balisticians please help

[kweidner]

Here's the problem. So I am working up a drop chart for my cz 22-250. Ave fps is 3688, extreme spread is 20 fps. My BC was unknown. The bullets are Watson 52 gr. (Ed Watson BR hollow point flat base) I have been working on this for a week or so. I guessed a .350 BC based on the drop at 400 and 500 yds. I shot this evening on quartering winds between 5-10 mph at 565 yds. I used (according to mil dot scope Sightron 6x24x42 Md) a 7.2 MOA shot. (2nd dot). Shots were between 3 and 6 inches low. I adjusted my BC so my drop 64.73 (shot) matched the BC of 3688 fps according to Pesja. My BC ended up at a .308. My adjusted table now shows 64.73 inches of drop at 565 yds. 85 degrees and 200 foot above sea level are my plug ins. This seems like a really high bc for a 52 grain pill. Is my math right? My vertical was less than 4 inches on 10 shots horizontal was 6.5. (gusting winds @ 3:00 and no flags) please help! This rifle, I feel. has great potential.

Ken

 

[Jon A]

Here's one minor thing:

I used (according to mil dot scope Sightron 6x24x42 Md) a 7.2 MOA shot. (2nd dot).

2nd dot will be 6.876 MOA, as each Mil is 3.438 MOA. They are 3.6 inches per hundred yards, which aren't exact MOA.

 

[kweidner]

JOn you are right. I probably should have included that I have also adjusted MOA on the spreadsheet to be exactly 1 inch. Sorry I over looked this info when stating problem.

 

[Jeff In TX]

Here's the problem. So I am working up a drop chart for my cz 22-250. Ave fps is 3688, extreme spread is 20 fps. My BC was unknown. The bullets are Watson 52 gr. (Ed Watson BR hollow point flat base) I have been working on this for a week or so. I guessed a .350 BC based on the drop at 400 and 500 yds. I shot this evening on quartering winds between 5-10 mph at 565 yds. I used (according to mil dot scope Sightron 6x24x42 Md) a 7.2 MOA shot. (2nd dot). Shots were between 3 and 6 inches low. I adjusted my BC so my drop 64.73 (shot) matched the BC of 3688 fps according to Pesja. My BC ended up at a .308. My adjusted table now shows 64.73 inches of drop at 565 yds. 85 degrees and 200 foot above sea level are my plug ins. This seems like a really high bc for a 52 grain pill. Is my math right? My vertical was less than 4 inches on 10 shots horizontal was 6.5. (gusting winds @ 3:00 and no flags) please help! This rifle, I feel. has great potential.

Ken

Ken,

Your guessing with way to many variables and unknowns. Since you have a chronograph, measure an exact 100 yards (not with a laser range finder) and shoot another 10 shot string and get your average 100 yard velocity. Let me know what it is and I'll calculate your exact BC out of your gun. If you can also get your 200 yard velocity average that will really help. I know it sounds crazy to shoot through your chronograph at those ranges, but I've shot through mine at 400 yards in the past which gets real interesting.

100 and 200 yards is no problem. Also measure your exact scope height.

Hope it helps

 

[kweidner]

I will do that Saturday Jeff. Thank you for your help. Scope is 1.75 centerline to center of bore.

Ken

 

[kweidner]

I will do that Saturday Jeff. Centerline of scope to centerline of bore is 1.75"