scottlep Posted October 3, 2013 Share Posted October 3, 2013 (edited) I am having a weird issue with my new (used...but new to me) 2011 STI open gun. I will try to explain it the best I can. Sorry if this gets long winded. The gun came with two 140mm mags and I just bought three more brand new 140mm STI mags. Here is the scenario. If I use each of the mags, shooting slowly, etc. they load in the gun fine and run great. But lets say I am practicing my reloads. I will start with say 5 rounds in each of the five mags. Lets say mag #1 and #2 are the used ones and mags #3, #4, #5 are the new ones. I will start the practice run with mag #1, run it empty, drop the mag, go to #2, run it dry (no problems so far), drop the mag, load #3....big problem. The trigger gets so hard to press that I almost cannot even get the gun to go bang. If I drop the mag, the problem goes away. I can pull the trigger with the normal amount of resistance. I put the same mag back it...run it dry with no problems, drop it, then load #4...the same thing....I can barely pull the trigger hard enough to get the gun to go off. If I force the trigger to make the gun go off and I don't drop the mag each subsequent trigger pull for that mag is very hard. Not as hard as the first one but much harder than the normal 2# pull. I detail stripped the gun last night and went over all the parts and gave it the best cleaning I think I have ever given a gun. But I still have the problem. I assume that it is something related to the newer mags since it never happens with the older mags. I haven't had time to compare the new and old mags with a set a calipers, but a visual check of the new mags really shows no major differences between the old and new. Also, the problem doesn't occur if I put the new mags in the gun empty. I just wanted to get a jump on gathering info since I am supposed to shoot a match with the gun this weekend and want to get it straightened out before then. Any info would be greatly appreciated!!! Sorry if this topic was covered in BE before. I searched but wasn't sure how to ask/search for the problem. Edited October 3, 2013 by scottlep Link to comment Share on other sites More sharing options...
Alan550 Posted October 3, 2013 Share Posted October 3, 2013 Checking the new ones with a caliper when they're loaded would be the best idea right now. My guess is that they swell some when loaded and are making contact with the trigger bow in some fashion. Alan~^~ Link to comment Share on other sites More sharing options...
scottlep Posted October 3, 2013 Author Share Posted October 3, 2013 (edited) Thanks Alan, I will do the measurement when I get home from work today. To add a little more info....the hard trigger pull doesn't seem like a dragging type resistance. It is more like one point of resistance. When I do force the trigger during the malfunction it goes off with more of a breaking action than a dragging. Hopes that makes sense. Edited October 3, 2013 by scottlep Link to comment Share on other sites More sharing options...
Sarge Posted October 3, 2013 Share Posted October 3, 2013 (edited) Mags out of spec pushing forward on the bow? Or bow out of spec Edited October 3, 2013 by Sarge Link to comment Share on other sites More sharing options...
748r_bb155 Posted October 3, 2013 Share Posted October 3, 2013 the mag is pressing on the mag release, pushing it forward. The overtravel screw bottoms out on the mag relase. So the overtravel stopp will engage the trigger bow to eary and you will not be able to pull the trigger all the way back. back off the overtravel screw and iy should work. What causes this is probably the slot (size or shape)in the magazine for the mag relase. had the same problem with sps 29 round magazine. Opend up the mag slot a little and backed out the overtravel screw on the trigger bow. eo Link to comment Share on other sites More sharing options...
scottlep Posted October 3, 2013 Author Share Posted October 3, 2013 Thanks 748, I will give that a try. I was going to try backing out the OT screw when I shot it today, but didn't have the correct size allan wrench with me. Link to comment Share on other sites More sharing options...
pxm142 Posted October 3, 2013 Share Posted October 3, 2013 I saw your post, and I am so happy someone else is having this problem! Wait, I mean, I am sorry you are having issues, but glad you posted about it! I went through this EXACT same problem with my Trubor last month. All this time I thought I just had bad luck... I had 3 mags that were just about impossible to shoot, and the rest were sporadic. After toying with the mag catch and overtravel, I finally filed down the inside, forward, upper edge of the trigger bow to gain some clearance. You could see the offending area sticking out a little when you looked down the magwell. I only took a few thousandths off, and now it runs perfect, with all of my magazines. Link to comment Share on other sites More sharing options...
scottlep Posted October 4, 2013 Author Share Posted October 4, 2013 Got it fixed. I backed out the OT screw a half turn and opened up the mag catch holes in the newer mags to the same size as the older mags. She is running like a raped ape now. Thank you all so much for your suggestions. You guys rock!!! Sent from my iPhone using Tapatalk - now Free Link to comment Share on other sites More sharing options...
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