LBHO Not working on all mags.

Nova-Wake

Nova-Wake

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It appears that cycling through my vz58 mags that a few won't actuate the last bolt hold open when i try to with them empty, sometimes they will sometimes they wont, why? some mags its frequent others it never happens some it does once in awhile? if there a fix? it seems that the little metal part on the mag that contacts the lever is the problem, but visibly they all look the same? i don't get it.


if i pull the mag towards me sometimes it fixes the problem, but i dont want to do that, do i have to little metal on the catch?
 
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this area will not contact every magazine, most of them do but not all.

vz5.jpg


I tested a piece of foil out on the mag, and it works. I know bumish but i was just testing.

vz4.jpg


So im wondering if there is anything aftermarket that resolves this? do the Raush and neitarms bolt releases offer more coverage?
 
how many different mags are causing the failure?

I would start by narrowing down the mag(s) that is/are causing the problem. If you can't rule out any mags then I would say it is a gun issue.

There should be little more then 1/16" of play between the magazine and the receiver. If you have a lot of back and forward slop then I would first try a mag from a source other then the one you used to get the current mags. If that mag is sloppy then either the mag release is out of spec or you can look at the receiver dims.

being that you are in the US, who made your receiver? Obiwanbonjovi is pretty expert in the US guns so he can help with receiver issues.
 
Seeing as you're US.. Are you storing your mags full? If your mag springs are getting tired that could cause this. There are mag springs available, I have a couple AK springs in some mags that work great. If you can find a double wound wire spring vs the factory-type single spring steel springs they have a much longer lifespan and can be stored full. There are a ton of spring sources down there, and the prices can't be beat.

Easy way to tell;

Take a mag that doesn't catch the bolt and one that does. Replace the components one by one until you find the culprit. If you find that it's not the spring and you've just lost material through use on the nipple that detents the bolt hold the easiest fix would be to add a little material to the base of the mag catch, rather than trying to modify each mag. If it comes to that send me your catch and I'll zap a bead on the base for you.. just cover shipping.
 
I got the same problem on mine. Then I changed the bolt carrier plus the retaining pin & seemed to fix the problem.
 
Satain said:
I got the same problem on mine. Then I changed the bolt carrier plus the retaining pin & seemed to fix the problem.
Click to expand...

Thats interesting.

A lot of the US guns have some pretty worn parts like the carriers depending on how well used the parts kit was. It may be a good idea to check how the contact surfaces look between the BHO and the carrier.
 
I looked at the bolt and i do not beleive its that with a bad mag in there it doesn't push on the bolt catch enough for it to protrude on the top side.

Ok playing around with the rifle i have found the following.

Out of 12 mags.

9 will engage the BHO when empty.

out of those 9 only 5 will engage it when cycling bullets through the rifle(not firing it just on the bed).

and 3 will not engage it either way.

i found that the ones not engaging the BHO after cycling ammo, miss the bolt catch on the bottom all together.

i found that the ones not engaging the BHO at all, would line up with the bolt catch but would not touch it.

The ones that work either way have contact and line up.

i have switched around springs and it help one or two but some not at all, I believe its a problem on the magazine nipple thing, some do not sit high enough some not far enough back. As for them missing it completely it seems that the bolt catch bottom doesn't extend far enough into the mag opening. But i could be wrong.

it the pic that mag catches the bolt catch but just on the tip, most will when dry but once i put a few rounds of ammo and cycle them only about half with catch it, the rest miss it completely.

vz6.jpg
 
Its hard to tell from your pic but I'd say that the mag isn't seating far enough into the receiver. The average I have here is .028" aka ~1/32" between the bottom of the receiver and the ridge that runs around the mag.

I would check all the mags and see if its just a mag issue or if all mags seem to have too much slop when installed. If they all have too much slop I'd say its a gun issue.

Gun Issue Solution:

1. Check to see that your mag release is to spec, if not change it out.

2. If it is to spec then check the pin diameter, if its under spec then change it out.

3. If its the hole size or location on the receiver then the easiest solution is to have a welder add a little material to the top of the mag release surface so the mags seat a bit highter. Don't worry about adding too much, you can just file it down till it fits. Gimme a minute and I'll post up the average measurements I have here.
 
Receiver hole diameter => .160"

Pin Diameter => .155"

Release hole diameter => .160"

Distance from bottom of receiver hole to bottom of receiver => .088"

Shortest distance from hole in the mag release to the mag release holding surface. => .247"

These are from rifles and parts that are proven functional.


Bolt Hold open measurements:

Average distance from the top of the bolt hold open to the bottom surface where the magazine actuates it => 1.010"

I can't comment on what the milspec tolerances are from the factory but based on my experience with function parts like these in the VZ58 it is generally +/-.003".
 
now i have a reason to buy a digital caliper huh, well it seems that most slant forward a tiny bit a real tiny bit but i have some new ones and if i cycle ammo it just misses the bolt catch, only my 10rnders hit it no matter what i do. all mags have a tiny bit of play if i pull them towards me, it will pull it against the bolt catch and the button will indent a little.

most are at or less than this for a slant. all slant a tiny bit.
vz7.jpg
 
All mine site pretty well parallel to the receiver. I would tend to think that something in the gun (note all the dims I posted earlier) is not right. Can I ask who made the receiver on your gun?
 
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