.243 energy calculation

gallmans

Active Member
A question for the more informed than I, please. I wish to calculate what my .243 CZ 550 is putting out as I have recently read an article by Bruce Potts of shooting times (2nd Jan2013 edition) which warns of the depleted speed and energy when barrels are shortened. My CZ has a barrel of 20.5 ins measured from the start of the chamber to the crown and an ASE Utra S5 muzzle mounted moderator. I have always been pleased with the results I get, which are almost always reasonably sized fallow bucks in the Essex area, and am not really considering changing rifles because of one article. However, a seed of doubt has been sown and as a result I have borrowed a chronograph from a pal to check out the speed and energy to reassure myself. Whilst it tells you how to operate the chrono it doesn't give the formula to calculate energy from muzzle speed. Any help and opinions would be appreciated.

Regards,

Gallmans
 
Good link B500.

Can also use -

Mass ( in grains ) x Velocity Squared divided by 450240

eg

100 grain bullet at 3000fps would be 100x9,000,000/ 450240 = 1998.9 ft lbs
 
Many thanks. I have saved the link and the formula and will let you know how I get on.

Regards,
Gallmans
 
in principle it is a best guess

altitude, humidity and air temperature can impact muzzle velocity as significantly as barrel length and with a marginal bullet and barrel choice you could be very nervous by the time you do your calculations

on the whole the deer don't know the difference and the FLO's don't carry Chronos for spot checks, and even if they did proving that the bullet you just fired is identical to the ones in the magazine for both MV and load would be a legal minefield!

if you are concerned at all get a bigger rifle!
 
A question for the more informed than I, please. I wish to calculate what my .243 CZ 550 is putting out as I have recently read an article by Bruce Potts of shooting times (2nd Jan2013 edition) which warns of the depleted speed and energy when barrels are shortened. My CZ has a barrel of 20.5 ins measured from the start of the chamber to the crown and an ASE Utra S5 muzzle mounted moderator. I have always been pleased with the results I get, which are almost always reasonably sized fallow bucks in the Essex area, and am not really considering changing rifles because of one article. However, a seed of doubt has been sown and as a result I have borrowed a chronograph from a pal to check out the speed and energy to reassure myself. Whilst it tells you how to operate the chrono it doesn't give the formula to calculate energy from muzzle speed. Any help and opinions would be appreciated.

Regards,

Gallmans
If you are achieving clean kills and chronographing shows that you are up to speed (MV & ME) you have nothing to worry about. If you are reloading you may benefit from using a slightly faster powder with the shorter barrel. e.g. my own Blaser r8 .243 struggles to reach the published MV data using H4831 but Vit N140 produces excellent MV & accuracy. atb Tim
 
I have been fortunate that all kills have been clean with no seconds required, most are within 100yds or so. However, no exit wounds are ever achieved and most run for a brief period. This doesn't worry me unduly as my ground is fairly open and I check every beast when field dressed to confirm the shot placement. I do not reload my own and am using geco 105gr which seems to do the job and with good accuracy. I will post the results of the chrono exercise to see if they match with others when available. Many thanks for interest and observations.
Regards,
Gallmans
 
I appreciated the advice and the results were as follows:- average MV was chrono'd at 2909 fps using Geco 105 grain softpoints. Using the link provided the computer came up with 1973.5 ft/lbs energy. Many thanks for all help/advice rec'd.
 
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