BC measurement

[thomasair]

I was curious what the BC of the 25.4 gr Redesigned Monsters were out of my gun.

I shot one ten shot string at the muzzle. High 1006, Low 1000, Ave 1002, ES 6, SD 1.

I then moved the chrono 49y to the front of my 50y target stand. I took 10 more shots. High 890, Low 884, Ave 888, ES 6, SD 1.

Because the SD was very low, I was comfortable using the average of each to calculate. Using ChairGun I got a BC of .054.

When it’s less hot outside...I’m going to do the same test with the JSB slugs. Right now I find no drift advantages using the slugs at 50y. I suspect this is due to them not being fully stabilized at 50. I’m guessing I will see a very similar BC. We will find out.

Im also going to sample other velocities with the RDs to see if there is any advantage.

Mike 

 

[18.13]

From my limited testing with the RDS's the BC starts going down when you get above 950 fps.

 

[Scotchmo]

That's a great BC for .22 caliber pellets. What is the elevation of your shooting range?

It will be interesting to see the comparison to the JSB slugs.

Any chance of running it out to 75 or 100yds to see if the BC holds up?

Though I have yet to achieve acceptable accuracy with the 34gr Jumbo Beast, it would be interesting to see how they compare. If it's BC was substantially higher, it might be worth pursing for 100yds in windy environments.

I've considered getting a Labradar to make those long range BC measurements more convenient.

 

[Centercut]

I agree with Scott. A BC determined at 50 yards is interesting, and we appreciate the info., but it’s not useful to those that want to go out past 100 yards where an accurate BC is critical for hunting... The drop from 50 to 100 yards is minimal compared to the drop from 50 to say, 175 yards. For me where I shoot the drop with my hunting slug setup is about 9 inches from 50 to 100. However, from 50 to 175 is about 49 inches. So having a precise BC, and a gun with a low SD is critical to successfully hitting a small target like a juvenile ground squirrel. I’d be very interested in seeing the comparison of the BC between the RD Monsters and KO slugs at 100+ yards. 

 

[thomasair]

I’ll check at 100...but not gonna bother past that. I have found that BC is not all about the pellet. Different barrels can produce significantly different results with the same pellet. I’m also pretty sure I am shooting faster than optimal at 1000 FPS. Accuracy is very good, though.

Im at about 5000’. The BC is corrected for the elevation.

Mike 

 

[Scotchmo]

...I’m also pretty sure I am shooting faster than optimal at 1000 FPS. ...

Starting with a velocity that is a little higher than optimal for BC makes sense. As the velocity falls off with distance, the projectile will eventually be in the optimal velocity range. For longer distances, you might want to be at an even higher** muzzle velocity so as not to fall too far below that optimal velocity range.

**but staying subsonic

 

[thomasair]

Here are values for 25.4 RD, 34 Jumbo beast, and JSB KO 217 slug. Testing at 50y.

Please note I did not have the correct temp in ChairGun when I did the calculation posted earlier. I will change the value to .054.

BC testing

25.4 RD Monster 22 cal GA drag model

1002 and 888 49yd

87 degrees 20 RH 5000ft

BC .054



JSB KO Slug 217 22 cal G1 drag model 

986 and 932

90 degrees 15RH 5000ft

BC .1166 



JSB 34 gr 22 cal GA drag model

933 and 848

90 degrees 15RH 5000ft

BC .060

Mike 

 

[Scotchmo]

...
25.4 RD Monster 22 cal GA drag model...

BC .054



JSB 34 gr 22 cal GA drag model...

BC .060

The 34gr does not look all that much better and would require over 30% more FPE in order to achieve the same velocity. Probably not worth it in your case.

That Knockout BC is really good.

 

[Centercut]

I think that just shows how subjective our own observations can be when taken in a non controlled environment.

In the OP, Mike N said:

“When it’s less hot outside…I’m going to do the same test with the JSB slugs. Right now I find no drift advantages using the slugs at 50y. I suspect this is due to them not being fully stabilized at 50. I’m guessing I will see a very similar BC. We will find out.”

But in actual measurement it turns out that for him, the BC of the KO slug is twice that of the RD Monster pellet. So of course the slug has a 2 to 1 drift advantage over the pellet. It’s probably hard to discern accurately at such a short distance. I’d bet that at 100+ yards it would become more observable.

FYI, my BC measurements of the KO slug were much closer to the JSB declared value of 0.084. When I measured at about 500 feet above sea level and 80 degrees I came up with 0.087 at 110 yards at MV of 955 FPS. 

 

[Kim]

...
25.4 RD Monster 22 cal GA drag model...

BC .054



JSB 34 gr 22 cal GA drag model...

BC .060

The 34gr does not look all that much better and would require over 30% more FPE in order to achieve the same velocity. Probably not worth it in your case.

That Knockout BC is really good.

BC testing

25.4 RD Monster 22 cal GA drag model

1002 and 888 49yd

87 degrees 20 RH 5000ft

BC .054



JSB KO Slug 217 22 cal G1 drag model 

986 and 932

90 degrees 15RH 5000ft

BC .1166



Nice! Interesting that BC of slugs is ~2X pellets, but pellets shoot the same or better in the wind. Right?

If so how much should we care about BC, and if not BC what then?

 

[thomasair]

The interesting thing at 50 is that the exact velocity readings on my windicator produce exact same drift as the monsters. I have even shot as fast as I could alternating pellet, slug, pellet, etc and the basically go through the same holes.

1/2 the drift at 50? Nope, I’m certain I could see half the drift when I’m holding off an inch away. Don’t know what to make of it honestly. 


Mike 

 

[Centercut]

Not sure either. We can’t throw away over a hundred years of ballistics.

Perhaps re-do the slug. BC? Since the RDs seem logical but the KOs seem way high. 

 

[thomasair]

Even if the slug readings are wrong....the stated BC is still way higher than the pellets, and should be noticeable at 50. It is not.


The slugs show a clear advantage at 100.
I have shot good 50y cards with the slugs, but the pellets are easier to do so. Don’t have any explanation for their behavior at 50.

Mike 

 

[Centercut]

I agree, hard to explain. At least we’re not hearing the “takes time for the slug to go to sleep” BS which has been disproved scientifically so many times it’s silly. I was expecting to read about that again (not from you Mike) and would have either chuckled at that nonsense or puked, don’t know which.

 

[JungleShooter]

Mike,

thanks a lot for the data and the measurement details, I'll add it to my .22 BC table!  

I'd be interested to see if we can find an explanation of the slug's odd behavior of not being better in the wind at 50.

Matthias