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Discussion Starter · #1 ·
I was thinking of extending the barrel length on a ps90. I was wondering if all the gun powder burned off in a 16 inch barrel? If not how much longer would you need the barrel for a complete burn off? If this could be done would it the velocity of the bullet be faster and the range be farther? I know this is the opposite way people are going and sounds silly but I like going against the grain sometimes. Any information on this would help me allot in my top secret project. Thanks fn forum members!!:shock:
 

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Not a bad idea I guess Like everybody said the round has its limitations.
 

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There comes a point where the length of the barrel will actually slow the projectiles velocity.....
That is true, however for most calibers the barrel length required to incur velocity loss is much longer than you might think. Even relatively low power rounds like .45 ACP and 9mm benefit from a barrel length out to 17 inches before starting to lose some velocity. The lowly .22 LR keeps gaining up to 18" and likely would continue with even a few more inches. Off the to of my head I seem to recall that maximum velocity for 7.62 NATO can be had with something like a 32 inch barrel and .50 BMG with a 48 inch barrel. Obviously these lengths are well beyond what most people have on their rifles. I suspect the barrel length for maximum velocity of the 5.7 round is well beyond what anyone would consider for a PS90.

BBTI - Ballistics by the Inch :: Calibers/Cartridges
 

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Try it and let us know how it does.

Get a Chronograph, if you don't already have one.
 

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Yes, I am aware of the "Ballistics by the Inch" as well. However, what would be the purpose. If you want a longer barrel just upgrade to an AR15 and you will get more bang for your buck. The PS90 is a bull pup and I still see no purpose in increasing the length of the barrel other than to do it, which is a lofty goal by itself, but pretty useless as far as the firearm is concerned. I think you would be better off re-chambering the AR15 to accept the 5.7X28 mm ammo. Wait, this was already done - the AR57 upper. Although it only has a 16.4 inch barrel, it would be far less expensive to get a longer barrel for the AR57 upper then to try to add onto or make a longer barrel and shroud for the PS90 and the OP would have all the answers that he could want about length and velocity of the 5.7 round.

Ever wonder why FN designed the PS90 (as a civilian rifle) with a 16 inch vs 18 inch or even 20 inch barrel? Although I do not have the answer, I suspect it was to keep the bull pup design and not to go to a full sized rifle like the AR15 which would have obliterated the niche design of this particular firearm, along with the fact that the NFA requires that a rifle barrel be a minimum of 16 inches with an overall length of 26 inches to stay out of the NFA arena. I am sure that the bottom line on cost was a factor as well. Wonder why FN has not offered the PS90 with any longer barrels?

As I said, as an experiment is would be a nice train to ride on but the end result and cost of doing it is somewhat prohibitive I would think. To get all the data, you would need a 17in, 18in, 19in, through 26in barrel and shroud built to get all the results. And then as mentioned, there is the rifling that has to be considered, as well as the blow back design which is not conducive to longer barrels. Dwell time would have to be reworked and a new bolt group might have to be constructed or modified each time the barrel is lengthened.

Cha ching, cha ching, cha ching.....

Good luck on your TS project and keep us in the loop.
 

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I would think, due to the blowback design of the action, that at some point the barrel length would become moot because the pressure would drop from the breech end as the action opens. I may be far off on this assumption... perhaps the bullet leaves the barrel in nanoseconds where as the action opens in 1/10s or something... but I would think in a PS90 where the action is direct blow-back and the round was designed for a 10.4" barrel to begin with this may just be an exercise in "farting in the wind" where the cost FAR outweighs the barely negligible benefits.

But then, I could be wrong.
 
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Discussion Starter · #14 ·
Thank you for your imput all this information will help in makingthe right decision. more research is needed I'm sure. If anything evolves from this project I'll post it. Thanks fn forum members. Any more information on this will be appreciated!
 

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If you want to extend the range of the round, just aim higher and arc the bullets in.
That would only work to a certain point. After that, you would start to loose distance no matter how high the arc was. Also, it is most difficult to hit a target a 3 o'clock when you are aiming at 1 o'clock. You are just funnin' though.......
 

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If you want to extend the range of the round, just aim higher and arc the bullets in.
The highest you can arc your barrel up to achieve the longest range possible for a specific loading is 45degrees up, and that is only if you are firing in a vacuum.
Any higher and you lose range as HK just said.

Now, in the real world, we do not have a vacuum, bullets have to fight fluid, which is air in this case.
Since air exerts a fluid drag on a bullet, even if it is a boat tail, the max you can arc your bullets is by tilting your barrel up is around 30degrees.
Raise your barrel up any higher and again, like HK said, you lose range.

To aim with such howitzer firing angles, you had better be good with trig and draw up some firing tables for each loadings, or carry with your a calculator or computer and appropriate app to do that calculation for you.
And before your shoot, you had better know the range of the target too.

Aside that you could hit a target very far away, you also have to consider the energy loss, again due to the fluid dynamics of aerodynamic drag.
Shoot a target too far away and the bullet will bounce off his forehead like an airsoft pellet only to piss him off.
Or possibly amuse him a little and make him laugh.

Anyway, I digressed too much here.

The point is going with a longer barrel, say 18in or 20in, can capture more wasted powder burn to accelreate the 5.7 projectile a little more to give it more muzzle velocity and thus more muzzle energy.
The question is loading: too little powder (such as some subsonic loadings of the 5.7) and you could put yourself in danger of a squib (not enough powder to push it all the way out the barrel).
On the other side, too much loading and sure, you will push the projectile all the way out the muzzle, but you could blow up the action and the firing chamber, etc.
 

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If you want higher velocity buy some of the Elite Ammo stuff that's out there, you'll get some incredible performance out of the 16" barrel. You can also get into reloading for it and do some neat things too.
 

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If you want higher velocity buy some of the Elite Ammo stuff that's out there, you'll get some incredible performance out of the 16" barrel. You can also get into reloading for it and do some neat things too.
Make sure you read some of the old threads about that ammo.

People have had issues. I'm sure some other's will comment.
 
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