Yes, that’s the jam experienced in all four of the ProMagsOriginally Posted by JCN
Yes, that’s the jam experienced in all four of the ProMags
I think flat nose bullets are more susceptible for obvious reasons so that’s what I used to recreate the issue when you told me it was HST sensitive.
Once I confirm function / assess reliability and tweak a few more mags I’ll get a sense of which tuning techniques were necessary.
For this mag I used a number of complementary tuning techniques once I discovered what the issue was.
I think most people can acknowledge that regardless of what they think of my bluntness or lack of tact, I solve problems usually pretty effectively.
And in general, the philosophy of problem solving is that you can push or you can pull or you can do both.
What I mean by that is there usually isn’t just a single, simplistic solution. There are two things (or more) contributing and you can improve margin and reserve by adjusting or modifying either parameter.
Just like comps and recoil springs. You can adjust the ammo, the comp size, the spring weight or all of the above.
For my competition MPX, I wouldn’t have to change springs if I were content with using higher power ammo but it’s a game that I want to master so I fix the ammo as the constant to reduce degrees of freedom and I try to work the other variables to give me back the margin.
Same thing here.
I could tell you to use pointy round nose bullets only and keep your feed ramp polished and slippery and that could put a band aid on the issue without tuning the magazine. But that doesn’t give you margin back.
With a reliable factory 15 rounder, there’s a template at least for reliability so I have something to compare dimensions and functions to as a gold standard which also helps.
I did a lot to that tuned mag yesterday and will run it at the range with flat nose bullets to see if I can get reliability. If it’s very reliable, I’ll do less to the next mag and see if I hit the critical parts of improvement.
I’m leaving the gun dirty and feed ramp dirty to test margin because the factory mags run fine with a dirty feed ramp.
@JCN, thanks for all of your time and expertise on this problem. The head-scratcher with the ProMags is that they nose-down with three different types of 115-124 gr FMJ ammo at the same failure rate as the HST and RA9T ammo. I’m sending four mags off to you today for your tinkering.
I’ll talk about what I’ve done so far. Not sure that it’s all necessary yet but I’ll walk through the thought process in case people are interested.
Nose diving bullets is common on the Czechmate big sticks, mainly due to the control rib and neck area being too loose where it condenses from double to single stack.
There is binding there so there isn’t enough support from below to keep bullets tipped up.
So I thought that’s where this was going.
But the dimensions of the ProMag calipered out to be very similar to the OEM mag so I wasn’t that convinced.
Then I took apart and looked at followers. The ProMag front of the follower is more angled and could “fall down” more easily so I tried swapping followers and that definitely helped.
But that’s not a solution unless I absolutely have to do that.
So I swapped back, knowing I have that in my back pocket in case I need more reliability that I can’t get otherwise.
I settled on massaging the geometry of the upper contact surfaces so we shall see.
Minor grinding was involved.
Additional thoughts. @CarlK
If this first mag runs very well with “the full Monty” then I’ll know that I have a solution and will work on just different parts of the solution with each of the new mags I ordered before working on yours.
If I can’t get it reliable with standard tuning then I might get creative with the follower and start epoxy molding a front ledge so the angle matches the OEM mag better since I know the OEM follower works better when I swapped them for proof of concept testing.
Welp. Tuned mag did better but still not the reliability I would like.
So modification.
Front lip ramp.
Stretched and angled the top small coils to help upward pressure on the follower.
EDIT: hand cycled and much better.
But I do think I need to clean my feed ramp and maybe polish it for further reliability.
Interestingly Sig has changed the feed ramp geometry so this might be a known issue that could use extra margin.
Last edited by JCN; 02-09-2022 at 04:34 PM.
I could go farther on the mag body but I think the issue is mainly in the spring and follower.
Left to right 9mm TSO, 9mm CZ75B and Promag springs and followers.
Factory 9mm TSO springs mocked up to the ProMag follower. Note how they are basically designed to help keep upward tension on the nose?
Drill press hole
Voila!
I checked by hand cycling and MUCH more positive upward engagement.
Next test will be live fire and if that works then trial of this spring in an otherwise stock ProMag.
I can just imagine grumpy people saying “what a pain in the ass! I would never fuck with all that stuff!”
But I enjoy figuring stuff out. It’s fun for me.
Especially in the case where there is no good alternative.
It’s also the reason I post. So people can just cut to the chase and work the solution rather than have to do the problem solving if that’s not their cuppa.
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