biggulp

I run a TTI +11 and 1 spare 30 rounder modded to 34 but I'm not even sure I know how to reload that thing on the clock I do keep an extra mag pouch in the range bag in case there's a multiple reload qualifier.

If it's going to be a match gun then an aluminum bodied C-More is pretty much impossible to beat. Click switch for positive on/off/brightness adjustment, any dot size you want, huge viewing window, and good battery life. When you're rounding up the spare mags, be sure to grab a couple of TTI +11s. Only downside to the setup is that you may forget how to do a reload As others have noted, a lot of the reliability issues that get talked about were with the non-PCC version and/or are self inflicted. If you run it with factory guts and keep it lubed, it'll be rock solid. Start dicking with springs and the gas system to chase mouse fart loads and you'll probably hate life. Mine runs everything from hot 115 nato stuff to the Syntech action pistol stuff flawlessly. My last couple of matches, I've used my BORA (bag of random ammo) which is a mix of Magtech, Blazer, Federal, WWB, etc., in everything from 115-150 grain. Mags were loaded with random handfuls of ammo and aside from the syntech stuff (red bullets) I had no clue what I was running. MPX didn't care as I ended up 3rd and 6th out of about 75 shooters

If you want to mess around with swapping weights and working up specific loads and all the other "tuning" get the JP. If you want to load mags and shoot and have basically zero dot movement, get the MPX. I had a really well tuned QC10 build. It was nice and accurate, but no amount of tuning made it "soft shooting" because that's just the nature of direct blowback.

Completely relax your arms and hands at your sides. Now slowly raise your dominate arm so it's pointing straight ahead. Chances are pretty close to 100% that your hand is not vertical. In theory, keeping that natural alignment/slight cant when shooting one handed will allow for better recoil control. In practice, the gun still moves, just in a different direction. Would likely take a LOT of rounds down range to re-train and realize any gains from the change.

If you want to use a QD mount for your Sandman, you'll either need to send the barrel to be properly threaded (Class3Machining was about $70 total last time I sent one) or take your chances with a jam nut and just hope the device/suppressor ends up concentric to the bore.

Phantom triggers are supposed to be available this month, so there will be real world reviews by the time you're ready to buy. That being said, if I had to pick today, I'd vote Phantom. It's supposed to be designed to run in the MPX

MPX mags are ~$15 more than factory G17 33 rounders. Yeah, it stings up front, but it's basically a one time expense.

MPX recoil impulse with any ammo will be more "forgiving" than any blowback gun with that same ammo. Does that matter when doing static drills with a perfectly tuned blowback gun? Probably not, especially if you've got thousands of rounds behind the trigger with that blowback gun. Does that matter when you're on the clock, running through a stage changing levels/distances/target types (mixed steel and paper)? Absolutely. Does that make the MPX absolutely superior to a blowback AR9? Nope.

L&M Precision can convert the X5 to RMR foot print for $45. Not sure if that applies to the newer ones, but worth checking out.

I ran a Kaw Valley gen 2 BCG in my Colt pattern AR-9. Only issue I ever experienced was a broken firing pin which was caused by the Hiperfire trigger I was using at the time. Should also note that I never experienced a failure related to the bolt. Discovered the broken firing pin during routine cleaning. It had been ~500 rounds since the last cleaning, so no idea how many it fired wihle broken.

Give the Timney a chance. Mine broke at 4.5 lbs out of the box, but after several hundred rounds it's closer to 4 on the guage and feels lighter than that.

I've used CLP on everything that required oil for the last ~15 years, I have not found a reason to try anything else. I've got an M16 that has been through a LOT of 1,000+ round range days with most of it being suppressed. If CLP was going to fail, I'd have seen it. I will say that after a long day of suppressed full auto, when I'm caked in blowback I do wish it had that minty fresh frog lube smell

I run the Comp-Tac pouches. No issues with retention/removal with 41 rounds of Sig/TTI goodness. Used the Colt mag version of the Comp-Tac pouch last season with 1 on the hip and 1 horizontal in front and never had a problem.

Most of the problems I've seen with PSA PCCs have been related to the ejector angle and have been easily corrected.

"Because I can". If you feel like you have to justify your purchase/ownership of any firearm to anyone (other than a spouse who may be impacted financially), you're doing it wrong.

I built a ~5.5 lb blowback AR, ran it for a season, and loved it. Decided to switch to the MPX platform for less dot movement, it's about 1 lb heavier, but totally worth it.

See if you can find someone local with a sight pusher. Removing sights isn't rocket science, but I've seen to many "slips" that resulted in nasty marring.

I'm a big fan of the CompTac PLM pouches.. They're well built and did a great job holding fully loaded Colt pattern mags horizontal on the belt while my uncoordinated ass plodded along.

I have that buffer with a carbine buffer tube and ~2,500 rounds through my build with no buffer related issues. ETA: Check the QA section of the Brownell's listing.. It's designed for a carbine tube. https://www.brownells.com/rifle-parts/receiver-parts/recoil-parts/recoil-buffers/ar-15-fm-9-heavy-buffer-sku100024850-105914-203715.aspx?rrec=true

I.D. is 1.95 x 1.4 O.D. is 2.2 x 1.6 (not including the height of the short section of rail at the muzzle end) ETA: that o.d. was from the bottom of the muzzle end which has a short protrusion. O.D. not including the section of rail or the protrusion is right at 2 inches

Measuring from the lower half of the muzzle end: To the far end of the hand guard is 15.75 inches To the point where the top of the receiver ends is 12.125 inches I don't have a scale, but in a other thread I saw the weight listed as 11.2 ounces

Made it to the range on Saturday afternoon and ran 250 rounds though the MPX and I'm pretty well thrilled with the way it handles. Double taps were unfairly easy, and a 30 round mag dump as fast as I could pull the trigger resulted in a ~2 inch hole in the target at 20 yards. Of the 250 rounds, 200 were S&B 115 grain stuff and the rest were Magtech 124. In my AR9, the 115 grain stuff caused significantly more dot bounce, but with the MPX even when I mixed them up randomly in the mag, I couldn't tell a difference. Next stop is ILWT to pick up some spare parts. Is there any reason not to go with their spare parts kit vs. buying individual bits?

Quite a bit, actually. For ~$1,600 street price, you get a 4.5 lb Timney trigger with no creep, a handguard that weighs 11 oz and is comfortable, and a useful stock. It's something you can buy, clean, throw a red dot on, and go shoot a full season of matches with. Or, you can buy a gen 2 for ~$1,400 street price, get a trigger that most feel has to be replaced, a handguard that isn't exactly suited for competition, and a stock that definitely isn't built for comfort. Most definitely not something you will want to throw a red dot on and shoot a full season of matches with. On the barrel thing: If you want to play with brakes/suppressor mounts, it's fantastic and that wasn't something you could do with the pinned/welded barrel. If you absolutely HATE the extra length, you can select the exact brake you want and have the barrel cut and the brake pinned/welded.

Thanks for all of the information! Got my hands on the MPX last night and it's pretty darn nice out of the box. Hitting the range this weekend, but here's my observations/opinions so far: - Feels a little front heavy compared to my AR9, but I expected as much as that's a 5.25 lb build with a ~19 oz barrel. - Trigger is exactly 4.5 lbs over a 10 pull average and no creep - Stock is surprisingly comfortable but I'll withhold judgment until I've put a few hundred rounds through it - RTS2 was to low, C-More on AD-QD mount was to high, and C-More on the factory base is perfect - Love the ease of disassembly Ordered an Odin mag release and some TTI +11s. A magwell is on the list, but I want to practice reloads for a bit to figure out if the Springer will work or if I have to go with a full sized. On a side note, Sig must have run out of oil the day they built mine, it was pretty much bone dry. A good cleaning and lube and she's ready to go!

Last season, I ran a QC10 Colt pattern build (QC10 upper/lower, KVP barrel/bolt) and after switching from Hiperfire to a Timney drop in, it became boringly reliable. I'd clean it, run a practice session (~200 rounds), then a match (~250 rounds), then repeat. Over the entire season, I never had a failure that wasn't related to the Hiperfire. As much as I loved it, I wanted something a little softer shooting and didn't want to fight with tuning which always seems to introduce function issues. For some reason, the new MPX PCC has really grabbed my attention. With matches starting in about a month, I decided to go ahead and grab one so I could get some range time with it. From you guys who have run the MPX platform in matches, is there anything I should know or look out for? I've got the MPX and 4 extra mags coming. It will wear either a click switch C-more (currently on the QC10) or an RTS2 (spare). Any other gadgets/gizmos I should grab? Thanks!