Reader’s Digest version: Looks like the combination of the KelTec brass heavyweight bolt and the Midwest Industries optic mount (specifically, the need to keep the bolt open while the sub is folded and wrestle the retention cord around the charging handle when folded) may have deformed the charging handle hole enough to prevent the bolt from coming out of the tube. Pics attached.
I have 2 SUB2Ks, 8 and 9 months old. they’re functionally identical in terms of MCARBO parts installed. One’s a MCARBO edition and the other was a base carbine that I sent off to KelTec to have them install all the MCARBO parts. Both have about 800 rounds through them with no issues until now.
The only difference between them is that the MCARBO edition carbine has a RDS on the Midwest Industries Mini Picatinny Rail Optic Mount, with a Performance Services LLC Handguard Stabilizer under it. The MI optic mount requires that the bolt be open when folded and a lanyard looped around the charging handle to keep it clear and keep it from accidentally releasing and smacking the optic. Both have the MCARBO Recoilless Charging Handle with locking pin installed.
Just broke them both down for their first deep cleaning, and can’t get the bolt/bolt head combo out of the tube on the gun with the optic mount. In the pics you can see my non-optic sub behind the one with the MI mount. It looks like the charging handle hole in the brass bolt is elongated to the rear and has some brass material ridged up behind it. It cycles fine when firing, but won’t budge past the slot in the tube, while the other one allows the bolt head and bolt to just slide right out when I tilt it down.
When folded, it takes some effort to get that MI paracord lanyard lanyard looped around the fat charging handle, and my guess is that the combination of soft brass, applying force to get the lanyard on, and the force on the charging handle applied by the bolt being constantly held open that way all combined to deform the hole in the bolt. Gonna send it to KT and have them figure it out so I don’t do more damage trying to get it out.
Just thought I’d send up a warning flag in case anyone else is running this parts combo.