JBM Ballistics accuracy

N

ndking1126

New member
Not entirely sure if this belongs here, so please feel free to move as necessary.

I am going to rebarrel a .223 into .243 and was reseaching what kind of ballistic performance I could expect. I am also going to get into handloading and plan to shoot either Berger or Sierra Matching bullets from it.

I used JBM Ballistics for the handloads (using a reasonable velocity I could expect and manufacturers data on BC of the bullets). I live at about 6K ft of elevataion, so I used that. I'm guessing companies like Federal use much lower elevation.

I know these are premium bullets and I accounted for the elevation, but the numbers it came back with are much, much better than I was expecting.

Anybody ever found their application to not be accurate? I thought they were the benchmark for ballistic software? :confused:
 
The 243 is a fine long range contender. George Gardner (of GA Precision) uses a 115gr DTAC bullet which keeps up with the high BC 6.5 bore bullets quite nicely. http://www.6mmbr.com/243Win.html

Also you are at 6,000 feet, which is generally equal to 6 MOA less drop at any given distance.

Anyways, you are looking at pushing a bullet with a BC over 0.500 faster around 2,900 fps, which is a lot better than a 308 pushing a .505 175 SMK at 2600 fps (although some people load theirs hotter).

Still, when that same 308 pushing that 175 SMK can accurately hit targets at 1K at sea level, your 243 will do just fine.

Jimro
 
I've read that 6mmbr page more than once! :)

I put a lot of research into going .243 or staying at .223. I am confident it can shoot the long distances which is ultimately why I went with it over the .223. When I found out Berger says their rounds are great for hunting, I got curious about using it as a field hunting rifle (as in sit at one in of the field and shoot deer that show up 400-500 yards on the other side) but I didn't know what kind of energy they would have at those distances. So off to JBM I went and boy was I surprised. I went back to Federal's website thinking maybe I had mixed up their numbers in my head. But nope, just a much bigger difference than I was expecting.

I fully get that Federals numbers are only from one specific set of circumstances, and that there are many factors involved in external ballistics, but when you get specific and see the differences, it's pretty surprising.
 
In general 'normal environment' is used, which I believe is 59 degree and 0 ft elevation.

So yes it will be different. Many people also find using the G7 coefficient instead of g1 for rifle's to be more accurate. Otherwise, as long as you input all the environment settings correctly, the estimated trajectory should be pretty damn close every time. The hard part is putting in the exact environment correctly...
 
Using G7 will supposedly help but you can more than often get the same results with G1 although G7 was created around Boat tailed bullets from what i understand. Brian Litz (Berger's Ballistician) has been shooting long range for a while and has a book "Applied Ballistics" that will give a ton of good insight and also give you his recorded BCs throughout tons of test. Which i find are more accurate than factory specs. Since Berger gets their data from them, you can get the G7 BC of the projectile on berger's site which has worked for me with JBM. You can never expect it to be 100% accurate but it gets me on target. First time i shot my 175gr BT LRs at 300yds JBM called for 1.4 mils. Shot a 3 shot group came back and checked it i was an inch high, came down a 10th of a mil hit the bullseye. Real world collected data in different environments will always trump ballistic solutions. It takes a lot of time but best bet is to get a data recording book and shoot at known distances, use JBM to get you on target then record what it takes to get near bullseye.

http://www.appliedballisticsllc.com/
 
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