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Does minimizing throat jump improve accuracy of 9mm luger pistols?

This is a discussion on Does minimizing throat jump improve accuracy of 9mm luger pistols? within the Ammo and Reloading forums, part of the Gun Forum category; Does anyone who reloads here try to obtain the best "throat jump" when choosing or creating a load recipe for 9mm (or any pistol for ...


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Old 04-20-2017, 08:53 AM   #1
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Does minimizing throat jump improve accuracy of 9mm luger pistols?

Does anyone who reloads here try to obtain the best "throat jump" when choosing or creating a load recipe for 9mm (or any pistol for that matter) ?

I ran across the concept in the article referenced below and I am wondering if this is a good reason to try and use recipes that call for the max COAL in order to minimize the distance between the ogive of the bullet and the lands of the barrel.

It could also be the case that this does not really pertain to pistols.

Here is the article (it has two parts):

Effects of COAL and CBTO | Part 1 | Berger Bullets Blog

Effects of COAL and CBTO | Part 2 | Berger Bullets Blog

Regards,
-John
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Old 04-20-2017, 10:40 AM   #2
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I've never done it with handguns, but have experimented with it pretty extensively with precision rifles, and it sometimes made a huge difference there, but not always.

Every rifle is it's own separate thing.
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Old 04-20-2017, 11:56 AM   #3
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What flash said.
I do it for precision rifles only.

warning warning
John, you had 200 rounds fire 100%, do not touch anything on your seating dies.
The wrath of God will decend on you, your hair will fall out, your car wiil throw a rod, cow will go dry and hens quit laying.
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Old 04-20-2017, 12:01 PM   #4
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Not to mention the fact that the fleas of a thousand camels will nest in your nostrils.
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Old 04-20-2017, 12:16 PM   #5
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We're going to have to keep a close eye on him.
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Old 04-28-2017, 04:23 AM   #6
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Ya'll crack me up


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Old 05-03-2017, 05:01 PM   #7
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I have actually found better accuracy with shorter OAL's in 9mm.
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Old 05-19-2017, 06:11 PM   #8
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You guys are funny... but yeah, if what you did is working well, don't touch a thing!

COAL is important, when following a recipe, because of volume in the case behind the bullet, and managing pressures. If a reputable loader specifies a projectile and powder combination, and lists a OAL for that combo, it's likely that they have found the best velocity for that combination, within safe limits.

So, trying to seat longer to close the gap will change the performance. I would be willing to bet that any potential improvement would be mitigated by the change in powder performance.

If I were loading for maximum accuracy, I would sort my brass by brand, then sort by length of case, then pay close attention to my crimp.

Hope this helps!
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Old 05-20-2017, 05:05 AM   #9
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In rifles, I've never found the reloading data COAL to have the best accuracy and that's understandable as all guns are a law unto themselves and what's accurate in one probably won't be as accurate in the next one.

I've observed this a number of times in my life, the most blatant example being when I was 17 and my best buddy and I each bought .30-06 rifles. They had consecutive serial numbers and appeared identical.

I worked up a load for mine, and got great accuracy. Then we tried it in his and got patterns instead of groups.

That's pretty much normal.
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Old 06-04-2017, 04:54 AM   #10
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Yeah, I completely agree with you on that with rifles. FB, do you use a chrony, and if so, what brand.


for the OP, I have to imagine that on a 9mm pistol, when range shooting out to 10 or 13 yards, you are not going to see a vast difference in performance for reducing jump. I would bet that you would encounter feeding issues before you collected any good data on performance. Here's a thought, since most semi-autos are designed to eat as many manufacturer's ammo as possible (and they all vary a bit) maybe you can do some research on that particular gun and find out the preferred OAL the manufacturer suggests. They must have an opinion on the best length, as used during their own testing.?.?
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Old 06-04-2017, 07:02 AM   #11
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To the best of my knowledge, no handgun or rifle manufacturer has ever specified a COAL for their guns. Too many variables to even attempt to do this.
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Old 06-04-2017, 12:21 PM   #12
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I think that it may possibly improve accuracy, but you probably would not see the difference in the typical use of a handgun. I think that long range shooting from a bench rest (or ransom rest) using telescopic sights would required to determine the difference it makes.

You also may not be able to load the rounds into your mags, and end up with a single shot firearm.

Last edited by Mainer; 06-04-2017 at 12:24 PM.
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Old 06-04-2017, 04:07 PM   #13
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I have tried 8 different powders, and adjusted each one minimum to maximum.
I have tried 4 bullets.

The only time I saw accuracy really effected was 10mm.
Saw a lot of difference, and quit it before finding the best solution.

With 9mm, 40, and 45 I never really saw a difference in accuracy that I could say was not my hand.
I did find powders and loads I liked more.
I settled on Titegroup and Power Pistol.
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