energy at muzzle vs. felt recoil

[willymc]

Is there any correlation between changes in energy (ft/lbs) at the muzzle and felt recoil? I ask because I have a T/C Contender chambered for the 35 Remington. All I have shot in it is the Remington 150 grain PSP Core-lokt. I'm comfortable with the felt recoil of that round. Much more and it wouldn't be as much fun to shoot. That round has an energy at the muzzle of 1762 ft/lbs @ 2300 fps. I found another brand of 35 Remington that I may try out. It has a 180 grain flat nose soft point. The energy at the muzzle is 1753 ft/lbs @ 2095 fps. That's a 20% increase in bullet weight and a .05% decrease in energy at the muzzle and a decrease of 9.7% in velocity. Do you think there will be much of a difference in felt recoil? If so, what is the determining factor? Thanks!

 

[rcmodel]

Recoil Calculator:
http://www.handloads.com/calc/recoil.asp

Just type in the specifics it asks for.

Use 38.0 grains for a WAG powder charge in both loads.

rc

 

[willymc]

Thanks, RC!

 

[kozak6]

Momentum is generally more relevant in recoil calculations.

The 180 grain load has more momentum, so it should have more recoil.

Momentum is basically mass times velocity. For a quick and dirty calculation for purposes of comparison, you can just multiply it out as long as your units are consistent in the loads you are comparing.

 

[MachIVshooter]

Correlation, yes, but recoil cannot be calculated from ME.

The primary factors are:

Bullet weight
Charge weight
Muzzle velocity
Gun weight

With those four variables having numbers assigned, free recoil energy and velocity can be calculated. Notice I said free recoil; Felt recoil is a different animal, and cannot be calculated. For instance, a 30-06 in a modern 7 lb sporter has greater free recoil than a MAS 36 with ball ammo, but go shoot one of each and tell us which hurt more.

 

[1911Tuner]

It's not energy that determines felt recoil. Momentum does. Your brain scarcely has time to process actual recoil. By the time you realize that something has happened, the recoil produced by firing the cartridge is over. What you detect is momentum after the fact.

Muzzle velocity doesn't determine the level of recoil. It's the rate of bullet and breechbolt acceleration that factors in. It's entirely possible for one cartridge to produce higher recoil and lower velocity than another one...and vice-versa.

 

[woad_yurt]

Felt recoil is a different animal, and cannot be calculated.

Yup. There's another variable, the geometry of the gun itself.

I have an as-issued K98k and a friend of mine has a M1 Garand. Since they fire rounds of approximately the same power and bullet weight and since the Garand is semi-auto and the heavier of the two, one would expect it to kick less. Instead, it thumps one quite a bit more than the Mauser.

The geometry of the stock or grips, and thus the gun itself, is a large factor. The same principle explains why a smaller boxer can sometimes hit harder than a larger one. The hardest hitting boxers are the ones who have their body geometry down pat. I guess one could quantify the geometry of a gun mathematically but it would take some seriously tedious and time-consuming work which I don't think anyone has done yet. At least I haven't seen it.

Now, if one is using the same gun and comparing different loads in it, everything I've just said is moot.

 

[willymc]

I'm talking same gun here. 1 cartridge has a 150 grain bullet leaving the barrel at 2300 fps and the other has a 180 grain bullet leaving the barrel at 2095 fps. Energy (in ft/lbs) at the muzzle, is about the same for both cartridges. From the different calculations I have looked at, it appears I'm looking at an approx. 10% increase in recoil with the 180 grain bullet.

 

[1911Tuner]

Muzzle energy isn't a reliable yardstick to judge recoil by.

Example:

The M193 round...55 grains at 3250 fps...produces almost as much muzzle energy as the original .45-70 Govt "Cavalry" load with its 405 grains at 1300 fps. (1289 vs 1519 ft lbs) If you fire both in a fixed-breech, 7.5-pound rifle, the 5.56 will give you a little kiss...while the old cavalry round will belt the soup out of you.

Mometum. Mass X Velocity. That's what you detect as recoil.

 

[kozak6]

Right.

Kinetic energy is directly proportional to the square of velocity, so changes in velocity, even small changes, can have a great effect on energy.

 

[willymc]

So, on the 150 grain bullet I have 150x2300=345000. On the slower, but heavier, 180 grain bullet I have 180x2095=377100. Using mass x velocity I have about a 9.3% increase in recoil with the 180 grain bullet.

 

[1911Tuner]

The calculated momentum factor is 49 for the 150-grain bullet and 53 for the 180.

Taylor KO factor is 15 and 16 respectively.

Energy? Flip a coin.

The heavier bullet will retain more of its original energy and momentum over a longer distance and will lose a smaller percentage of its muzzle velocity at any distance. The 180 will penetrate deeper in a given medium.

 

[MachIVshooter]

The heavier bullet will retain more of its original energy and momentum over a longer distance and will lose a smaller percentage of its muzzle velocity at any distance. The 180 will penetrate deeper in a given medium.

I'll just add that this attribute comes at a cost of trajectory.