1. ## .243 energy calculation

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

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

3. Many thanks. I have saved the link and the formula and will let you know how I get on.

Regards,
Gallmans

4. 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!

5. Try one of these...no muzzle energy issues at all!

6. Originally Posted by Jager SA
Try one of these...no muzzle energy issues at all!
Is that the new range of Lego?
saw that in the Toys'R'Us brochure

7. Originally Posted by bewsher500
Is that the new range of Lego? saw that in the Toys'R'Us brochure

8. Originally Posted by Jager SA
ah yes, I can see the plastic nuts and bolts

9. Originally Posted by gallmans
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

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