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Bolt mods to fix failure to feed.


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I get failure to feeds often enough as to make it a problem during a 3 gun match. (Thank god for the left side charging handle)

As normal everyone says "tune the mags". My big issue with this is that the bolt tab that strips the shell just barely hits the rim. Say by 1/32". To raise the shell you have to bend the feed lips right where they are connected at the back of the mag. I don't like that fact and it is almost impossible to get it up high enough and then control the shell with the front of the lips.

This especially with the long mags as they drop down some against the mag catch and effectively lower the magazine and thus the shells.

 

I decided to look at the bolt as the issue. My thoughts were that the tab was not long enough. When the barrel is off you can see the feed ramp and thethe slot that the loading tab fits into. I noticed that there was a large amount of room in the slot below the tab.  So why not lengthen the tab and  stop screwing with the mags. (unless they present the shell at the wrong angle and that is another issue entirely)

 

I went to my gunsmith and looked at the problem, He agreed with me se we set to fixing it.

Tig welded a bead to the bottom of the loading tab and then reshaped it to match the back ramp side of the tab. ( the ramped rear side allows the bolt to move backwards over the nest shell and smoothly press it down. The tab is now 1/16" longer and easily overlaps the shell rim while still fitting in the ramp slot and clearing the rear of the magazine. The bead itself was pretty hard so we will see how it lasts or wears.

 

Took it out yesterday for test and tune and it worked flawlessly. I had two failure to feed and that was the soft federal bulk back hulls. Running WinAA or Remington STS the gun fed perfectly.

I did have one issue and that was scratching of the top of the follower as the empty bolt slides home. I had not rolled the front edge of the new tab much. It was kind of sharp and scratching the plastic. Fixed that and no more scratching!

 

This is a big big move forward for my gun. Now I will not be thinking every time I pull the trigger during a match will I have to cycle the bolt to fix a FTF.

Here are the pics!!!

 

Original bolt with the short tab.

20140315_1908041024x768_zps0138b1a9.jpg

 

New extended Tab. This is before rolling the leading edge more.

 

20140401_1709201024x768_zpse4c3584d.jpg

 

Bead of weld (ignore the lower scratch, it was made with an awl)

20140401_1401461024x768_zpsdc6f74ce.jpg

 

Shaped tab.

 

20140401_1706061024x768_zpscda4baac.jpg

 

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Nice. Do you think that bead will hold up or fracture after a lot of shooting ?

I'm glad to see people working on bolt upgrade ideas. To me the bolt is really the last 

missing link in perfecting this gun.

Edited by SHOTGUN MESSIAH
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Consider that the tig bead was really hard I am hoping it will be ok.

I imagine it could crack and fall off but It really isn't getting "hit" by anything. Just contacting the rim of the case and stripping ot off the mag. Not alot of force in the big scheme.

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I get failure to feeds often enough as to make it a problem during a 3 gun match. (Thank god for the left side charging handle)

As normal everyone says "tune the mags". My big issue with this is that the bolt tab that strips the shell just barely hits the rim. Say by 1/32". To raise the shell you have to bend the feed lips right where they are connected at the back of the mag. I don't like that fact and it is almost impossible to get it up high enough and then control the shell with the front of the lips.

This especially with the long mags as they drop down some against the mag catch and effectively lower the magazine and thus the shells.

 

I decided to look at the bolt as the issue. My thoughts were that the tab was not long enough. When the barrel is off you can see the feed ramp and thethe slot that the loading tab fits into. I noticed that there was a large amount of room in the slot below the tab.  So why not lengthen the tab and  stop screwing with the mags. (unless they present the shell at the wrong angle and that is another issue entirely)

 

I went to my gunsmith and looked at the problem, He agreed with me se we set to fixing it.

Tig welded a bead to the bottom of the loading tab and then reshaped it to match the back ramp side of the tab. ( the ramped rear side allows the bolt to move backwards over the nest shell and smoothly press it down. The tab is now 1/16" longer and easily overlaps the shell rim while still fitting in the ramp slot and clearing the rear of the magazine. The bead itself was pretty hard so we will see how it lasts or wears.

 

Took it out yesterday for test and tune and it worked flawlessly. I had two failure to feed and that was the soft federal bulk back hulls. Running WinAA or Remington STS the gun fed perfectly.

I did have one issue and that was scratching of the top of the follower as the empty bolt slides home. I had not rolled the front edge of the new tab much. It was kind of sharp and scratching the plastic. Fixed that and no more scratching!

 

This is a big big move forward for my gun. Now I will not be thinking every time I pull the trigger during a match will I have to cycle the bolt to fix a FTF.

Here are the pics!!!

 

Original bolt with the short tab.

 

New extended Tab. This is before rolling the leading edge more.

 

Bead of weld (ignore the lower scratch, it was made with an awl)

 

Shaped tab.

 

How much did he charge for it? I have a spare bolt that could use that fix too...

Edited by gose
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Yes it was hand/belt ground by me. We did not cut it on the mill.

All I did was work it to get a slope in the bottom of the tab. As Jim said the bottom just needs to not drag on the next shell and as I found not cut into the follower.

It can really all be done with diamond files if you don't have the 1" belt sander. Doesn't have to be perfect since all it does is push the next shell forward.

The welder charged me $20 to sand blast for prep. Then he clamped the bolt face to a piece of aluminum (to create a straight edge parallel with the bolt face)and Tig weld the bead on it.

Any real welding shop can do it.

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  • 8 months later...

OMG, who knows how many rounds are through the modded bolt at this point.

A whole season of 3 gun almost every weekend.

Not a mark, nick or wear on it!

Every once in a while I'll have a round not strip but it is always because I havent stretched a mag spring in a 18 rounder in a while.

Never miss a shell with a stock mag.....never.

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Adjusting the feed lips to allow the rounds to present higher accomplishes the same thing

 

Not in my case. The bolt was so messed up that RAAC got me a new one. Even after adjusting the feedlips, the bolt wasnt anywhere near picking up a round. New bolt ran fine until it cracked, so unless you guys start cranking out bolts or I get a new one from XN, trying to fix the original one that's not (yet) cracked is currently my only option.

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Jim,

You know how different each gun is, On mine opening up the feed lips didnt present the shell high enough. Open the lips far enough and eventually they stop holding the shells.

Lenghtening the tab fixed all the problems.

Most particularly it fixed ever haveing to mess with the feed lips for higher presentation. Never again!!!

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