Depends if the bullet was designed to work with a specific barrel length or not. I'm off to wiki walk for figures. BRB
edit.
PS-90, with the longer barrel, has a peak MV of 2300 fps in old money.
P-90 has a peak MV of 2,350 fps in old money.
Marginal drop there, as I suspected. Longer barrels don't always lead to better performance.
^ PS-90 and P-90 don't use the exact same model of ammo despite the same caliber. Commercial grade 5.7mm != military grade 5.7mm.
Yeah, I went a bit further and found this page:
http://www.thetruthaboutguns.com/2011/03/jeffrey-lynch/gun-review-fnh-ps90/
There's all sorts of different figures in here about muzzle velocities and types of ammo.
Night Clerk of the Apacalypse.
Best bet is to bench test fire with a chronograph with all of the various loads. Especially the various commercial loads. IIRC there is a fairly high velocity commercial round that has some ridicously high muzzle velocity out of the PS-90. It only fires a 28 gr bullet but has enough powder for something like 3,000 f/s muzzle velocity.
The military rounds are designed to work more specifically out of the 10" barrel vs the 16" barrel so there is likely a bit of difference there. If the drop off is slight its probably just past the max barrel length for the cartridge.
edited 17th Jul '14 6:21:12 PM by TuefelHundenIV
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3000 meters per second?
That's a bit high.
Night Clerk of the Apacalypse.
Lol meant feet per second. Yes the PS-90 is a hyper velocity personal fire arm. It should be 914m/s.
edited 17th Jul '14 6:20:57 PM by TuefelHundenIV
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That's quite good going for that length of barrel. The Abomination has a muzzle velocity of 940m/s and that's got a barrel as long as your average prison sentence for fraud over here. 
20.4 inches to be exact.
Must have some uber-quick burning propellent as well as a lighter bullet head.
...
If only the P-90 had been mine. It was designed for my role in life as a signaller after all. I would have petted it, cleaned it, kept it safe. And called it Vera. ![[lol]](https://static.tvtropes.org/pmwiki/pub/images/lol2v12_4863.png "[lol]"){kind=small}
Night Clerk of the Apacalypse.
The one that hits 3,00 FPS is 28 grain bullet out of a 16" barrel. That is pretty light. It probably is as you noted backed by a fast burning powder.
The Baseline p90 gets something like 2,500 out of one of the SS-195 variants. That is out of a 10" barrel> That is pretty good in and of itself.
It is certainly an interesting fire arm. I like its top down feed and ambidextrous features. The FN Bull pup designs all seem to work rather well and people comment that they are generaly comfortable to carry and wield.
edited 17th Jul '14 6:34:49 PM by TuefelHundenIV
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Blowout soon fellow Stalker
Not exactly cheap though
Oh really when?
Yeah, true. But worth it. It's been one of my "must get to fire this weapon at some point in my life" list items for decades. There has to be ranges in France where I could get hold of it on a range-day.
All I need then is a passport and a ferry ticket of some sort.
That's a bit high.
The AP sabot round on the Abrams flies at around half that.
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914m/s for a .22-caliber spitzer isn't bad at all. I mean, it's not quite at the insanity of the .22-250 "why yes that round just hit 4000fps" Remington, but it's very respectable.
Charlie Stross's cheerful, optimistic predictions for 2017, part one of three.
There's a guy on the wiki page for that round who made rifles that fired bullets of that calibre at 4500 fps...
http://en.wikipedia.org/wiki/.22-250_Remington
Holy heck.
Cripes. More impressive in metric.
1,371.6 metres per second.
edited 17th Jul '14 10:18:18 PM by TamH70
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Just as a reminder, yes, that's the same .22-diameter round that in tests easily outpenetrated 7.62mm ball ammo against aluminum armor using factory loads. APCR the bitch and hotload it, and watch it lance armored cars.
Charlie Stross's cheerful, optimistic predictions for 2017, part one of three.
Miniguns.
Lots of miniguns. Loaded with that hot .22-250. Imagine the possibilities.
That may be my new varmint gun.
What size of varmints? Cape Buffalo?
Great white sharks.
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The 22-250 is supposedly quite popular out in the prairie states as a varmint gun, since the high muzzle velocity means that it's less affected by the occasionally-pretty-fierce-winds.
Charlie Stross's cheerful, optimistic predictions for 2017, part one of three.
It comes in Black Rifle form too, courtesy of those fine folks at Olympic Arms.
Night Clerk of the Apacalypse.
Holy crap why would you do that to a .22?
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Blowout soon fellow Stalker
Because fuck squirrels apparently.
Oh really when?
Fucking squirrels deserve to die.
'80s TV Action Hero
It's actually my civic duty as a gun-toting Scotsman to kill grey squirrels on sight. The government basically put out a hit on them as a species because they are invasive and are killing off the native reds.
'All he needs is for somebody to throw handgrenades at him for the rest of his life...'
True. The longer barrel regularly improves accuracy compared to the shorter barrels on pistols.
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