Hey all,
Just got a new 581 Gb (Tactical with standard polymer stock).
I've got 2 Promag 20s, 1 old Ruger 20, and the new Ruger 5 shot mag that all function fine and lock the bolt open on last round.

The 20rd that came with the gun won't lock the bolt on an empty mag.
I've got another new 20rd (Ruger factory marking on the side of the mag and baseplate) that acts the same way.

Has anyone heard of issues with new factory 20rd mags?
(It seems to be a follower issue. I took the follower out of the 5 round and put it in one of bad 20s and it fed rounds fine and locked open the bolt.)

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Its either worn followers or dirt inside the cover plate that operates the bolt lock. Go for simple first, clean out the bolt lock, check for dirt and junk around the spring, use a blaster spray or take off the side plate cover. Watch out for the spring flying in a crazy direction.

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I've got 6 new 20 rounders and have never had an issue with any of them.

My Ruger 20's run fine.

I've bought a 20 and 30 with no trouble. I'm about to buy 2 more 20's and one more 30. I'll let you know how it goes.

I just bought a 581 tactical Friday and suffered the exact same problem with the 20 rnd and an extra 30 rnd i bought for it. It was a very easy fix. I took a pair of needle nose pliers and bent the base of the lip out just a tad. The feed lip moved maybe 1/32". Now the follower comes up enough to activate the bolt catch and it feeds perfectly.

Thanks for the replies.
I've cleaned out the bolt lock and the gun just came back from the factory.
(Shooting low.)
As I said, several other mags work just fine, and the two problem mags are new Ruger factory.
My next step will be to measure the followers and take measurements of the feed lips.

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Fixed them!

Measured the feed lips with a micro and the distance between the lips on working mags and non-working mags was basically the same.
So I just got some pliers and bent the inside lip until the follower activated the bolt stop.
They hand clycle rounds OK, so I think I'm good.

I would expect to do this with Promags, but new Ruger factory mags???!!!

Oh well, at least they work and I didn't have to send them back.

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