Quick Change Upper....

[DonT]

Well I got a couple of barrels for my MGI Quick Change upper, one being a used 300 Whisper Barrel with hole drilled for a carbine, the other a bull barrel in .2.23. This was mated to a collapsable stock lower I had.

Played havoc trying to get it to cycle reliably with light loads. Would continually short stroke. Finally picked up an adjustable gas block and shortened a rifle length return spring to 3 coils shorter than the carbine recoil spring. Problem solved.

What a treat to shoot. Going from .223 to .300 takes all of about 3 minutes, and this includes changing the recoil springs. The looks you get at the range are priceless. I through 2 levers, grab the barrel and yank it our of the upper.

Have not had a lot of time to dial it in but appears that the change in point of impact when changing the barrel out and going back to the original (Example, sight in the .223, swap it out for the .300, then go back to the .223 again) is about 1 inch at 100 yards. I think that is pretty fair. I am also finding that when swapping barrels the windage within 1 moa on either barrel but the elevation needs to come up 12 inches over the .223 zero

Anyhow once I get it all worked out and set up I will try to get some pics posted...

Have a Great Day Folks....

DonT

[Artful]

I saw this upper (and their lower) at the SAR gunshow (Dec. 1-3) in Phoenix - looked very nice, looked at prototype in 7.62 Nato - I hope they can get this working and it holds up. - is the point of impact change repeatable at all - any pattern you have noticed?

[DonT]

Haven't had much time to check out repeatability as the cold weather has slowed down the amount of shooting I can do. Still working loads up for each fo the barrels. Once this is done I am going to test to see if there is a pattern and if so what it is.

Will continue to post here as to results...

DonT

[DonT]

Had a chance the last few days, been unseasonably warm here, to do a little more testing on the upper.

I now have a:
Varmint heavy .223 barrel 20" long
Heavy 7.62X39 Barrel 20" long
Light .300/.221 (whisper) Barrel 16.5" long

Using the .223 as my start point with a zero at 100 yards I need to adjust point of aim as follows:
7.62X39 I need to go up 2.5" from the .223 setting
.300/.221 (Whisper) I need to go up 9.5" and to the right 4" from the .223 setting.

As for repeatability, thru the testing of rounds I was able to consistently return to the .223 barrel throughout the test and be within 1" (1 moa) of the original setting. In other words I could shoot the .223 pull it, go to the 7.62X39 or .300/.221, dial in the correction for that caliber then go back to the .223 barrel and reset for the this barrel and with no sighters the rifle would hit within 1" or less of where it started.

This seems to speak very well for both the upper and the Bushnell 3200 10X mildot that is sitting on top of the upper.

I am having issues with the 7.62X39 feeding but this is a common issue with the round when used on an AR platform & I knew that. I am currently using it with a singleshot (bobs lead sled) mag and will be ordering some additional mags as I feel this is where the problem lies at the current time. Even if this is not remedy this issue I am getting 1 - 1.5" groups with the winchester white box and the group opens to 1.5 to 2" with Wolf ammo. I am very pleased with this at this point and feel it can be improved on when I start handloading for this caliber.

The .223 will give consistent sub 1" groups at 100 yds and I am still working on loads for the .300/.221. I do not know how many rounds went thru the .300/.221 barrel before I got it so the 2-3" groups I am currently getting may be the best this little light barrel will turn out but I am still determined to keep at it to see if I can find a load that will provide better accuracy...

If you have any specific questions let me know and I will do my best to answer them....

DonT