Charlie--pellet weight?

[daved]

In a post on the hunting gate, Black Mamba mentioned he had to return his Shadow to you for repairs because shooting heavy weight pellets prematurely fatigued the spring.  Obviously no fault of yours, but how about some guidelines.  I've heard opinions both ways as to whether it causes damage, but no one's ever said where the lines are between light, mid, and heavyweight pellets.  I know that .177's range from 5 gr. to over 16.  I know that my CFX (pre-tune, at least, should be back Tues!) seems to do best with pellets at about 8.3 or so.  But I've never shot Kodiaks because of the weight, even though they are supposed to be one of the best.  So how about some guidelines for us poor newbies.  Obviously, we want accuracy, but no one wants to damage their guns.  Thanks!

Dave

[CharlieDaTuna]

An occasional heavy pellet through the gun usually causes no damage but in Dave's case, he put well over 1000 rounds of Crosman Ultra Magnums through his Shadow, a pellet weighing about 10.5 gr usually, causing an excessive amount of early spring fatigue. That's fairly heavy for a standard .177 and over time a price will be paid. Every time the gun was fired, the spring was being stressed. In fact, when I removed the spring, it's set length was a bit under ten inches when normally it is about 10 3/4 inches as well as severely canted into being "S" shaped as I remember it.

It's of my opinion that optimum a pellet for most off the shelf .177 pellet guns should be somewhere in the 7.6 to 8.8  gr range. Pellets in that range are usually the most efficient weight for optimum velocity, foot pound energy, and accuracy at mid-range to extended distances yet will not cause stress or damage to the gun itself.

Again, this is just my opinion based on past experience. But it's usually pretty easy to tell when a gun is torn down if the spring has been stressed by either detonation or excessively heavy pellets or both if you know what you are looking at.

Am I missing something...The power plant for a shadow .177cal is the same as shadow .22cal Gamo (and other manufacturers) just changes the barrel. with that being said a avg pellet for a .22 cal is about 14grs. is this not heavier than the Crosman Ultra Magnums 10.5grs..177cal So how can the "22" airgun handel the weight?

[CharlieDaTuna]

The volume in the power plant is the same but the barrel diameter is different and offsets the weight factor. It is the volume of compressed air behind the weight that makes the difference in what the heavier pellet weight influences. The heavier the pellet weight in a given diameter, the more it takes to move it and the more reaction there is to that movement.  With the barrel being .22 diameter, which offsets the weight factor between .177 and .22 caliber, there is more area for expansion of the compressed air that is being delivered from the compression chamber as the pellet is moving down the barrel over a given distance (for the air to expand into) behind the pellet, and to absorb that volume of air than there would be in .177 for the same distance.

When a heavy pellet is used in either caliber beyond an acceptable level for that gun, when the gun is fired and the piston is on it's way home, it will reach a point that if the volume of air has not been evenly and thoroughly released enough, a "back pressure"  can build up in the compression area. The pellet, because of it's weight, has not yet moved far enough down the barrel to allow for the high volume of air behind it to enter and has backed up into the compression chamber causing an excessive build up of pressure. It can easily be enough for there to be detonation (explosion) and that in turn drives the piston backwards like a cannon shot in the opposite direction.

I'm sure there are others that can explain it better than I but this should help.

[-=ed]

Not many people know the difference between an explosion and detonation.

So   Should I not shoot Kodiaks with my B-19 .22 caliber???

[vinceb]

I don't think there is a difference. There IS a difference between burning and detonation....

[CharlieDaTuna]

Vince is right. The "detonation" I referred to is an explosion if you will. There is a big difference in "burning" or dieseling and detonation though.

[CharlieDaTuna]

THe Beeman Kodiak is a bit over 21 gr. if I remember correctly and is pretty heavy. I would venture to say that a steady diet of them will cause spring fatigue rather quickly and shorten the life of the spring considerably. I myself would stay under 16gr.

[-=ed]

Many people use detonation when they mean confligration.

I used to work with explosives a bit, and was also a Pyro man for a while.

Sorry if I was cryptic or unclear.