BC Variation of .25 caliber JSB pellets due to environmental condition changes
- Thread starter SMH77
- Start date
@smh77, Sean, what I'm trying to wrap my brain around is the reason that the BC with the LW Poly barrel is significantly better than with the standard rifled LW barrel. And why its hard for me to reason is that from all accounts, the diabolo shaped pellets are drag stabilized. So it would appear that it shouldn't really make a difference what type of barrel the pellets are shot from. But you have shown that there is a difference in BC from varying barrels. I would assume the FX ST and STX barrels also show a significant difference, but I haven't seen any comparisons as you have done.
Upvote 0
Well, here’s what I can offer (Centercut): I can shoot the same pellet (or two) through both the Polygon and LW Rifled barrel on the same day with the HS tension turned down as low as possible, and then I can shoot the same two pellets through my son’s FX WC mk II (same caliber) for a comparison. The one thing that will have to be accepted is that his gun will shoot about 40-50 fps slower than the polygon barrel-unless I dig in and play with the regulator, and HS tension (which I’m not ready to do on that gun yet). We can see what that data shows and diacuss from there? The conditions will be similar enough that I think we can call them ‘constant’ despite slightly changing during the day. I would like to do this when the wind isn’t too crazy (like now) and its neither aiding nor opposing the pellet soas to affect the 50 yard velocity and skew and comparison of the results.
Regarding the ‘why’: let’s gather the data above and see what it says first to confirm it really IS real. Assuming it is, I have some thoughts on the ‘why’ behind it that i can share...
Sean
Regarding the ‘why’: let’s gather the data above and see what it says first to confirm it really IS real. Assuming it is, I have some thoughts on the ‘why’ behind it that i can share...
Sean
Upvote 0
Sounds like a plan. Is your son's FX ST or STX? And if you have both can you run both? That would be the definitive study. I think as long as the velocities are fairly close its fine, I also have some thoughts on the why, but it depends if the BC with the Poly is better than the BC with the ST. I think you know where I'm going with this, the consensus seems to be that the rifling marks from the regular rifled barrel affect performance and BC, and the Poly doesn't make nearly the same marks on the pellet. So if the ST BC is significantly less than the Poly, then what? Perhaps spin does factor into it even though the diabolo pellets are supposedly drag stabilized...
Mike
Mike
Upvote 0
Other question is whether it is the rifling marks or deforming of the skirt to seal against the barrel.
Upvote 0
Well, I had enough time to get the data tonight, so now I'm in the process of crunching the numbers. I took screen shots of weather conditions all throughout so I could account for any changes taking place. Bottom line: I don't think we'll see a ton of difference between the results in the barrels (just looking at the number).
Tested:
LW Polygon Barrel, .25 cal with JSB Heavy Mk I and Mk II pellets @ ~ 890 fps mv
LW Polygon Barrel, .25 cal with JSB Heavy Mk I and Mk II pellets @ ~ 860 fps mv
FX WC ST barrel (factory barrel), .25 cal with JSB Heavy Mk I and Mk II pellets @ ~ 860 fps mv
Stay tuned for more...
Sean
Tested:
LW Polygon Barrel, .25 cal with JSB Heavy Mk I and Mk II pellets @ ~ 890 fps mv
LW Polygon Barrel, .25 cal with JSB Heavy Mk I and Mk II pellets @ ~ 860 fps mv
FX WC ST barrel (factory barrel), .25 cal with JSB Heavy Mk I and Mk II pellets @ ~ 860 fps mv
Stay tuned for more...
Sean
Upvote 0
Ok, I was wrong, there is a difference between barrels like I originally suspected. I think I'll pull this out into a separate post as there will likely be more people interested in the comparison and may not find it barried at the bottom of this thread. Here's the chart with the results:
Sean
Sean
Upvote 0