Powerloss by shortening a barrel. Question?

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Jan
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Powerloss by shortening a barrel. Question?

#1 Post by Jan »

Hi I just want an estimate of how much power I would loose if a barrel of approximately 21.5 inches was shortened to 10 inches. With the 21.5 inch barrel the rifle shoots 470 fps. Alternatively what if it was shortened to 6 inches?

I guess I could have put this in the Mods and repairs forum.
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MC 84
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#2 Post by MC 84 »

going from 21-10 would probably be a significant decrese in power. I wouldnt be surprised if you lost 100+ fps. maybe someone that knows more will add to this
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sniper
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#3 Post by sniper »

my quick guess would be 30 - 50 fps drop
and also about 1/2" in 10 yards trajectory.
TCooper
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#4 Post by TCooper »

What kind of power source? What airgun are you referring to?

Some power sources suffer heavy from less barrel. The popular TX200HC springer has a short 9.5" barrel and does quite well. Most CO2 airguns do much better with a longer barrel than shorter.

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Joben
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#5 Post by Joben »

yeh, realy depends on the gun and the power plant.

Magnum springers with long barrels have been known to GAIN a couple fps when choped down to around 15", and to loose only a bit with each inch shorter. In contrast, with co2 and the longer the better.

thats a realy long barrel...what is is a Slavina 630?
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Jan
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#6 Post by Jan »

Well I did figure that quite a bit a bit of power would be lost. :9 But I'd like to bring the barrel length down to atleast 13 inches. Anyone know if even that might be possible without loosing a ton of power??

Joben - yes it is a Slavia 630. I am modding it for a project I am working on, and shortening the barrel is pretty must completely nessecary. I wonder if a can get a stronger spring for it or something.
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RossB
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Cardew's Experiments

#7 Post by RossB »

Cardew, Cardew, & Elsom did extensive research on barrel length and other aspects (piston, mainspring, transfer port, lubrication etc.) of spring airguns.
They published their results in "The Airgun from Trigger to Muzzle" in 1976 and in the subsequent "Trigger to Target" updates.
I consider the books a "must read" for spring gun tinkerers.
They found barrel length to be an insignificant factor.
Transfer port size, barrel chamfer, fuel combustion etc. were far more critical to velocity.
On a Weihrauch HW35 in .22 they discovered that velocity peaked in 6" of barrel and remained constant until 25".
Velocity then decreased due to friction.
The Slavia 630 in .177 would probably yield slightly different numbers but I would bet that the 10" barrel chop will not affect velocity.
I've made a couple of 8" barrelled buccaneer pistols out of $25 Chinese POJ .177 air rifles and noted no power drops.
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Jan
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#8 Post by Jan »

Wow. Very interesting. Anyone else agree with Ross? If that's all true then it is definate good news!
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#9 Post by sniper »

Well, you can imagine how Diana P5 & HW45 .177 with such short barrel
can hit 580 - 600 fps.
gamerule9
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#10 Post by gamerule9 »

you will loose fps and accuracy... accuracy more than the fps
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#11 Post by jezX »

i hate that fn book ...................
springers will be affected by barrel length .
i think you will lose some f/s but it will stay over 440f/s evn at 10 ''
the guns spring and the piston travel need to be considerd not all springers are hw35
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DoctorFrankengun
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Re: Cardew's Experiments

#12 Post by DoctorFrankengun »

RossB wrote: I've made a couple of 8" barrelled buccaneer pistols out of $25 Chinese POJ .177 air rifles and noted no power drops.
Photos, we want photos [-o< [-o< [-o<
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DoctorFrankengun
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#13 Post by DoctorFrankengun »

Jan,

It seems a shame to chop a fine gun like the 630. Can't you find a cheap POS or a used gun?
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