Difference in recoil between same bullet weight and different calibers

[WildBoarHunter]

Is someone able to calculate the procent of difference between recoil of a 6,5×55 123 gr bullet traveling at 870 m/s and 8×57 IS 126 gr bullet traveling at 940 m/s. What would be the increase of recoil in % between them if we count the same barrel length and similar rifle weight. Are there other things to consider, like bullet diameter, the amount of powder charge or anything else?

 

[Longstrider]

Assuming (and it's a big assumption) that rifles are same weight and bullets are of same weight the only factor that could affect recoil is energy. Find the muzzle energy of the bullet and it will correspond exactly to the actual recoil (Thank you Mr Newton )
Percieved recoil may differ due to differing rifle design and differing butt-pad (hard vs soft) etc, but actual recoil will only ever be a direct opposite of muzzle energy.

 

[WildBoarHunter]

Fox 123 gr 6,5×55 muzzle energy is 3017 J at muzzle.
Sax Kjg 126 gr 8×57 IS muzzle energy is 3622 J at muzzle.

I'm asking this as I own both calibers and both ammo and I'm trying to figure it out how much difference in recoil will be felt by my shoulder.

So the actual difference in recoil should be about 20 % ?

 

[Lancaster]

The formula that I have requires the powder weight, do you have that?
I had a quick play with GRT and it gave 14j for the 6.5x55 and 17j for the 8x57

 

[Longstrider]

About 17% fella.

Why worry though ?

 

[big ears]

Mr Newton says that for every action there is an equal and opposite reaction.

Muzzle energy does not take into account of bullet inertia and acceleration down barrel.

But as rough guess yes about 20%.

Whether that’s what you perceive is a different matter.

 

[enfieldspares]

Stock fir will make the most real world difference. The theory is that everything else being equal...weight...shape...velocity...the smaller base diameter cartridge will have more recoil. Reason is the base area is smaller. Which is why a .177 PCP air rifle gives less shots that an .22 PCP air rifle with equal weight pellets at same velocity and same air charge. The smaller base is less efficient at "using" the gas pushing it along. In the OP's cartridge example that means more recoil.

 

[Heym SR20]

Its pretty much basic physics.

First conservation of momentum

So

Mass of (projectile plus powder) x velocity = mass of rifle x recoil velocity of rifle.


Then to work out recoil energy

Mass of rifle x recoil velocity of rifle x recoil velocity of rifle.

So if you keep bullet, powder charge and rifle weight the same increasing velocity will increase recoil velocity and energy.

If you keep the same amount of powder, same bullet weight but increase the bore diameter, you will increase the surface area on which the gases push hence increasing the force the bullet so it will achieve a higher velocity at the muzzle. This will further enhanced as there will surface area in contact with the barrel thus less drag.

But it also comes down to felt recoil. A slow burning powder accelerates a bullet with a steady force so gives much a shove on the shoulder. A fast burning powder gives a much faster acceleration and a snappier recoil.

 

[nun_hunter]

As some have mentioned acceleration is a big factor. You can accelerate a wider bullet for a given weight faster than a narrow bullet and that faster acceleration will give a bit more recoil. This is why a 338 Federal will achieve a higher velocity for a 180 grain bullet compared to the parent case 308 Winchester given the same (shorter) barrel length.

 

[WildBoarHunter]

I had some 8×57 IS 200 gr bullet loads that kicked way too hard for my taste. So have gone down to 126 gr as I'm trying to get closer to the manageable recoil of a 123 gr 6,5×55. The latter is charged by 43 gr N550. Not sure about Sax Kjg though as the cartridges are factory and their load data lists a variety of powders.

 

[jthyttin]

First of all, in my experience the perceived recoil is not linear. A shooter, that doesn't pay close attention to recoil, will perceive recoil as "nothing" up to a point where it starts to annoy them very fast. And before annoyance, recoil will affect POI etc. for everybody but very few experienced shots. If you don't find recoil unpleasant, it doesn't mean it won't affect your shooting. Regardless of flinch.

A rifle (+shooter) is not a "closed system" where recoil starts when bullet exits the muzzle. But the powder gases willl contribute to recoil at that point, and the average velocity is far greater than bullet. IIRC Vihtavuori used to quote 2000m/s for average when gases are erupting at the muzzle. Of course the velocity differs with 16" or 28" barrel.

Just about only way to compare YOUR perception of recoil between two different rifles, in two different chamberings, and firing two different loads would be to try it out. Please remember that 126gr load in 8mm might not be able to achieve same penetration etc. as 200gr 8mm or 123gr 6.5mm.

 

[Heym SR20]

However the 8x57 and 30-06 have always been at the upper end of the recoil spectrum, whereas the 6.5x55 has always been at the bottom end of the spectrum.

And the 8x57 is shooting the light bullets at a higher velocity. They may or may not have less felt recoil. I suspect not.

Shooting technique is probably key to learning to use the 8x57. And grt away from shooting it prone or off the bench. Use your forehand to hold the fore end to properly control the recoil.

I many shooters in this age of moderators, bipods etc never actually learn to control a recoiling rifle. Using a technique that works for a PCP or rimfire - ie lightly holding and touching off a light trigger doesn’t work for a big rifle. It might as regards pure accuracy but it will slap you about and is not repeatable.

A good firm grip and squeeze the rifle as you shoot will control things and make it much more nicer to shoot.

 

[NullMac]

Yes, you can calculate it tooo...

Recoil calculator

Ignore the drivel above

 

[WildBoarHunter]

I once compared a 200 gr Hot Cor and 160 gr Fox bullets by shooting them and the Fox did produce markedly less felt recoil. So a 126 gr bullet might be worth a try recoil wise.