blue109

I've got that same 2 1/8 measure as you on my Matrix upper and the same Anderson carrier you have in your pic.. Looks like the KAK carrier just doesn't have enough relief cut into it.

BCM slipping? Thought they were suppose to be the milspec masters!

Some of those definitely look like the cutout is closer to the bolt than yours. Several of them have the gas ports in the cutout, your gas ports are on the flat logo part. I'll check mine out when I get home.

Glad you got part 1 figured out. Carrier looks like it's seated just fine so I'd guess the way they shaped the cutout just doesn't play nice with that upper? Maybe that ejection port is slightly further back on yours that whatever upper they tested with? Take a measure from the front of the receiver to the detent on the door and we can compare.

Lol I edited back a page and tagged you to see if you could move this stuff to my thread. Could you split it from Tom's and then merge it with mine? Just a thought for continuity sake

The rail works as-is, It's just pushed forward too far and isn't quite perfect. I don't think it's fully seated in the slots like it should be and that destroys the whole purpose of the build....So looks like I need a slot cut.

It's not an optic issue. I am an optic mount guru. The low aero is still too tall.

Do that all the time. I have 25yds marked off in my back yard and an X painted on the wall. I use a step ladder as a bench.

I don't need offset mounts with my guns...They have continuous top rails and all of those push the scope too high anyway

Primary arms has a good sale on ADM mounts at the moment if you plan on jumping ship. I'm going to do my taxes tomorrow and see if I can swing a few

This is the mega...Perfect fit. The matrix is the same setup but the entire rail should be one slot further back but it can't because the upper seems to be one slot short

The optic isn't the issue, it's the SPR sleeve touching the rear sight. The rear sight is too far forward. The sleeve and the sight both need to be a slot further back than they are right now.

That explains that lol. It still works, it's just not optimal. Hey @MikedaddyH or @shibiwan...Feel like cutting a slot for me? One more bit of info to add to the Matrix files

Have you tried removing the bolt from the carrier and just seeing if the carrier will line up with the door or the rear that way? Snap some pics of those areas. Pics of the carrier in the upper from the bottom and from the ejection port for reference

I have never checked a 5.56 gun, and only buy reputable 5.56 barrels/bolts. 308s are another story. No standard means headspace can vary by manufacturer. You are pretty safe buying from the big guys, but there are ALOT of small operations making 308 parts

The barrel doesn't rotate, the barrel nut does. Shims to correct a headspace issue would need to be ridiculously thin. No way you could make them durable. Edit...Re-reading this it looks like you mean shimming between the extension and barrel? That would require the barrel to twist I suppose, but I'd guess the same issue would apply.

Oh poop...?

1:9

@shepp any way to do some moderator magic and cut from here down and stick it into my matrix thread? Unclutter Tom's build and add it to where it's relevant? @98Z5V or anyone else with a matrix gun and other make 308. Can you do me a solid? Line your matrix gun up alongside your other brand, and tell me if the first rail slot closest to the charging handle is in the same position for both guns? Are all the rail slots in the same place in relation to the front and rear of the receiver? I seem to have a clearance issue with my SPR top rail almost touching the rear sight but I can't move it back any further. It's in the last slot. I don't think this was an issue with DPMS

My dissy/ASA upper has the armalite clamp on FSB. I laser borsighted it , and with the rear KAC sight dead center, but noticed later that the FSB was definitely canted a little. I got the FSB to where it looks perfectly centered and the rear sight is pushed pretty far right but the aimpoint lined up right with the front post. Both configurations were confirmed with 55gr ammo on paper at 50. Both worked at that distance. It really bugs me with the rear being off center, but the FSB was worse. I guess as long as it's zeroed I can live with it.

Sexy. The ARF dissy picture thread has pretty much every combination possible.

Having so much fun with this

Racists

Yeah...Something not right there. No experience with the LRP but you don't need to break a mount in. It works or it doesn't. Is this one you can set the tension before you clamp it? It's possible to be too tight. You shouldn't need to crank it down to close the lever, the cam is suppose to do the work. Also are you pushing it forward hard into the slot while tightening it?