Yes they are but you may have to adjust the feed lips for your gun. Jim has some good videos on utube for setting the feed lips and working on mka mags.
I just got a upper from ar15parts.com for my PSA glock lower. Not side charging and didn't know if I would like their handguard either. I really like the handguard and will be putting rounds down range this weekend.
JP Enterprises GMR-13 is a side charging upper.
Shotgun shells were not not meant to be feed from a box magazine. It takes a good quality shell/hull to take that kind of abuse. There is a learning curve to running and maintaining a box fed shotgun.
I have a Tac-12 and wish I got to use it more. Had a RO almost got mad at me telling me to get my shotgun for the second time. Realized he was talking to me and held magazine out, he was good then.
Thanks to Jay, Jomar, Brian and all the other folks that made this match happen. This was a great match and thanks to the sponsors for their generous donations.
Looking forward to coming back again and taking down the heavy pipes
Go to the contact us section at bottom of web page and there is a couple of other numbers for parks administrators. The RV pads are in a good place and protected from the Nebraska winds.
Just run your 40 like you would in a pistol match, not worth down loading. Harder to miss with the larger bullet!
If you really get into it you can get a 9mm latter if you want.
I recently shipped a scope mount to Canada for a customer and did it threw a exporter. Exporter took care of all paperwork dealing with ITAR and customs for both sides of border.
If part attaches to the firearm it would be under ITAR the way I understood it. Not worth getting in trouble for find a exporter. Exporter charged one fee for each line item/part number. If multiple parts all the same part number it was one fee per part number. Customer may get several for friends and make export fees less per item. Customer pays all fees all I did was ship mount to exporter on USA side of the border.