Thread: Glock 29 kaboom
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Old 02-12-2013, 02:37   #88
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Originally Posted by ModGlock17 View Post
Remember that the spring's force = 0.5 * k * square(distance) plus mfg rated force.
Yes, you are correct, it's called Hooke's law. I ignored it for this calculation due to the small amount of distance the slide has to travel, so the spring force remains relatively unchanged.

Originally Posted by ModGlock17 View Post
Now, turn to the issue of "nearly" in battery, a strong spring would regenerate enough velocity and force from recoil, to slam it into full battery a little more authoritatively. Right?
This would seem to be true, especially if the slide were to travel full length in recoil (which I believe it has to for reliable cycling). Upon slide return to battery, beginning at the physical slide stop, the heavier weight spring is going to accelerate the slide faster than a lighter weight spring, so the final velocity of the slide when it reaches full battery will be higher. I'm not sure how important this is, but it would seem that if there were any friction/dirt/ammo tolerance issues impeding full lock up, that a heavier spring would certainly help overcome that.

The other benefit to the heavier spring, and the one that applies most to those of us who shoot hot ammo, is that the slide velocity will be lower when the slide reaches the physical stop at the end of recoil. This means less battering of your frame.

I admit, I used to believe that the heavier spring helped maintain lock up, but I no longer believe that. I'm more inclined to believe the numbers.

Originally Posted by Any Cal.
Spring specs seem to vary, but in general the rated weight in Glock springs is the spring force at full compression, not the installed length.
I checked my G29 with the stock spring, and this is true. It only takes about 5.5lbs of force to start the slide moving from full battery, but about 19lbs of force just before the slide hits the slide stop limits. I also checked my G20 with a Wolff 22lb spring, and it too starts to move from full battery around 5.5lbs, with right at 22lbs near the stop limit. I don't have a very good way to measure this, I used a baby scale that measures to the nearest 0.1 ounce. But it was repeatable.

So, my initial assumption was incorrect that the slide and barrel were working against a 17-22lb opposing force. It's more like 5-7lbs of force. Fortunately, it makes so little difference since it's working against an accelerating force of 2320 lbs, that for practical purposes, it can be ignored. So it doesn't affect the original numbers. But for the non-believers, this also disproves any possible benefit that an extra weight spring might have on lock up timing. There just isn't that much difference in spring force between a 17 and 22 lb spring in that first .210" of travel.
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