolt, i can delink each and every round, without slingshotting the bolt handle. I can row it quickly, keeping my hand on it the entire time and delink and chamber each round.

I left the gas setting on #3, with the mg34 spring, car stock and thin spacer i took it out and fired one round from a belt into my trap. It ejected, delinked, fed and chambered the next round.

I will go run another couple belts this weekend but i THINK this is going to be the sweet spot for me.....hopefully.

Heres a quick video from last weekend. The first belt was nothing but trouble. This is the 2nd belt, i pulled it out the nut sack, hit it with some rem oil. i broke about 30 rounds or so off this belt, so this is only 70ish.



https://youtu.be/AGxVHNOIDwg

if its in the aluminium stop shooting that thing now and get the feed ramp from Mark Genovese

If you dont have it get it anyways

I will have to look him up. Ive heard of the thing he makes, but not sure what in the world it is exactly. lol.

But no, FL didn't grind on the aluminum, just down in the barrel extension closer to the chamber side. Not much grinding really, more of a polishing i suppose.

I pulled the 3 position gas plug, they drilled those holes way out. I haven't measured but the largest hole is probably .030" bigger than it was.

FWIW, Jeff Zimba has a three-part series of videos out on his "Big Shooterist" youtube channel on the SCR.  In the third one he demonstrates firing with a 200-round belt hanging freely from the gun.  I haven't watched the first two videos, but there might be some info in there you can use.

I did that as well, if its too much the tip of the bullet will pass and not get deflected into the chamber and the shoulder will hit and jam the gun.

get the feed guide, it helps a lot IMO.

here is a pic, you can see where it hits on the guide, vs near the lugs. I think the gun runs better with it, as the rounds dont hang up on the lugs as much

Ahh, i didn't expect it to go up in the top cover. Makes sense though. Ill have to pick one up for giggles and see how i like it.

I took the shrike back out today with the wife and kid.

Fucking thing ran like a hot knife through butter. Ran about 500 rounds through it, 300 or so from nut sacks. Zero Issues. I did have the gas turned off for the first shot fired, my mistake :D

MG34 Spring cut to about 32 coils. 31 or 32 i can't recall, ill pull it back out it count them. I think i could cut another one or two coils off it and still run 100%. I might give that a try, since these are repop springs i don't mind hacking them up.

*OVER GASSED*!! Holy crap man! the holes they drilled out are surely large enough! The buffer is coming back HARD against the end of the tube. First time a 556 bruised my shoulder.

Im going to mess with the gas settings a bit and see if i can't tone that down. Its definetely running Fast and Reliable right now. I think with a little more tweaking we can reign in this beast and refine her a little bit.

I went to chop off the barrel last night, but didn't have any OD un28 inserts. grrrrr. live by the carbide, die by the carbide. Plenty of ID un28's though....just to add to the insult.

I will try the other gas settings, but I'm going to chop the barrel down to 12.5 before i worry about it too much. The chop alone may be more then enough to settle down the rearward bolt velocity. That mg34 spring is like a wet noodle with as much gas they got running to it....i was shocked. I expected it to be under gassed for that spring. But nope. Away she went.

Next up. Dry Links!  Fwiw I'm using New Manufacture M27 links fresh out the box. i get em for 35/k from UNAMMO. I figure if it won't run with off the shelf linked ammo, i don't want it.

https://youtu.be/IaqjSf1-0zQ

I bought a spare 16 inch  barrel on the Labor Day sale and recently got around to trying it out. With magazines it ejects but the bolt does not  not go back  far enough to strip an new round. I have tried a working gas plug and piston with the same results. The gas block is tight and the gas port measures .078.

Should I drill it out?

With my original barrel it works great. 200 round mag dumps no problem. I have had to stretch links to get it to work reliably with links.

I stretched the links to the maximum specification, 9.242 mm or .364 inches

I messed with a trigger pull gauge to determine how much force is required to make my upper work reliably with links. New links require about 8 lbs to strip links and I found that under 5 lbs works well.

If stretched much more they loosen up too much after a few firings.

Which spring are you using? Really sucks how temperamental these guys are.  I wonder how much it would cost to have a batch of links permanently lubed with NIB or some other coating.

I am using the shrike recoil spring with their aluminum 1/16 inch spacer with a Colt H2 buffer.

dont loosen them anymore, you have a gun/gas problem.

what ammo? tried different types?

I would try a different spring, a older used one before drilling.

get the gun to run to make sure you have a gas problem vs a feeding problem

I got that.
it works fine with the original barrel, 750 rpm on setting 3. It even works (mostly) on setting 1.

Withe the new barrel it the bolt wont go back far enough to lock on the bolt catch when fed from magazines on any gas setting.

It is  a barrel problem.

i sold my shrike a long time ago, i can't recall.... can anyone tell me if the extractor itself is shared with the AR15? I have one on the way and im buying the extractor spring and want to buy a new extractor too just in case.

also, for anyone having to "stretch" the links... i have said this since the day i bought mine(once fired surplus links) you dont need to stretch them. they need to be CLEAN. wet tumble them if you can for 15-20 minutes, then dry with a fan or air of some kind. NO LUBE ON THEM OF ANY KIND. they ran like a scalded dog through my last shrike. not a single link problem.

What type of liquid to use for wet tumble?

water, dawn dish soap, stainless steel media pins.

oh..... I see

It didn't work for me. Your mileage may vary.

it worked perfectly for me with used links. my links wouldn't feed worth a crap before they were cleaned.