Balistic coeffiant of Crossbows.

Dimitri · Super Member Joined: Nov 25, 2005 Posts: 5946

Well I was doing some testing and came to the conclusion crossbow bolts in 400gr have a balistic co-efficant of .07 Shocked

Using the information for balistics from Excaliber's site ( www.excaliburcrossbow.com/ ) and a online balistics calculator (Point blank Online doesnt like going that low in FPS it seems) (from this site www.biggameinfo.com/in...lcalc.ascx ) with a FPS of 350fps the arrow will be only 317.8fps at 50 yards so playing with the BC of the arrow I came to the conclusion is .07 Smile

Hope this helps someone. Very Happy

Dimitri

PaulS

the calculations that are being used are calculated with a very low sectional density and the BC reflects that. If you could list the sectional density of the bolt for the crossbow you would get a much higher BC.

Dimitri · Super Member Joined: Nov 25, 2005 Posts: 5946

Perhaps Paul, I dont know enough on the subject but its sort of nice having a better chart then is normally offered by crossbow manufactures to me. The SD was 0.357 (That calculated it I didn't). Smile

Tell me how do you calculate Sectional Desity ?? Confused

Dimitri

GroovyJack · Member Joined: May 21, 2005 Posts: 621 Location: Bama

Sectional Density is a bullets weight in pounds divided by its diameter squared ..IOW
150 grain 308 SD is 150/7000 / .094864 (.308 squared ) or .226
180 grain .308 SD is 180/7000 / .094864 ( .308 squared ) or .271
I dont see how you could get an accurate SD for a cross bolt , where' ya get the diameter ??

Dimitri · Super Member Joined: Nov 25, 2005 Posts: 5946

I wasnt sure what to put for the diameter so I used .400" Smile

Dimitri

GroovyJack · Member Joined: May 21, 2005 Posts: 621 Location: Bama

No broadhead ?? I dont think SD with a crossbow relates to SD in a rifle , IOW , not comparing apples and apples ..
A 500 grain 458 bullet has an SD of .340 , and I dont think that crossbow bolt is gonna out penetrate the 458 ..
SD is a measure of ability to do work , comparing bullets , or looked at another way the higher the SD the harder it is to stop the bullet , or the more it penetrates , momentum .. Now that crossbolt may out penetrate the rifle bullet in a bag of sand , but which ya want with a mad bull elephant ??
Changing subject , I'm curious , why a crossbow ??

Dimitri · Super Member Joined: Nov 25, 2005 Posts: 5946

GroovyJack,

I've got a broad head on them but I discounted it for my calculations. As most broad heads supposidly shoot pretty much the same as feild points. Wink

Reason for the crossbow is we have archery season from the start of Octomber to the End of Decemeber. And in theory you can get up to 6 EXTRA Buck or Doe Archery tags (for a total of 7 deer tags with the General Buck tag) here so it lets me hunt more. Smile

Eventhough to be honest I havnt seen a deer (well close enough to shoot) yet this season but I've only been out 2 times.

But I only have 2 tags didnt get many just my general tag and a doe validation sticker for it for the area I've been going to and another achery tag for another area I might end up going once or twice so I figured I might as well get a seperate tag so I can get a buck or doe there and still have my general tag. Smile

Dimitri

PaulS

what makes you think that two 400 grain 40 caliber projectiles won't penetrate the same distance if one happens to be 20 inches long and the other is a lead bullet?
They have the same weight and the same cross-sectional area? The biggest difference is the resistance caused by the area of the sides - the longer the sides the quicker it will decellerate.

ammohouse

I'm new here but the new crossbows ain't primitive weapons.