SIGforum
Should one be able to close the bolt on an empty Colt pattern Metal Form Mag?

This topic can be found at:
https://sigforum.com/eve/forums/a/tpc/f/630601935/m/9450008225

November 09, 2026, 04:25 PM
Black92LX
Should one be able to close the bolt on an empty Colt pattern Metal Form Mag?
Likely a dumb question but on dedicated Colt pattern lower, no mag block conversion, should you be able to close the bolt with an empty mag inserted??

I only have Metal Form mags (was told that is who makes Colt mags). So I can’t test others.

Gun functions as normal when the magazine is loaded.
Upon emptying the magazine or charging the rifle on an empty magazine the bolt locks back (as it should).
If I hit the bolt release with an empty magazine inserted the bolt release will not move to drop the bolt. Remove the mag and hit the bolt release bolt drops just fine.

It appears the last round bolt catch is a metal tab that comes up the spine of the mag. I am guessing that just stays engaged and no way to back that down and let the bolt drop with the empty mag in the gun?


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November 09, 2026, 05:04 PM
OttoSig
Yes, it does on mine anyway.

Both LRBHO and then closes on the empty mag, which seems logical.

ETA: AI says stuck bolt catch, which makes sense.

What manufacturer lower is it? I assume you’ve tried multiple magazines?

When I had my FFL, and even still, I sold Metalforms mags above all else. They were (can’t attest to STILL) were colt OEM. Both form reviews and personal use Metalform were like Mecgar Sig mags, they just worked.

One question: you said, “ guessing that just stays engaged and no way to back that down and let the bolt drop with the empty mag in the gun?”. Does this lower NOT have a bolt release? The bolt release gets that back down.





Eight years to retirement! Just waiting!
November 09, 2026, 05:57 PM
Black92LX
Got it working.
Took the BCG out oiled it and got some oil underneath the bolt release. First try after that was a little hard but the bolt closed on the empty mag and subsequent tries were much easier and smoother. Guess she just needed some lube.


————————————————
The world's not perfect, but it's not that bad.
If we got each other, and that's all we have.
I will be your brother, and I'll hold your hand.
You should know I'll be there for you!
November 10, 2026, 10:42 AM
egregore
quote:
If I hit the bolt release with an empty magazine inserted the bolt release will not move to drop the bolt. Remove the mag and hit the bolt release bolt drops just fine.

Well, yeah. The magazine follower is pushing up and exerting pressure on the bolt stop. Of course it's going to be difficult. This is pretty much true of any magazine. I also fail to see the point of releasing an open bolt on an empty mag.
November 10, 2026, 11:24 AM
Mars_Attacks
Colt pattern mags have a very strong spring.

It takes a lot of effort to press the bolt latch.


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