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Discussion Starter #1
Check out this little bugger I just put together:





Custom Built AR45 SBR based on the CMMG Guard.
-CMMG Guard 45 bolt carrier and 8" barrel in .45 ACP/.45 Super/.450 SMC
-Anderson MFG .458 Socom upper
-MVB USC Magazine Adapter
-H&K USC Magazines
-Seekins Precision NOXS 7" rail
-No name brand .578x28 muzzle brake I found (has those stupid 13/16-16 oil filter threads on the outside... it's the best I could get without spending a fortune).

The normal Guard 45 built by CMMG uses Glock magazines, but since I already had an SBR, I wanted to utilize it. So, after about a YEAR of searching, I finally found a picture of an AR using an H&K USC magazine. That led me to MVB Industries and their magazine well adapter.

Guys, I can't even express the tinglies you get down south feeling up this gun. It's so tiny and lightweight... Prior to the sights going on it, it weighed in at just under 6lbs. I sold two firearms to fund this project... I have high hopes for this gun.

While I was building this gun, I was so hyped that I fired up the press and loaded up 500 rounds of .45 ACP and about 150 rounds of .45 super. I was supposed to go shoot this gun on Saturday, but I wound up buying a new car instead. This coming Saturday is the day... I just have to make it through the week... just through the week...
 

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Man.

Dang.

I don't know what to say.

If you knew how long I've been wanting to build a 45acp AR.

I'll probably have to hit you up to find out more of the particulars.

I had to give you a winner ribbon on this topic and I rarely hand those out.
 

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Interesting. I was watching the CMMG, but haven't seen much press out of the 45 guard. 45 is where it's at... But I'm waiting for my 10mm....
 

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Which leads me to: Why does HK hate us and not bring the USC back in an 8" braced form?
Ya, but straight blow back. I mean the King of roller lock goodness to blowback.... But then we are back to they hate us.
 

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Discussion Starter #9
Interesting. I was watching the CMMG, but haven't seen much press out of the 45 guard. 45 is where it's at... But I'm waiting for my 10mm....
When they bring out a 10mm barrel/bcg combo, I'll be building one of those as well. I just need to find magazines that will work... Or pony up and build a pistol that uses Glock mags.
 

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When they bring out a 10mm barrel/bcg combo, I'll be building one of those as well. I just need to find magazines that will work... Or pony up and build a pistol that uses Glock mags.
For the platform, 45/10 is what makes sense. I decided to stop waiting and ordered a MP5/10 clone.
 

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Discussion Starter #11
All right, I actually weighed the gun yesterday with an actual scale, and I was way off... it's much lighter than I thought...

Empty without magazine or any tuning weights: 4lbs 14oz
With empty magazine and no tuning weights (standard 45 ACP config): 5lbs 3oz
With empty mag and heaviest tuning weight (.45 Super config): 5lbs 7oz

So, official weight in the configuration I will primarily shoot is just under 5.5lbs. God, I love this thing. I cannot wait to get it out on the range this weekend...

Just five more days... five... more...
 
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For the platform, 45/10 is what makes sense. I decided to stop waiting and ordered a MP5/10 clone.
Whoaaaa.. I haven't looked, but are magazines actually available for that bad boy?
 

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Discussion Starter #13
Man.

Dang.

I don't know what to say.

If you knew how long I've been wanting to build a 45acp AR.

I'll probably have to hit you up to find out more of the particulars.

I had to give you a winner ribbon on this topic and I rarely hand those out.
I'll do my best to do some shooting videos with it this weekend. I have high hopes for this gun. I can't wait to chronograph the .45 Super loads out of it also. I'm estimating at least 1450fps with my go-to 200gr hardcast load... that's 933 ft-lbs of energy... I have to stop... I'm getting a chub thinking about it.
 
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Whoaaaa.. I haven't looked, but are magazines actually available for that bad boy?
HK mags. MP 40/10 mags, straight from HK Parts. The German ones are pricey, US ones are half. I have a batch waiting for action.
 

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Discussion Starter #15
HK mags. MP 40/10 mags, straight from HK Parts. The German ones are pricey, US ones are half. I have a batch waiting for action.
I expect gun porn when you get it in.
 

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I expect gun porn when you get it in.
Absolutely! And I know we don't know each other that well... And I hope you don't think this is too forward... But your piece gives me a chub too...
 

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Well, I went and shot the gun...

HOLY CHIT! I LOVE THIS GUN.

I got through about 250ish rounds of 230gr ball, 45 rounds of assorted hollow points (230gr Hornady XTP and 160gr Barnes Tac-XP), and about 45 rounds of .45 Super (230gr Ball and 200gr Hard Cast). I had to quit early because my fingers were getting bloody and bruised trying to load the goddamn USC magazines.



The gun eats ball .45 ACP ammunition like a growing Labrador puppy eats kibble, and it handles .45 Super like a champ. With the muzzle brake, recoil is incredibly mild and follow up shots are quick and precise. I didn't do an official accuracy test this past weekend, but during the rough sight-in process, I was getting big, jagged 1" holes at 15 yards shooting off-hand. That's not saying much, but it's a good sign!

I did not use the tuning weights at all when shooting this weekend. I was initially worried that shooting .45 Super without the tuning weights might cause some overpressure due to early extraction. HOWEVER, there were no signs of overpressure whatsoever. In fact, the .45 Super brass looks considerably better out of this gun compared to my 1911 (see below - same exact load, 1911 is the first piece of brass with significant primer flattening and flowing, Guard brass are the next three back)



Recoil is significantly heavier with the .45 Super, and I will be putting the 2oz weight into the bolt carrier group to prevent battering the gun too hard in the future.

I did experience two legit failures the entire trip, both were hollow points. One 230gr XTP, and one 160gr Tac-XP. Both were the same kind of failure to feed, getting stuck in an upward pointing orientation, with the edge of the hollow point catching on the barrel extension. I don't plan on ever using those Barnes bullets regularly, I just happened to have them and loaded them up. They do look nice after hitting steel, though...





I did experience a couple other stoppages, but they were just hammer follow while I was trying to bump fire like an idiot, so I don't count those. I then had one other significant stoppage... but it wasn't gun or ammo related. One of the magazines, mid string of fire, decided to fail. The catch tab on one of the magazines just decided to snap and the mag fell out of the gun. I thought I hadn't seated it well, but upon closer inspection, I realized that the tab was missing (found it on the ground).



I sent an e-mail to ProMag hoping to get a replacement... I haven't heard back yet. I'm going to be saving my pennies and ordering a couple of H&K factory USC magazines eventually... It will take time to save up the money, though because they aren't cheap.

Overall, this gun is a fantastic success. I cannot wait to do some legitimate accuracy testing with it and chronograph some .45 Super loads out of it. Eventually, I'll do a full writeup and post a link.
 
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That's pretty awesome. So what was your reason to convert to USC mags? Why not stick with cheap Glock mags?
 

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That's pretty awesome. So what was your reason to convert to USC mags? Why not stick with cheap Glock mags?
I already had an AR Lower with an SBR tax stamp on it and large frame Glock mags are too big to fit in a standard AR mag well. I wanted to use what I had available, so conversion was my only hope. I chose the USC magazine because Promag magazines are cheap and available... but I'm actually kicking myself because there is another magazine option with a conversion adapter made by Macon Armory available, but I chose against it because the proprietary magazines are $50 a pop. HOWEVER, considering that Factory H&K mags are almost $60 themselves, it would have been wiser for me to go the Macon route... That, and I think you can use the Uplula magazine loaders with the Macon magazines... Oh well... Live and learn.
 
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