Bolt hold open with a single round still in magazine

KSPeacekeeper

Member

Joined: Jan 2018

Posts: 498

EE: 100% (138)

KS, USA

Posted: 12/6/2025 7:00:40 PM EDT

Question for anyone here reading……

Ok just 400 rounds into my MK1 11.5”. Added a Hux can and Aimpoint optic, but no structural changes to the firearm.

I’m consistently mag after mag getting bolt locking to the rear with a single round still in the mag. I will then drop the bolt and fire the last round and it will lock back on an empty magazine like it should.

It is doing this with Duramags and magpul mags. I haven’t added a bad lever or any mods to bolt catch. Not a one off, but repeated with each magazine. I’ve never had this happen before. Same magazines function fine in all my other 11.5s.

Can anyone help me out?

RD20

Joined: Nov 2020

Posts: 842

EE: 0% (0)

OH, USA

Posted: 12/8/2025 2:23:07 AM EDT

[#1]

Sounds like the can is adding pressure and activating the bolt catch when the magazines follower is exposed.

You could try a heavier buffer, spring, or combo of the two after you verify your bolt catch isn't floppy due to an underpowered spring.

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Bolt hold open with a single round still in magazine

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Bolt hold open with a single round still in magazine

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Bolt hold open with a single round still in magazine