under powered .243

[faz 68 0]

Hi ive just had my .243 tikka t3 chronographed and it turns out its only producing 1580 ft lb, i was a bit shocked as its not deer legal, the ammunition is norma 100 grain soft nose and the barrel has been shortened to 20 inches which im aware will cause some loss of energy, i was wondering has anyone else experienced anything similar or can explain why the energy is so low

 

thks steve

[matt_hooks 188]

Your pushing the 100gr pill at 2670 fps or so to give 1580 ft.lb. To make the deer legal energy level (1700 ft.lb) with a 100gr pill you need 2770 fps. So you need to find another 100 fps or so.

 

Your shortened barrel won't be helping you. For the .243, various figures are given, but you can expect a drop per inch below the standard 22" barrel of between 25 fps/inch and 50 fps/inch. So if your barrel were a "standard" 22", then you might JUST make the required velocity.

 

It surprises me that the Norma are loaded so anaemically.

 

Do you have any pictures of the fired cases?

[jamie g 17]

see thats the trouble with a shorter barrel and factory ammo. if you reloaded your own you could make that difference up fairly easy with a faster burning powder

[tegater 789]

If you are using standard factory ammo the difference in barrel length shouldn't put it below the legal limit, unless the original mv is low.

 

What are Norma quoting as the mv from a 24" barrel?

[dicehorn 38]

It is a common fact that chronographs can vary from one make to another. Also bear in mind we are talking muzzle velocity and not 12 - 15 feet away where the chronograph is sighted

[faz 68 0]

thanks for your replies, i think i will have to get some ammunition loaded for the rifle to give it a bit more poke!

[matt_hooks 188]

You might struggle to make the necessary MV. A 20" barrel is quite short, and the .243 has a tendency to drop off quickly, being a high density load. You might reach dangerous pressures before you reach deer legal MV's. Twelve feet from the muzzle should make very little difference to the velocity, certainly not enough to push it up to legal levels!

[Jingzy1 3]

Have a look at the stated MV from Norma, then compare that to what the chrono gave. That would be a good starting point. Try a different manufacturer of cartridge if you can get one and compare the results before panicking.

Where are you shooting Scotland / England? The laws are different so you could compromise depending on the species you are shooting. You may be able to drop the bullet weight and get the results you want as the bullet weight in England in not so much of a factor as it is in Scotland.

 

I also stopped using Norma cartridges years ago, they are poor performers.

 

Unfortunately I have the wrong laptop with me which has all my balistics stuff on it or I could give you more exact answers.

 

Good Luck

[bewsher500 3]

i doubt the deer will know!

that variance could be made up on a hot day vs a cold one

 

I deliberately load my .243 with 100gr doing approx 2600-2700 for roe stalking.....mind you I am in Scotland