CMMG Guard upper & QC10 / colt lower

[MemphisMechanic]

My comp port basically is a popple hole. A small upward port where you still have not lost gas to anything else.

 

But if were further back I believe it would work more. That said, cutting my barrel down to 14” (my comp is 2.1” so barrel is shorter than 14.5) meant that any popple holes would be pretty much underneath my support hand. 

 

Had to abandon the experiment and focus on flattening out the comp.

[nate89]

I have the QC10 colt lower and am looking at the guard upper.  I really appreciate  the pictures and descriptions of the mods you did to make the gun function.  I wonder if buying uzi mags might be easier than modifying the colt mags.  Could you just cut a brand new hole for the mag catch at the appropriate height in the uzi mag?  That would eliminate the need to weld up the colt mag after cutting the hole larger.  Looking forward to trying this out for myself.

[BartCarter]

2 hours ago, nate89 said:

I have the QC10 colt lower and am looking at the guard upper.  I really appreciate  the pictures and descriptions of the mods you did to make the gun function.  I wonder if buying uzi mags might be easier than modifying the colt mags.  Could you just cut a brand new hole for the mag catch at the appropriate height in the uzi mag?  That would eliminate the need to weld up the colt mag after cutting the hole larger.  Looking forward to trying this out for myself.

Do you need to monopod the gun?  If not, just modify the mag catch and then you don't have to do anything to any mags.  Simple, less costly, less time consuming. 

[MemphisMechanic]

3 hours ago, nate89 said:

I have the QC10 colt lower and am looking at the guard upper.  I really appreciate  the pictures and descriptions of the mods you did to make the gun function.  I wonder if buying uzi mags might be easier than modifying the colt mags.  Could you just cut a brand new hole for the mag catch at the appropriate height in the uzi mag?  That would eliminate the need to weld up the colt mag after cutting the hole larger.  Looking forward to trying this out for myself.

 

That would indeed work. Remove the mag catch, get the magazine in the right spot, and use a scribe to mark where to cut.

[nate89]

18 hours ago, BartCarter said:

Do you need to monopod the gun?  If not, just modify the mag catch and then you don't have to do anything to any mags.  Simple, less costly, less time consuming. 

I don't really plan on it, it just seems that with the ability for the mag to move around within the boundaries of the larger hole in the mag (relative to the now smaller mag catch) that it could lead to problems.  But mag catches are cheap and that seems like the quick fix, at least initially.  If there aren't any problems I'd just run it that way.

[nate89]

17 hours ago, MemphisMechanic said:

 

That would indeed work. Remove the mag catch, get the magazine in the right spot, and use a scribe to mark where to cut.

I might buy a couple uzi mags and give it a try when the upper shows up.  If nothing else I like to tinker with stuff and it would be interesting to try.

[nate89]

The perfect (but most likely never to happen) is to get QC10 to mill the hole for the mag catch a bit lower and sell it as a guard-specific lower.  It would be such a niche market (maybe a few hundred sales max?) that it makes no business sense.  I can still dream though..

[MemphisMechanic]

27 minutes ago, nate89 said:

I don't really plan on it, it just seems that with the ability for the mag to move around within the boundaries of the larger hole in the mag (relative to the now smaller mag catch) that it could lead to problems.  But mag catches are cheap and that seems like the quick fix, at least initially.  If there aren't any problems I'd just run it that way.

 

I doubt it’d be a problem in USPSA where you never go prone. That said, I chose to weld & relocate the window 1/8”ish higher to keep the wobble to a minimum. But doing so was simple for me; walk into the garage and flick the welder on.

[nate89]

Putting a welder in my hands would be the easiest and fastest way to destroy a perfectly functional magazine haha.  

[MemphisMechanic]

27 minutes ago, nate89 said:

The perfect (but most likely never to happen) is to get QC10 to mill the hole for the mag catch a bit lower and sell it as a guard-specific lower.  It would be such a niche market (maybe a few hundred sales max?) that it makes no business sense.  I can still dream though..

There’s another alternative a guy suggested to me:

 

You have to cut down the blowback gun’s ejector flush with the lower to run a guard upper. There’s plenty of space to make that piece of steel L-shaped, so it turns forward and acts as an upward travel stop, resting on top of the magazine’s back corner.

 

Then you could simply enlarge the window to fit. The mag release keeps the mag from sliding down, and this new piece keeps it from being able to move upward.

[MemphisMechanic]

(I plan to try my hand at just such an overtravel stop at some point.)

 

@nate89 don’t worry about messing a mag up. If you send me one or two that turn out to be overcut, I can weld them for you so you can have another go.  

[nate89]

23 minutes ago, MemphisMechanic said:

There’s another alternative a guy suggested to me:

 

You have to cut down the blowback gun’s ejector flush with the lower to run a guard upper. There’s plenty of space to make that piece of steel L-shaped, so it turns forward and acts as an upward travel stop, resting on top of the magazine’s back corner.

 

Then you could simply enlarge the window to fit. The mag release keeps the mag from sliding down, and this new piece keeps it from being able to move upward.

Interesting.  Nice to know that I'm not the only one wanting the colt mags/guard upper, and that the other people are pretty clever in figuring out solutions that I can use.  

[nate89]

23 minutes ago, MemphisMechanic said:

(I plan to try my hand at just such an overtravel stop at some point.)

 

@nate89 don’t worry about messing a mag up. If you send me one or two that turn out to be overcut, I can weld them for you so you can have another go.  

 

Thanks much, I might have to take you up on that, depending on how my tinkering skills are that particular day!