JSB Knock Outs 10gr .177

Average shooting country is not the south pole and not the saraha desert. Average shooting country is where most people like to live because the average temperature is above freezing and below 50

The Guinness world record, .177 for distance is sub 12 foot pounds with the 7.33 gr pellet at 850 fps!

This from the guy who has done the world's furtherest shot. Big bore 1265m, 1777 yards

(Quote)
thank you, with this I want to take a longer break from shooting above 1200m.
It was for a velocity of 260 m/s = 853 fps, at a higher velocity the BC would be slightly higher.
My friend from abroad who also uses ATP Smooth 49.5gr but at higher speed measured BC G1 0.238 at speeds of 294 m/s 964 fps ( end quote)
Think you better look at what fps the guns were set to not the fps they can produce. To because all of the Dr top guys aren't shooting over 1000fps

Here's a 🔗 to video. Go to very end even then you'll here them say “maybe 900fps“
https://youtu.be/FQW3x8EqZi0?si=QIhfqRaXMI6hJoca


Edited by kruzaroad - 15 Oct 2024 at 4:58am

The speed of sound in feet per second (fps) depends on the temperature and the material through which it travels:

At 0° C (32° F): The speed of sound is 1,086.9 ft/s.

At 20° C (68° F): The speed of sound is 1,130 ft/s.

At room temperature: The speed of sound is 1,125 ft/s.

The speed of sound is faster in warm air and slower in cold air. The speed of sound in water at 8° C (46° F) is about 4,721 ft/s.

Transonic is the level that both sub and super sonlc airflow start to form on different parts of the projectile,the projectile shape plays a part in that formation. It affects any projectile. It happens mostly when dropping to out of supersonic but if your right up on the edge of that speed,airflow differences created by the slug can induce the effect. Most of the stuff I've looked at has shooters around 950fps max if they want to say under transonic. As you can see temp could effect that margin.
Look at speed of sound in water.
At least that's my understanding of it.

It does.
https://youtu.be/HpDKxVuRWto?si=AYxd76u6ZpF3VujU

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.

Looking good Pete.

Nice shooting Pete.

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...