TT springs in a TF basepad?

[optimator]

I recently bought two TTI and one TF mag extension for my 9mm M&P. I did purchase these used. Today I got 3 new extra power extended TTI springs. After putting one of them in the mag with the TF extension, it will only hold 18. 19 if I really jam it in. Do the TT springs need to be trimmed to work properly in the TF basepads?

[swordfish]

Which ones did you get? The 140mm extensions? The Taylor Freelance should be +6. I can only get +5 with my Brownells +10% power springs though, which brings my round count to 22 in each mag.

According to TTI's website "

Replacement spring for high-capacity magazines with TTI Firepower Base Pads for M&P.

Designed exclusively to work with the TTI base pads. Each coil compresses and stacks into the neighboring coil to provide the highest capacity available in your magazines." So no, it shouldn't need to be trimmed. How do they work with the TTI basepads?

[optimator]

With the TT spring the TF basepad will only hold 19. With a stock mag spring I can get 23. The TT baspads take 23 no problem. Weird.

Edited April 15, 2016 by optimator

[swordfish]

If the extensions are the same length, my assumption would be the spring is binding on the TF extension as it gets compressed. Although it could also be the follower. maybe the spring misaligns the follower on the way down. Part of the reason the stock mags only hold 17 is the amount of space the spring takes up. If the spring is out of the way, I bet with just the follower and the stock mag you could hold 19. Maybe see if there's an overlap of the TF extension on the inside of the mag well, or try beveling the bottom edge of the follower if it looks like it could use it.