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Holdopen #34---It's a balancing act.

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Dances with AutoMags View Drop Down
Callahan's Auto Mag
Callahan's Auto Mag
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Joined: 13 Oct 2011
Location: Valley Glen
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    Posted: 03 Feb 2019 at 9:43pm

 

Holdopen #34---It's a balancing act.

 

It should be a simple matter to rack-back the bolt of an Auto Mag being examined. With an empty magazine installed, the holdopen should engage, holding the bolt back.  This scenario must be successfully addressed before the holdopen working under fire can be resolved.  If pulling the bolt back with an empty magazine installed doesn't activate the holdopen, it is probably the case that the holdopen doesn't work while firing the last round either.  Cry

I had a guy come by my table at the Great Western Gun Show back in the 90's.  He had an Auto Mag that he said never had a working holdopen.  He said he had it to several gun-smiths that told him it was POS and he should sell it.  He asked if I could trouble-shoot it for him.  I admit the it had me baffled for a while before I started taking the gun apart.  The bolt just would not come back far enough to engage the holdopen.  I pulled out the recoil-rod springs and all looked ok.  I looked down the recoil-rod tubes and I saw it.  There at the end of the tubes, I pulled out two .25-inch pieces of recoil rod spring.  Someone had added the spring pieces for some reason.  I re-assembled the gun and the holdopen worked just fine.

I have one of Jurras's Backpackers that doesn't have a working holdopen.  Lee had the holdopen gold plated. The minimum wage worker on the polishing wheel, polished off the 90-degree angle of the holdopen where it engages the bolt-face.  The bolt-face just funnels the holdopen down out of its way as it slams into battery.  Too much metal was removed to be able to file the holdopen back into compliance. 

I have seen dozens of Auto Mags with a troubled holdopen due to bad grips.  The holdopen, or follower-pin rubs on the bad grips. Sometimes the pin moves out too far and rubs on good grips or catches on the frame.  The pin can also move into the follower and not reliably activate the holdopen.  It is best, while trouble-shooting a holdopen problem, to have the grips off of the gun.  

The factory holdopen pin has a serrated shaft and a mushroom shaped head.

   

Here is the balancing-act part of curing a holdopen problem.  The follower pin has the magazine spring pressing it upward.  The holdopen assembly #34 is pushed downward by holdopen-spring #35.  When the follower pin of an empty magazine engages with the holdopen, the follower pin pressure must over-ride the holdopen spring.  The magazine spring easily over-comes the holdopen spring.  If the holdopen-spring is too long, it fully compresses and won't allow the holdopen to rise enough to hold the bolt.  If the holdopen will rise to its fully up position, it may be the case that the spring is fully compressed.  This may look ok to you but the last bit of compression of the holdopen-spring may be enough to win the battle with the magazine spring, preventing the holdopen from engaging the bolt.

 

I have assembled many Auto Mags and the holdopen-springs usually have to have a turn or two removed for reliable holdopen function. 

 

An armed society is a polite society.
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Pantera Mike View Drop Down
International Auto Mag
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pantera Mike Quote  Post ReplyReply Direct Link To This Post Posted: 04 Feb 2019 at 6:02am
Thanks very much Bruce!

Besides having a mangled holdopen, I also considered that the holdopen spring might have a bit too much pizazz and is overcoming the magazine spring. It really is a balancing act, because if it is too light, the holdopen could bounce up under recoil and engage the bolt with rounds remaining in the magazine. 

I am planning on getting a new holdopen and spring. Would you advise trimming the spring before installation?
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Dances with AutoMags View Drop Down
Callahan's Auto Mag
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dances with AutoMags Quote  Post ReplyReply Direct Link To This Post Posted: 04 Feb 2019 at 4:53pm
If this was my gun, I would remove the hold-open and file the follower pin engagement tab back into shape.  It looks salvageable.
Mike, would you adjust the valve gaps on your Pantera before assembling the engine ?  I would re-assemble the gun and fine tune the hold-open spring as needed.  Maybe someone here can do this work for you.  You could take it to a gun-smith who probably doesn't have much knowledge or experience with the gun and won't have a part #30 tool.  A good smith may still be able to figure it out....this is not that complicated.
Bruce
 
If someone is real clever, they may be able to file the hold-open back into shape without removing hold-open. 
 
Yes......hydraulic lifters. 
 
It is written to never re-use part #30 retaining ring.  It can also be installed backwards if you are not watching for it. 
An armed society is a polite society.
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