JSB Knock Outs 10gr .177

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Posted: 09 Oct 2024 at 12:29am

Got these today…
More testing to follow.

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RangerPete View Drop Down

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Posted: 11 Oct 2024 at 6:39pm

I tried lubeing some of these slugs, to see if some lubrication would make any difference to their velocity and more importantly if it would tighten up their groups. I used an old bottle of Napier Pellet Power lube that I have had for a long time. 1 drop per 100 slugs.

Well the long and the short of it is, the velocity went up, from an average of 993fps to an average of 999fps.
No noticeable difference in group size. So not really worth the effort of lubing them.

I've been using the 10grainers for a while now and been very happy with their terminal ballistic performance (expansion and stopping power), but the groups are not as tight as I'd like.
At 35 yards I'd get 3 touching, and two out the group. Not very far out, but far enough to know its not me, and far enough for it to bug me.

So what could be causing this...?
1 - it could be me, but its not. I know when I've pulled a shot.
2 - it could be the slugs? Inconsistencies with weight, damaged skirts, damaged pellets...? maybe, but when visually inspected they all look perfect, in fact I cant see any damage to any of them. Could be weight and head size, but Ive been shooting JSB for years and have faith in their quality.
3 - it could be the rifle. Barrel, or tuneing/pressure. Do I try go faster, or maybe slower? Try fine tunning the hammer spring pre tensioner screw? Is the twist rate just not fast enough for slugs? Maybe it just needs a clean?

Well I dont think its me and I dont think its the slugs, so time to look at the rifle.

Some barrels shoot beautifully their entire lives and never ask to be cleaned once.
Some barrels like a clean once in a while, and some demand to be cleaned after every use.
I was hoping Little Emma would be the first kind. I've put over 1000 projectiles through her barrel since I got her a few months ago, and never cleaned her, so maybe its time?

They say when you are trying to perfect something you should never change more than one variable at a time...
Well I got overly excited and changed two.
The results are good, but now I dont know if it was one or both changes that gave the better results.
I cleaned the barrel, AND I tried the 13.43gr slugs before fully testing the groupings of the 10grainers

Well I'm happy with the results either way. At 40yards I'm getting one hole groups.
I kept the power wheel on no.7, and the velocity has dropped from 999fps with the lubed 10grainers, to 892fps with the unlubed 13.4grainers. The power has gone up from 22.3FPE to 23.7FPE
I'm happy with all of that.
I prefer the idea of sending a projectile down range (on someone elses property) at 892fps in stead of 999fps.
I also fine tuned them with one eighth turn adjustments on the hammer spring pre tensioner screw. The extreme spread of velocities in a group went from 19 feet difference at the worst, to 3 feet difference at its best where it now is, so thats pretty consistent.

The next question is what will the bigger slugs terminal performance be like?
Are they going to expand as beautifully as the faster 10gr's or are they going to start passing through a rabbit?
Will they have the same devastating stopping/knock down power?

More testing and necropsys needed...

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RangerPete View Drop Down

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Posted: 11 Oct 2024 at 6:42pm

Changing from the 10grainers to the 13.4grainers, velocity has dropped by about 100fps, kinetic energy has gone up from 22.3FPE to 23.7FPE
And groups seem to have tightened up at 40yards.

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Posted: 12 Oct 2024 at 12:58am

Nice shooting Pete.

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Posted: 12 Oct 2024 at 8:06am

How did it affect the arc of the pellet in flight. Thats huge fps drop.
You too taking note of dye numbers on slug tin? Think your pellet size checker will be help but flyers are a part of air rifle shooting. My weighing and sizing has helped limit flyers but they still happen.
I tend to wonder if at times that during feeding a pellet in, maybe it goes a tad bit less strait than usual and takes or flatens a tiny flat spot on head. Or maybe in the case of hollow point slug,just slightly nicks the hollow point tip.

Edited by kruzaroad - 12 Oct 2024 at 8:08am

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Posted: 12 Oct 2024 at 8:13am

Looking good Pete.

With the power wheel, if you feel that turning down a notch increases accuracy, will one more notch tighten again, or open the group up? Once you know that, maybe there's a sweeter spot in between those notches. Of course you then have to adjust the micro adjustment, but if you record the increments you go in, maybe you can find that sweet, sweet spot.

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Posted: 12 Oct 2024 at 10:30pm

The drop in velocity doesn't bother me at all. Both are still pretty fast, basically 1000fps vs 900fps.

Zeored at 35 or 40 yards, their trajectories are with in a few mm of each other out to 50yards.
Basically identical out to 50y.
Where it gets interesting is if you look at the 100 yard figures...

10gr slug - at 100 yards drop is 11.9 inches, velocity 727fps, energy 11.7FPE
13,4gr slug - at 100 yards drop is 12.9 inches, velocity 731fps, energy 15.92FPE

The 13,4grain slugs are 34% (3,4grains) heavier, and leave the muzzel 10% slower than the 10grainers.
The difference in drop at 100 yards is only 1 inch, BUT, because of their much better BC the heavier slug is now traveling faster than the 10grainer, and is carrying 37% more energy.
That is amazing.
The BC's by the way are 0.047 for the 10grainer and 0.066 for the 13grainer.

I was out at that difficult race track again last night, the one with the wild rabbits you cant get close to.
The close shots are 60yards, and from there its anything out to a 100yards.
I took Little Emma and used the 13.43gr slugs. Finished on 24 rabbits and 6 hares.
Well they certainly do hit hard, which was to be expected. Unfortunately I was under pressure for time so I did not collect any rabbits for necropsys, so I still cannot tell you if they expand like the 10grainers and weither or not they pass through. But I'm sure I'll have a few carcasses to investigate in the not too distant future.

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Posted: 13 Oct 2024 at 4:04am

Uuum doesnt a thousand fps put you into transonic where as 900fps doesnt?
Is this the gun your trying to sort the flyers out on.

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Posted: 13 Oct 2024 at 6:53pm

Ja, I'd say 1000fps is trans-sonnic, but I dont think trans-sonic applies to slugs, completely different shape to pellets.
Nothing I have ever read about slugs makes any reference to trans-sonic problems, in fact most slugs seem to perform best at 1000fps and more!

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