Help with magazine issues

[frankge]

Hello all,

 

Boy I wish my eyes were still good and I could still shoot limited with a 100% gun and mags. 

 

Anyway, have an STI GrandMaster Trubor in 9mm major. My load is 124g JHP @ 1.168 with 8.4 HS-6 which runs ~175pf and gun operates the load with no issue. I have fits with the magazines. They are 2 old style STI 140mm, 1 old style STI 170mm (28 rnds), and 1 new style STI 9mm/38 super (29 rnds). They ran good for a short period of time and now its almost every stage they hiccup. It appears to be primarily nose-dives. I put Hardy spacers in them, actually had to in the "new" STI to get it to run right. They all have Grams guts with Dawson basepads.

 

I am going through each one with a tuning kit and replacing all the mag springs even though they are about 4mos old. I do shoot a lot. I have heard all kinds of advice including dump them and go MBX. I'd rather not and giving it one last try. I have done searches and though informative, don't really give good advice as it seems more opinion.

 

So, tuning all feed lips .350-.355 in front to .005-.010 to back, replacing springs, keeping spacers (should these be glued?). Recoil spring is 9lbs and about 3mos old - gun shoot pretty flat.

 

Like I said if this doesn't work I'll be buying MBXs because I have enough problems shooting on my own without Gffing every other stage.

 

Thanks! 

 

 

 

 

Edited November 3, 2017 by frankge
sp

[frankge]

ok, so tuning the mags - rear feed lip at .350 and front at .360 - still hit the feed ramp pretty solid. Opened it up to .370 and now bullet points right at the breach or just hit top of feed ramp. Going by Atlas recommendations was .350x.360 but you should check to see that the bullet points at the breech. Go figure, I'll see with some live fire and next match.

[bigbob21]

I had similar issue on a new gun.

just because your bullet length fits in your chamber doesn’t mean the bullet itself (the jhp tip) feeds well...
I had issues like you, where the rounds would get stuck on the barrel ramp.
I’ve got a mixture of mags. Some fed well from the start and some didn’t.

I ended up shortening my oal and switching bullet brands before I was able to feed consistently with all my mags.
Also check your extractor. If it’s too tight, it might be holding onto the top round too long and could cause the following round from the mag to drag and get caught in the cycle...

Just my 2 cents...
Still new to open myself.


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[zzt]

I have STI 126 mags with Grams guts and Extended base pads.  I have STI 140 mags with Grams guts and base plate.  I have 1st gen SVI mags that didn't work with Grams guts, but run fine with TTI guts and base pads.  I also have MBX mags.

 

I'm tired of screwing around tuning STI feed lips.  Frankly, I'm tired of STI anything.  I sold all my STI tuned mags.  I kept three to use for dry fire practice.  I have two SVI 140s and one SVI big stick, all with TTI guts and base pads.  I use them for times when I have to drop a mag on dust or loose dirt.  If it is grass of stone, I use my MBX mags.  They run and run, and take abuse that would send STI mags back to the tuning shop for feed lip remedy.  The MBX runs so well I'm considering selling the three SVI mags and buying more MBX.  I'm way to old to be fussing with this stuff, and I have zero tolerance for failures during a match.  BTW, I HATE spacers.

Edited November 4, 2017 by zzt

[RonPogi]

13 hours ago, zzt said:

I have STI 126 mags with Grams guts and Extended base pads.  I have STI 140 mags with Grams guts and base plate.  I have 1st gen SVI mags that didn't work with Grams guts, but run fine with TTI guts and base pads.  I also have MBX mags.

 

I'm tired of screwing around tuning STI feed lips.  Frankly, I'm tired of STI anything.  I sold all my STI tuned mags.  I kept three to use for dry fire practice.  I have two SVI 140s and one SVI big stick, all with TTI guts and base pads.  I use them for times when I have to drop a mag on dust or loose dirt.  If it is grass of stone, I use my MBX mags.  They run and run, and take abuse that would send STI mags back to the tuning shop for feed lip remedy.  The MBX runs so well I'm considering selling the three SVI mags and buying more MBX.  I'm way to old to be fussing with this stuff, and I have zero tolerance for failures during a match.  BTW, I HATE spacers.

exactly what I did.  +1

Edited November 5, 2017 by RonPogi

[OPENB]

I switched to MG 124 CMJ bullets. Best feeding profile, non-exposed base so no lead in the comp. Problem solved. The Everglades Ammo competition JHP bullets look good with the rounded profile, I may try some. I use old style SV & STI. 

[Hi-Power Jack]

I haven't had trouble with my old STI or old SVI mags using MG124 gr JHP's, anywhere

from 1.145" - 1.170".   I've standardized now at 1.160".     

[OPENB]

I had the same feed ramp jams with PD 124 JHP & either old style mags. Too bad, nice bullets for the cost.

[Jumprun13k]

I have a bunch of STI Mags that are mostly good to go. But I prefer the MBX mags myself. I am leaning towards selling the STIs to finance some new MBX.

[frankge]

I've been reloading RMR JHPs and they have a rounded nose profile...

 

[theWacoKid]

Constantly overlooked "mag problem" is the catch interface. Look for abnormal wear on mag catch, magazine cutout, or grip pocket. Try some different mag catches too. 

[frankge]

it looks like the round is not pointing at the breach, just below it so most impact the upper part of the ramp on the way in. Is that mag catch? It appears that even with that situation the mags are running ok - at least with me manually racking the rounds with each full magazine.

[Steelix]

You open up the front of the feed lips to .360-.365, that will angle the bullet up a little more. But hitting the top of the ramp is ok. All my magazines are tuned a little different, as the magazines are stamped and the mag catch hole can be in a different spot on each magazine.