How much recoil difference between a 4" and 6" .357 shooting .38 Specials?

[Pudge]

Correct and that is why I state that the formulas are estimating an average gas velocity due to the difficulty of actually calculating it (CFD modeling anyone). Most of them estimate the average gas velocity based on some multiple of the muzzle velocity and the only way to get exact measurements is with a ballistic pendulum or a recoil force measure system.

Again the differences are real but relatively low percentage of the total recoil impulse in a pistol cartridges due to the ratio of bullet mass to propellant mass. 20gr of propellant pushing a 125gr bullet even if the average velocity of propellant gas is actually 2x in our short barrel instead of the standard formula estimate of 1.5x still only changes things by about 6%. Again you are correct with a short barrel you expect and we can measure that the propellant play a slightly larger role in the recoil impulse then it does in a longer barrel but it is still relatively small do the fact that the bullet is so much heavier than the propellant. In rifle cartridges this ratio starts to get more meaningful. In shotguns its nearly negligible in many cases.

Where does the energy of the gas velocity go in those 2"?

 

[mcb]

Where does the energy of the gas velocity go in those 2"?

Noise, heat, pushing the air around.

In extreme cases some of that energy never gets released, remaining un-burnt. Despite gun powder having its own oxidizer as the pressure drops once the bullet leaves the barrel, partially burnt powder grains can actually be extinguished in the air at normal atmospheric pressures. You see this if you clean up an indoor pistol range lots of partially burnt powder on the ground in front of the firing line. Low pressure short barrel guns like 380 ACP and 38 Special are especially good at this.

 

[wagonburner]

Again the differences are real but relatively low percentage of the total recoil impulse in a pistol cartridges due to the ratio of bullet mass to propellant mass. .

No, in some cases the gas causes more recoil than the bullet, especially in short barrels. This can easily be observed when a hard recoiling gun is fitted with an efficient brake.

See the attached pic is a 375 H&H handgun (yes, 375 H&H). It can be shot one handed without too much fuss. (I'll forward you the URL if you want to see me shooting it). As it is, it has zero climb and just bump backwards about 6 inches when shot. Without the brake it jumps out of my hands and is literally capable of putting you in hospital if it hits you. I have no means to measure the recoil, but I can tell you the difference between braked and un-braked is huge. Pic taken after before I mounted sights. The brake is a JP Recoil Eliminater

Any formula that produces results that differs from observing the actual is flawed (for obvious reasons). Shorter barreled guns recoil more than their longer barreled counterparts. That is an undeniable fact observed by anyone that compares them. The formula you refer to is useful when comparing different loads for the same firearm, not for the same load in different guns.

 

[mcb]

No, in some cases the gas causes more recoil than the bullet, especially in short barrels. This can easily be observed when a hard recoiling gun is fitted with an efficient brake.

See the attached pic is a 375 H&H handgun (yes, 375 H&H). It can be shot one handed without too much fuss. (I'll forward you the URL if you want to see me shooting it). As it is, it has zero climb and just bump backwards about 6 inches when shot. Without the brake it jumps out of my hands and is literally capable of putting you in hospital if it hits you. I have no means to measure the recoil, but I can tell you the difference between braked and un-braked is huge. Pic taken after before I mounted sights. The brake is a JP Recoil Eliminater

Any formula that produces results that differs from observing the actual is flawed (for obvious reasons). Shorter barreled guns recoil more than their longer barreled counterparts. That is an undeniable fact observed by anyone that compares them. The formula you refer to is useful when comparing different loads for the same firearm, not for the same load in different guns.

View attachment 898634

Again the formula is reasonably accurate for most common usages of the formulas. If you are going to go find a fringe cases like a rifle cartridge 375 H&H in a pistol (I did 450 Marlin in a 10-inch Encore and it was sort of mean) then yes the formula that relies on an estimates created from observations of very different firearms is of course not going to give you an accurate estimation.

The formulas discussed here (particularly the SAAMI recoil formulas I think we are all referring too without stating explicitly https://saami.org/technical-information/recoil-formulae/ ) cover the guns discussed in the OP in this thread close enough for this discussion. I suspect the un-measurable factors like muzzle blast/flash and the particulars of individuals shooting them have more impact on the felt-recoil differences between a 4-inch and 6-inch steel revolver shooting 38 specials than the actual difference that would be measured in recoil impulse contributed by the muzzle exit pressure.

If you have a copy of ANSYS Autodyn CFD (computation fluid dynamic) software, enough time and/or computer power, and a degree in mechanical engineering (the Navier-Stokes lovers not the Newton lovers) we could create a pretty accurate model of any particular gun. That software is not cheap or intuitive to use... the engineers are a dime a dozen...

With the proliferation of inexpensive high speed cameras and open source tracking software it is pretty easy to do a simplified ballistic pendulum (you don't need to let it swing to full height) using the high speed camera and software it is easy to get free recoil velocity. This is really good at measuring and comparing the efficiency of muzzle breaks and calculating free recoil energy. Recoil force based systems are still a bit more expensive but are getting cheaper.

TL;DR Your right wagonburner but in OP's case is just doesn't matter that much.

 

[fxvr5]

See the attached pic is a 375 H&H handgun (yes, 375 H&H). It can be shot one handed without too much fuss. (I'll forward you the URL if you want to see me shooting it). As it is, it has zero climb and just bump backwards about 6 inches when shot. Without the brake it jumps out of my hands and is literally capable of putting you in hospital if it hits you. I have no means to measure the recoil, but I can tell you the difference between braked and un-braked is huge.

You're confusing recoil force generated by the cartridge with felt recoil that is changed by use of a brake/compensator. The round produces the same recoil force with or without the muzzle break. Muzzle brakes/compensators change the felt recoil.

Muzzle breaks and compensators can be very effective in reducing muzzle rise and felt recoil because the gas force pushes forward on the baffle(s) in the brake, which reduces rearward force, and with vertical ports typical of compensators redirecting the gas force upwards, muzzle rise is dramatically reduced. But this addresses felt recoil, not the actual recoil force of the cartridge. (I used to have a JP recoil eliminator on a 223 rifle. Loved it. Worked very well.) Even a compensated 38 Super pistol can have as much as around 80% of its muzzle rise reduced when using the right powder. https://www.shootingtimes.com/editorial/compensators-pressure-gas/99170

Cartridges with large amounts of gunpowder can have a large proportion of the recoil force produced by the gunpowder itself, as shown in this article; https://www.shootingtimes.com/editorial/gunpowder-contribution-to-recoil/328788

But, I digress. Since you are unhappy with referencing this with respect to different barrel lengths in a 38/357 caliber revolver, please tell us what numbers to use in the formula for gas speed to account for different barrel lengths. You can plug those into a formula and tell us what the 'real' recoil is.

 

[mcb]

You're confusing recoil force generated by the cartridge with felt recoil that is changed by use of a brake/compensator. The round produces the same recoil force with or without the muzzle break. Muzzle brakes/compensators change the felt recoil.

{snip}

This is incorrect. A muzzle brake actually reduces the total recoil-impulse. For every bit of gas momentum you redirect off the axis of the bore you reduce the amount of recoil impulse you feel from that portion of the propellant gases. If we redirect gasses at X degrees to the bore axis the recoil-impulse they contribute is reduced by the cosine of the angle of redirection. So if we had a magic brake that could redirect all the gases at 90 degrees to the bore axis would eliminate the recoil from the propellant mass, not just felt-recoil but measurable recoil-impulse. If that magic brake redirects that gasses back at the shooter in the reverse direction of the bullets path you can start to reduce the un-braked recoil-impulse by a theoretical maximum of twice what the propellant would have contribute total un-redirected gases recoil-impulse. Yes that is impossible to achieve in practice. But this principal is why the supper efficient brakes have lots of gills angle back as much as possible without endangering the shooter (bystanders beware).

If the porting is symmetric, as with most rifle brakes, then no moment is generated. The symmetric porting cancels each others moments. If the porting is asymmetric then a moment will be generate by this imbalance momentum change such as is common in pistol compensators or ported pistol and shotgun barrels. When done right this can control muzzle rise as well as reduce recoil.

 

[wagonburner]

You're confusing recoil force generated by the cartridge with felt recoil that is changed by use of a brake/compensator.

I'm confusing nothing. A 4" 686 shooting the same ammo as 6" 686 will recoil more. I have shot both weapons back to back hundreds of times. You haven't. In fact, you have never ever in your whole life shot two of the same model guns with different barrel lengths back to back. I know, because if you had you wouldn't be arguing with me now.

But this addresses felt recoil, not the actual recoil force of the cartridge.

Well we aren't talking about the "recoil force of the cartridge", but the difference in recoil between two revolvers, a 4" 686 and a 6" 686 using the same 38spl ammo.

But, I digress. Since you are unhappy with referencing this with respect to different barrel lengths in a 38/357 caliber revolver, please tell us what numbers to use in the formula for gas speed to account for different barrel lengths. You can plug those into a formula and tell us what the 'real

My reference to the velocity of the charge was to point out that the formula did not take it into consideration. I don't need to "plug in" anything anywhere. I'm not the one relying on google and a flawed formula to get my "facts". I actually go out and shoot the guns myself and in this case I happen to own, and have shot many many times, the exact guns the OP mentions.

Yet you want to tell me you know better than me which gun recoils more? Are you kidding me?

 

[wagonburner]

The formulas discussed here (particularly the SAAMI recoil formulas I think we are all referring too without stating explicitly https://saami.org/technical-information/recoil-formulae/ ) cover the guns discussed in the OP in this thread close enough for this discussion.

The SAAMI recoil formula is "interesting" as it seems to depart from the other models I have seen in that it calculates energy (FRE).

 

[mcb]

The SAAMI recoil formula is "interesting" as it seems to depart from the other models I have seen in that it calculates energy (FRE).

Yes I discussed that in my first rambling post in this thread. It is somewhat more useful as it takes into account the weight of the gun firing it.

 

[jmr40]

Don't confuse actual recoil with felt recoil. The longer barrel might add 50 fps, but the added weight will basically offset that extra speed. You'd be splitting some mighty fine hairs on actual recoil

Plugging in the numbers here and assuming 50 fps more speed with a 6" barrel, but a 4 oz heavier gun, the 4" barrel has 12/100 ft lbs more recoil. 5.02 ft lbs vs 4.9 ft lbs. 5 ft lbs recoil is hardly noticeable anyway and most people can't accurately differentiate between recoil until there is 3-5 ft lbs difference between 2 different guns

http://www.shooterscalculator.com/recoil-calculator.php

But in my experience the 6" gun will be more comfortable to shoot. That isn't the same as having less recoil.

 

[Huntolive]

Recoil with 38 Special in a 6 inch barreled or 4 inch barrel 357???

Come on man

Even with 357 recoil should be mild.

In my view recoil barely begins 357 and only becomes an issue in 44 magnum and above

Stay away from 454 Casull Buffalo bore above 300 grains by all means

 

[Steve C]

Low recoil .38 spl target ammo like wad cutters will have little recoil regardless of what barrel length firearm you shoot them from. Heavier handguns will have less recoil as a matter of physics but difference in felt recoil in revolvers of similar weight like a 4" vs a 6" of the same model steel revolver will be barely noticeable using the same ammunition.

 

[Big_Al]

Short & sweet answer, shooting 38's you won't notice the difference.

 

[Huntolive]

Wow I can't believe this ridiculous post has continued this long.
I think it should have ended with something like:
With 38 Special in a 357 Magnum with any Barrel over 3 in recoil is a non-issue

 

[GEM]

I have deleted a bunch of personal bickering. If you disagree with a post be factual. If you think someone has crossed a rule line, report it to staff.

This is a good place to close.