Home Forums Hunting & Shooting Ask The Gunwriters Recoil ft. lbs question.

Guys, Can you tell me how many recoil ft lbs are put out by a 150gr. 30-06 vs. a 150gr. 7mm08, this being with a typical hunting load, right around the max pressure, with rifles weighing approx. the same. Thanks, Jay

You haven't listed the two pairs of figures needed for the calculation � the muzzle velocities and charge weights of both loads. Here's a pair of equations that you can use to figure-out the answer to your question for yourself:

Let
V = velocity of the rifle (ft/sec)
v = muzzle velocity (ft/sec)
W = weight of the rifle (lb)
w = weight of the bullet (grains)
p = weight of the powder charge (grains)
k = adjustment constant for high-pressure, high-velocity rifle (1.75 to 2.00*)
E = recoil energy (ft-lb)
(* use 2.00 for very high velocity from very short barrel � in answering this presumably hypothetical question, you'll probably want to use the same figure for k.)

V = (wv + kvp) � 7,000W

E = �(W � 32.16) � V�

for example:
the rifle weighs 8.2 lb
the muzzle velocity = 2,900 ft/sec
the bullet weighs 165 gr
the powder charge weighs 58 gr
the adjustment constant = 1.75 (typical barrel length and muzzle velocity)

� multiply 165 times 2,900:
478,500
� multiply 1.75 times 2,900, then times 58:
294,350
� add 478,500 + 294,350:
772,850
� multiply 7,000 times 8.2:
57,400
� divide 772,850 by 57,400:
13.4643 ft/sec (recoil velocity)

� divide 8.2 by 32.16:
0.255
� multiply 13.4643 by 13.4643:
181.2874
� multiply � times 0.255, then by 181.2874:
23.1 ft-lb (recoil energy)

(I hope but can't guarantee that I've got the math right!) <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />

Well, I went with 2900 fps for the 30/06 and 2750 fps for the 7/08. You're looking at approx. 21 ft/lb for the /06 and 17 ft/lb for the 7/08. For comparative purposes, these are close enough. The 06 will give a bit more kick, but not much.

Safe Shooting!
Steve Redgwell
303british.com

That looks like work, Ken. I'm too lazy. I use the recoil calculator at http://sst.benchrest.com/ . I don't know if it's correct, but I feel better. <img src="/ubbthreads/images/graemlins/smile.gif" alt="" /> I punched in the same numbers that you used and came up with the same result.

It had better come out the same! It's everyone's favourite subject - math. I suspect that JAGOFF is attempting to determine which rifle/cartridge will give him a lighter push.

Safe Shooting!
Steve Redgwell
303british.com

Steve, I know the 708 will give me a lighter push, got both an 06 and 708, just wanted to know precise recoil for both(for argumentative purposes), but like you said, it isn't much. Thanks all for responses, Jay

Beartooth Bullets have a very handy recoil calculator available for free - check out their websight.

Does "k" change much for shotgun loads? I have no experience with any rifle larger than a 7 Remmie or an '06, but plenty with stout shotgun loads. Touched off a couple turkey loads the other day--1 7/8 ozs of shot at perhaps 13-1400 fps. It was definitely stouter than I expected and I wondered how it would compare to a .338 Winnie or a .375.

MR. Howell:

Thanx for that information. I used the link to the recoil calculator and confirmed a suspicion. That is my 308 kicks "less" than VB's 25-284!

Here are the numbers I used: (a) 25-284 uses a 75 grain V Max @ 3700 fps over a 58 grain powder charge in a 7 pound rifle generates 19 ft/pounds of recoil; (b) 308 Win uses a 165 grain Interbond @ 2700 fps over 46 grains of Varget = 18 ft/pounds.

No wonder I thought it kicked pretty good for a "low recoil" rifle!

This also adds weight to my argument that a 308 reduced load (to 30/30 velocity) with a 170 grain bullet is a "better" youth load.

The Calcs are as follows: 170 grain Corelock at 2200 fps over 36 grains of Varget (Min load from my data) in the same 7.5 pound 308 = 11 ft/pounds of recoil. (I am pulling some of this data from a very thin memory, but the result seems about in line with my experience.)

Good Shooting,

BMT

I "guestimated the parameters" for the recoil calculator and got 30 ft pounds of recoil in a 8 pound shotgun. So, yeah, I would say it kicks real good!

BMT

k = 1.25 for low-pressure, long-barrel guns (e g shotguns)
k = 1.50 for low-pressure rifles, handguns, very short shotguns
k = 1.75 for typical high-pressure rifles
k = 2.00 for very short rifles and very high velocity

The constant k compensates (more or less) for the fact that recoil comes from more than the gun's reaction to the velocity of the exiting bullet. A second factor is the jet-propulsion effect of the powder gas that gushes forward out the muzzle after the bullet exits.

Some of the propellant gas remains in the barrel, so it's hard to put numbers to the jet-propulsion effect. The volume of this remaining gas varies, of course, with the size of the chamber and bore. The gas gushes out under higher pressure from a shorter barrel. The gas expands at a rate determined by the ratio of bore volume to net case capacity (expansion ratio).

The adjustment constant k is a sort of "finagle factor' � an educated guess at how to compensate for these known but immeasurable variations in the behavior of the propellant gas in such a wide variety of chambers, bores, barrel lengths, and muzzle velocities.

It's interesting to note that you mentioned the jet propulsion effect on recoil.Case in point:With all components being equal in two of my 30/06 180gr.loads with the exception of a 3gr. powder difference and nearly identical velocities my shoulder can tell the difference between loads.The H4831 is sort of a push whereas the H4350 is very sharp and it gets old pretty quick. So my question is this.Is there a difference between calculated recoil and felt recoil or is it all in our heads? Comments please.

Some say that there is a difference. Others say that there isn't. I flat don't know, and I don't know how to quantify personal impressions.

Some note or theorize that an especially loud muzzle blast adds to and emphasizes the over-all "felt" effect of the shot. Makes sense.

A lot of felt recoil depends on how you hold the gun. For months, my buddy Wyatt Keith chortled at the thought of having me shoot his nearly weightless single-barrel 12-gauge. He often said (laughing at the prospect) "It'll kick you right out from under your hat!" Clearly, he was eager to see that happen.

Finally, on a weekend trip home, he brought it back � with two boxes of hot buckshot loads. After five rounds, he couldn't take any more kick, and he had a huge black-and-blue bruise covering the entire front of his right shoulder. I shot the rest of that box of shells and all of the next box, but suffered no pain and developed no bruise. Same gun. Same loads.

The reasons were painfully obvious. Wyatt � short and stocky � gritted his teeth and leaned hard into the gun, and it didn't move him much. He was determined not to let that gun kick him out from under his hat, and it didn't. The muzzle didn't rise more than a few inches. On the other hand, I � at six-plus and about 140 pounds � stayed limber and let the gun jolt me back a step and turn my upper body around about 90� and bend me backward at the waist until the muzzle pointed almost straight up.

Wyatt nearly strangled with glee at every shot that I took. But he groaned every time he shifted gears or turned the steering wheel of his Pontiac.

I think it's safe to say that
� the physical recoil velocity and energy of the same shotgun, with the same loads, was the same no matter who was shooting 'em, and
� Wyatt felt the same recoil much more than I did.

Thanks for the reply and the good laugh.To paraphrase:
"Only the shoulder knows"

There is another consideration when discussing recoil. The drop at heel, and its affect on your shoulder. When you think that it all comes down to a small area on the butt that actually does the pushing, how it contacts you is important too. Naturally, a proper shooting technique and fit is the first thing.

Generally speaking, if you can get a straight back push from your stock, recoil can be less painful. This is accomplished in two ways. A straighter comb and a non slip butt pad.

When you have a stock with a larger drop at heel, it tends to ride along your shoulder. This, in combination with a slippery butt pad, can cause problems with some rifles.

Under recoil, if your rifle delivers its push without moving around, it will "feel" like less.

An old Rem 760 pump 3006 I use to have would leave a bruise on my shoulder after only 7 shots. My 700 3006 with a Hi-Tech stock and a Pach. Decel. pad, no problem till about 40 shots. It's even a pound or two lighter. There is definately something to stock design. I'm mucho happier now <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />.
Dave.

Hey All
there is something to be said for stock design and the posture of the shooter. I have only a few arms that will recoil a bit ruff. But theyare used for special purposes. The stock design on them are all have a bit more drop than I like.
Bearbeater

Stock fitting is an area that most people don't really look at. As an example, Tikka rifles have inserts available to correct the fit. Getting a gunsmith to fit and replace/install a butt pad is a lower cost way to improve your shooting too.

When a rifle is more comfortable to hold and fire, you shoot better. Not every rifle is good "off the rack".

Safe Shooting! <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />
Steve Redgwell
303british.com