I have one in 45acp. I had trouble big time!
Factory ammo is just too hot for this carbine! Factory pressures create far too much bolt thrust for the original bolt& spring. The action simply moves way too violently to reliably feed the following round.
I took 50 rounds of factory (3 different types) "150 rounds", and pulled all of them.
I measured the powder charges to get an average for each type of ammo.
Reduced the charge by .4 grains, and reloaded them to the original OAL.
I also resized and belled the cases for proper bullet tension.
Result: a significant reduction in damaged cases or missfeeds!
Only three missfeeds in the whole 150 rounds. Not too bad now.
This reduced load gives me the typical velocity that 45ACP should shoot at.
I feel that JR carbine manufacturing just made a bad call on the buffer spring compression poundage.
Other than this, i love the little carbine!
It shoots cast bullets very well also!