18grain vs 25grain pellet

[kshitij]

To give a brief back story, the friend i go shooting with has a Hatsan AT44 tactical in .177 and he uses the 10grain jsb pellets regularly. Accuracy with these on his rifle is spot on and he is able to get less than 1inch dia groupings of 10 shots at 50Meters easily. He has tried various brands of pellets of similar weight and found the JSBs to best suit his rifle. Out of curiosity he went ahead and bought heavier 15 grain pellets from JSB and Gamo. When he tried these, the pellets were all over the place and he couldnt get them to group in any manner, no matter what he tried.
This got me worried as I regularly shoot the .22 JSB Exact 18 grain pellets which give almost hole in hole accuracy at 50meters with the diana. But out of impulse, i recently got a pack of 10 tins of JSB monster 25 grain pellets and was worried that my heavier pellets are gonna be crappy groupers too.
So today morning when we went shooting, I decided to give the monsters a try. Was half ready to write off the ten tins.
When i started shooting, i got the biggest surprise of all, the 25gr pellets shot spot on without having to make any changes to the scope which was zeroed for 18gr pellets. So then i swap the pellets back to the 18gr ones and again i am spot on on the target. Was amused that despite a difference of about 7gr or close to 50% weight difference the two pellets were grouping fantastically without any change to the scope settings. The only difference i found between the two pellets is how the rifle felt while shooting each one. The heavier pellet giving a noticeable kick while shooting.
Mentioned this to the 'getafix' of our IFG forum and he came back with a very convincing theory and explanation as to what could be the cause for the two pellets shooting so similarly.
I leave it to him to share the theory with you guys too...

[brihacharan]

To give a brief back story, the friend i go shooting with has a Hatsan AT44 tactical in .177 and he uses the 10grain jsb pellets regularly. Accuracy with these on his rifle is spot on and he is able to get less than 1inch dia groupings of 10 shots at 50Meters easily. He has tried various brands of pellets of similar weight and found the JSBs to best suit his rifle. Out of curiosity he went ahead and bought heavier 15 grain pellets from JSB and Gamo. When he tried these, the pellets were all over the place and he couldnt get them to group in any manner, no matter what he tried.
This got me worried as I regularly shoot the .22 JSB Exact 18 grain pellets which give almost hole in hole accuracy at 50meters with the diana. But out of impulse, i recently got a pack of 10 tins of JSB monster 25 grain pellets and was worried that my heavier pellets are gonna be crappy groupers too.
So today morning when we went shooting, I decided to give the monsters a try. Was half ready to write off the ten tins.
When i started shooting, i got the biggest surprise of all, the 25gr pellets shot spot on without having to make any changes to the scope which was zeroed for 18gr pellets. So then i swap the pellets back to the 18gr ones and again i am spot on on the target. Was amused that despite a difference of about 7gr or close to 50% weight difference the two pellets were grouping fantastically without any change to the scope settings. The only difference i found between the two pellets is how the rifle felt while shooting each one. The heavier pellet giving a noticeable kick while shooting.
Mentioned this to the 'getafix' of our IFG forum and he came back with a very convincing theory and explanation as to what could be the cause for the two pellets shooting so similarly.
I leave it to him to share the theory with you guys too...

Hi Kshitij .....
> Now that you've put the ball in my court....I'm taking a swipe at it
> I've had a similar experience many years ago while shooting 180gr & 220gr bullets from my Winchester 30-06....
> Although I had zeroed my scope at 70yds with 180gr bullets - the 220gr bullets too hit within millimeters on the target....
> Puzzled - I discussed this with more experienced & knowledgeable friends which opened up my understanding as to how it could've happened....
> The mystery lay in the simple fact that:
1. When the scope was zeroed at 70 yds with 180gr bullets the group was 1" approx...
2. When 220gr bullets were fired - due to the excess weight of the bullet the rifle's barrel "Bucked Up" a few millimeters when the bullet exited the muzzle, which amounted to that much "Hold Over" which resulted in the shot hitting close to the one hit by the 180gr bullet
> When Kshitij told me about his experience very similar to mine though with an air arm using 18gr & 25gr pellets I wasn't a bit surprised!!!!!
> Looking back this is a blessing in disguise - that scopes don't need to be re-zeroed (under normal circumstances) especially if one is "Plinking for Glory"
> BTW - I have experienced this phenomenon with my Samurai 3G(Super tuned IHP35 0.22cal) using PH 15gr & GSmith 19gr pellets

Briha

[kshitij]

Brihaji, the getafix avatar perfectly suits you, delivering the magic potions to us

So effectively all the calculations and assumptions based on the weight of the pellet affecting the point of impact goes for a toss. Never knew the "barrel buck" phenomenon and it would have never occurred to me that it could affect the path of the projectile to such an extent. Living and learning

Wonder why the same didn't apply to the .177 Hatsan. It is a 40joule rifle so shooting 15 gr pellets should hardly be a big deal...