What a difference 4-1/2" makes

[jdub]

I was bored last night so I took the 12" .22 MellonAir barrel off my 2240 and put the stock barrel back on just to see how the balance and accuracy are since I have the long LDC on it.  Balance was good but the accuracy suffered a bit.  The real eye-opener was when I chronied it.   With 13.7 gr H&N wadcutters I was averaging around 405 fps.  Significantly slower than the MellonAir barrel.

I put the MellonAir barrel back on tonight and chronied it again just to make sure I wasn't imagining things.  With the same 13.7 gr pellets it averaged just over 487 fps.   That's a pretty huge jump for 4-1/2" inches of barrel so I'm wondering if something else is different as well.  I verified the readings with two other types of pellets. 

487 fps with a 13.7 gr pellet is right up there with my .20 cal R7 shooting 13.8 gr pellets.   Pretty cool.

[Trophyhunter49]

Yep size does matter, LOL In some things. Like in how LONG your barrel is

[Crosshairs]

Thats good news for you i bet you were happy leave the longer barrel on.When i built my first 1377 i added a 24" barrel and got 100 fps more then with the stock barrel. Funny how things work in the air gun world.
                               Mike

[breakfastchef]

A general rule seems to be that you may gain an additional 10-15 fps per inch of barrel beyond the stock barrel. Though TKO insists that the LDC should not affect velocity, I think it does to the positive, to a small degree. You numbers look excellent, but should be checked again to verify accuracy.

[JEBert]

That works out to 18.2 fps per inch of barrel increase.  If nothing else is different, that is very good.  I have a 12" barrel in the works for my newest 2300KT.
I'm curious about what other mods have been done to this pistol, if any?
Cheers,

[jdub]

That works out to 18.2 fps per inch of barrel increase.  If nothing else is different, that is very good.  I have a 12" barrel in the works for my newest 2300KT.
I'm curious about what other mods have been done to this pistol, if any?
Cheers,

The only other mods are a standard Crosman steel receiver and I turned a delrin spring guide for it it.  The spring, valve, hammer and rest of the firing mechanism are stock. 

[1377x]

was you at the same distance as the first time you ran it across the chrony .its best to take readings at least two feet away ,chrony recommends three feet away
the spring guide could be acting as a pre-load

[jdub]

Chrony is 3' from muzzle both times.   I think the big increase in velocity might be due to a marginal stock barrel.   I thought 405 fps seemed seemed slow for a stock 2240.

[1377x]

405 is about average listed at 420 is it not?
a 2240 is the only crosman i have that was bought new i still have the clamshell but havent looked at the spex

[Plekto]

It's really a bit of a bell curve.  That is, the first few inches make a lot more difference.  So 12-14 inches will get you almost 100fps faster, and anything beyond that is smaller and smaller gains until the difference between 18 and 24 inches is pretty much nothing.

I have a much stronger spring (almost twice stock near as I can tell) and a slight tune on the valve/etc (polishing and cleaning mostly). and mine shoots about 480fps with a 12" barrel on a warm day.  That's with 14.66gr FTS.  Needless to say, I'm happy as a clam.  Stock, it was close to 400 like yours was.  Note - like yours, it's an aftermarket non-match barrel (probably Melon as well, not sure) that's been cut down, so that's also a part of it I suspect.

Why this all works  (for those reading who don't know yet) is because CO2 is an expanding gas, exactly like a firearm.  HPA doesn't expand and so it's pretty much like a spring-piston in that you get an initial blast and then the pellet is on its way.  With CO2, the heavier the pellet is and more time it spends in the barrel, the more time the liquid has to turn fully into gas and to push and expand against it (up to a point around 18 inches, IME, for .22, 22-26 inches for .177).  CO2 guns love heavy pellets and longer barrels.  Also, larger calibers are more efficient due to the greater volume behind the pellet as it travels down the barrel.  A few .375 2240s were made years ago by Quackenbush and they were putting out about 280 fps.    Note - that's with a 84gr ball.   12 inch .375 barrel and 12 ft-lbs. 

note - now that 9mm pellets are fairly common, I'd personally love to see a 9mm version of the 2240 at the custom shop.    I'd even "Settle" for a .25 caliber model.  I'd be the first to buy either if they were available, in case Crosman is listening/reading this.  There currently are no .25 or 9mm pistols on the market.  It's a simple matter to put a riser block in and add a larger caliber barrel to a .2240.   To do it ourselves, though, it's close to a $150 affair as we have to buy a barrel and get it cut and machined to fit.  Paying, say, $150 for a 2500KT or 2900KT would be a no-brainer. (just make the stock barrel 12-14 inches)  You'd sell out as fast as you could make them.

[ped]

so would you say that 18" is the optimum length for a .22 as i found that when i shortened a 24" barrel to 10" i lost 5.5fpe, this was with 31.02gr .25 pellets running on hpa at 1500psi
ped

[Plekto]

Well, HPA is totally different than CO2.   HPA simply works best with the longest barrel that you can get since it's running at much higher pressures and is a single massive blast of air.(it doesn't expand in volume over time once released) 

For CO2, 14-16 inches is optimal in .22 as near as I can tell.  18-24 inches is a very modest gain, if any.(depends on temperature, really at that point).  Most people settle for 12 inches as it gets too long and unwieldy otherwise if you put a brake on it.