King Arms - Extra Tight Magwell - Doesn't Fit Anything

[Firewalker]

So, I don't know if the paint is extra thick on this one, but I have KA Sig 556 shorty that I'm having a hell of a time finding mags for. All that seems to fit are the short "10 Round" AR Mags made by MAG. I have some old regular length MAG mags that are supposed to fit like a charm, but they don't get in there at all. KA mags fit, but finding them for a decent price is a chore. I bought this gun to standardize down and allow for mag sharing, it's not going well.

So far, the mags that have been tested have been:

Magpul PMAGS & EMAGS (all)
G&P M4 Mags
MAG Full Sized M4 Mags
STAR Mags (plastic HK)
And a few "unknowns" I have in my collection (I'm certain one of them is a TM mag).

Obviously I need to take down the magwell a bit, I'm just wondering what I'm going to need to pick-up to do so? I don't have anything for power tools but a regular 4.5" Angle Grinder.

I'm primarily looking for people who've worked on the KA Sig 556's to chime in here, as I can't really find much on google. A lot of "Use sandpaper and a file" or "Dremel it down" but no real specifics.

[m102404]

How blocked/bad is it? Does it go in a bit and then stop dead...or can't even get them started into the magwell?

If you can get one type of mag in but not another you might be able to pick out where the wear marks are and just address that spot.

Alternatively you could compare the mag that fits vs. the mags that don't...compare dimensions/corner profiles/etc...and see where it's binding up. Calipers would be handy...you can get really cheap plastic ones for a buck and it'd probably be close enough for this sort of thing, but an ok caliper is pretty cheap at Can Tire and they'll last forever.

You could also use a piece of abrasive paper on the loosest mag and "sand" the inside...using the mag as a sanding block. Careful not to over do it front to back. Side to side as well. The corner profiles don't matter as much since the mags will index on the flats of the sides/front/back.

[Stealth]

Originally Posted by m102404

Careful not to over do it front to back. Side to side as well.

I can't stress this enough. I've seen some guns with loose-ass mags because the owner over-filed the mag well to accept one type of mag, leaving other mags too loose and causing feeding issues.

Only take off what you need.

[Firewalker]

Yeah most of the trouble one get in but get stuck half way in or so.

I'll jam a few mags in there and get some marking in there and draw file the trouble spots.

Mag tolerances are +|- 1mm so not a ton to remove.