morning all, i just wanted to ask a few -point of impact- questions. i have been doing a little paper punching and have noticed different p-o-i on several pellets. i seem to have acumulated quite a variety of them and decided to try them all in the same gun (daina34). this particular gun is the most consistent shooter out of 6 or 7 that i have. if i do my part it will do 1"- 1 1/4" groups at 40 yds with cpl's and my current scope setup. not bad...good enough for me. any way, i have noticed quite a different -poi- on different styles and brands.
i have enver had so many pellet choices until the infamous internet came along.
the question is...why does it change so much? especially left and right impact. groups dont really open up just the point of impact changes. i have never had crow mags group that well in most guns at longer ranges.they are left 3 inches. but it may have been inconsistent firing before i noticed it with a decent gun. i noticed in a post awhile back(harry's i think)the mention of twist rate and the unbeleivable rpm the pellet actually has. would a pellet with more(or less) lead engaging the rifling make that much difference? im talking 2 inches difference at 35-40 yds. most to the left side of the desired impact.i am wondering about the crown but like i said the groups are good, just a marked difference on poi. any suggestions or info is greatly appreciated.thanks
tom
This is an excellet book, I just got it the other day. It will tell you the drop rate for each pellet at diffent ranges and at different velocitys .
and the correct MOA in 1/4 or 1/8 inch needed to ajust for each range.
Its really great if your into precision shooting.
there are computer programs too, but this is a finished work I can just reference.It has many of the most common type pellets we use, crossman premiers, beeman kodiacks, cromagnums RWS domes ect.
i understand pellet drop, i am curious about windage
October 10 2008, 5:05 AM
issues. as to say, 1 inch group center target, cpl's. rack 5 gamo tomahawks same gun, same session, 1 inch group, 2 inches left of center target.no drop of course till i use the heavies. crow mags seem to go right a little bit, and dont group as well. anyway thank you for answering my post
tom
The vibrations the gun goes through when shooting are incredible.
If you do not believe me, do a simple test: Attach a laser to the muzzle of the gun, then position yourself in a safe place where you can see the target from up close, and have someone else fire the gun. You can also look at the laser dot with a scope from the firing line, but it is important that someone else fires the gun.
You will see how much movement the laser dot has. These are the harmonics. And we (shooters) are part of the system. Our weight, our muscles, all contribute to the distribution of weights that make up the oscillatory system.
The POI depends more on the harmonics than on anything else. If the muzzle is pointing just a little more to the left when the pellet departs it, then that pellet is going to go west. If the muzzle is pointing just a little bit to the right, then the pellet is gonna go east. Muzzles, IMHE, describe almost full circles when the shot cycle is going on. If not circles, as it is a very fast phenomenon, at least ellipses. Someone should make a high speed videotape of this.
So, airguns can and will shoot different pellets not only to different vertical POI's, but also to different lateral POI's.
i remember a while back seeing something about sniper training (powder burners)and they were tuning thier muzzles with some sort of weight or something. would that be the same ?the last i tried the search it wasnt working.
that shortening a barrel would reduce osilations because it would make it relatively stiffer (cross section to length ratio being greater). shortening and adding a muzzle break or weights would dampen out vibrations and osilations i think.
barrels don't need to be very long in these rifles. only long enough to comsume all of the expansion of the compressed air. i think that optimum length could be computed by figuring the volume of the cylinder
of the compression tube and then making sure the volume of the cylinder of the barrel is in balance. doing that might also increase velocity by ensuring that the pellet does not become a balistic missile until it has actually left the bore. my diana has around a 17" barrel but perhaps 13" or 15" would be
optimum. i have not done the calcuations because i have not had the compression tube out yet. just thinking out loud here.
The tuned muzzle brakes are like the Browning "B.O.S.S." system. You turn a dial in the brake and it redirects the expelling gasses. Or maybe shifts the barrel weight slightly, I can't remember which. If it's changing the venting pattern, I don't think it will be of much help on an air gun. Someone came out with one for air guns a while back (Vortek, Vortex?) but I don't think they caught on, at least not with springers. Barrel tuners are used to locate the "sweet spot" on a rifle barrel. They can be a sliding ring affair or a device in the stock which applies pressure to a certain point beneath the barrel. These tend to optimize the barrel's vibration. Again, I've only seen them on firearms, not air guns. I guess they could do the same thing but air guns have a lot more in the way of harmonics if they are springers.
