Marvel Precision .22 conversion Doubling?

I bought a used Marvel Precision Unit 1 .22 conversion that the previous owner said would frequently double on his Springfield 1911. (firing 2 rounds with 1 press of the trigger)

I put 200 rounds through it with my bottom which is a very old custom gun. It doubled on my bottom once, but it was enough to make me wonder what could be the root cause of this condition-but not bad enough to make me not want to keep it. It shoots great and is great practice for CF&1911 stages without the extra ammo expense.

I think I found the 2 rounds of brass that were involved in the doubling and I did not find any unusual or noteworthy differences in the brass or the firing pin marks.

I thought it was possible that there wasn't a positive contact to the disconnector but it seems to actuate the disconnector properly after about 3/8" of slide movement. I no longer suspect a problem with the disconnector.

In this case of 200+ trigger pulls, is it just possible that I released the trigger so that it reset and then pulled it again in the period of time that made a cyclical double fire? (I've used this bottom for years and never doubled it with .45s going through it)

I've never seen a malfunction like this. Is this something anyone else has seen?

Two things to check. Is the firing pin able to move freely in

the breach block? And does the breach block have any

movment in the slide? Oh yea also check the top of the

chamber for damage from a broken firing pin. After that

dang if I know!

I had some doubling with a Marvel U1. The problem was there wasn't enough tension on the left leaf of the sear spring. I was trying to get a 2 lb trigger pull and lightened the sear spring tension too much.



Since you didn't have the problem with a 45 top end on the receiver this might not be your problem but you could check the sear spring tension.



Like Dave C. said check your firing pin for free movement - maybe some brake cleaner or gunscrubber sprayed in both ends of the firing pin?? and re-oil with a light oil.



Disassembly of the U1 is difficult. Marvel Precision has great customer service, you might send it to them for inspection.

Give Kurt a call at Marvel Precision. It won't cost much to send him the unit Priority Flat Rate and I'm sure he'll come up with the answer.

Like Art said, I'd check the sear spring first for the proper tension on the middle arm, which controls pressure on the disconnector.