Weighing pellets

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Stoohundred
Posts: 122
Joined: Mon Oct 19, 2015 9:48 am

Weighing pellets

Thu Nov 19, 2015 10:14 am

Just read a post on STB from someone who weighed out 100 pellets from a tin of jsb's and they found than they varied from 8.3grn up to 8.7grn with most of them being around 8.5-8.6grn

This got me thinking, so I put all the details into chair gun to see if the difference in pellet weight made any difference to the point of impact.

So at 780fps, I tried 8.2grn and 8.8grn and found that at 55 yards there was Absoloutly NO change in the point of impact!

However I didn't input any windage so maybe there could a variation in how they are effected by the wind, but as the wind is so variable anyway my opinion is that this would be negligible.

I am yet to try it at different fps variations but maybe this shows that consistency of pellet weight is less important than some may think, and maybe it's size that matters? Am thinking of trying out some pellet sizers to se if there is any notable difference.

And will also try some other variables on chairgun (scope height, windage ect.)
AA MPR FT .177 8-40x60 Tasco Custom Shop (FT Setup)
S200 MK2 .177 Robert Lane Reg Hawke Airmax 3-12x50 SF FOR SALE

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Stoohundred
Posts: 122
Joined: Mon Oct 19, 2015 9:48 am

Re: Weighing pellets

Thu Nov 19, 2015 11:03 am

Just had another think and realise I've got this a little backwards.

On a perfectly consistent rifle, the pellet weight would effect the FPS which would in turn effect the POI

So I did a check and found that at with an 8.4 grain pellet,

a variation of 1fps was a 0.5mm change in POI @55 yards
A variation of 5fps was a 2.2mm change in POI @55 yards
A variation of 10fps was a 4.4mm change in POI @55 yards

So the question is I guess, how much does pellet weight effect the FPS? Is there a way of working this out?

Any well tuned rifle should be able to stay within 10fps over 40 shots , so I guess the maximum advantage one could gain is a variation of 5mm on POI which could make all the difference in tricky conditions.

So if I can work out how the pellet weight effects the FPS (on a perfectly consistent rifle) then would be able to work out what the POI change would be on a 8.2 or an 8.8 grain pellet.

If it's anywhere above a 5-10 FPS difference then I guess there would be a useable advantage to weighing pellets.
AA MPR FT .177 8-40x60 Tasco Custom Shop (FT Setup)
S200 MK2 .177 Robert Lane Reg Hawke Airmax 3-12x50 SF FOR SALE

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Stoohundred
Posts: 122
Joined: Mon Oct 19, 2015 9:48 am

Re: Weighing pellets

Thu Nov 19, 2015 12:15 pm

So, I found a website calculator that would convert FT LBS and Grains into FPS

And the following grain values @ 11.5 ft lbs are

8.8 grn = 767 FPS
8.7 grn = 771 FPS
8.6 grn = 776 FPS
8.5 grn = 780 FPS
8.4 grn = 785 FPS
8.3 grn = 789 FPS
8.2 grn = 795 FPS

So a variation of (X grains) @ 55 yards

0.1 grn = 4-5 FPS = 2.2mm POI shift
0.2 grn = 9 FPS = 3.9mm POI shift
0.3 grn = 13-14 FPS = 5.6mm POI shift
0.4 grn = 18 FPS = 7.4mm POI shift
0.5 grn = 22 FPS = 15.6mm POI shift

So if my maths is correct (please correct me if I'm wrong) then weighing your pellets could make a massive difference, as just a 0.3 grain difference would alter the POI by over 5mm which on a reduced kill zone (12mm) could make all the difference.
AA MPR FT .177 8-40x60 Tasco Custom Shop (FT Setup)
S200 MK2 .177 Robert Lane Reg Hawke Airmax 3-12x50 SF FOR SALE

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gary martin
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Joined: Thu Feb 19, 2015 8:21 pm

Re: Weighing pellets

Thu Nov 19, 2015 5:11 pm

for comps, my tolerance is 0.1grain. not sure that it makes that much difference, but it just means there is something i can rule out.

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Stoohundred
Posts: 122
Joined: Mon Oct 19, 2015 9:48 am

Re: Weighing pellets

Thu Nov 19, 2015 5:27 pm

All these calculations are done for a distance of 55 yards and below 35 yards any variation is all below 0.5mm so wouldn't make much difference for the closer shots.

But if it's possible that a pellet could put you out by 5-6mm in already tricky conditions where wind could be pushing ur pellets up or down too, then 5mm could really make a difference.

Anyone here tried the hand selected pellets you can buy in packs of 200?

I only shoot about 10 comps a year so 2 boxes would do me for the season.
AA MPR FT .177 8-40x60 Tasco Custom Shop (FT Setup)
S200 MK2 .177 Robert Lane Reg Hawke Airmax 3-12x50 SF FOR SALE

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Raj
Posts: 2005
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Location: Rugby

Re: Weighing pellets

Thu Nov 19, 2015 7:09 pm

The only time I have weighed pellets is when setting up a rifle with a regulator and checking for consistency over a chrono.
For hunting I make sure I dont kill above 30 yards and for and general shooting, life is just too short to be weighing pellets :)
“It's the Indian, not the arrow"

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Stoohundred
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Re: Weighing pellets

Thu Nov 19, 2015 7:33 pm

Yeah, am talking purely for FT use realy, or maybe for HFT, don't really hunt much anymore.

I'm fairly new to FT and HFT and have been promoted up to B grade for FT and to A grade for HFT next year so I realy need to up my game to be anywhere near the top half of the table, there are some very experienced shooters with realy expensive setups costing more than both my cars, so I'm gonna need any edge I can get.
AA MPR FT .177 8-40x60 Tasco Custom Shop (FT Setup)
S200 MK2 .177 Robert Lane Reg Hawke Airmax 3-12x50 SF FOR SALE

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gary martin
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Joined: Thu Feb 19, 2015 8:21 pm

Re: Weighing pellets

Thu Nov 19, 2015 9:04 pm

Stoohundred wrote:Yeah, am talking purely for FT use realy, or maybe for HFT, don't really hunt much anymore.

I'm fairly new to FT and HFT and have been promoted up to B grade for FT and to A grade for HFT next year so I realy need to up my game to be anywhere near the top half of the table, there are some very experienced shooters with realy expensive setups costing more than both my cars, so I'm gonna need any edge I can get.



im in A grade for FT, to be honest, the best way of improving is concentrating on doing the same thing over and over again. you will get consistancy then. the weighing of pellets only takes a possible problem out of mind. the difference it makes is only theretical via chairgun. even with weighed pellets, the muzzle velocity still has a variant. i do weigh mine though. get a batch that suits your barrel, then weigh some for comps.

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