Originally Posted by
Steyr
To explain.
You have the calibre size such as .177 .20 .22 .25....
You then the head size such as 4.51 4.52 4.53.......
You also have grain weight such as 7.9 8.4 10.2......the heavier the more loopy the traj will be
You will find that where the barrel is made may suggest that a specific head size will work better. This is basically down to whether the barrel is metric or imperial so a uk barrel may be imperial and a german may be metric so a very fine difference.
However....each barrel is individual and you have to try many brands to find the composition of material the barrel likes. Two consecutive barrels may not like the same pellet. One may love JSB Exact and single hole and the other may hate them.
Even then....you have head size....a 4.51 may shotgun but the 4.52 might be tighter than a gnats sphincter.
Its a little bit of dark magic and down to testing and scrounging pellets to try.
Just to make it more complicated the dies the maker uses wear out so the actual pellet it produces can gradually change as the die wears. As it does so...the pellet from that die may shift in group tightness as production changes.
Some barrels open groups if cleaned or they become dirty. Again...you have to find out if your barrell likes to be dirty or clean. And if cleaned....does it need shots to stabalise again and if so how many.
The pellet material can be lead and if so...what hardness or it may also have antimony in it to make it harder still. The potential problem with antimony is that as you shoot a pellet it lays down a skim of material which has another layer put down by following shots. Then one pellet will scoop it up and become a flyer. This is usually shown in a regular pattern say every 9th or 10th pellet will do a scoot job on you.
The thing is that if you weighed and head sized every pellet in a tin of .177 8.4 grn 4.52 pellets......there WiLL be a variation in weight and head size. Weight can affect POI due to changes in trajectory especially at range and the head size can be 4.51 to 4.53 for example.
However....that tin of 4.52 may be tight grouping even though its weight and head size spans all three head sizes??? Yet if you chose a 4.53 tin.....that must have 4.52 head sizes...it wont group coz your barrel doesnt like them. Weird as hell.
Sometimes it doesnt pay to be too analytical...just accept that is the way it works.
and will be happy when the majority of shots go to where I want them .
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