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Discussion Starter · #1 ·
I have a XD40 SC with maybe 300 to 400 rds through it. I noticed last week while I was qualifying for my CCW that the slide would lock back prematurely once in awhile. I was aware that this could be a thumb placement issue but couldn't rule it out at the time.

Yesterday my son and I both had the issue a few times again. I was careful with my thumb but still not 100% sure it wasn't my problem. Just a note first time I was shooting Winchester 100 rd box and second time reloads and Winchester 100 rd box.

I read the article that said sometimes the rounds were hitting the slide lock on the inside, so I stripped my gun and put boths mags in to check clearance. Both looked good, even removed a rd at a time to see if it was any different with say only 6 rds, 5 rds, and etc left in mag. At this point I decided that it must be my thumb placement and would pat better attention next range trip.

But what didn't look right is how the high or low the round would sit with mag in gun. The lower sitting one is the 10 rd mag and the higher one is my 9 rd mag. Both are what came with the 40 SC brand new. Any input?
 

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Discussion Starter · #2 ·
This is the 10 rd mag looks like.



This is the 9 rd mag.


Is it just me or do they sit at different height and angles?

 

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I am carrying my Glock today...I will try to post pictures of my mags when I get home...see how it compares
 

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Discussion Starter · #4 ·
Thanks, this is my carry gun and if the premature slide lock is my thumb placement then I can work on that. Next I need to see if it's just one mag or both that it happens with. Like I said the only difference is how high or low the rd sits in each mag. My 9 rd mag sits higher and more of an angle.
 

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I bought a XD40sc in early 2008 and I had the same problem, other people shot it and it would lock back once in a while. I tried to make it lock back with my thumb but that would not happen. I called Springfield and they said to send it in, got it back in a week, no note on what they did, but about 4000 rounds later it has not happened again. Call SA and talk to them.
 

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Discussion Starter · #8 ·
I bought a XD40sc in early 2008 and I had the same problem, other people shot it and it would lock back once in a while. I tried to make it lock back with my thumb but that would not happen. I called Springfield and they said to send it in, got it back in a week, no note on what they did, but about 4000 rounds later it has not happened again. Call SA and talk to them.

May be what I do. The two different mags sitting differently may be an issue also.
 

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I bought a XD40sc in early 2008 and I had the same problem, other people shot it and it would lock back once in a while. I tried to make it lock back with my thumb but that would not happen. I called Springfield and they said to send it in, got it back in a week, no note on what they did, but about 4000 rounds later it has not happened again. Call SA and talk to them.
They almost always replace the slide stop. When a gun and slide stop are both just slightly out of spec in the wrong directions they can cause this issue with certain bullet nose profiles. Only seems to happen with the foatys.
SA will fix you up ron.
 

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When a gun and slide stop are both just slightly out of spec in the wrong directions they can cause this issue with certain bullet nose profiles. Only seems to happen with the foatys.
SA will fix you up ron.
Good point!

When you have a machined or cast piece, you have a tolerance on the dimensions. For an example, a 1" piece can be .995 to 1.005. Now, let's say the mating piece is 1.008 to 1.013. to allow clearance. If the smaller part is made to the highest limit and the other part is made to the lowest limit, you have a very tight fit. If it's the other way, the small part is made to the low limits and the large part is made to the high limits, you have a very sloppy fit.
 

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Good point!

When you have a machined or cast piece, you have a tolerance on the dimensions. For an example, a 1" piece can be .995 to 1.005. Now, let's say the mating piece is 1.008 to 1.013. to allow clearance. If the smaller part is made to the highest limit and the other part is made to the lowest limit, you have a very tight fit. If it's the other way, the small part is made to the low limits and the large part is made to the high limits, you have a very sloppy fit.
AKA: Tolerance stacking.
 

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Yup. but people who don't have machining and tolerancing experience might not know that term. Lots of people don't understand that a "1 inch" part may NOT be 1". :eek:
That's who I was pointing that at, I know you know yur stuff.
 

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mine do not do that OP...the pictures tell it all...reloaded them with Golden Sabre this morning, sorry for the delay
 

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Discussion Starter · #16 ·
mine do not do that OP...the pictures tell it all...reloaded them with Golden Sabre this morning, sorry for the delay

No problem at all, thanks for getting back. I think there's an issue with my 9 rd mag. Whether that is what's causing the premature slide lock or a seperate issue all together? Sounds like a good reason to hit the range. If the slide locks before mag is empty on just the one mag and not the other, then that may be my problem. :confused:
 

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The 9 round mag looks like it's holding the rounds at too severe of an angle. The bullet casing should be at the same angle as the back angle of the mag.


Pull the mag apart and make sure the follower in installed properly seated against the spring.
 

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The 9 round mag looks like it's holding the rounds at too severe of an angle. The bullet casing should be at the same angle as the back angle of the mag.


Pull the mag apart and make sure the follower in installed properly seated against the spring.
^^this^^
 

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Discussion Starter · #19 ·
The 9 round mag looks like it's holding the rounds at too severe of an angle. The bullet casing should be at the same angle as the back angle of the mag.


Pull the mag apart and make sure the follower in installed properly seated against the spring.
I'll do that. I'll update asap. Thanks.
 
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