98Z5V

^^^ You are WAY good on that receiver extension. By FAR.

PM system works well. If he can't receive PMs, you might be SOL...

Yes. However, you could creatively chop the one you have, and it'll clear to fit.

DAMN!

I almost bought a new Sig M400 SWAT (LE/MIL-only model) today... I'm just sayin'... https://www.sigsauer.com/store/sigm400-swat-ap.html

MagPul MOE K2 grip - you'll like it. LaRue MBT-2S trigger - can't beat that thing for the price($125), and I like mine alot. Start with the Primary Arms red dot, this one: http://www.primaryarms.com/primary-arms-micro-dot-with-removable-base-eta-early-july-2016-md-rbgii Muzzle device - you ever gonna suppress this thing? Or just want a decent comp on there? Or, want to eliminate all muzzle flash? Talk to me, goose!

^^^ Exactly so. Gonna be tough to eyeball boresight a scope on a slug-only shotgun. Fastest way on that is laser. Same with "aiming aids" on pistols...

Just make sure that receiver extension is screwed into the lower far enough to properly capture the buffer retainer. If it's not, that buffer retainer WILL shoot out, while shooting the firearm, and it will jam something up, causing you grief... On the other issue with the port door - I'd grind the leading edge of that port door ball-and-detent housing, if it was mine, and test it out. I think that's the issue, as pointed out by others. Port doors are easy to replace...

Nah, you're good, brother. His last post was 31 Jan,and the last time he was here was 31 Jan. I was hoping he'd come back one more time to list his trigger in the For Sale section, but I don't think he'll be back anymore... Sucks, too - I was gonna offer him 50 feet of used garden hose for it.

^^^ That was part of Colt's "self-imposed ban," wasn't it? Along with larger trigger/hammer pins, and different pivot/takedown pins?

Who knows? There are tons of companies that offer front sight bases... I probably can't even name them all, after hours of searching company names... I doubt they all train the people that assemble the barrels, though, about a specific direction for installing front sight base taper pins - just ream the holes with the tapered reamer, and smack the pins in... I can guarantee you that the only two companies that will do it exactly to the M16/M4 TDP, every single time, will be Colt and FN...

That technique won't work on pistols or shotguns. But, my laser boresighter does.

He's not reading... Just replying...

Other rear sights also work, like the KAC, the DICK Swan, but not many... Because of the shape of the back of that PRI Continuous Top Rail... Tell me you get it now... You gotta...

See the rear sight inferface with that top rail?

See this Mk 12 Mod 0 here? It's the PRI Continuous Top Rail. That rail goes in a specific position in order for it's cutouts to clear the barrel nut. Now, PRI also makes a rear sight that matches the taper to the back of that top rail. Issue - Matrix .308AR upper receiver needs ONE MORE PIC SLOT at the back of the upper receiver in order to mount up the PRI Top Rail. Comprende?...

It's not in the optic mount, Mike. At all.

Yep. Can't remember who, though, but I chimed in on that, too. I had that issue on my Spike's 5.56 billet set. Had to install a Tubb CWS to cure it. Caught it when it started chewing the hell out of the face of my buffer.

Get some pics of the interference and what's wearing, where... That'll help. Sounds like it's all at the back of the upper receiver, or bolt-to-buffer. Just so you know, the bolt DOES push the buffer off the buffer retainer pin, ever time you close the receivers. When the rifle is closed, that buffer never touches the buffer retainer pin. If it did, during operation, it would shear that pin right off as soon as you fired it, and it recoiled, and closed on the next round.

FWIW, after it's zero'd, it won't need to be adjusted anymore. Would it not get to a zero-state the way it is now?

You're good, Dave - you're busy enough as it is, and that's understandable. People can PM you, as well.

Military rifles will all be assembled the same way. FNs and Colts. "Mil-Spec" doesn't necessarily mean that other manufacturers will still go in from the same side,every single time, with those pins. Just that they use taper pins to secure the front sight tower. Find the small side of those pins, and hit the shiit out of them. Hard.

TOTAL? Or, RIGHT NOW?...

HAHA!!! I love the ending!!!!

Bad news, brother - DEFINITELY DIFFERENT. That first Pic slot on the Matrix is easily 3/8" further forward when compare to an Aero Precision 308 upper. Aero in the front, Matrix in the back. Can't find my calipers right now, but the last pic is the difference in measurements between the back of the upper tang and the edge of the first slot in the Pic rail.