earthshine402 Posted February 23, 2016 Share Posted February 23, 2016 (edited) I am gearing up for shooting open, I plan on purchasing a used custom 38 super build. I bought some STI magazine tubes - 140mm and 170mm. I put new TTI base pads and Grams springs and followers in them. I tuned the magazines according to instructions in the Dawson mag tuning kit - I have done this in .40 with success. However, after loading up some dummy rounds in 38 super and super comp, when pulling the rounds out of the magazine one at a time, a good number of them don't snap fully up right up against the feed lips. The case head does, but some of them sort of angle down, in a nose-dive fashion. This doesn't happen so much in the 170s, but in the 140's it happens quite a bit.I'm not sure this will be desired for feeding purposes. I thought 38 was supposed to be more reliable with regards to the magazines and feeding, but this doesn't seem right. I know I may be a little pre-mature in asking this question as I do not yet own the open pistol, but I'm just doing my homework and preparing so I can take it out and race with it as soon as possible when I do get it. Any advice on this is appreciated. Thanks Edited February 23, 2016 by earthshine402 Link to comment Share on other sites More sharing options...
mwray Posted February 23, 2016 Share Posted February 23, 2016 Maybe you could try some MBX mags Link to comment Share on other sites More sharing options...
Rye Posted February 23, 2016 Share Posted February 23, 2016 Have you tried it without tuning the mags? Link to comment Share on other sites More sharing options...
earthshine402 Posted February 23, 2016 Author Share Posted February 23, 2016 Maybe you could try some MBX mags I will eventually if I can't solve this issue, but that is not my concern at the moment. Lots of guys have run STI mags in 38 successfully, and I would like to try to figure it out. Link to comment Share on other sites More sharing options...
earthshine402 Posted February 23, 2016 Author Share Posted February 23, 2016 Have you tried it without tuning the mags? yes, it did it before I tuned the mags. Maybe I need to be more precise on the feed lip dimensions. Link to comment Share on other sites More sharing options...
Shadyscott999 Posted February 23, 2016 Share Posted February 23, 2016 What is your OAL? Link to comment Share on other sites More sharing options...
earthshine402 Posted February 23, 2016 Author Share Posted February 23, 2016 What is your OAL? MG JHP 124gr, If I remember correctly, OAL is 1.235", but I'll double check when I can. Link to comment Share on other sites More sharing options...
Glk21C Posted February 23, 2016 Share Posted February 23, 2016 It's possible with the jhp 1.235 might be a smidge too long when the round is feeding up the tube. Might be. Try first some at 1.225, might help. There is also the chance the double stack to single stack transition inside the tube is not to spec. Does the tuning guide from Dawson cover that? Good luck, hopefully it's just an oal adjustment. Link to comment Share on other sites More sharing options...
earthshine402 Posted February 23, 2016 Author Share Posted February 23, 2016 It's possible with the jhp 1.235 might be a smidge too long when the round is feeding up the tube. Might be. Try first some at 1.225, might help. There is also the chance the double stack to single stack transition inside the tube is not to spec. Does the tuning guide from Dawson cover that? Good luck, hopefully it's just an oal adjustment. Thanks, I'll try some dummy rounds at a shorter OAL. The Dawson tuning guide does not cover tuning the double-to-single stack transition. It covers: magazine dimension - front-to-back, polishing inside, deburring feed lips, feed lip dimensions front-to-rear. Link to comment Share on other sites More sharing options...
Bamboo Posted February 23, 2016 Share Posted February 23, 2016 I've had good luck with MG JHPs in 38 super at 1.235" OAL in STI mags (Grams follower/Dawson base pads) as well as with MBX mags. Another thought - I gather that you are hand stripping the rounds and not feeding them through a gun? When you get your gun try hand cycling your dummy rounds at 1.235" through the gun. The slide will strip the rounds off crisply and the second round down should snap up crisply if all is working right. It is hard to replicate all the nuances and dynamics of what is happening by stripping the rounds out by hand. Link to comment Share on other sites More sharing options...
earthshine402 Posted February 23, 2016 Author Share Posted February 23, 2016 I've had good luck with MG JHPs in 38 super at 1.235" OAL in STI mags (Grams follower/Dawson base pads) as well as with MBX mags. Another thought - I gather that you are hand stripping the rounds and not feeding them through a gun? When you get your gun try hand cycling your dummy rounds at 1.235" through the gun. The slide will strip the rounds off crisply and the second round down should snap up crisply if all is working right. It is hard to replicate all the nuances and dynamics of what is happening by stripping the rounds out by hand. you gather correctly.. I do not yet have the open gun.. just trying to prepare as much as possible before I have it so I can run it right from the get go - fast! A friend has just suggested the same thing - see how they go in the gun, during live fire. It is possible that I'm just worrying too much and asking questions about something that might not occur during live fire. Link to comment Share on other sites More sharing options...
Aircooled6racer Posted February 23, 2016 Share Posted February 23, 2016 Hello: Try some Dawson followers and ISMI mag springs. I have been running this combo in STI tubes for 9mm with no spacers. So far they are working very well in 140mm. The 170mm needs some more testing still. Thanks, Eric Link to comment Share on other sites More sharing options...
Shadyscott999 Posted February 24, 2016 Share Posted February 24, 2016 What is your OAL? MG JHP 124gr, If I remember correctly, OAL is 1.235", but I'll double check when I can. might try shortening the ammo a bit. I can't run JHP's at 1.234 without the bullet contacting the front of the tube an inch down or so. Link to comment Share on other sites More sharing options...
misterkhan Posted March 2, 2016 Share Posted March 2, 2016 I've had that occur when my springs were getting weak, replaced them and all better. Link to comment Share on other sites More sharing options...
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