New Ballistic Coefficients...

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big6x6

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This morning I wanted to put to rest the actual BCs for some of the new polymer-tipped bullets....

These BCs are calculated using actual velocities taken using identical Pro Chrono chrnongraphs at zero and 100yds. All bullets were fired from the same Savage 10ML-II stainless/laminate. All velocities were measured using the same charge of 40gr SR-4759. The listed BC is an average of 3-shots/readings. I tried to keep all factors as close to being the same as possible....

The BCs are closer than you may think!




2006rangepics%20264.jpg



The "players" from left to right:
T/C 250gr Bonded Shockwave, Barnes 250gr T-MZ, Traditions 275gr T-Shock XLR, T/C 300gr Bonded Shockwave, Knight 290gr USS-PTBT, Barnes 285gr Spit-Fire.

From lowest to highest:
250gr Bonded Shockwave- 0.197
250gr TMZ- 0.207
275gr T-Shock XLR- 0.214
275gr Barnes XBP- 0.224 (added 06/28/06)
300gr Bonded Shockwave- 0.239
290gr TMZ- 0.240
285gr Spitfire- 0.251

I included the 285gr Barnes Spitfire because it has always given me some of the highest BCs around for a .45cal bullet. It still is the BC champ.
 
That is interesting. Who would have thought the Hollow pointed 285 Spitfire would out BC all those tipped bullets.
 
Great report Chuck,Just curious how long did it take to do these comparisons Seems like a fun good time.
Ken
 
IndianaHunter said:
Chuck, real world data is fantastic. How closely do they match the mfg's data?

Hey Pat!
Actually VERY closely... This was the highest BCs I've ever gotten for the Shockwaves but I can't believe they are anything other than accurate. At least for yesterday they are accurate! :D At any rate...these are the BCs I'm going to use.

From lowest to highest numbers in ( ) are factory claims:
250gr Bonded Shockwave- 0.197(0.210)
250gr TMZ- 0.207(0.210)
275gr T-Shock- 0.214(No factory data)
300gr Bonded Shockwave- 0.239(0.250)
290gr USS-PTBT- 0.240(0.241)
285gr Spitfire- 0.251(0.239)



Great report Chuck,Just curious how long did it take to do these comparisons Seems like a fun good time.
Ken

Thanks Ken! It DID take a while! Setting everything up takes a while. Of couse shooting a bunch of shots downrange and recording velocities a zero and 100yds for each shot takes a while too. I shot FOUR shots to get three readings because I didn't really know where the different bullets were going to hit. I certainly did't want my 100yd chronograh to end up with a hole in it! But as you said it IS fun and I enjoy doing it...

I basically wanted to see how much if any ballistic advantage could be available within the bullets I'm considering using this fall. As my data showed, trajectory speaking there was really no difference between the 250gr bullets or the 290/300gr bullets..


Chuck, throw one of Bull Shop's .451 conicals in that mix for grins.

You GOT it!
 
Hello. I've been lurking for awhile after being directed here by one of your members as I have an interest in ballistic coefficiencies as they relate to modern sabot shotgun slugs.

It's my understanding that the same bullet whether fired from a muzzle loader or shotgun at the same velocity should exhibit the same BC, correct? Provided of course that both sabots do their job imparting rotation to the bullets.

I also recently noticed on the Barnes website that they plan to re-test all their bullets at 10-300 yards in order to provide more accurate BC data for their products. I noticed the tests stickied here (which were GREAT info, thanks for sharing your findings) were shot from 10-100 yards. Do you expect the BC will change much for the Barnes you shot when they're retested at 300 yards? Why or why not?

Thanks again. It's nice to sit back and soak up usable info that you guys so freely share :)
 
Great test. It's nice to see what the actual, real world, BCs really are. I had heard that Barnes numbers were pretty close to actual and it appears that they are. Most of the othes were fairly close also.
 
Chuck, I did a similiar test 3-4 years ago but just on 250,300XTPs and 250SSTs. The BCs were rather low, as expected; but then, when I did the range work out to 300yds, I found that the observed drops were significantly less than expected. I shot enough shots to get good info on both BCs and drops: used T-36 Weaver, Hart rest, etc to get good info. This leads me to believe the problem lies in the formula we are currently using which normally has the G-1 factored in. I do not believe our projectiles follow the model bullet used for the G-1 coef to be predictable for longer ranges. The velocity loss method does give a good bullet comparison though. I, now, calculate BCs by shooting groups out to 300yds, calculating the center of the groups and running them backwards thru the formula to get a "workable" BC to use in the formula. I posted a message similiar to this 1-2 years ago, but it came under serious attack by a previous board member and in the interest of peace didn't push my thoughts. I still believe the drop method and calculating the BC this way will give a more accurate workable BC. All that said, the newer projectiles such as you tested may well fit the G-1 model better than the XTPs did. Thanks for all the work and sharing it.
 
I strongly agree with your theory. None of the bullets I shoot are predictable past 150 yards basing bullet drop on 100 BC. My favorite load should drop 6" on its way to 200 yards but averages more often than not 4"!
 
I to have noticed this discrepancy, and believe you are correct about where its coming from.
Its been a long time since I study this but if I remember correctly the BC changes as the bullet drops below certain speeds. Lee
 
BC's are nice and somewhat helpful in getting you in the "ballpark", but nothing real world testing to actually see POI!
Thanks for sharing Chuck :wink:
Rich De
 
Between a bullet's BC and it's SG stability (above 1.4), which would be considered more important in muzzleloader size bullets and velocities?
 
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