given the exact same rifle (barrel length, weight, stock etc) one chambered in .308 winchester and the other .300 winchester magnum, both shooting 165 gr bullets at the same velocity (2700 fps), will the recoil be the same?

It will depend on the type of load used.

You could have your 2700 f/s in the 300 Winchester by either a backed off load of the powders you would normally use for the 300 Win and 165s, such as 4350 or 4831 or you could achieve your 2700 with full pressure loads of much quicker powders.

In theory, the loads doing 2700 with backed off charges of powders like 4350 or 4831 would recoil more than a 308 because a greater weight of powder is being used than would be the case for the 308.

On the other hand, if a quick powder was used to get 2700 f/s in the 300 Win and the powder weighed the same as in the 308, then in theory recoil would be the same as the 308.

If the reason behind your question is to establish whether you can laod a 300 Win to basically duplicate a 308 in ballistics and recoil, then the answer is "yes"

Powders like 3031, 4895, 4064 and Varget would be the choices. However it can take some fiddling to get the desired accuracy. Quite often such loads will shoot amazingly well, although you will often get the odd flyer.

Mike

No. The 300WM will have slightly more because it will require marginally more powder to push a bullet of the same weight to the same velocity. Because the recoil is directly related to the mass of material going out the barrel (for every action, there is a equal and opposite reaction), the 300WM will have more recoil. I just ran the numbers on my ballistic program and the difference in powder charge would cause a 30-06 shooting 57grs of powder to have 19.4Lbs of recoil vs. 22.6Lbs for a 30-338 shooting 69grs of powder. The difference in caliber from 30-06 vs. .308 is of no consequence to your question. Ku-dude

Everything being equal the 300 mag burning 80 grains of powder per round while the 308 burns 42 grains of powder per round, the recoil in the 300 mag will be more.

The others who have replied to you here are all correct. When you figure the mass of the ejecta from a load, you must include the mass (weight) of the powder along with the mass of the bullet. Since the .300 mag will use more powder to reach the same velocity as the .308, the recoil of the .300 mag will be greater.

If you have the Lyman reloading manual available, there is a discussion of recoil in it, along with a formula for calculating recoil. That formula includes the mass of the powder as one of its variables.

I'll bet your shoulder won't be able to tell the difference. The miniscule difference in the mass of the powder used in the .308 cargridge versus the .300 WinMag (maybe a few grains?) when compared to the mass of the bullet leaving the muzzle is so small as to be disregarded.

If the gun weighs the same, and the bullet weight is the same, and the muzzle velocity is the same, yes, by calculation you will see a difference, but doubtful you'd be able to tell which is which.

IMHO

i can tell between a 416 rem and a 416 rigby, same bullet, roughly same gun... but 20 more grains of powder.

308 and 300 winnie? Do those guns recoil?
just kidding
jeffe

Yes, you can tell a difference if recoil if there is more powder used in the 300 Win Mag than in the 308.

Calculating Recoil in a firearm is based on the total mss and velocity of what is coming out of the barrel, as stated above. To do a quick calculation for recoil you first calculate the momentum of everything going out of the barrel:

Momentum forward = mass bullet*velocity bullet + mass powder*velocity of powder

Use grains for the mass of the bullet and powder and feet per second for velocity. A good number for velocity of the powder is 4000 fps. This will give you units of grains feet per second. If you are shooting a shotgun remember to include a third term for the wad.

Divide this number by 7000, the number of grains in a pound, to get momentum forward in pounds feet per second.

Then use conservation of momentum, or momentum forward equals momentum backward, to find the velocity of your rifle.

The equation:
Momentum backward = mass gun * velocity of the rifle.

is rearranged to solve for velocity of the rifle, so we use:

Velocity of the rifle = (momentum backward)/(mass gun)

This will give the velocity of the gun moving backwards into your shoulder in feet per second. Remember to use the weight of the loaded rifle, including a scope if you use one.

Then use kinetic energy to find the energy of the recoil.

Kinetic energy is found with the equation:

KE= (0.5) (mass of the rifle) *(velocity rifle) (velocity rifle)

This gives units of pounds feet squared per second squared. Because we usually think of recoil in foot pounds, divide this number by the gravity constant 32.174 to convert your answer to foot pounds.

If you do the numbers you will find that the weight of the powder charge has a big effect on the recoil. That is why super magnums like the 30-378 Weatherby and the 300 RUM give such punishing recoil, and why smaller cartridges like the 308 and the 300 WSM give lower recoil.

So, to answer your question, if you had equal weight rifles (9 lbs), each loaded with a 165 gr bullet, each shooting 2700 fps, but the 308 was loaded with 42 grains of powder, and the 300 Win Mag was loaded with 70 grains of powder, recoil for the .308 would be 11.57 ft lbs and recoil for the 300 Win Mag would be 16.57, which is a noticeable difference.

A rule of thumb is a rifle that shoots 14 ft lbs or less is comfortable to target shoot all day long, but a rifle that shoots more than 14 ft lbs is uncomfortable (Col. Whelen�s rule).

Of coarse felt recoil is a little different. My guess is that you feel more recoil the faster you are hit with the rifle. So, if you have a soft recoil pad then the energy of the recoil is spread out giving less felt recoil than a rifle with a metal butt plate. Also, if you are getting hit in the face with the comb of the stock, then you will definitely feel more recoil.

I got this information from articles in the American Rifleman written by William C. Davis, Jr. and published in February 1977 & July 1980.

Ben

Actually, the caculated recoil energy depends on whose algorithm you use, and what assumptions you make about the effect of the powder charge. I know of at least three methods for calculating recoil. The first of these is the well-known formula stated above by Ben_Wazzu, and widely published in the American Rifleman. One obvious assumption of this algorithm is that the powder leaves the muzzle at a velocity of 4000 fps. As Ben states, this is a common and well accepted assumption. Another more subtle assumption has to do with the direction of the energy impulses associated with the burning powder. As Ben clearly illustrates, this algorithm begins with calculation of momentum.

A second algorithm for calculating recoil is the Newtonian Free Recoil algorith, which begins with the calculation of the impulse energy associated with the burning of the powder:

RecoilImpulse = ((BulletWeight * MuzzleVelocity) + (4000 * PowderCharge)) / 225400

RecoilVelocity = (32.174 * RecoilImpulse) / FirearmWeight

RecoilEnergy = (FirearmWeight * (RecoilVelocity ^ 2)) / 64.348

(Note that "RecoilVelocity ^ 2" means "RecoilVelocity squared".)

Using the Newtonian Free Recoil algorithm, the .308 Winchester produces about 13.2 ft-lb of recoil energy, and the .300 Winchester Magnum produces about 18.5 ft-lb of recoil energy.

A third algorithm for calculating recoil energy is proposed by Art Pejsa. Pejsa refutes the assumption that the powder exits the barrel at 4000 fps. He also argues that the impulse energy is not just directed along forward/backward vectors, but rather it is directed in all directions simultaneously. His algorithm is as follows:

RecoilEnergy = (((1 + (7.3 / (BulletWeight ^ 0.5))) * BulletWeight * MuzzleVelocity / 7000) ^ 2) / (64.34 * FirearmWeight)

(Note that "BulletWeight ^ 0.5" means the "square root of BulletWeight".)

Using Pejsa's algorithm, both the .308 Winchester and the .300 Winchester Magnum have about 17.2 ft-lb of recoil energy. One really interesting aspect of Pejsa's approach is that he defines firearm and cartridge efficiency in terms how much energy is delivered to the target by the bullet at impact, versus how much energy is delivered to the shooter by the stock of the gun.

However, as Ben_Wazzu so clearly points out at the end of his message, "felt recoil is a little different". I would go so far as to say that felt recoil is really the only thing that matters. The various algorithms for calculating recoil energy are OK for giving us a crude estimate of felt recoil, but the don't even begin to take into consideration things like stock design, butt pads, etc.

For several different estimates of recoil energy and firearm/cartridge efficiency, take a look at AccuLoad by AEM Enterprises, Inc. at http://www.aement.com

Ben_Wazzu,

I understand all the formulae (successfully graduated with a Bachelor of Science in Mechanical Engineering, albeit 20 years ago.)

In my inexperience with such things, I guess I was not aware of the huge difference in powder charge between the .308 and the .300 WinMag to make the same mass of bullet achieve the same muzzle velocity.

I certainly agree that a 14% increase in discharge mass would give a noticeably larger felt recoil.

I stand corrected.

Tim

[ 12-13-2002, 02:46: Message edited by: TimB99 ]

It always amazes me how many technical people post of these forums. I guess reloading is a little like lab work, but then you get to shoot your product. That is more fun, in my option.

TimB99, I bought a 300 Win Mag and then discovered I have very little tolerance for recoil. At that point I did the research and found out about the powder making such a big difference in recoil. The first book I found was �Small Arms Design� by Col. Whelen, and he did not take powder into account when calculating recoil, and then I found the NRA article. Of course, when I bought the gun I got �magnumitis� and went for the fast shooter. If my 300 Win Mag wasn�t such an accurate rifle I would sell it and get a 308. I didn�t mean to step on any toes.

GunGeek, I have to say that I liked your formulas as well.

On another note, the reason muzzle breaks reduce felt recoil is that they let the hot gasses from the powder escape perpendicularly to the direction of the rifle bullet and rifle. This means less momentum transfer to the shooter and therefore less felt recoil. The down side is that the concussion wave and the sound wave hit the shooter to a greater extent when a muzzle break is used.

I guess I should do some work now�

Ben

Heck ... even a geek can like guns!

Ben_Wazzu,

No toes injured in the encounter.

Cheers!

Tim