I was "taste-testing" three different brands of .357 Mag each having 158 grains and each resulting in different recoils.
Why is that? What makes one hotter than the next?

Very simple. "What makes one hotter than the next?" It's loaded
hotter. More powder, loaded to higher pressure or higher velocity. Just
because various brands of factory ammo are for a specific cartridge
and have the same weight bullet doesn't mean they are all loaded to
the same specifications. There are significant differences between
brands with all calibers of ammo...sometimes. That's one reason
many shooters own chronographs.

Is there any indication on the box (or specs) that tell the buyer what the "degree of hotness" is?

When I worked at the LGS, lots of folks confused the " Grains" as powder charge.. The ### grains on the box is actually the weight of the projectile / bullet. And has nothing to do with the powder charge.
They wondered why the recoil of a 148 grain WC felt lighter than a 125 grain JHP.

7000 grains = a pound. 437.5 grains = a oz.

Not usually on the box. Some publish MV, but unless you know what test barrel they used, it may be far off in your gun. The common unvented 10" test barrels always give higher MV than you can get in a real revolver, even with a 10" barrel.

We chrono junkies are always pleased ( and somewhat surprised) when we test something like the Speer short barrel 135gr +P .38 using our model 442 and actually get the published MV. Some of the manufacturers' data is, well, (cough, cough)....optimistic?

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Science plus Art

Yes, I do understand that.
Actually, it's bullet mass and not weight if I remember correctly.

In general the major manufacturers (Federal, Remington, Winchester, CCI) load their ammo to the same velocities +/- a few fps. You can go on their websites and find the velocity for the particular ammo you bought.

It's been my experience after putting several factory loads from the major companies over the chronograph that their published velocities are what one gets within normal differences one can expect from different firearms. The current published velocities from these companies are usually shot from a 4" vented test barrel for revolver ammo in the .38 - .357 cartridges normally fired in revolvers. Most data will have the test barrel length listed. The velocities listed on Hornady ammo is usually higher than listed by the other manufacturers but they seem to test from a 6" barrel and the actual velocities measured are in line with the major companies.

The smaller "custom" load companies like Buffalo Bore, DRT and Corbon will have load velocities that exceed the same bullet weight loaded by the Big 4.

Perceived recoil can be influenced by muzzle blast and flash. Ammo that produces more blast and flash gives the shooter an impression of more recoil and power even though measured velocity and real physical recoil may be the same to loads with less blast.

?? Ahhhh ?? No. Actually it is weight ..
Grains are a unit of measure. When a box of ammo states it's a 158 Grains JHP .. It means the projectile weighs 158 grains and is a jacketed hollow point.

Technically, the recoil formula is e=1/2mv^2.....the plug n chug online calculators, just use gun weight/32.17 and bullet/7000 for m. But, let's not get nerdy here.

As stated if mass is same, then velocity must be different if recoil is different.

What about tight versus loose internal gun dimensions? Wouldn't that affect recoil?
The tighter gun might recoil more than the looser gun with both having the same velocity.

Not really. Some brands of ammo have velocity specs and
trajectory values on the bottom of the box. These are based
on standard factory specifications however and do not actually
indicate what the ammo in the box will do. The reality is that
most factory ammo will fail to meet factory velocity specs in
the average gun the user owns. There are some brands and
some cartridges that will actually exceed factory specs
however and that's when the chronograph earns it's purchase
price. This gives the owner time to quickly lay in a stash of the
"good stuff" before its all gone.

It has been a long time since I figured recoil. Yes that looks like the formula.
But, doesn't the mass refer to the bullet weight,, the powder weight,, and the firearm weight ??
Like I said it's been a long time since I figured it out long hand..

http://www.saami.org/PubResources/GunRecoilFormulae.pdf

Three brands of ammo all with 158 grain projectiles, all have the same projectile weight.
But not necessary the same powder charge or the same velocity.
So, velocity & powder charge would be the variable in the formula.

It was rather common for folks to come into the LGS and think the 158 grains on the box was a indication of the powder charge and Not bullet weight. Didn't know if that was what the OP was referring to or not. If he was wanting the recoil formula, I misunderstood , sorry.

No. Grains indicate weight.

Mass and weight are different. Mass is an amount of "stuff," or matter. Simply stated, weight is stuff plus gravity. Or, the force resulting from the application of gravity to a given mass.

The grain indication on ammo boxes refers to the weight of the bullet. The type and weight of the powder is not given and it is that that accounts for most of the difference in recoil.

__________________
USAF, 69-92
Vietnam, 72-73

Engineers, physicists and optimists are all famous for ending the summation of variables in a problem by saying, "All else being equal". And of course, it never is. The physics of a projectile being pushed out of a firearm are many facited and mostly known, but very hard to quantify firearm to firearm. Take consecutively manufactured S&W M 27s with 6" barrels; clean, break them in with identical loads, clean again, lubricate identically and then chronograph sufficient identical as possible loads thru them over a really good chronograph under the same atmospheric and temperature conditions and you are apt to find a considerable difference in mean measured velocities. Why? Because of those darn differences that creep into every manufactured product and the materials that are used in that product(s), i.e. powder, primer, case metal, crimp tension, barrel material, dimension tolerances of chamber, barrel, rifling, on and on and on.

It always gave me a chuckle to read reputable gunwriters writing on the (pick one) great, average, poor accuracy of a particular rifle or handgun all based on his one time experience shooting that gun. Usually not one of those writers knew anything about Statistical Analysis and what can actually be claimed as fact from one occurrence of anything. Short answer, "Not Much". Impressions could be written about but not claimed as fact. But I digress from your very good question.

Ammunition Ballisticans will shoot a particular load thru the company's choice of test gun in such quantity so as to develop from their recorded data what is known as a Bell Shaped Curve. Then when the time comes for the Marketer's to tell the Production people just what velocity to claim for such and such load, the Ballisticans hope they don't go much over what their Bell Curve showed as "Mean". That 'means' that 50% of the velocities were higher and 50% lower. The Marketers will never use "Average" velocity as it is usually a lower figure than "Mean".

To sum up all the above gobley-gook, every handgun and every rifle is a law unto itself for velocity and accuracy at any given time under the conditions at that time. Everything we sum up in generalizations are just learned impressions and approximations.

The actual velocity of the next shot from your handgun depends solely on all the variables it is subject to and has nothing to do with the velocity of the shot before or any of the shots before. Obviously the velocity of multiple shots from the same handgun usually vary only in a narrow range, but my whole point is that no shot ever is a exact duplicate of any other of the shots in that set. ..............

+1 Big Cholla and 44.

Then you get into 'Felt Recoil' with compensated / muzzle brake guns and everything goes out the window. A round that kicks like a mule out of a non-comp. gun may hardly bounce in a comp. gun.

Sorry, got off track again re: the 158 grains ..

What would drive ammo manufacturers to use varying amounts of powder in the same type of round?
Has a "standard" ever been proposed?
Sure would make life a bit easier unless I'm missing something very obvious.

You're missing something very obvious and very American: personal choice.
I even go further and load my own .357, ranging from an 1100 fps personal defense load for my model 65 to a max load of Win 296 under a 158gr softpoint for my 8" barrel 686. Most people don't want to shoot my max 158gr .357 load in a stubby--at least not twice.

__________________
Science plus Art

Money, for one.

Manufacturers are likely to use as little powder as they find suitable for their customer's needs, or the market niche for their ammo. Fractions of a grain add up quickly with the volumes of ammo produced, and drop quickly to the bottom line.

Winchester White Box, generally considered entry-level or 'plinking' ammo, is often loaded mildly for the bullet weight. This is sufficient for the price point and little more.

On the other end, Buffalo Bore offers a premium product and a much stiffer load. The increased speeds are well advertised on their boxes, and not too far off of what folks find in the field.


The multitudinous combinations of bullets and powders available are the reason for the thick reloading manuals the roll-your-own crowd use.

" Standard " . yes there is, SAAMI, Sporting Arms & Ammunition Mfg. Institute , since 1926.

' Manufacturers to vary ', Then who would have the lastest and greatest claim to fame ?

We would still be using lead round nose with black powder .

You can compare the published ballistics of manufactured ammo here. The higher the velocity, the more felt recoil usually.

Ballistics 101 | All the ballistic charts. Finally, in one place

Some manufactures use a 6" test barrel and some use a different length barrel. The only ones that often list a popular gun's ballistics with their ammo is Buffalo Bore and Underwood.

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U.S. Navy - U.S. Army, ret

In my chronograph testing, WWB consistently runs as fast or faster than many others. For example, three lots of standard WWB 115 gr. FMJ averaged 1156fps, 1227fps, and 1173fps out of a S&W M&P 9c. Rem 115 UMC was 1157, and Fed. Champion 115 FMJ was 1169.

__________________
USAF, 69-92
Vietnam, 72-73

Unless you are using the bullets somewhere besides Earth, weight and mass can be used interchangeably for any practical purposes.

"Mean" and "Average" are synonymous. You are thinking of the "median" number.

I think people summed it up well, price, choice, etc, all factor in. Not everyone wants a full power load and not everyone wants a light target load. In semi-auto calibers you will find there is a tighter range of performance across brands, because they need to reliably cycle typical firearms. With revolvers, there is no such requirement.

The best way to gauge how a bullet performs is to buy a chronograph. The 2nd best way is probably to read other people's chronograph results? Even if their speeds won't be your speeds, their relative differences will likely be your relative differences.

If you state your preference, whether for stout stuff or mild stuff, I'm sure people can make some suggestions.