RAW .30 cal, JSB Light (44.75 grain) Ballistic Coefficient, measured

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SMH77

SMH77

Member
Oct 28, 2017
997
73
Wisconsin, United States
Just as a PSA, I figured I'd share with you the results of my measurement today of the BC of a JSB .30 cal light (44.75 grain) pellet. First, it was very cold outside (21.9F) so I had limited time (heat) and daylight to get this measurement completed.

Pellets were measured and selected at 44.8 grain
Muzzle velocity averaged (~ 6 inches from muzzle): 861.2 fps
Distance to far measurement: 43.8 yards
Velocity measured at 43.8 yards averaged: 738.6 fps

I opened up Chairgun (both Mac version and iphone version) and adjusted the environmental conditions, altitude, etc. I then went to the BC calculator app, plugged in the above data, and it calculated a BC for the pellet of 0.0427. Seems to be right in the ballpark of other readings that have been reported.

I believe the RAW .30 cal barrel is a Lothar Walther traditional rifled barrel (no idea of the twist rate).

I was planning to perform the same measurement on the .30 cal JSB Heavies (50.15 grain) but ran out of daylight, and heat.

Does anyone know: will the difference in temperature affect the BC, or does it factor out because I entered in the environmental data in chairgun?

Notes: same chrony was used at both distances. Velocities were held super tightly (muzzle was: 861.9, 861.5, 860.3; 43.8 yards was 738.5, 738.8, 738.5).

So, in conclusion, the JSB 'light' .30 cal pellet (44.75 grain), through my RAW at that distance had a BC of 0.0427.

Hope this is helpful for anyone looking for data from this gun / setup?


Sean
 
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Thanks. Shouldn’t make that much of a difference from near sea level. I asked because I live and shoot sometimes near sea level, and other times an hour away at 3500 ft. Now that does make a difference. Especially at 75 to 100 yards...

and because I had intended to do the BC testing myself on those two pellets. The Club where I shoot has a 50 yard tunnel that can be used for testing. It’s basically a 30 inch pipe underground. So no wind affects at all. Can set up chrony at muzzle and at 50 yards and get exact results. I plan to do this sometime in January. 

My Bobcat shoots the 44.75 at 880 fps and the 50.1 at 845 fps, so our results should be similar. 
 
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"Centercut"Thanks. Shouldn’t make that much of a difference from near sea level. I asked because I live and shoot sometimes near sea level, and other times an hour away at 3500 ft. Now that does make a difference. Especially at 75 to 100 yards...
and because I had intended to do the BC testing myself on those two pellets. The Club where I shoot has a 50 yard tunnel that can be used for testing. It’s basically a 30 inch pipe underground. So no wind affects at all. Can set up chrony at muzzle and at 50 yards and get exact results. I plan to do this sometime in January. 
My Bobcat shoots the 44.75 at 880 fps and the 50.1 at 845 fps, so our results should be similar.
Click to expand...
Please post the results when you have them. I have heard conflicting messages on whether a smooth twist barrel and a LW barrel produce similar results for BC with the same pellets, so the results will be interesting to see.
 
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THANK YOU, Sean, for shooting real pellets over a real chrony in the real world! The BC numbers I've seen for the .30 JSB 44.75gn always seemed unrealistically LOW. Then there was all of the poly barrel .25 hype and it being somehow ballistically superior to the .30 - not buying it! Haha. When I bought my .30 RAW, I asked Martin what he believed was the better bore for 100 yard shooting and it was .30 cal. .042 BC is pretty darn high, so it's no surprise. 

Thanks again - +1 to you

​Brian
 
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No problem Brian and thank you! I am interested to learn this information for myself, and I figure others are as well. I'm taking some vacation time today and we have great weather, and excellent shooting conditions so I plan to test the BC's of 3 different .30 cal pellets today: JSB lites (44.75 grn), JSB Heavies (50.15 grn), and the H&N Baracudas (46.30 grn). I'll report back what I find for BC's. Temps will be a bit lower, like in the mid 40's, but that's pretty warm for how its been lately.

I plan to repeat this test using the same method over different temps throughout the year also to see how temp affects the BC's. I'll summarize what I find and put it in a document. I plan to do the same testing (and I've done some already) with the .25 cal pellets too.

Chrony #1 position will be at 1 yard, Chrony #2 position will be at 50 yards. Shooting the same exact spot on the target for each pellet, and chrony position.


Sean


 
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Just finished the comparison and compiled the results. I'll start a new thread and copy the link here. I was surprised by the results: the BC of the H&N baracuda's was the best of the bunch, and seemed to have the tightest spread / lowest STD of the 3 pellets. The BC of the JSB Lites was a bit higher compared to what I showed in this thread also-not surprising because the temp was a bit warmer, and the testing method a bit different too.


Sean
 
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"Brian.in.MI"THANK YOU, Sean, for shooting real pellets over a real chrony in the real world! The BC numbers I've seen for the .30 JSB 44.75gn always seemed unrealistically LOW. Then there was all of the poly barrel .25 hype and it being somehow ballistically superior to the .30 - not buying it! Haha. When I bought my .30 RAW, I asked Martin what he believed was the better bore for 100 yard shooting and it was .30 cal. .042 BC is pretty darn high, so it's no surprise. 
Thanks again - +1 to you
​Brian
Click to expand...
Brian,

I just retested the JSB 0.30 cal pellet (44.75 grain) at 66F, and the BC was even higher yet. Take a look in the other thread on the .30 cal pellet BC's that I have and you'll see the updated data on the second page of the post. In short, it went from 0.0458 @ 44F, up to 0.0493 @ 66F. Obviously I expect it to continue to rise (over 0.050) as the temp continues to increase, and humidity rises (humidity wasn't too bad for this test).


Sean


Sean
 
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