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SirTonySteel · New Member

Before hopping up your 850, note that it puts out slightly more ME with a heavy pellet vs a light pellet. I get 661 fps (11.86 ft/lbs) with a CPL and 518 fps (12.7 ft/lbs) with a Kodiak in 22 cal. What that says is that the heavy pellet takes advantage of the CO2 charge better than the light pellet. The lighter pellet has some blowby when it leaves the barrel that is power wasted. The valve is pretty much balanced and any hop up would require the use of only the heaviest of pellets to use all the extra CO2.
The chrono allows us to "talk" to the airgun and see just what it likes to "eat". [/b]

AirGunEric · Site Admin

Really more a question of terminology than anything; but is wasting some of the Co² charge because it pushes a lighter pellet out the barrel too quickly, thus leaving some unexpanded Co² trailing out the muzzle after the pellet has already exited really what we call "blowby"? More of an "unspent fuel" I'd think, whereas 'blowby' would be the Co² leaking out around the pellet inside the barrel?

Either way- good tip- knowing the 850 can be a bit wasteful of gas with lighter pellets is handy!

What were the weights on those pellets? It would be handy to figure out where the "sweet spot" in pellet weight is or isn't- although that might be particular to a specific gun (i.e. different from one AM850 to another). Have you tried even heavier pellets to see what happens?

SirTonySteel · New Member

Right. Blowby is during and this would be after. You may have noticed that match pistols and rifles have very, very similar ME's. They were designed that way. If the ME with a heavy pellet were just slightly less than with a light pellet that would mean that there is no excess air leaving the muzzle after the shot to disturb the pellet's flight. Some pistols and rifles are adjustable and a savvy match shooter will set it up this way to reduce the turbulance as the match pellet leaves the bore. There is a delicate balance between this excess air and a pellet going too slow so as to increase barrel time. Get rid of the pellet quickly but not at the expense of pellet stability.
In this case of the 850, I used the CPL at 14.3 gr and the Kodiak at 21.3 gr. By using the lightest and the heaviest pellet, and comparing the two, this balance can be found. Examples are the Pardini K-60, Crosman Skanaker and the already balanced by design Daisy 7xx or IZH-46m. Not only an interesting phenomenon but practical in that it balances power, economy and accuracy.

Alstone · Moderator & Site Supporter

Hi SirTonySteel
I get the same effect on a couple of my guns, but the reason for this is due to the fit of the pellet in the bore, if I use the same pellet in three diffrent sizes (Daystate FT .177 in 4.51,4.52 and 4.53) all 8.44g, you can see the fps rise according to the tightness of the fit in the barrel, my Walther Winchester gets its highest fps on the 4.52 but falls off by 25fps on the 4.53, where as my QB78 shoots at its best using 4.51 .

Al

SirTonySteel · New Member

The math and physics of this sport is almost as much fun as the shooting itself. My weakness is match pistols but my Condor is available for the heavy duty work. Variables such as pellet weight, size or sized or seated, and the power source all enter into it. The chrono is my friend.
Probably no coincidence that the 850 is so close to 12 ft/lbs of ME. That makes it a World seller. Good to know you Brits can play with the same toy we do. Enjoy!