More FPE if I convert from 22 cal to 25 cal with same barrel length ?

[ninsei]

Hi.  Considering converting my 2250 PCP to 25 cal:  Looking for more FPE.  Currently running an 18 inch barrel and would prefer to keep that barrel length.  With same tube setup (PCP tube with Disco valve), I assume I would get more FPE just cause the pellets would be heavier.

 

[Doug Wall]

"I assume I would get more FPE just cause the pellets would be heavier."
Not necessarily! The velocity with a .25 pellet is going to be lower. Very often, given a set valve set-up, you are only going to get a certain amount of FPE per shot, and upping the caliber might not get you any more.  If you play with the valve to get more power, you will get less shots.

[oldpro]

Hi.  Considering converting my 2250 PCP to 25 cal:  Looking for more FPE.  Currently running an 18 inch barrel and would prefer to keep that barrel length.  With same tube setup (PCP tube with Disco valve), I assume I would get more FPE just cause the pellets would be heavier.

You would get more FPE but not just because the pellets are heavier because air needs area to push on to make power so the larger area of the bore will yield more fpe. Hope that helps

[Sfttailrdr46]

Bigger heavier bullets are a small part of the equation, you also need more air at more volume to get the best results I have a formerly .25 Gen 2 Marauder the stock .25 barrel was 20" when I had it converted to .30 caliber to achieve 100 + FPE it was necessary to enlarge the transfer port ,re-barrel with a 24" .30 barrel and a Cothran Powerhouse valve and a few other things done to tune the rifle to shoot well at that power level

[rsterne]

Generally changing from a .22 cal to a .25 cal will give more FPE in CO2 or PCPs, because the area the pressure pushes on is greater.... Springers don't follow this rule going from .22 to .25 cal, because the larger caliber drops the initial pressure when the pellet launches, although generally a .22 has more FPE than a .177.... it just runs our of air by the time you increase to .25 cal.... Pumpers can deliver more FPE in a larger caliber, but you may have to pump more.... In a 2250 PCP, unless your gun is a very mild tune, you will likely see more FPE in .25 cal, but at lower velocity because the pellets are usually quite a bit heavier....

Bob

[redlined_b16a]

So a .22 cal 25grain vs a .25 cal 25 grain

Would the .25 cal deliver more fpe

Would the extra area for air to push propel the .25 at a faster fps?

[Ribbonstone]

YEs...if all else "even" it should shoot a bit faster.

Basically the same as previous post, just worded differently.

All we got it 3K air at the start of an PCP's fill (or whatever fill pressure your PCP uses).  Valve opens, same pressure, nothing is going to get a stronger or weaker push.  Can get a longer or shorter push (depending on how long the valve stays open/how much air is used).

But, that push can act on more pellet area.  Area...that is why it is psi...it's that "square inch" thing.

Basically the area of a .25 is about .05 square inches (si)....a .22 is about .04 square inches.  Certainly 1/100th doesn't sound like "jack", but it's still a good percentage difference.

So smack .05si with 3000psi and you get 150 pounds of force.....smack .04si with 3000psi and you get 120 pounds of force.

BUT...don't think is has to maintain that 1.5:1.2 proportion....that bigger .25 bore is bigger all the way down the bore, so the pressure may start off at 3K, but (if the valve spits out the same volume of 3K air for each caliber) it also declines a bit quicker as the pellet travels down the barrel and the volume increases.

But over all, would expect the 25gr. 25 to exit the muzzle going faster than the 25gr. 22.


COMPLICATIONS.

If you start off with an "airhog" .22, that uses a lot of air per shot (low efficiency) are very likely to see more of an energy increase when swapping to .25.  That "excess" air in a .22 bore can be put to better use in the larger volume .25 bore.

If you start off with a very efficient .22, may see very a much smaller energy gain in .25.

[Habanero69er]

Anthony, ever consider trying one of the heavier .22 pellets before making the jump to .25?

There are 25, 30 & 34g H&Ns, 28 & 32g Eun Jins just to name a few.

[UmarexOctane]

Anthony, ever consider trying one of the heavier .22 pellets before making the jump to .25?

There are 25, 30 & 34g H&Ns, 28 & 32g Eun Jins just to name a few.

Exactly; this would be my go to solution if all you're looking for is more energy down range.  Try shooting the heavy for caliber pellets like the "Pile-Drivers" or something along that line.  They are not conventionally shaped like the first generation air gun ammo we are accustomed to seeing or shooting.

Even at lower velocities boat-tailed projectiles like the "Pile-Driver" pellets in .22 caliber will still out perform conventional pellets.  This is due to the slightly better ballistic coefficient they bring to the table. 

Before spending your hard earned money on a barrel swap from .22 to .25 caliber that you may not be happy with in the end, it may be somewhat more logical to at least try before you buy.

Tim M.

[Ribbonstone]

Without any stated proof or justification of the reasons for this post...think this may be a velocity / energy-seaker.

Certqinly have gotten some .22's up to +50 foot pounds using wide-open type tuning and heavier .22 pellets.


Indications are that if the same rifle had a .25 barrel, would be doing +60/65 foot pounds with the .25's heaviest pellets.

NEVWER MIND that the .22 pellet might arrive at 50yards (or 75 or 100) with  nearly the same energy (that's all about BC), most folks consentrate on what they measure at the muzzle and disreguard the rest.




For a few hunting seasons back (been a couple of years) I tried the same weight at the same speed, different calibers.  Couldnt get the all, but can find 13.4-13.5gr. in .177/5mm/22.  Launch them at the same speed, get the same muzzle energy.

Then one hunting season, trried 21-23gr. in 5mm/22/25 at about the same speed/energy.  The 21gr. .177 piledrivers weren't availble then, ofr I'd have tossed them into the mix and had all 4 "common" calibers with the same weight/same basic speed/same energy...leaving only down range velocity/energy retention and diameter as a the variables (first two aren't "jack" inside my normal tree-squirrel hunting distance of  30-35yards).


Personally...I'd try a few on the really heavy end of the .22 line up....may be pleasantly surprised.