Need some suggestions for polymer mag modification

[Bowhunter-tw]

Hi All,

I have 3d printed a follower, spacer, and spring retainer to convert a 5rnd 308 AICS mag to an 8-9 rnd grendel/arc mag. Everything fits great but im have trouble with the feed lips. As you can see in the side view the cartridge wants to tip up towards the front of the lips. I need to add material to the forward edges to retain the smaller diameter grendel case. I tried some jb weld specific for polymer but it would not dry hard enough and would not allow smooth feeding. Looking for suggestion on epoxies or compounds that I could build up the feed lip and will cure as hard as the original polymer material.

 

[DaveTooley]

Can't help you with what epoxy might or might not work but single stack mags feed better with a slight nose up attitude. Yours probably release the cartridge too soon and it pops up. I think I'd just print another one and close the opening up. Easy enough to remove material. Not so easy to add it back.

 

[Eagle Six]

There might be something out there, but nothing I can think off that will adhere, be shapeable and have the strength to hold under the spring pressure. I think I would tinker around with maybe a thicker spacer moving the round a bit further to the front and adjusting the spring to hold more pressure on the base of the cartridge. Not sure that makes sense!!

 

[LVLAaron]

MDT makes mags for the short cartridges. They're spendy but very nice mags.

 

[muleystalker]

First off if the JB weld wouldn't dry hard then your mix ratio was off. You also might want to re think your design of your your 3d spacer. Think about lessening the spacer in the rear and add a spacer on the forward end of the magazine, this would put the cartridge back into the feed rails more and give you material to work with. You can also try Devcon 100110 Plastic Steel putty, it is tuff stuff though so don't build it up too much at once.

 

[DonB]

I have had some luck with using a heat gun and reforming lips on polymer mags.

Also if epoxy or JB weld will not stick to it you can drill a few small holes and let the epoxy run thru the holes as you are shaping it. This will keep it in place.