That’s a good idea... In order to compare BC between the .25 heavy and the .30 pellets it might be beneficial to shoot them at close to the same speed. I was surprised that the difference between the light and heavy .30 was so small...
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.30 Cal Ammo Shootout: BC's and other stuff measured!
- Thread starter SMH77
- Start date
Yeah, I was talking about the differences between the lite and heavy JSB's in both the .25 and .30 cal's with my buddy the other day. The thing is, there is a large difference in mass in the .25 cal (Heavies are 33.7% more massive than the lites) while only a minor difference in the .30 cals (Heavies are 12.1% more massive than the lites). Thus, for the .30 cal Heavies to have the same 'mass increase' as they do in the .25 cal size, the .30 cal 'heavies' should be 59.81 grains. I'm hoping a new JSB pellet in .30 cal will come along with these proportions-even if they must be single loaded only...
When looking at the BC's however, the delta in .25 cal is a massive 63.1%, while the delta in .30 cal BC is a paltry 3.7%. I can't quite put my finger on it, but the geometric form of the .25 cal heavy is distinctly different than the lite, and the form differences between the two .30 cal JSB's is really inconsequential (visually) to me(so what, the fattened up the waist some?).
I do hope that JSB makes the same radical form factor in a 'monster' .30 cal pellet that mimics what they've done in the .25 caliber heavy pellet. I would love to test that, and see how it shoots...
Do the smaller calibers (.22 or .177) have versions that are similar in 'form factor' as the .25 cal heavies? I'm just not familiar with them since the smallest caliber I own right now is .25 caliber...
Sean
When looking at the BC's however, the delta in .25 cal is a massive 63.1%, while the delta in .30 cal BC is a paltry 3.7%. I can't quite put my finger on it, but the geometric form of the .25 cal heavy is distinctly different than the lite, and the form differences between the two .30 cal JSB's is really inconsequential (visually) to me(so what, the fattened up the waist some?).
I do hope that JSB makes the same radical form factor in a 'monster' .30 cal pellet that mimics what they've done in the .25 caliber heavy pellet. I would love to test that, and see how it shoots...
Do the smaller calibers (.22 or .177) have versions that are similar in 'form factor' as the .25 cal heavies? I'm just not familiar with them since the smallest caliber I own right now is .25 caliber...
Sean
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Yes, JSB REVISED Monster 25.4 gr 0.22 cal is the same general shape as the 33.9 gr .25 cal Heavy Kings. I did another bc test yesterday on this pellet shot from my BSA JB OZ 1 rifle with .22 barrel at 880 fps for an average 0.051 bc raw data at the farm. That equals the bc of the .25 cal 33.9 gr Mk 1 under same conditions. They group very well from that rifle and obviously carry more energy and momentum down range than the 0.25 original 25.4 gr Kings.
JSB also make a .22 cal 33.9 gr pellet which is the same profile but much longer. I don't have a barrel with an appropriate rifling twist rate; or one that will shoot those fast enough to stabilize them, hence cannot report good groupings.
Your .30 cal reported groups are outstanding. My FX Crown is shooting similar groups in best air with 33.9 gr King Heavies skirt sized to 0.2515 to easily load the magazine, and lubricated with Krytech wax to reduce barrel cleaning. .... Kind regards Harry..
Thanks Harry-I appreciate the info and kind words.
I shot again tonight after work, though the conditions weren’t as well. I had one group going that was on par with my best, and then got realy mental on the last shot (plus the breeze started up). Kids arguing inside the house made it hard to focus too. Oh well, it was at a .250” group for the first 4 shots, then opened up when I blew thw last one. Middle group was 4 shots to confirm sighting at 75 yards. The group above it was heading towards a 1/4”, until I blew it. All others were 5 shot groups at 75 yards. The middle and lower row was obviously when the wind started to pick up.
I need to get some wind flags, LOL-its obvious that I didn’t try to compensate for the wind when it flared up...
Sean
I shot again tonight after work, though the conditions weren’t as well. I had one group going that was on par with my best, and then got realy mental on the last shot (plus the breeze started up). Kids arguing inside the house made it hard to focus too. Oh well, it was at a .250” group for the first 4 shots, then opened up when I blew thw last one. Middle group was 4 shots to confirm sighting at 75 yards. The group above it was heading towards a 1/4”, until I blew it. All others were 5 shot groups at 75 yards. The middle and lower row was obviously when the wind started to pick up.
I need to get some wind flags, LOL-its obvious that I didn’t try to compensate for the wind when it flared up...
Sean
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Enjoyed following your tread Sean. Thanks for sharing. The new H&N pellets look promising. I wonder how consistent they are in weight and head size ect.
With the higher BC it would be interesting to see results after sorting them.
Michael
With the higher BC it would be interesting to see results after sorting them.
Michael
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Beautiful mid-60’s weather here today so i plan to do a quick test of BC on just one pellet to see how it changes over temp. Then I plan to convert to .25 LW (non-polygon) barrel and try to get all the data on the .25 cal pellets before I loose daylight. Hope the temp doesn’t drop and affect readings...
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As expected, the warmer temps caused the BC to increase. I didn't test all 3 pellets, just the JSB lites to give me an indication of what would happen based on temp. I also didn't take my time to shoot groups, just wanted to get the BC data so I could move on to map the .25 caliber, LW (non-polygon barrel) to see what would happen there. I have that data now and will start another post once I've compiled it all. I'll also discuss the change in BC from the LW rifled (traditional) barrel to the LW polygon barrel-as there were some interesting findings there...
Here are the results for the .30 cal, at 66F.
Here are the results for the .30 cal, at 66F.
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Thanks again... Looking forward to your "procedure" so that when we do this we use the same baseline distances, etc. I think what surprised me the most is that the JSB Heavies weren't that much better than the Lites, and were actually worse than the H&N. Not sure it will be the same on a ST barrel, but we'll see. The BC for the Heavies are usually advertised as being approx. 0.01 better than the Lites. If you look at Chairgun, or Strelok Pro, it shows .042 or .043 for the Lites, and .051 or .052 for the Heavies, which is a considerable difference. We'll see when the data comes in on the .30 Bobcat Mk2. I have the Polymags, Lites and Heavies, but no H&N pellets to test...
Mike
Mike
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