Why do colt mags fit tighter than other mags. I got a colt and a USA mag at a gun show and the USA (very cheep, I will not ever buy another one) and the Colt is tight going in. I have a DPMS Lower.

I used Colt made mags for 20 and 30 rds that are of course pinned to 5 as per our stupid law.

I never had any problem with them at all.  They work just perfect regarding feed and drop.

Here in Canada, Colt mags are considered the best available by users and dealers.  Of course we would be happy if we can get HK SA-80 mags.  So, far no trouble with Colt.

Colt subcontracts to the same companies that have the current military contract for GI mags.  They install their own baseplates.

Paying more for Colt mags is paying for that pony on the baseplate.

Actually my colt magazines fit great into my Colt preban rifle. Remember don't always trust what the baseplate says about who the magazine where made by. I've seen some colt 30rd mag bodies that I'm sure where made by Sanchez because the pinning resembled a Sanchez body. I've also noticed that Sanchez magazines fit tight into my Colt rifle but other USGI mags fit just fine.

Look at the quality of the magazine and not the baseplate name and you'll be a lot better off in the end.

I have noticed on the 2 colt mags I have they have 9 welds on each side.