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 June 22, 2008, 06:50 PM #1 Moloch Senior Member   Join Date: November 27, 2005 Posts: 1,305 Sectional density - Round ball I was just running some numbers on beartooth bullets ballisticians corner.-the relative penetration calculator. With the calculator I've got 9.81'' of relative penetration with a 133 grain .45 round ball. Next I calculated the relative penetration of a 1500 grain 1.00'' ball, and guess what I've got? 21'' of penetration! How can that be? All round ball bullets have the same sectional density as the weight/size ratio is the same, the bigger ball needs the increased weight to make a larger wound channel as deep as a smaller ball. -but the penetration should be equal right? I dont get it. # Does round ball penetration go up with the same amount of size increase of ball? What I mean is, if I have a .45 round ball, If I take a 50% bigger ball with 50% more weight it penetrates is 50% more than the .45? The link to the calculator. http://www.beartoothbullets.com/resc...v1=133&v2=0.45
 June 22, 2008, 07:10 PM #2 Sarge Senior Member   Join Date: May 12, 2002 Location: MO Posts: 5,038 Well, no. The heavier ball will penetrate deeper. It is exactly why the early hunters used 4 and 8 bores for African game, instead of Tennessee squirrel guns. There are some things that simply don't follow a mathematical pattern, and this is one of them. __________________ “Nine-tenths of tactics are certain, and taught in books: but the irrational tenth is like the kingfisher flashing across the pool, and that is the test of generals. It can only be ensured by instinct, sharpened by thought practicing the stroke so often that at the crisis it is as natural as a reflex.” ~ T. E. Lawrence
 June 22, 2008, 08:31 PM #3 Moloch Senior Member   Join Date: November 27, 2005 Posts: 1,305 I am well aware that the heavier ball will penetrate deeper, but why? Everything is mathematically explainable, this case is no exception.
 June 22, 2008, 08:44 PM #4 Hawg Senior Member   Join Date: September 8, 2007 Location: Mississippi Posts: 12,923 I think a thing called momentum plays a part in it. It takes more to stop a bigger bullet. That should have been heavier bullet. Last edited by Hawg; June 23, 2008 at 03:40 AM. Reason: correction
 June 22, 2008, 10:07 PM #5 FL-Flinter Senior Member   Join Date: June 24, 2007 Location: West Central Florida Posts: 207 I don't recall how the SD comes into play for the formulas when used for RB's but I can tell you these things: 0.440" RB driven from a 36" bore with 80gr of 2F will enter the chest of a whitetail at 40yds, cut the boiler almost in half, penetrate at an angle to the opposing hind quarter and come to rest against the bone. Same ball & load effectively enters the WT nose at 30yds emptying the brain box through a 2.5" diameter hole in the rear. Same ball & load at 60yds goes through a WT boiler room taking out the boiler and lays under the hide on the opposit side. 0.575" RB driven from a 34" bore with 100gr of 2F will effectively take out one WT front shoulder and penetrate at an angle exiting through a 1.5" hole in the rib cage on the opposit side on a WT at 85yds then go another 10yds or so before burying itself about 2" deep in a pine tree. Same ball & load at 65yds will enter the WT's neck from dead front center at spine level and open a hole a foot plus long like a zipper where the spine used to be over the shoulders, no idea where it went from there. Same ball & load on WT 70yds out that suspected I was there somewhere punched through both shoulder bones with ease and without destroying all the meat (was supposed to be a boiler room hit not a shoulder breaker - he started turning to bolt) I don't care what the math says, RB's work just fine. __________________ "Carry the battle to them. Don't let them bring it to you. Put them on the defensive and don't ever apologize for anything." Harry S. Truman [email protected]
 June 23, 2008, 09:56 PM #6 Dave Haven Senior Member   Join Date: February 1, 2000 Location: near Flagstaff, AZ Posts: 790 Sectional density = mass/dia^2; and mass of a round ball is proportional to dia^3, therefore, sectional density of a round ball is directly proportional to ball diameter. A larger ball has a higher sectional density.
 June 24, 2008, 10:33 PM #7 FL-Flinter Senior Member   Join Date: June 24, 2007 Location: West Central Florida Posts: 207 Dave, I thought there was a longer formula to obtain a number for use in a penetration calculator program when dealing with round balls as opposed to conical bullets? __________________ "Carry the battle to them. Don't let them bring it to you. Put them on the defensive and don't ever apologize for anything." Harry S. Truman [email protected]

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