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  #1  
Old 09-06-2018, 12:53 PM
zukiphile
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Should my pieces and parts pistol be this ammo sensitive?



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I've had a bunch of MKIIs and they've all been very reliable with anything I stuck in their magazines. This is my first problem. Maybe I've done everything wrong.

The Pistol
MKIII lower with VQ kit - This lower was part of a MKIII that fed reliably
MKII 50th anniversary upper and bolt - never used on anything but the MKIII lower
MKIII and MKIV magazines

The Problem
CCI powder coated, Aguila SV, Remington Golden Bullet and Federal Automatch jam exactly the same way. The bullet starts up the ramp, but the brass is bent by the bolt so the front half of the cartridge sits on the ramp keeping the bolt from closing; the bottom half of the cartridge sits under the bolt, keeping the magazine from dropping freely until the bolt is pulled back. This happens more often with the MKIV magazines than the MKIII magazines. MKII magazines are too tight to seat.

Remington Subsonic and CCI SV function flawlessly.

As noted, I've never had a picky Ruger before. My MKII with VQ upper cycles everything. Is finicky feeding just a risk we run in a parts and pieces build, or is there something specific I should seek to fix?
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  #2  
Old 09-08-2018, 01:02 AM
Flash_80 is online now

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Swapping uppers can result in some funny things I imagine. There is some variance in the lowers as well. My cousin and I both bought MKIII 22/45 frames only at the first of the year to build with Pac-Lite uppers. The block that holds the upper in on his sits considerably lower than mine does. If we remove or install his receiver, we basically beat it on with a rubber mallet. Mine has a few strips of a cut up coke can on it as shims because its so loose. It will basically fall off when you pull the mainspring. Took a month and a half to get both running as they should, though our biggest problems were light strikes.

My MKIII 22/45 hasn't had any feed issues, but my MKIV had issues with the next to the last round with golden turds or any bullet that wasn't totally smooth on the sides. Fixed that thanks to Test Engineer's advice on sanding off the tops of the mag followers to where they were level. No issues in like 10 months with that ever since. I scribed the followers with a razor blade, used a dremel to shave them down, and sanded them smooth again once the bulk of the material was removed. For that issue, it only happened on the next to the last round for that gun. It jammed #9 and shaved the top off of what would be the last round. That was a MKIV standard lower and a VQ LLV4 upper.

My main question is what is the difference between a MKIII and a MKIV magazine if its not a 22/45? They should be the same for a standard target frame.
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  #3  
Old 09-08-2018, 07:04 AM
zukiphile
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Quote:
Originally Posted by Flash_80 View Post
My main question is what is the difference between a MKIII and a MKIV magazine if its not a 22/45? They should be the same for a standard target frame.
It is a 22/45 lower. I had read that MKIV magazines were reliable in MKIIIs (22/45s), so I ordered a two pack.

My guess I developed in idle office moments was that the feed lips were too close together, making the cartridge approach the chamber at the wrong angle. When I examine them, I'll look at the follower now too.

Thanks.
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  #4  
Old 09-09-2018, 12:33 AM
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Quote:
Originally Posted by zukiphile View Post
I've had a bunch of MKIIs and they've all been very reliable with anything I stuck in their magazines. This is my first problem. Maybe I've done everything wrong.

The Pistol
MKIII lower with VQ kit - This lower was part of a MKIII that fed reliably
MKII 50th anniversary upper and bolt - never used on anything but the MKIII lower
MKIII and MKIV magazines

The Problem
CCI powder coated, Aguila SV, Remington Golden Bullet and Federal Automatch jam exactly the same way. The bullet starts up the ramp, but the brass is bent by the bolt so the front half of the cartridge sits on the ramp keeping the bolt from closing; the bottom half of the cartridge sits under the bolt, keeping the magazine from dropping freely until the bolt is pulled back. This happens more often with the MKIV magazines than the MKIII magazines. MKII magazines are too tight to seat.

Remington Subsonic and CCI SV function flawlessly.

As noted, I've never had a picky Ruger before. My MKII with VQ upper cycles everything. Is finicky feeding just a risk we run in a parts and pieces build, or is there something specific I should seek to fix?
You're experiencing what I call "over-run jams" (where the bolt over-runs the rim of the feeding round).

These don't occur in guns that use the heal release because that release lifts the mags up to the stops. Guns that use the push-button release allow the mags to "sag" and in effect they become pendulums. Mags that can move around are horrible for reliability.

It seams that your MKII upper must sit a little higher than the MKIII upper that fed okay did. But making it sit lower is not trivial or easy. Another possible fix is to try to find another mag release that holds the mags higher. I consider this to be a gamble, unless you have access to a number of releases to try out. Your best bet IMO is to shim the mags or the mag well. You will have better luck using only MKIII 22/45 mags for this.

The problem is that the bolt pushes the round forward at the top of the mag, which transfers some of that energy (thru friction) to the top of the mag itself. Because the mag sags so the stops are not engaged, the mag moves forward/down at the top/front and moves back/up at the bottom/rear. This makes the round go up the feed ramp at an increased angle and allows the bolt to ride up and over the rim. The problem is even more acute with shorter OAL rounds than it is with longer varieties.

Adding a small pad to the top of the MKIII base plate where the back end lifts to the frame will reduce the rotation enough to stop the over-runs. This section of base plate was removed on the MKIV mags, so another shim location would be needed to fix your problem with them.

I've got shims inside the mag wells of both - my MKII and my MKIII to force optimal feeding. It's one of my biggest complaints about the entire history of mark pistols. The mags are designed to feed best when positioned at the BACK of the mag wells, but the mag releases, bolts, (and mag disconnect junk) are all designed to push the mags to the FRONT.

It's no wonder many people have feeding problems.
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  #5  
Old 09-09-2018, 08:43 AM
zukiphile
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Quote:
Originally Posted by Test_Engineer View Post
You're experiencing what I call "over-run jams" (where the bolt over-runs the rim of the feeding round).
Exactly so.

Quote:
Originally Posted by Test_Engineer View Post
It seams that your MKII upper must sit a little higher than the MKIII upper that fed okay did. But making it sit lower is not trivial or easy. Another possible fix is to try to find another mag release that holds the mags higher. I consider this to be a gamble, unless you have access to a number of releases to try out.
I agree. If the release held the magazine appreciably higher, it might not even catch. It's tight enough that a simple press doesn't always seat the magazine.

Quote:
Originally Posted by Test_Engineer View Post
The problem is that the bolt pushes the round forward at the top of the mag, which transfers some of that energy (thru friction) to the top of the mag itself. Because the mag sags so the stops are not engaged, the mag moves forward/down at the top/front and moves back/up at the bottom/rear.
Given the amply tight release fit, I am surprised by the amount of play I observed after reading that. Your diagnosis makes sense

Unofrtunately, I wasn't able to re-create the failure by exaggerating the forward position of the magazine and hand cycling the least reliable kind of round, Aguila. That doesn't mean that your dx is incorrect; I modified the magazines before reading your post.

I noticed that just before the feed lips end the MKIV magazine feed lips hold the rims lower than the MKIII items do, so I rounded the sharp forward corner of the feed lips and widened them toward the front somewhat.

Thanks for the insight.
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  #6  
Old 09-09-2018, 11:23 AM
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Quote:
Originally Posted by zukiphile View Post
I modified the magazines before reading your post.

I noticed that just before the feed lips end the MKIV magazine feed lips hold the rims lower than the MKIII items do, so I rounded the sharp forward corner of the feed lips and widened them toward the front somewhat.
I've been trading away magazines modified like this 3 for 1. I started with 10 and now have 1 left and 3 unrounded lip mags. The problem with rounding the lips is they can no longer control the front of the rounds as they feed up the ramp. This results in "pop-up jams" where the rounds ram into the top of the chamber mouth. In effect, rounding is trading one type of jam for another.

That said, new mags typically come out of the package with the rear lips parallel. They work best with the front of those lips about 0.020" closer together than the rear. I set all of mine to 0.210" at the back and 0.190" at the front. New mags are usually set pretty close to 0.180" in both front and back. So adjusting the lips a little wider does help the rounds sit somewhat higher.

I hope you get yours to run okay. Feed jams and FTFire problems are the pits!
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  #7  
Old 09-10-2018, 10:09 AM
zukiphile
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Quote:
Originally Posted by Test_Engineer View Post
That said, new mags typically come out of the package with the rear lips parallel. They work best with the front of those lips about 0.020" closer together than the rear. I set all of mine to 0.210" at the back and 0.190" at the front. New mags are usually set pretty close to 0.180" in both front and back. So adjusting the lips a little wider does help the rounds sit somewhat higher.
These MKIV magazines' feed lips were decided non-parallel, conspicuously closer together toward the front.

Quote:
Originally Posted by Test_Engineer View Post
I've got shims inside the mag wells of both - my MKII and my MKIII to force optimal feeding.
I've been lucky with my 20 year old MKII, which may explain why I know so little about reliability tuning. It functions with everything

A shim inside the magazine well makes sense to me. If this problem persists, I may try a drop of glue right at the top and front of the well.
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  #8  
Old 09-19-2018, 01:00 PM
zukiphile
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Test Engineer,

I thank you for the dx. Some glue in the frame to support the magazine very near the top of the magazine eliminated most of the over-run failures. I don't believe I'd have had the patience to track that down on my own.

My remaining reliability issue is a failure of the FP to light of a round of Aguila, a round that is completely reliable in an AR. It looks as if the FP is striking too high. I want to try a bolt from another pistol, and may order some spare FPs to see whether that's the problem.

Yes, I could clear up these problems by using other ammunition and sticking with MKIII magazines, but where would be the fun in that?
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