Pellet Weight Difference

With my .30 I found no difference. Sort a bunch and put the heaviest with the lightest (excluding truly 'wrong' pellets) and shoot them and see if they group any differently than the others.

There can always be a couple rounds that are simply incorrect in some way. Sorting does give you the chance to eliminate those and you put your eyes and hands on each one. But I think those are generally more useful than having the pellets sorted in groups.

MikeAllen said:

How much difference does pellet weight make for the POI at 50 or 100 yards? I'm particularly interested in .25 caliber.

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OK, let's assume that a different pellet weight will result in a different muzzle velocity MV — assuming that the gun is perfectly even in its power output.

Let's assume a 50FPE gun, with two typical .25cal pellets:
(1) JSB Domed 25.39gr | 0.037BC | 942fps MV = 50FPE

(2) JSB Heavy Mk2 33.95gr | 0.046BC | 815fps MV = 50FPE


Let's assume a fairly large weight error of 1.0gr with the resulting velocity offset:
(1) 25.39 ➔ 24.39gr
942fps ➔ 952fps

(2) 33.95 ➔ 32.95gr
814fps ➔ 826fps

Using Chairgun (mobile), the graphs and tables can be adjusted to use the same barrel angle as one of the 4 selected pellets.



POI Error at 50y:
The 25.39gr will hit 0.1" higher when it is 1.0gr too light (24.39gr).

The 33.95gr will hit 0.2" higher when it is 1.0gr too light (32.95gr).


POI Error at 100y:
The 25.39gr will hit 0.42" higher when it is 1.0gr too light (24.39gr).

The 33.95gr will hit 0.84" higher when it is 1.0gr too light (32.95gr).

➠ Now, you need to see if you can live with that.


Below a graph that shows the POI error at 100y for the 33.95gr pellet (the 25.39gr is not correctly displayed in this graph).
● green line = 33.95gr
● purple line = 32.95gr = 1.0gr too light ➔ hits 0.84" high







Cheers,

Matthias

MikeAllen said:

How much difference in pellet weight makes a difference in accuracy/POI at 50 or 100 yards? I know this probably depends on caliber - I'm particularly interested in .25 caliber weight differences and benchrest accuracy. Just trying to eliminate variables!

Click to expand...

a balistic drop calculator might be handy for that or order a tin of JSB's for a variety of weights

JungleShooter said:

OK, let's assume that a different pellet weight will result in a different muzzle velocity MV — assuming that the gun is perfectly even in its power output.

Let's assume a 50FPE gun, with two typical .25cal pellets:
(1) JSB Domed 25.39gr | 0.037BC | 942fps MV = 50FPE

(2) JSB Heavy Mk2 33.95gr | 0.046BC | 815fps MV = 50FPE


Let's assume a fairly large weight error of 1.0gr with the resulting velocity offset:
(1) 25.39 ➔ 24.39gr
942fps ➔ 952fps

(2) 33.95 ➔ 32.95gr
814fps ➔ 826fps

Using Chairgun (mobile), the graphs and tables can be adjusted to use the same barrel angle as one of the 4 selected pellets.



POI Error at 50y:
The 25.39gr will hit 0.1" higher when it is 1.0gr too light (24.39gr).

The 33.95gr will hit 0.2" higher when it is 1.0gr too light (32.95gr).


POI Error at 100y:
The 25.39gr will hit 0.42" higher when it is 1.0gr too light (24.39gr).

The 33.95gr will hit 0.84" higher when it is 1.0gr too light (32.95gr).

➠ Now, you need to see if you can live with that.


Below a graph that shows the POI error at 100y for the 33.95gr pellet (the 25.39gr is not correctly displayed in this graph).
● green line = 33.95gr
● purple line = 32.95gr = 1.0gr too light ➔ hits 0.84" high



View attachment 494394



Cheers,

Matthias

Click to expand...

Wow..Sweet write-up...Thank You @JungleShooter

MikeAllen said:

So true about the JSB's! Also true for the FX's (which, yes, are made by JSB). I'm finding the AEA Center Punch pellets to be very consistent in weight. No hesitation shooting right from the tin.

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i did a sorting of 1000 JTS pellets for weight ..i ended up with 2 piles within 1/10th of a grain using a scale to 1/100th and 4 that were under target weights ...none over...super impressed. Did another 1k...same results.
if i had done the same with JSB's ..i'd have 10 piles of various weights

Similar ..not quite the same

A more concerning problem with pellets with a large weight variation is where in the pellet is the extra weight, or the loss in weight, and is it on the centre line or somewhere else? If the weight change is off the centre line it will give an off-centre CG and that can ruin groups, much more than just the pure weight effect.

MikeAllen said:

I guess that could be the case even if they all weighed the same!

Click to expand...

Can be yes, it only needs to be a few thou out to give a problem.

Ballisticboy said:

Can be yes, it only needs to be a few thou out to give a problem.

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Only a few thousandths of a grain off the centerline to cause a problem? or a few thousandths of a distance?
Are there any practical tools to check concentricity or where the center of gravity is relative to the "centerline"?

I sorted some H&N 18gr pellets by weight and by head size. I could not see any difference when sorted by weight only. But when I sorted by head size only, the bulk end in the 5.52mm tin. I had very few 5.54mm or the other extreme 5.50mm was even less, sometimes even nothing of the extremes from a tin. My rifle prefer 5.52mm which give the smallest groups and tolerate 5.51mm. The 5.53mm will result in bigger groups and more flyers. The 5.52mm is not immune to flyers but it is less.

Sorting JSB 18gr, again weight did not make a difference. Sorting by head size the bulk is 5.53mm followed by 5.54mm and then 5.52mm and even a few 5.55. Even the 5.52mm is not giving small groups as the H&N unsorted.

When I take the H&N 18gr sorted by head size 5.52mm only and further sort it by weight, I see no difference in group size nor amount of flyers.

I sorted other pellets as well but only give this as an example as this is what I sorted the most.

Oval test: All pellets are a bit oval and I assume off balance, I found none to be perfectly round. H&N is in fact more oval than JSB.