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Tuning JP SCS system for least dot bounce?

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My very un-expert opinion is that the VV N320 powder was completely burned up well short of the end of the barrel, so the rest of the barrel just provided drag on the bullet.
 



I imagine that is what is happening. Similar to how slower burn powders improve muzzle brake performance.

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15 hours ago, LowSpeedHighDrag said:

 

My very un-expert opinion is that the VV N320 powder was completely burned up well short of the end of the barrel, so the rest of the barrel just provided drag on the bullet.

 

If that's the case then velocity / PF will be higher. 

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1 hour ago, LowSpeedHighDrag said:

 

Sorry, wouldn't it slow down the bullet and cause a drop in PF?

 

 

You'd think so

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13 hours ago, RexKramer said:

 

 

You'd think so

 

I'm curious at what barrel length the N320 powder would be completely burned up.  It may be at a longer length than a pistol but shorter than the rifle.

 

Again, just a guess, I've never tried to do the experiment.

Edited by LowSpeedHighDrag

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12 hours ago, LowSpeedHighDrag said:

 

I'm curious at what barrel length the N320 powder would be completely burned up.  It may be at a longer length than a pistol but shorter than the rifle.

 

Again, just a guess, I've never tried to do the experiment.

 

I read (yeah one of the worst phrases to use) that fast burning powders such as N320 and Titegroup will be fully burned by the time the bullet gets to the end of a 14.5/16" barrel.  The thread was originally discussing the best brakes for PCC and came to the conclusion that even with slow burning powders there wasn't too much "oomph" from the gas at the end of a long 9mm barrel. Obviously there is gas coming out, but it's not enough to work a brake to much effectiveness.  During the course of that discussion a few people were talking about velocity loss with fast powders and longer barrels.

 

Now exactly how long a barrel needs to be to have this happen with a certain load work up?  I have no idea. To test it you'd need two rifles that are identical other than the barrel length. Say a 8" and 16" barrel. Maybe even a 12" barrel in between.

 

 

Edited by RexKramer

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I read (yeah one of the worst phrases to use) that fast burning powders such as N320 and Titegroup will be fully burned by the time the bullet gets to the end of a 14.5/16" barrel.  The thread was originally discussing the best brakes for PCC and came to the conclusion that even with slow burning powders there wasn't too much "oomph" from the gas at the end of a long 9mm barrel. Obviously there is gas coming out, but it's not enough to work a brake to much effectiveness.  During the course of that discussion a few people were talking about velocity loss with fast powders and longer barrels.
 
Now exactly how long a barrel needs to be to have this happen with a certain load work up?  I have no idea. To test it you'd need two rifles that are identical other than the barrel length. Say a 8" and 16" barrel. Maybe even a 12" barrel in between.
 
 



All my tightgroup Pistol loads pickup a minimum of 150fps out of a 16” barrel. They also pickup quite a bit in an 8” sbr. I have never tested a 12” barrel to see if it is faster than a 16” but I doubt it would be.


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I can run some numbers in quickload when I have the opportunity.

 

But I think the question is incorrectly put. The question is not really about slow vs. fast burning powders nor about if a bullet starts slowing down with a powder that is fully burned before the bullet exits the muzzle. An exposion is the rapid change of state from solid state into gas. The question should be if the powder burned has generated enough gas (=pressure) to be able to accelerate the bullet until it exits the barrel.  This is more a function of mass in the powder burned => gas volume vs volume of barrel vs friction/drag. 

 

I understand the thinking, however. A slower powder generally needs more powder to generate the same power factor. More mass burned = more gas. 

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For a powder like N320, I believe it's all burned in about 11.5". This info from a well known gunmaker.

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