STI mags with TTI internals

[buckonz]

I have 126mm STI .40 mags, which I've upgraded with:

- SVI IPSC Base Pads

- TTI Universal Follower

- TTI 11 Coil Spring (with 1 coil removed)

I removed a single coil from the TTI spring as they were designed for 140mm STI mags.

I can get 18 x .40 rounds in the Mag, however in my DVC Limited when I get to the very last round in the Mag, the following happens:

1. The slide lock engages.

2. When you press the Slide Release the last round fails to feed.

I'm assuming I should just replace the springs without cutting them.

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[buckonz]

I have been advised that the last round probably isn't sitting proud enough and expanding the spring a bit, especially the few coils closest to the follower, should help.

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[jcc7x7]

Check how much engagement your slide stop is hitting the follower.

You may need to trim the follower or slide stop. If you want your slide not to lock back on the last shot file off the tab on the follower that hits the SS. That will stop the slide locking back pre maturely and allow the last round to move up higher so it gets picked up by the slide

[lucas]

I use grams for my 40 STI and every mag, I had to trim down the follower to lock back without leaving a round in the mag. All guns may react different. for mine I trim down the thickness almost half way down ,then I shoot it ,and if it still is not correct I use my knife to scrape a little more each time as needed.

STI tubes have varying feed lip specs to the point that not one of my 6 tube followers have the same amount of trimming. However, with 126mm mags in 45acp I had problems not with locking back leaving a round but locking back period. Out of 11 tubes I finally have 5 with grams spring /follower that do lock back. With the 45 ,I had not only to deal with varying feed lip specs, but apparently the followers are aswell. Some of the grams spring/follower did not like any of my tubes.

Never the less ,I for one will continue to primarily stay with Grams.

[Sarge]

Are you using it for something that requires the slide to lock open? Most competitive shooters just trim them off so the slide does NOT lock back at all.

[buckonz]

Thanks for the replies.

I'm aware that a lot of competive shooters have their guns/mags set up so the slide does NOT lock back on an empty mag, however I don't completely understand why?

[BeerBaron]

it's to

Thanks for the replies.

I'm aware that a lot of competive shooters have their guns/mags set up so the slide does NOT lock back on an empty mag, however I don't completely understand why?

it's done to prevent the exact issue you're having. that is premature lockback on last round.

sometime you can tune around it, but to ensure 100% reliability and no chance of it locking back with a round still in the mag many shooters just totally disable the ability for it to lock back.

[EkuJustice]

For one, the competition followers tilt some so they are a pain to set to lock back when empty and not when only one round is left. As springs wear, that changes so it may not always lock back when you want it to and only when you want it too.

Second, with a slide locked back it is easy to over insert a mag into the gun which is not easy to get unjammed on the clock and can break an ejector. this is bigger issue with the longer 140/170 mags especially with the taran style base pads ie dont extend up the mag at all.

Third, there isnt really a reason to have it lock back. In limited and open the gun really shouldnt be run dry. ON the divisions where capacity is limited IDPA/Limited 10 the capacity of the aftermarket followers isnt needed so the best bet and most reliable option to lock back is the factory guts.

[MatchShooterSupply]

I know Grams followers lock the slide with 1 round just have to do a little filling on the follow imagine the same for TTI