JSB Knock Outs 10gr .177

What is an average shooting country?
That's got to be the biggest load of cat trap I've ever heard.
India has a strong air rifle following high arse temps. Canada had a strong air rifle following they hit sub zero. Asian areas can be hot and have a near 100% humidity that affects flight etc etc

The “crack” is called a sonic boom and happens when an object breaks through the sound barrier, I.e. goes faster than the speed of sound (on that day, at that altitude, at that temp etc…)

As Kruza says above, speed of sound is dependent on the density of air (or other medium) it is traveling through, hence the altitude and temperature dependency. But as a general rule of thumb on most average shooting days, in most average shooting countries, it is between 1100 and 1150fps.

All the top guys who are shooting slugs in extreme long range and bench rest competitions shoot slugs between 950 and 1100 fps and you never hear any sonic booms when they are shooting.

As far as transsonic pressure waves effecting projectile stability goes, all those top guys are shooting sub moa groups at 100, 120, 150 even 200 yards. So transsonic speeds don’t seem to be effecting their slug performance in any way.

I could be wrong, but isn't any object that goes faster than sound going to create the "crack"?

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!

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.