Why is it that two different powders recoil differently for the same given velocity and bullet weight? It doesn't seem to correlate with powder burn rate.

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I hope unclenick will weigh in. If you are getting very different felt recoil with similar (measured?) bullet velocity, with the same rifle, cartridge, and bullet weight, but with different powders, the difference is in the barrel pressure and the 'jet effect' of the gas leaving the muzzle. You are relating to the same rifle, cartridge, right?

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Yeah. Loading the same gun, same cases, primers, bullets, everything but different powder.

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Do the charge weights of the powder vary significantly? By 20% or more? For example, a full house 44RM load, with H110, will use more than 10 more grains of powder than a load that uses Unique powder. The H110 load will recoil noticeably more. If you're getting the exact same velocity from the same bullet, fired from the same gun, and the only difference in the load is the powder used, then felt recoil differences can be attributed to charge weight.

Also, the "sharpness" of recoil, is sometimes noted with faster powders, whereas slow powders may create "heavy" recoil. Then again, recoil is very subjective and many folks equate greater sound with greater recoil. How big of a difference are you observing in felt recoil?

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There's some jet effect if you're talking about total calculated 'push,' but the feeling of 'kick,' if that's what you're talking about, has a lot to do with pressure rise time (rate). Slower powders give many shooters a feeling of a slightly softer kick. IME (I'm recoil averse), there is _sometimes_ even a slightly different feel between ball and stick powders, due I believe to their different pressure rise curves.

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Jason has it. Recoil difference is mostly (but not completely*) the result of the ejected mass, assuming equal velocity in the loads.

A 240-gr bullet over 20 grains of powder has a total ejected weight of 260 grains, for example. A load with half that much (of a faster) powder would have only a 250-grain ejected mass - and will have less recoil.

Whether the shooter can discern the difference involves other factors such as muzzle blast, grip, and more.


* The jet effect is important but much less so than ejecta mass. A slower powder that has a higher residual pressure at muzzle exit will have a higher velocity gas jet and therefore higher recoil than a fast powder whose pressure drops off more before muzzle exit.

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Hm, food for thought. I've always tried to find a powder that filled the case so there was never any chance of a double charge.

I've been playing with different loads for my 500jrh. I'm not really recoil shy, but I also don't feel the need to push it as far as I can. I have 420g, and 450g WFN, and I want to push them about 1100fps.

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Right. That's all to do with calculated recoil, which has little or nothing to do with a human's perception of 'kick.' So, I'm not disagreeing with you at all, just pointing out for the O.P. some stuff that many on the internet, present company excepted of course, gloss over (and frankly don't appear to understand).

To illustrate the difference between purely calculated recoil and 'kick,' which would cause you more irritation:
1) To be 'hit' by an 80,000 lb semi truck going 1/4 of 1 mph, or
2) To be hit by a baseball thrown at 100 mph?

Those two have the same amount of kinetic energy, but the baseball will 'kick' a whole lot harder.

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I had posted the same observation a year or two ago. My 444 Marlin with a 265 grain bullet exhibits a lot less recoil when loaded with H4198 than H322 or RE7, all at the same velocity.

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Because it is difficult to measure the speed of the ejecting powder gas, some folks ignore this. That's a mistake - there would definitely be a difference between 10 grains of Unique vs. 20 grains of 296 when loaded at the same (max) chamber pressures.

Another ten grains of powder doesn't seem like it would have a noticeable effect, but the powder gasses are going to be going faster than the bullet when they finally clear the muzzle.

Part of the equation may just be that our brains can't separate the effects of the muzzle blast and noise from the actual recoil.

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This how I've thought of it for some time now, shooting my 20ga shotgun lead me to this conclusion, but I will say that BIG BOOM! is often had with great recoil too!, the scab on the bridge of my nose right now from my 450 Marlin is proof of that!

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QL suggests that these three powders would be very similar in recoil, if predicated on charge weight. They are within a few percentage points of one another. They are certainly not very far apart on the burn rate chart. I think that may be another phenomenon altogether?

If you ask a kid which gun kicks harder, a 44/40 or a 243, he's going to say the 243, every time. Why? Even though the recoil of the two is really quite similar, the 243 is a lot louder. I've seen kids flinch and back away from the 243, but they'll shoot that 44/40 lever-gun, with a metal crescent butt-plate, until I lie and tell 'em I'm out of ammo. (Whet their appetite...don't satisfy it! )

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Recoil is physics. Physics is physics. Plug the numbers into a formula and you get the ft-lbs of recoil generated at point the gun contacts the body. Caliber doesn't have anything to do with it.

However, how we handle it is very subjective. Things like size and shape of the grips or stock, angle of stock to the centerline of the bore, and so on. Noise, as has been noted, is a big factor, but so is muzzle blast. Take two loads that have the same velocity, but one generates a big bright muzzle flash is going to make a lot of people gun shy.

I learned early on when I started working with heavy caliber rifles that if you use good ear plugs and a good pairs of earmuffs that cuts down sound severely, recoil is much less of a problem. Straight combed stocks also make it much more manageable than a monte carlo type.

The type of powder, at least in my opinion, makes much less difference as far as felt recoil goes than does the geometry of the piece, and the muzzle blast. Here's a good example: When I got my AR, the stock A2 muzzle brake made it distinctly unpleasant to shoot from the bench. It was so bad in fact, that I didn't enjoy shooting it. Then, I replaced the stock brake with one that directed all the noise and gas downrange away from the bench, and me. What a difference! Same rifle, same ammo, but it felt completely different.

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I think I'm just whining because I can't find a load I like.

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The real difference in recoil (not necessarily the perceived difference, for reasons already given) boils down to rocket effect (also called after effect and muzzle blast effect). The proof is simple. You may have noticed a lot of muzzle brake designs vent the gas in all directions around the muzzle without favoring one direction over another. Since the even distribution of gas jets neutralizes one another's push on the muzzle, you might have wondered why they do anything for recoil at all? The answer is that they bleed off the muzzle pressure before it can jet forward. If it jets forward, it acts as an impulse rocket motor (no, not the same as Star Trek "impulse power", but jets like the astronauts tried out on space walks that were powered by firing large caps as the gas source).

Those brakes work great (if you wear enough hearing protection) with high pressure loads that use heavy charges of slow powders. But they have less effect on lighter charges of faster powder because there is less muzzle pressure and lower powder mass for them to bleed off. There are other tricks. If you surrounded one of these brakes with a tube that diverted the gases forward, you'd get a lot less noise but a little less recoil reduction because you are still propelling gas mass forward. But because that would happen at a much lower pressure, the gas mass would be accelerated less, and thus cause less reward thrust.

The SAAMI standard method of calculating recoil energy is available for free, here.

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