Why do pellet grain sizes impact the POI?

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Arch_E

Arch_E

Member
Feb 13, 2019
201
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Louisiana, United States
My Crosman Venom Dusk .177 prefers an 8.2-8.64 grain pellet. With the 8.64 H&N FTT, I get (mostly) 1.25" CTC hits at 22-28 yards (where I'm thinning the varmints (squirrels) that have damaged my back porch and house soffits. So, I'm getting effective results (even if I can't win competitions).



My question derives from my continued testing of pellets, both lighter and heavier. When I shoot a JSB Diablo 7.33, the POI is almost a mil-dot up and to the right, very consistently--so it's not just a bad aim by me. Other 6.9-7.48 pellets will generally cover the area, but I'm not hitting what I'm aiming for, that's for sure. It's like "tight" flyers that don't stray too far but just don't nail the bullseye. 



Any insight?



Thanks,



Arch_E
 
Pellets unlike a slug have their own unique aerodynamics. Pellets are actually similar to the shuttle cock used in badminton as far as the way they travel through the air. If you could fire one backwards they would turn around before they hit the target. 

Manufacturers try their best to make everyone think theirs is the best but even with 2 guns off the same assembly line you need to test the accuracy.
 
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Well,... the JSB Diablo 7.33 gr. pellets are shaped much like the 8.64 H&N FTTs and the 10.5 CPUMs. Since the 10.5 and 10.6 pellets tend to drop a mil-dot, I'm not surprised that a lighter pellet would shoot a mil-dot higher; but I am surprised that it consistently shoots to the right of the POA (and it's not me pulling the shot). All this is for my Crosman Venom since my Weihrauchs shoot various pellets equally well. 



I'm just trying to understand what it is that makes one rifle more pellet picky than another.

Thanks

Arch_E
 
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It’s not just about the weight. They have different skirt sizes, different head sizes, shapes can be slightly different, the mass/balance point can be vastly different, SD will be different. It’s not as cut and dry as it may seem. Even different lots of the exact same pellet can and will shoot differently. Find the one that shoots best and buy many tins from a single lot. That’s the best insurance you can give yourself.

If you want to shoot other pellets, just keep track of the POI and dope in a notebook so when you shoot them you’ll be dialed in. Different pellets might shoot dead low, 6 O’clock, others high right or left, you just never know until you try. Don’t let it bother you too much just take diligent notes!

As far as rifles go, barrels are made a variety of ways and include: smooth twist, smooth twist x, standard rifling, polygonal rifling, etc... how the pellets fit in the barrel and the type and depth of the rifling(lands and grooves) and the barrels choke combined with the particular pellet, determine the rifles “pickiness” when it comes to pellets or slugs. Then you also have to consider twist rates, velocities, etc. and how everything interacts as a system. You beginning to see that there’s a lot to it? Find a pellet that shoots and stick with it! Good luck. Stoti
 
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