Marvel conversion - getting light strikes

I have a Marvel 22 conversion (unit 1 non lock back aluminum) with about 5K rounds through it on a dedicated lower. Lately I've been getting frequent light strikes and failures to fire.  I replaced the firing pin and the problem still persists.  The tip of the old pin seemed worn on one side by about 0.005" but otherwise looked OK. Prior to replacing the pin the unit was deep cleaned.  Looking at the FTF cartridges they seem to be hit by pin but the indentations are not sharp and don't seem very deep.  Same lot of ammo shoots fine in my Ruger MK3 so don't think its that.  Curious if anyone else has had this issue and found a solution.  Thanks

Clean chamber and breech face thoroughly. If you have done that and tried different ammo then go to a heavier main spring. Try 18 or 19 lb.

I would say try replacing the recoil spring. Could be firing a couple hundredths out of battery rather than actually light strikes. Just a thought.

Your experience mirrors mine. Unit 1 lock back bought toward the end of Dennis's ownership. Had tons of issues. In the 2 years I've had it it's been so Dennis once, Travis Ferking twice and Jon once. Had issues included lead shaving and light strikes. Just got it back from a stay with Dennis for light strikes for the 2nd time. Had to go up to a 21# hammer spring after its return to get it to strike hard enough. Shot a couple matches now with just one failure which wasn't a FTF.

I would try CCI SV with a 9# recoil spring and try 20-21# hammer springs. Also make sure everything is clean, full strip down to the innards. Even with a 21# hammer spring I still only have a 2 5/8 pounds trigger.

Recoil spring.  I ended up with a 8#  in mine that resolved the issue.

How is too heavy of a recoil spring going to cause light strikes? I've heard the opposite, if the spring is too light it can lead to not enough force returning the slide and can leave it slightly out of battery or not seat the next round fully. That's why I have a 9# installed, I previously had an 8# in there.

I believe it all about the right balance with whatever ammo ammo you are running. The light slide seems a bit more particular.

I've still never seen a conversion with near as good of a firing pin strike as most all dedicated 22's. I think there's till room for improvement with the current conversions like Nelson & Marvel.

Thanks for the ideas. All helpful. I forgot to mention this but I did try heavier recoil spring (I normally shoot a 7# and went up to stock 9#) but problem persists.  The next things I'll try will be heavier mainspring and the over travel adjustment. I read on Bob Marvel's troubleshooting steps that if over travel it is set too tight it can interfere with the hammer fall. I did recently tweak on that.

As far as cleaning I did brush the chamber and got everything in the slide assembly squared away - but maybe I need to turn attention to the innards of the lower.  Or, perhaps swap out the upper to my other 45 lowers to see what happens. 

The Marvel has shot well and been as dependable as a Maytag up to this point so here's hoping for a fix.

If a 7 lb spring ran fine from the get go put.a new one in

Also have you examined the rounds that failed for shaved lead or being bent

I recently installed a new 7# spring and it ran fine for last 500 rounds or so before trouble started.  The rounds don't have any lead shaving or show signs of being bent.  Appreciate the input tho.

WillH wrote:I have a Marvel 22 conversion (unit 1 non lock back aluminum) with about 5K rounds through it on a dedicated lower. Lately I've been getting frequent light strikes and failures to fire.  I replaced the firing pin and the problem still persists.  The tip of the old pin seemed worn on one side by about 0.005" but otherwise looked OK. Prior to replacing the pin the unit was deep cleaned.  Looking at the FTF cartridges they seem to be hit by pin but the indentations are not sharp and don't seem very deep.  Same lot of ammo shoots fine in my Ruger MK3 so don't think its that.  Curious if anyone else has had this issue and found a solution.  Thanks

I had the same problem with my Nelson conversion.  I struggled with light hit/no fires for a couple of years and thousands of rounds, until I noticed that the cases from other bullseye 22's all had deeper hits.  In addition, the other guns left a smaller and deeper indentation on the case than my Nelson.  I did some measuring and found that the face of the firing pin on my Nelson was between 1.4 and 2 times larger than the face on other guns which distributes the impact force over a larger area and makes a lighter hit. 
I decided to attempt a fix.  First I made sure my back up 22 was working, then I carefully stoned about 40% from the Nelson firing pin face (I removed material from each of the two long sides of the firing pin).  The good news was I did not need the back up 22,  I haven't had a light hit in over 5000 rounds.  I think the Marvel shares same design features of the Nelson so I would suggest comparing the cases from your 22 to the cases of other bullseye guns.  If it is larger than the rest try making your old firing pin smaller. 
Doug W

Doug those are excellent observations. I've noted the exact same thing on my quest to eliminate light strikes. My Marvel leaves a fat and shallow strike. Most dedicated 22's have very pronounced small footprint hits. I'm up and running with a 21# hammer spring but if I have issues again I'll be trying your fix.

22 firing pin nose shapes are interesting.. the smith 41 had a chisel shape that worked very well.

http://www.shootforum.com/forum/viewtopic.php?f=20&t=15043

I have done this to other 22s with good success.

djw1cav wrote:

WillH wrote:I have a Marvel 22 conversion (unit 1 non lock back aluminum) with about 5K rounds through it on a dedicated lower. Lately I've been getting frequent light strikes and failures to fire.  I replaced the firing pin and the problem still persists.  The tip of the old pin seemed worn on one side by about 0.005" but otherwise looked OK. Prior to replacing the pin the unit was deep cleaned.  Looking at the FTF cartridges they seem to be hit by pin but the indentations are not sharp and don't seem very deep.  Same lot of ammo shoots fine in my Ruger MK3 so don't think its that.  Curious if anyone else has had this issue and found a solution.  Thanks

I had the same problem with my Nelson conversion.  I struggled with light hit/no fires for a couple of years and thousands of rounds, until I noticed that the cases from other bullseye 22's all had deeper hits.  In addition, the other guns left a smaller and deeper indentation on the case than my Nelson.  I did some measuring and found that the face of the firing pin on my Nelson was between 1.4 and 2 times larger than the face on other guns which distributes the impact force over a larger area and makes a lighter hit. 
I decided to attempt a fix.  First I made sure my back up 22 was working, then I carefully stoned about 40% from the Nelson firing pin face (I removed material from each of the two long sides of the firing pin).  The good news was I did not need the back up 22,  I haven't had a light hit in over 5000 rounds.  I think the Marvel shares same design features of the Nelson so I would suggest comparing the cases from your 22 to the cases of other bullseye guns.  If it is larger than the rest try making your old firing pin smaller. 
Doug W

That is a great observation and idea. I happened to have a bag of spent 22 casings to look at - some fired with my Ruger Mk3 and others from Marvel.  As you say, the Marvel strikes are wider and more shallow by quite a bit. With the spent brass I also did some experiments comparing dents with the over travel screw set short (just where hammer will fall) and that with it set longer (1.5 turns out).  I found that setting it very short caused shallower dent than when backed out further.  I had recently tweaked the over travel so hoping that this change will be the cure on my next range trip.  If that doesn't work I think I will try your advice to stone down some to make it narrower - and/or maybe forge another pin a couple of thousands longer. Marvel seems (in my non-gunsmith opinion) to need a pin both a couple thousands longer and sharper on tip.

If your overtravel adjustment is causing a difference in firing pin strikes it is because when you have it set up shorter the half cock on the hammer is most likely hitting the sear as it rotates past it. They are not supposed to make contact. I would recommend learning how to tell when this is happening; it will cause damage to your sear engagement surfaces.
Jon

you can make the tip smaller or narrower but the leading edges need to be slightly rounded.. the chisel shape pushes the brass out of the way.. a much smaller nose, landing in the correct area on the rim works very well. The hammerli trailside/Xesse has a very small impact area and works perfectly.. looks like a pin punch

firing pin protrusion should be checked also.. usually around .007 less than you headspace on the bolt face

Jon Eulette wrote:If your overtravel adjustment is causing a difference in firing pin strikes it is because when you have it set up shorter the half cock on the hammer is most likely hitting the sear as it rotates past it. They are not supposed to make contact. I would recommend learning how to tell when this is happening; it will cause damage to your sear engagement surfaces.
Jon

This seems like good advice.  When I set the over travel (which apparently was too short) the approach I took was to tighten it until the hammer wouldn't fall then back it out until it just did then I went out an extra 1/2 turn.  After my recent discovery that it seemed to cause light strikes I went perhaps another 1 full turn past that. It's hard for me to tell what's going on.  Guidance on setting it properly would be appreciated (i.e. back out x number of turns past non-functional, etc.).  Or maybe it varies by individual gun? -Will

easiest way to test it is simply hold the hammer back then pull the trigger...Slowly lower the hammer and feel for any catch or drag.. usually on the half safety but you'll feel it. I really don't try and get the trigger stop that close.. usually like a touch of follow through on the trigger.

Update:  After following the above advice I re-adjusted my over travel screw and the light strike problem was cured.  It must have been too tight rubbing on the hammer before.  Shot over 100 rounds today at practice without any problems and the brass dents seem normal again.