98Z5V

That is a REALLY smart approach to take - that's awesome! Learn what you can ahead of time, then figure out what you want to do and which way to attack it - that's damn smart. Welcome aboard.

That's a pretty damn great idea, right there.

You can see the node coming in, towards the 23.6gr charge. Run that one,and run another test - higher by a 0.1gr or two. I've never seen anyone run ladders at 0.1gr spread - that has to suck. I run them at 0.3gr spreads, narrow in, then run than at 0.2gr spreads. I stick with the 0.2 that works the best. The only other time I've deviated from that is running my 5.56 75gr Hornady BPBT loads at 0.1gr, then finalizing. I will probably do that with my Win Mag, as well (0.1gr spread) as it's the only one I've got.

The B&T platform is amazing technology. Very solid. I only wish I could justify spending the $$$ for one. They're badass.

Any pistol caliber AR that you guys make, that's blow-back operation, better have some KNS anti-rotation pins in it, or you're breaking a hammer pin. Mark my words. I have a 9mm and a .45ACP.

Not yet. Armalite AR-10 Carbine gas(longer than AR15 midlength) on a 13.5", though.

Yeah, then those fuckers HACK the PSA website, find all orders for standard-capacity magazines destined for CA - and they have a "list." Not long after that, they start the no-knocks, and kick your door in to raid you...

There absolutely MUST BE a correlation to that slot in the mag body, and the centerline of the BCG. No other way around it. I have no idea what that measurement is, but you could find it from Armalite AR-10 prints - because it is the original, and it always works. The reason there MUST BE a correlation to that, is - the bottom of the bolt face has to strip the next round out of the magazine during the cycling process, when the magazine is seated and locked. The bolt face takes this force, because of the cam pin - the cam pin isn't allowed to rotate until it gets to the cam pin cutout in the upper - that bolt is locked in place in the BCG body, extended, while the cam pin is traveling down your charging handle groove, in the upper receiver - it's solid, not moving into the BCG body - and stripping the next round. Now, there will definitely be some variance, or tolerance, in what's too high and what's to low, in the relation of those two parts - but it can't be much. 20-thou? 30-thou? I don't know. Within limits, manufacturers can do whatever they want for mag catch placement in the lower - as long as they are within that range or tolerance in BCG centerline over the top of that mag catch. And it will work. They are working within the limits of their own upper AND lower receiver dimensions to achieve that distance between those two parts. If a manufacturer fuks that up - your gun doesn't feed/strip the next round, OR the BCG slams into the back of your mag body. It can only be those two things. This is the beauty of "not having a standard or pattern to follow..." I will measure the 4 previous rifles I listed - Top of mag catch to BCG centerline. I'll bet it's pretty close on all of them, despite having a difference of 30-thou in mag catch placement over the 4 guns.

The top of the mag catch is what holds the mag in place. Now, a slot that's way too wide (over 0.250") would allow the mag catch to "rotate" down in the too-wide slot, which would effectively lower the seated height of the mag. But the top of the catch is what determines mag height - and retention. A fully loaded 20-rd LR/SR-20 PMag weighs 2 lbs. The top portion of the mag catch itself, and the top of the indentation in the mag body, is what determines the height of the mag when it's seated. That business is all determined by the top of the mag catch, and this - this is what the 2lbs hangs in the gun from:

This looks like is might be pretty good...

There are still some great companies out there. I'll pick up a few Hex Mags just because of this.

I've got a couple of the extended scope mounts, and one extended 30mm red dot mount - they're great.

This is directly for @jtallen83 I saw this guy on the way in to work this morning, and I immediately cracked up, thinking about you, brother... Custom flatbed Dodge diesel, built by the sound of it, and some giant welder permanently mounted to the flatbed... Obviously, he's making good money... Check out the bottom of his mudflaps...

So, is this thing solved, man?... It functions now?...

Go hit my past posts here, man, and fire up some answers - what uppers and lowers are you working with here? This is the ground-truth, right here, in mis-matching manufacturers. I stand strong on this one - THAT is the major problem here...

I was only stating the measurements of the guns I could easily get to, and reported exactly what I saw on the guns I have. They all run, or I'd chop them up and sell the scrap, man. Personally, I was shocked at the differences I saw, because they all run like mad. The numbers I got were way off that first print number or 0.687", too. But they run... I don't have a single one that has a different upper than the lower, though. Same manufacturers, but way different numbers in mag catch placement. Of note, on measuring AP lowers - you can't accurately measure that lower if you don't disengage the mag catch, and rotate it out of the way. The AP lowers have a taper/chamfer on the top side of the lower shelf, that you can't accurately measure, if that mag catch is seated...

A manufacturer can put that mag catch placement anywhere they want, within obvious limits of the platform, brother. As long as they account for that "higher or lower" placement in their exact placement of that BCG channel that they bore in the upper - on their own upper that mates to that lower. They can literally do what they want, within functional limits. When people try to match different uppers and lower from different manufacturers - is when we see these issues. Or, you try to by an IRA billet machined matched set that never worked from the get go, because the dimensions were off, fundamentally...

From @panel77s history, he started with a PSA upper, and machined his own lower from Blitzkrieg or AMT, if I'm not mistaken. So, right off the bat, you've attempted to adapt a self-proclaimed proprietary upper onto an 80% lower, that you machined (or someone machined). And, there's a question as to why there are issues now.

I tuned out a 0.640 on my Matrix tonight. That thing runs like a champ. I also measured a few 0.660s and a 0.670 from the same exact manufacturer, with the only difference being - matched sets versus rack-grade parts. Is there a difference on what they make? I don't know, but that 0.670" measurement was from the first AP that I ever built, quite awhile ago. All the ones I bought after that were matched sets, but were all at 0.660". Did a machining operation change, somewhere? I don't know. But they all run - because the builder of the lower, with that mag catch-height spec that they made - also machined the height in the upper for the BCG placement. That's the only rational way I can explain why I have a rifle with a mag catch of 0.640" that runs like a champ (same upper), and multiple rifles running 0.660" and running - another with a 0.670" and running... And the distance listed earlier in this thread was 0.687"... So, in one gun, I can be almost 50-thou off of a published number - but that thing runs like a champ, with the exact same mags as all the other ones, with a spec that doesn't meet that number of 0.687", and is under by about 30-thou - but they work?... Great!... One of those 0.660s is my hybrid-bastard-from-hell, too - the 13.5" Armalite/DPMS/Aero gun. That thing will eat any ammo I can fit in a mag. The issue here is the different manufacturers of the parts you're using - and the blatantly obvious fact that there is no "spec" on these things. That's the real problem here. Pick a lower. But pick the same upper. Stick with what "is supposed to work" instead of piling parts together. I'm off my on this - but I still want the details on the parts you've tried. That will tell future members what to stay away from, on combinations that don't work.

I certainly didn't quote you in that, man. No, that was not you...

First - in red above - I certainly hope you're not talking about me. But it you are, then let's just drag that out and get it done with. Next - what upper and lower combination are you running, from how many different manufacturers, and what are you expecting to happen? Please list, by manufacturer, what exact upper, and what exact lower, that you've tried to use here - and what the failure was, with each combination? It's pretty common knowledge that you should use the same upper as the lower, when you build these things, and hoping for a perfect rifle when you mis-match this shiit it pretty much like playing the lottery. ^^^ This tells me alot about the combinations you've tried. I have difference measurements in my lowers - with the different mag catch placement - but they all work with MagPul 20s over two different Gens, and with Lancers. Because I'm using the same uppers, as my lowers. That's MY observations on this mess...

You seemed a little pissy in that post. I understand, kinda - but you need to understand that we're here trying to help you out. So, on that note, you need to give up alot of information. Please allow me to respond, again, before you do - and I'll make my points. I wanted to address this first, though.

I had to shave and cut and polish a bolt catch to get it running, on one of these. I'll try to find the info on it. There are pics up and everything, with measurements of what I took off, and what finally worked. I swear it was that first AP that I did, but I built that Matrix right after that one, too, within a month or two - it could have been that Matrix. I'll find it. I know a couple guys here saved my ass on that Matrix, and sent me the pivot and takedown pins for it - they're different from everything else. @blue109 sent me one, and @jtallen83 sent me the other. Those guys are the only reason that gun is pinned together right now.

One interesting thing I didn't mention about these guns - never had a feeding issue, not even one, from MagPul 20 rounders , either 2nd Gen or 3rd Gen (there was no 1st Gen .308 mags from them), or from the Lancer mags. So, with those difference specs on the mag catch placement, MagPul 20s and the Lancers work just fine. Zero feeding issues on those platforms listed above. I had one hell of a bolt catch problem on one of these things, and I can't remember which one it was. It certainly wasn't the original DPMS LR-308. I think it was one of the Aero setups, but it could have been the Matrix. I documented it here, but I don't know what one it was now...

Any one interested in a .375 CheyTac? I'm only asking because I promised to ask - for my Gun Pusher. I talked him into trading this for a SCAR Heavy that he had. He didn't get the optic. This is not a typical .375 CheyTac that you can "click and order" from Cheyenne Tactical's website - and you can see that in the pics. THis one was custom ordered, and the previous owner had to wait for it to be built. My GP already bought the SCAR Heavy, and paid for it - the buyer that wanted it backed out, his Net-30 went by, and he had to pay it off - so he owned the SCAR. This was an even across trade, minus that bitchin' NightForce, so he now owns the .375. He will sell it - and I don't want him to. I'm still working on the "sweet talk" of "you know, this is already paid for - you owe NOTHING on this gun..." We will be "Demo testing" this thing real soon. We found a farmer a little further south that has over a mile of flat, unobstructed ground, and will let us on there anytime we want. I think we have to pay him back by shooting coyotes when he needs it. Uh, BONUS!... So, officially, this is for sale, but I don't want it to be for sale... If you guys wanna shoot this beast at the Fall Shoot, then DON'T BUY IT!!!... If you guys know anything about this cartridge.... WOW! It's THE distance crusher...