1. Barrel length and energy

If shorter barrel produce less Velocity (fps) But is the any guide to the affects of shorter barrels and Energy (ft/lb) ............

What I am getting at is each inch I cut of the barrel how much Energy will I loose?

My question comes as ammo manufacturers quote their specifications from long heavy barrels that are not always found on sporting rifles.

Thanks Muir

2. Originally Posted by john444334
If shorter barrel produce less Velocity (fps) But is the any guide to the affects of shorter barrels and Energy (ft/lb) ?............

My question comes as ammo manufacturers quote their specifications from long heavy barrels that are not always found on sporting rifles.
I think you answwered your own question. If the velocity is reduced due to reduced barrel length, then the resulting energy will also be less. Actual chronograph data will allow you to calculate energy with some accuracy.~Muir

3. Shall we go 1/2's on a chronograph John?
​Are the ones on ebay any good?

4. Here's some interesting reading regarding barrel length:-
And as Muir says - Validate the figures with a chronograph. A Chrony F1 will cost about £90 if you buy it from here;http://www.merlinarchery.co.uk/chron...graph-f-1.html and will do every thing you need (until you put a bullet through the screen )

5. You can calculate your MV energy when you know the MV. The formula is (Lyman manual):
Bullet weight x MV x MV divided by 450400 = answer.
i.e. 100gn x 3000 x 3000 divide by 450400 = 1998.22 ft.lbs

The old rule of thumb used to be & probably still is: Under 3000fps each in off = 20fps reduction. Over 3000fps = 30fps reduction.. these are approximates given in the Speer manual.

The same formula applies if you fit a longer barrel.
Hope this helps. ATB

6. Thank you for the formula and the links,

I have seen a couple of posted lately that would suggest a .243 with a 18" barrel using a 100gr bullet would be legally be to slow for Scotland. But using this Formula that would not be the case?

7. Originally Posted by john444334
Thank you for the formula and the links,

I have seen a couple of posted lately that would suggest a .243 with a 18" barrel using a 100gr bullet would be legally be to slow for Scotland. But using this Formula that would not be the case?
Until you know the velocity, measured with your particular load through your rifle it's just guess work. I have seldom found the velocity figures printed in load tables (or on factory ammo boxes) match measured speed,

Even such vagaries as a different primer, neck tension, bullet type, temperature etc. may have a significant effect on velocity and hence energy.

8. Originally Posted by john444334
Thank you for the formula and the links,

I have seen a couple of posted lately that would suggest a .243 with a 18" barrel using a 100gr bullet would be legally be to slow for Scotland. But using this Formula that would not be the case?
A .243 with an 18 barrel would struggle to be legal for more than muntjack and CWD in England

9. Originally Posted by john444334
Thank you for the formula and the links, I have seen a couple of posted lately that would suggest a .243 with a 18" barrel using a 100gr bullet would be legally be to slow for Scotland. But using this Formula that would not be the case?
You need to chrono your load then use the formula. The formula is right, the rest is down to your MV & a short piece of arithmetic. ATB

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