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7 Foot to 15 Foot Velocity Drop


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Was testing some 9mm loads today at 7 feet. Using a Glock 17 and an M&P 9. Both guns were running almost identical averages with the same load.

As my buddy was getting ready for Double Tap and the loads were running close to 140PF, he says he was going to drop the charge.

I said lets see what it is at 15 feet before you go dropping the load. The velocity average dropped by 50 FPS.

We are looking at each other like WTH?!?! So he gets the other gun and fires it at the longer distance too.

Same exact 50 FPS drop.

Has anybody else seen a 50 FPS drop in about 8 feet? The chrono we used was my CED Millineum. These were 10 round groups.

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Not a whole lot of information given, but if you are shooting 9mm 147gr RN bullets at 140 PF, the muzzle velocity is approximately 952 fps. Using a simple ballistic calculator found on the internet (http://www.handloads.com/calc/), the velocity at 5 yards is 947 fps and at 10 yards is 942 fps. A far cry from a 50 fps drop.

Kind of confirms muzzle blast causing false readings up close.

Bill

Edited by Flatland Shooter
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Not a whole lot of information given, but if you are shooting 9mm 147gr RN bullets at 140 PF, the muzzle velocity is approximately 952 fps. Using a simple ballistic calculator found on the internet (http://www.handloads.com/calc/), the velocity at 5 yards is 947 fps and at 10 yards is 942 fps. A far cry from a 50 fps drop.

Kind of confirms muzzle blast causing false readings up close.

Bill

That's a whole lot closer to what we were expecting and makes perfect sense. Thanks.

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