Zooma I'll try and answer.
Rifles? now that is different.
Its not that rifles are more sensitive to size or weight than pistols, it's that the targets are so tight the difference can actually make the difference between a 9 and a ten. The width of the ten at 10 mts is 0.5mm, 20 thou in old money! and with world records running at max possible 400 ex 400 Ladies and 600/600 men, and the top shooters are all capable of shooting that. Good national levels are 380, 570, that's averaging 9.5.
The difference between a 9.5 and a 10 is around 1 mm, any one at that level must look for that last 0.5 mm in group size, its the difference between first and tenth! And to ensure it they must test for group size, and use electronic targets and Scatts to measure it.
The factors at that degree of precision are pellet size, weight, and consistancy, with barrel length, velocity, and cleanliness a factor. Top shooters looking for that degree will clean a barrel after every shoot.
Yana is not quite right, size will be a factor but weight is generally but not always more critical in a rifle, rifle pellets are usualy a bit heavier at around 8.3 gr whilst pistol are usualy around 7gr.
Do ordinary rifle shooter need that degree? Probably not, but would you be happy not knowing wether that squeaky nine was you or the pellet? So we do take care in selecting the pellets.
Interestingly you may not be aware that most of the new air rifle barrels are not a lot longer than pistol barrels, Both mine and my wifes Walthers are shortish barrels with the sight base on a carbon tube, this is done to shorten the lock time as the velocity is optimal in a pistol length barrel, we use RWS R10 4.5 size 8.3 gr weight.
And before you ask, the different weights of rifle pellets make little difference in a pistol, my guidance as I've already said is go for a quality make and try what suits your gun, it may or may not make any difference to a pistol grouping, but a rifle is different purely because of the tightness of the target.
Good shooting
Robin
Last edited by RobinC; 19-07-2011 at 09:23 AM.
Walther KK500 Alutec expert special - Barnard .223 "wilde" in a Walther KK500 Alutec stock, mmm...tasty!! - Keppeler 6 mmBR with Walther grip and wood! I may be a Walther-phile?