Marvel conversion spring

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Marvel conversion spring

Post by John Rahm on Fri Sep 14, 2012 12:53 am

Shooters,

I am challenged in understanding the workings of the mechanisms we shoot. My Marvel with a red dot on a dedicated Essex frame has begun to fail to cock the hammer after some shots even though the next round is loaded. I have tried the unit on other frames, but eventually a round will fire ... be ejected... and a new round loaded. However, the hammer is not cocked. this does not always occur in the same sequence in the magazine and in the worst case this will happen for three shots in a five shot string. It occurs with all magazines. If I cock the hammer manually, the round will fire.

It is my guess that I am having a problem with the weight of the marvel recoil spring. Do I need a heavier or weaker spring to get the hammer to cock after each round is ffired? Thanks for your assistance.

John in Minnesota

John Rahm

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Re: Marvel conversion spring

Post by KC's Kustom on Fri Sep 14, 2012 5:24 am

John,

Your recoil spring might be part of the problem. You would need to go with a lighter spring depending on your ammo. The first place I would look is your mainspring. Go lighter so there is less resistance for the slide to overcome and I bet your problem will go away.

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Re: Marvel conversion spring

Post by Steve B on Fri Sep 14, 2012 6:30 am

If your gun is cycling but the hammer doesn't remain cocked I would question how much tension you have on the center arm of the sear spring to the disconnector. Sounds like the hammer is following.

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Re: Marvel conversion spring

Post by Rob Kovach on Fri Sep 14, 2012 7:21 am

Steve B,

This is a very common problem with Marvel conversions. The Marvel is short cycling, meaning the slide is going only far enough to eject and strip a new round from the magazine, but not far enough for the hammer to make it to full cock. If the gun was doing the same thing when it was a .45, then we should have him look at the sear spring, but as someone who has had the same problem, KC has the correct direction. Start with the Mainspring. Even with HV ammo, my marvel wouldn't full cycle the hammer, or have reliable ejection/extraction without going down to an 18lb mainspring--no matter how light a recoil spring we put on the marvel. Once you tune the mainspring and recoil spring to your ammo, you should have a reliable marvel.

Rob Kovach
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Re: Marvel conversion spring

Post by John Rahm on Fri Sep 14, 2012 1:30 pm

Gentlemen,

Thank you for the helpful suggestions. I will try reducing the recoil spring first and then the main spring. I do not believe the hammer is following because, as Steve suggested, it is short cycling.

John

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Re: Marvel conversion spring

Post by jtg6 on Fri Sep 14, 2012 2:53 pm

John
I had the same problems after I built my gun, I found that a Model 41 recoil spring is the same size & is about a pound or 2 lighter, after putting that in I have not had any problems with the hammer cocking at all.
Good Luck!

jtg6

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Re: Marvel conversion spring

Post by Founder on Fri Sep 14, 2012 9:20 pm

Lets not call this a problem with Marvel conversions, the conversions work as designed. Variations in ammo, main springs, worn springs and properly fitted mainspring housings all have an impact on the function of the whole "package".

My Marvel performed flawlessly for 2 cases of ammo. Then when I switched to my recently purchased Aquila from the CMP I started having some failures. The ammo was slightly softer that the previous and was not cycling properly. I dropped down one pound on the recoil spring and have enjoyed flawless operation again since.

Any competitive firearm will require "balancing" the springs to get the desired effect of felt recoil and function. And that will change over time, like we always recommend with reloads. Find the one that shoots best from your gun/barrel then adjust springs for proper function.

The Marvel springs are inexpensive and last a long time. I have been playing with 8# IMSI springs and so far like what I see happening with them and install those in the conversions I sell and work on.

The Marvel springs are color coded
10# - Red
9# - no color
8# - Yellow
7# - Orange
6# - White


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