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+--- Thread: 3 year Study results of QCB Upper & Grendel (/showthread.php?tid=2567)
3 year Study results of QCB Upper & Grendel - LRRPF52 - 04-04-2012
After working with my 16" AA barrel/bolt combo in a Gen I MGI Quck Change Barrel Upper, I have made the following conclusions:
Finding sub-MOA accurate loads was an exercise in futility with the barrel mounted in the MGI Gen I upper, which I bought used in 2006.
I thought I had a mediocre barrel, and was only able to get one barely MOA group with 120gr SMK's.
After seeing that I was able to shoot a 6 or 7 round group with a .5 MOA vertical spread last week with Precision Firearms 123gr Scenar loads, but the horizontal spread was like a duckbill shotgun, I knew something whacky was going on.
I decided to drop the barrel in a standard AR15 upper, slap a rifle-length float tube on it, and take her back to the range.
After my trip to the range today, the first group out of the pen was .792" for 4 rounds, no flyers, no cherry-picking, just a nice sub-MOA 4-round group. The gun is extremely light, and very difficult to keep on-target, but it is a shooter.
![[Image: DSCF0404.jpg]](http://i1085.photobucket.com/albums/j422/LRRPF52/DSCF0404.jpg)
![[Image: DSCF0407.jpg]](http://i1085.photobucket.com/albums/j422/LRRPF52/DSCF0407.jpg)
![[Image: DSCF0405.jpg]](http://i1085.photobucket.com/albums/j422/LRRPF52/DSCF0405.jpg)
![[Image: DSCF0408.jpg]](http://i1085.photobucket.com/albums/j422/LRRPF52/DSCF0408.jpg)
My interest in it was more as a nice little hunting carbine, which it was capable of with 1.5-2.0 MOA accuracy, but the little ER Shaw AA button-rifled pipe can spit pretty tight for a $269 barrel/bolt combo.
3 year Study results of QCB Upper & Grendel - burnsome - 04-04-2012
thanks for the post and report. that's a good price for a fine shooter like that, and exactly what i'm looking to find for my 2nd Grendel build. i guess some barrels just dont shoot no matter what. i've fixed a few "non-shooters" over the years via drastic measures like cutting length, very agressive lapping, etc. which sometimes works, sometimes not. did you get it direct from ER Shaw or AA? i'm thinking about going with J&T if they sell anything like that combo.
3 year Study results of QCB Upper & Grendel - LRRPF52 - 04-05-2012
If you noticed, the barrel IS a shooter. The Quick-Change Barrel upper it was in didn't support being sub-MOA. It's now shooting great.
![[Image: DSCF0406.jpg]](http://i1085.photobucket.com/albums/j422/LRRPF52/DSCF0406.jpg)
3 year Study results of QCB Upper & Grendel - crispy - 04-06-2012
Interesting, Have you ever played with the the LMT MWS platform? I am wondering if that might exhibit the same issues.
3 year Study results of QCB Upper & Grendel - LRRPF52 - 04-06-2012
I doubt the LMT would do the same thing, since it locks up in a totally different manner, and many people report great accuracy with the MWS. The MWS pinches the barrel extesnion with a cross bolt torqued to a certain ft-loading, with another turn-bolt to secure the barrel extension flange.
I will also reiterate that I have the Gen I MGI QCB upper, which I purchased used from a guy who was into NFA stuff, and ran a lot of 9mm suppressed through it. He needed cash for another happy switch blaster, and sold it to me.
The MGI QCB has two vertical locking channels that have less than half of a circle on them. These internal faces rotate against a standard AR15 barrel's extension flange, holding the barrel in-place against the upper. I'm not sure they have anywhere near the foot-pound loading of a conventional barrel nut torqued to 35+ft-lbs. I had really tight vertical spread, but really wide horizontal spread.
I still love the MGI QCB upper, for a convenient little package that can be broken down smaller than a regular AR and fit into smaller cases. It would still be minute-of-badguy out to 300yds, but I'm an accuracy nazi who expects to be able to shoot sub-MOA if the barrel can deliver it, and that is what I wanted to know about this barrel.
3 year Study results of QCB Upper & Grendel - Variable - 04-06-2012
LRRPF52 Wrote:I doubt the LMT would do the same thing, since it locks up in a totally different manner, and many people report great accuracy with the MWS. The MWS pinches the barrel extesnion with a cross bolt torqued to a certain ft-loading, with another turn-bolt to secure the barrel extension flange.Well I definitely thank you for the info. I have been pondering over one for a long time. The briefcase picture was pretty tempting. I have one of their modular lowers for my Shrike, and I started to order their upper a couple of times. The price and lack of good reliable info held me back. I take your reviews seriously.
I will also reiterate that I have the Gen I MGI QCB upper, which I purchased used from a guy who was into NFA stuff, and ran a lot of 9mm suppressed through it. He needed cash for another happy switch blaster, and sold it to me.
The MGI QCB has two vertical locking channels that have less than half of a circle on them. These internal faces rotate against a standard AR15 barrel's extension flange, holding the barrel in-place against the upper. I'm not sure they have anywhere near the foot-pound loading of a conventional barrel nut torqued to 35+ft-lbs. I had really tight vertical spread, but really wide horizontal spread.
I still love the MGI QCB upper, for a convenient little package that can be broken down smaller than a regular AR and fit into smaller cases. It would still be minute-of-badguy out to 300yds, but I'm an accuracy nazi who expects to be able to shoot sub-MOA if the barrel can deliver it, and that is what I wanted to know about this barrel.
3 year Study results of QCB Upper & Grendel - crispy - 04-06-2012
+1 on the info! Good to hear, I will be lining up to get an MWS rifle and a .260 Rem barrel for it here shortly. It seems like a really cool concept that I am looking forward to trying out.
3 year Study results of QCB Upper & Grendel - LRRPF52 - 04-06-2012
Yeah, I love being able to pack a 16" AR15 carbine in my laptop case when we go camping or fishing. Other campers don't freak, and it makes vehcile load-out much easier. It's also convenient for the range for the same reasons. I'll drop one of my Melonited 5.56 barrels into it, and see what happens, but I've had the same horizontal spreading with my 5.56 pipes in it.
There was a guy who posted on the old forum that he gets sub-MOA groups with 2 of his MGI QCB uppers, but that was the extent of his posts, so I suspect that he had some fiduciary connection with MGI. Maybe their newer uppers hold accuracy, since they have changed some things with the design. I still like a lot of their products as a company, and the QCB upper serves its purpose for me.
Warped claimed that the Grendel does better with higher barrel nut torque than 35 ft-lbs.
3 year Study results of QCB Upper & Grendel - Variable - 04-07-2012
LRRPF52 Wrote:Yeah, I love being able to pack a 16" AR15 carbine in my laptop case when we go camping or fishing. Other campers don't freak, and it makes vehcile load-out much easier. It's also convenient for the range for the same reasons. I'll drop one of my Melonited 5.56 barrels into it, and see what happens, but I've had the same horizontal spreading with my 5.56 pipes in it.
There was a guy who posted on the old forum that he gets sub-MOA groups with 2 of his MGI QCB uppers, but that was the extent of his posts, so I suspect that he had some fiduciary connection with MGI. Maybe their newer uppers hold accuracy, since they have changed some things with the design. I still like a lot of their products as a company, and the QCB upper serves its purpose for me.
Warped claimed that the Grendel does better with higher barrel nut torque than 35 ft-lbs.
Sounds like you need to get a new upper, try it out, an then report back....
LOL!!!
3 year Study results of QCB Upper & Grendel - LRRPF52 - 04-07-2012
If you mean another Gen III or IV MGI upper, I'd rather not, since I don't like dedicated quad rails. That's why I jumped on the Gen I upper, and then machined off the 3 & 9 o'clock rails to make it more streamlined. I also ordered their rifle-length handguard extension, and contoured down the locking channels where they protrude from the tube. I then Cerakoted everything in Coyote Tan.
I'll have to post some pics of it when I get a chance.
3 year Study results of QCB Upper & Grendel - Variable - 04-07-2012
Please do. It sounds kinda neat.
The thing that always kept me away from switch barrels was the fact that AR upper receivers are really cheap if you stock up on them when they are on sale. I got some YHM ones that were really cheap one time. For the difference of a switch barrel upper you can put a receiver on each of the barrels you were going to switch normally (if you buy the uppers right).
The ability to make an AR disappear into a brief case is what got my attentiion though.
My M-96 Windrunner will fit into a back pack, but an AR in a brief case or laptop case would be pretty sweet!
3 year Study results of QCB Upper & Grendel - LRRPF52 - 04-12-2012
Updated with pics in OP and a few down on 1st Page.
3 year Study results of QCB Upper & Grendel - fanofflyn - 04-13-2012
LRRPF52, I've got a CQB-C that I played with briefly, just enough to make some brass marks on the deflector, and took apart and put back in the box. It was so tight I had to use a leather mallet to slide the lock on an off. Since I will likely never build a carbine length firearm again, I would be glad to just send it to you to let you play with if you want. It does have dedicated rails, but I don't know what gen it was, I've had it for a year or two. If you don't want it fine, I might trade it for something sometime, but because you've put up with my undereducated BS on this site, I'd send to you to have for free. This offer only applies to you, so no PM's from other people please.
I've been much happier with the VLTOR uppers, which are much beefier, but not quick change.
3 year Study results of QCB Upper & Grendel - LRRPF52 - 04-13-2012
That's an offer not seen every day. I would be interested to see if the new generation uppers from MGI might hold accuracy better.