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 Post subject: Does Size Really Matter?
PostPosted: Mon Apr 03, 2017 4:34 pm 
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Joined: Fri Feb 26, 2016 2:42 pm
Posts: 50
I've always assumed that a longer barrel meant greater muzzle velocity.
I had a chance to test this recently with a Crosman 2289, first with it's stock 14" barrel, then with a 24" barrel.
Each got five shots at 10 pumps and I was surprised to discover that the longer barrel actually produced slightly less muzzle velocity than shorter one! (Results below). Not at all what I was expecting.
Any ideas...?!?!


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PostPosted: Mon Apr 03, 2017 4:50 pm 
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Not enough air to push the pellet and Pellet ended up just dragging?


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PostPosted: Mon Apr 03, 2017 5:15 pm 
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The "Canadianized" 2289 is detuned, so doesn't act in a "normal" fashion compared to most pneumatics.... By the time the pellet has travelled 14", the air pressure in the valve has bled down to zero through the bleed hole in the back of it.... so there is nothing left to accelerate the pellet to a higher velocity....

Bob

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PostPosted: Mon Apr 03, 2017 5:18 pm 
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Location: Meaford, Ont.
Drag through the barrel but accuracy should be better with a longer barrel. Kind of a trade off in what you want. Three feet per second is nothing to worry about so I would be checking the two for accuracy. CHEERS!


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PostPosted: Mon Apr 03, 2017 7:34 pm 
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Location: mb
Arden wrote:
I've always assumed that a longer barrel meant greater muzzle velocity. . . .

It almost always will, as long as the rest of the "system" is optimised and/or adequate to the task. . . .
Arden wrote:
I had a chance to test this recently with a Crosman 2289, first with it's stock 14" barrel, then with a 24" barrel.
Each got five shots at 10 pumps and I was surprised to discover that the longer barrel actually produced slightly less muzzle velocity than shorter one! (Results below). Not at all what I was expecting.
Any ideas...?!?!

As mentioned by Bob; open or plugged valve bleed? Comparative resistance of pellets pushed by a rod through both barrels? In the Crosman barrel lottery, some are better finished than others. You might have a fairly snug 24" example, and possibly a looser 14". I'm with Bob, and betting on an open bleed. . .
Barrel length and accuracy are mostly unrelated, but as you've come this far, shooting and recording a few groups really does make sense. See if the longer pipe otherwise shows promise. . .
Good Luck!

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PostPosted: Mon Apr 03, 2017 7:49 pm 
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Isn't the 2289 a pistol ? Even with the long barrel on it.

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PostPosted: Mon Apr 03, 2017 8:14 pm 
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Yep, unless you change out the tube, the 13XX and XX89s are considered pistols in Canada.... regardless of barrel length....

Bob

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Airsonal;
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PostPosted: Tue Apr 04, 2017 12:27 am 
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To answer the title:

Image

Speaking of which - I'll be right back.

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PostPosted: Tue Apr 04, 2017 8:47 am 
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The 2289 comes with the shoulder stock, so it isn't a pistol - regardless of the barrel. That is my set-up (scoped, 24" barrel, shoulder stock) and it is def not a pistol.


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PostPosted: Tue Apr 04, 2017 9:13 am 
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dyslexic_nam wrote:
The 2289 comes with the shoulder stock, so it isn't a pistol - regardless of the barrel. That is my set-up (scoped, 24" barrel, shoulder stock) and it is def not a pistol.

Sorry, but wrong. . . Even with a 50" barrel, it'd be a pistol in the eyes of the law. 500fps limit

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PostPosted: Tue Apr 04, 2017 10:01 am 
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dyslexic_nam wrote:
The 2289 comes with the shoulder stock, so it isn't a pistol - regardless of the barrel. That is my set-up (scoped, 24" barrel, shoulder stock) and it is def not a pistol.


Even a 2250 is a pistol in the eyes of the RCMP, and the FRT. 2289 doesn't even meet the requirement for a non restricted firearm. Stock can come off w/o tools.

Stock on a 1911. Guess its a rifle now. NOPE

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PostPosted: Tue Apr 04, 2017 12:11 pm 
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Needs a flat top and valve tuning and then you will see a huge difference. :wink:


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PostPosted: Tue Apr 04, 2017 10:24 pm 
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Thanks for the info guys!
It did occur to me that the compressed air in the valve might not sufficiently "fill" the barrel behind a pellet. Still, hard to wrap my head around it...

To some of your points:

- the 2289 came factory modified for the Canadian market (bleed hole in valve),
- it does have a flat top piston (that and extended bolt prob are the only user mods),
- most importantly, in the eyes of the RCMP, The Firearms Act, and over-eager crown attorneys, the 13XX's and 2289's are PISTOLS! Barrel length, type of stock, overall length DO NOT MATTER. Without the bleed hole, a 1322/2289 could easily exceed 500fps at even five pumps. Because of the stamp on the pump tube, unless you have an RPAL and treat that airgun like a restricted weapon in every way (ie - storage, transportation, only shooting at approved range), you are tempting fate in a bad way. I'm no lawyer, but his isn't a point you want to quibble over with the cops & Crown.

Anyhooo, on that happy note, wheeliehd has the right idea: quit yakkin' & start shewtin'.


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PostPosted: Wed Apr 05, 2017 1:22 am 
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Arden wrote:
. . .Still, hard to wrap my head around it...

It's been suggested that the "right"(efficient/effective) length of .22 barrel for the 13XX valve, is somewhere around 18"(+/- 1ish").
Longer barrel needs larger valve volume, or higher initial pressure, or both.
Put a ping pong ball in a 1 foot piece of plumbing pipe, and blow firmly into the pipe. You can probably launch the ppong ball across the room.
Put the ppong ball in an 8 foot piece of the same pipe, and even with your best breath, you'll likely not get the ball to leave the pipe.
= Same scenario in your 2289. Too much of "what should be" a good thing.
Arden wrote:
. . . (bleed hole in valve). . . flat top piston. . and extended bolt prob are the only . . mods. . .

FTP and un-altered bleed? :? . . . interesting. . .
OEM pump and plugged bleed usually nets stouter legal figures. . .

If/When you become bored again of shewtin', you could start cutting that barrel an inch at a time(keep good notes :) ) to find out where the "sweet spot" is for your configuration.
Good Luck!

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PostPosted: Wed Apr 05, 2017 1:13 pm 
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I have an 18" Crosman bbl here in .22. Velocity has not that much of a gain over the 24" 22-60 bbl~ and it is not in the same league when it comes to groups at 20 yds. Your mileage may vary- I'd fully expect a 24" LW .22 bbl to outshoot both....

-D.S.

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