Ballistic Coefficients

[mausernut]

Does any know, or know where to find the ballistic coefficient for the the m41 6.5x55 ball ammunition.Would also like to find the one for the Spanish 7x57 138.9 gr ammunition. Tried several different searches and keep coming up blank.

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[browningautorifle]

Have you looked in the Speer books? They have coefficients, maybe not that very one but they'll have the 140gr 6.5 bullets likely, will be close.

[mausernut]

L find the BC's for spitzer boat tails are all over the place from .490 to .646. That's a bit of a difference.

[Parashooter]

Here's a few from a Scandinavian reference. The "Norma Pointed FMJ" is likely the M41 - or close to it.

Diameter Bullet name Weight BC SD

0.264 ins Lapua Scenar HP 139 grs 0.660 0.285
0.264 ins Norma Hollow Point 139 grs 0.510 0.285
0.264 ins Norma Pointed FMJ 139 grs 0.580 0.285
0.264 ins Norma Semi-pointed SP 139 grs 0.410 0.285
0.264 ins Norma Vulkan 139 grs 0.320 0.285
0.264 ins Barnes "X" S 140 grs 0.522 0.287
0.264 ins Hornady A-MAX 140 grs 0.618 0.287
0.264 ins Hornady SP 140 grs 0.465 0.287
0.264 ins Jensen J26 140 grs 0.595 0.287
0.264 ins Nosler Spitzer Partition 140 grs 0.490 0.287
0.264 ins Sierra HPBT MatchKing 140 grs 0.526 0.287
0.264 ins Sierra Spitzer Boat Tail 140 grs 0.490 0.287
0.264 ins Sierra HPBT MatchKing LD 142 grs 0.560 0.291

If you can find velocities at two different distances, preferably at least 100 yards apart, any number of calculators can figure the BC.

[CINDERS]

Get Hornadys HandBook Of Reloading Cartidges 4th Ed Tables & Charts has all the ballistic info on projectiles along with the drop figures, velocity and fpe. I use it after Quickload just to see how close its calcs are to ones in the book.
In reference to the Quickload program does it have updates I have had mine for years have tried to contact the manufacturers of it and lucked out. TIA

[mausernut]

I have the BC.s of commercial bullets. I have 6 manuals here. Was trying to find the BC's of the original military loads so I can try to match them so that the iron sights on the guns will work.

[CINDERS]

Problem is what another forumer and I discussed at length were the modern projectiles made today are far superior in their B.C than what was originally produced and replicating the ballistic trajectory to marry up with the iron sights may not work.
With the SMK 174Gn FMJBT the B.C changes dependent on what velocity you drive it at also consider the burn rates of modern powders in relation to what they used ages ago that could or may alter the harmonics in the barrel giving a different flight path or barrel exit.
I found a load that grouped well in my 303's for the .311SMK & Bullet Factory .312FMJHPFB then got the sight settings down pat for each rifle as they are the same but not the same if you get the drift from 100m (109.361yds) out to 600m(656.168yds) copied them into a book that goes with each rifle and thats it.
Yes it took time to do but its finished now and nothing changes except the conditions and my ability to dope them.

But good luck I am still to get off my date and do some load testing I promised to do in relation to this question by reducing the load weight to find a velecity where the trajectory matched the sights rather than try to find a bullet that had the same B.C.
We then get into the realm of if a high B.C projectile like the SMK is driven at such a velocity @1800fps what would the practical limits be range wise it worked out close to the MKVII round I think from memory. As they state to using a different B.C dependent on how fast you drive the projectile which Seirra provide for the 303 174gn SMK.
Thats fine say for 300m but what am I looking at with 600 will it be transonic or sub sonic at that range I can check ballistic charts till I am green as it does not corelate to relative humidity, wind, height above sea level and so on but I will try and get my ar*e down to the range to try the loads at 300m using a lab radar for velocity and my best shooter No.4 but don't hold your breath yet...............its xmas nearly.

[mausernut]

I just want these for hunting. If I get the original BC's then I can run a trajectory and then get my loads worked out to do about the same. I run the 180 grain Sierra Pro hunter at 2480 to 2500 for my 303 and the trajectory is close enough to the same that I can shoot out to 300 yards. And that is as far as I want to shoot with open sights on deer.

[bob q]

Using modern bullets you are wasting your time . Military bullets have different shape , size , jacket material , core hardness and bore friction . Add all this up and you will not find a modern bullet that will match the sights through out their range . You could just pick a good hunting bullet and shoot it to see where it hits .

[CINDERS]

What I did was sourced a WWII MKVII ball round ballistic table then used my other books to find a velocity of the modern 174gn SMK where the trajectory of mid flight for a 300yd zero which was close to the actual WWII vintage projectile. (No hope of matching it at all)
It worked out that (From memory) it was very close but as stated the velocity that the modern round had to be driven was below minimum loads for the powder I was normally using (AR2209 or H4350 for you in the U.S.)
I then had to find (Which I had) another powder where it was at the required velocity but that also was close to the minimum for that powder.
In the end of all of this data I think at the velocity required the SMK shot something like 6" lower mid flight trajectory for the same 300yd zero as the MKVII so it would be close but we are driving the modern projiectile well below the 2440fps that the normal MKVII goes.

Anyway thats what I came up with good luck its easier just to get a load that groups in your rifle go out shoot at your max distance* wanted for hunting get the sight setting note it down and go from there its what I did and countless others have as well.