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

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Aim1

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I have a Smith and Wesson 686 with a 6" Power Port barrel and it is a pleasure to shoot. I've been told with the full underlug and 6" barrel a Power Port really isn't necessary. Shooting low recoil .38 Specials and it feels like you could pleasantly shoot the gun all day long.

I was wondering if I went from the S&W 686 with 6" Power Port to a S&W 686 with a 4" non-ported barrel and shot the same .38 Special low recoil rounds would there be any difference in felt recoil?
 
Recoil is very subjective but to me there isn’t a difference with 38s. They are pleasant out of either length barrel due to just how heavy the gun is versus the low recoil of the 38 special. Your local range may well have a 4 inch GP or 686 to rent.
 
I find the barrel length has little to do with actual recoil and more to do with perceived visual recoil when you get into full size frames like the 686. My 2.5" 686 bucks no more than my 5.5" .357 SAA clone. However, the perception is that .357 is quite a bit more violent out of the shorter gun despite it actually weighing more. The fireball is impressive and the report is concussive.

I find myself more likely to have to blink away spots than actually fight muzzle climb.

All of the 686s I have shot have been absolute pussycats shooting even .38 +p. I think they are one of the nicest fighting revolvers out there.
 
Yes, there will be a difference in the recoil and also the way the gun recoils will be different. The 4" will recoil a little more and rotate more.

Rule of thumb:

All things equal, the shorter barrel will recoil a little more and be more inclined to rotate/roll in your hand.
All things equal, a heavier barrel will recoil less and be less inclined to rotate.

Depending on how your barrel is ported, the ports may make your gun less inclined to rotate.
 
In my opinion, the 4" recoil is slightly heavier and slightly snappier, but that there is not enough of a difference to worry about.

My additional opinion is that the flash and concussion from a ported gun is far worse than the actual recoil of a non-ported gun. There are folks who will argue with me on this point, but my experience bears it out conclusively, at least for me.
 
Here's some statistics for a 125 grain 357 Magnum load. Not counting powder charge weight which would be the same for both guns. Two inches of barrel will generally add ~100 fps.

4.125" S&W 686+ 2.437 lbs, 1450 fps = 4.28 ft lbs recoil.

6.0" S&W 686+ 2.750 lbs, 1550 fps = 4.33 ft lbs recoil.

The power port with reduce muzzle rise quite a bit. Not sure how much, but lets say 25%. So the 6" gun generates a little more recoil force but will have much less muzzle rise than the 4" unported gun.
 
Here's some statistics for a 125 grain 357 Magnum load. Not counting powder charge weight which would be the same for both guns. Two inches of barrel will generally add ~100 fps.

4.125" S&W 686+ 2.437 lbs, 1450 fps = 4.28 ft lbs recoil.

6.0" S&W 686+ 2.750 lbs, 1550 fps = 4.33 ft lbs recoil.

The power port with reduce muzzle rise quite a bit. Not sure how much, but lets say 25%. So the 6" gun generates a little more recoil force but will have much less muzzle rise than the 4" unported gun.

It doesn’t work like that. You negated to add in the effect of the gas exiting the front of the muzzle. Anybody who has shot the same gun with different barrel lengths will tell you the shorter barrel recoils more.
 
It doesn’t work like that. You negated to add in the effect of the gas exiting the front of the muzzle. Anybody who has shot the same gun with different barrel lengths will tell you the shorter barrel recoils more.

Adding the weight of the powder would add an nearly equal amount of force to the calculated recoil of each gun, so I did not feel it was necessary. The longer barrel would still have a calculated force slightly greater than the short barrel.

If I use 20 grains of powder, the recoil for the 4.125" barrel 2.437 lb gun is 6.57 ft lbs. The same powder for the 6" barrel 2.75 lb gun is 6.66 ft lbs recoil. (This formula used 1.5 times the speed of the bullet as the speed of the gas.)

Recoil velocity is faster in the lighter gun. Recoil speed for the 2.437 lb gun is 13.17 fps. Recoil speed for the 2.75 lb gun is 12.48 fps. This can affect perceived recoil.

I agree that the powder could/would have a greater impact on the recoil in the short barrel because the gas force at the muzzle would be at a higher pressure when the bullet exits in the short barrel because gas pressure declines and is lower by the time the bullet exits in a longer barrel. QuickLOAD can estimate those pressures for different barrel lengths if someone wants to do those calculations. Most formulas that calculate recoil use the same gas velocity value for all calculations, like I did when using 1.5X in my formula.
 
Adding the weight of the powder would add an nearly equal amount of force to the calculated recoil of each gun, so I did not feel it was necessary. The longer barrel would still have a calculated force slightly greater than the short barrel.

If I use 20 grains of powder, the recoil for the 4.125" barrel 2.437 lb gun is 6.57 ft lbs. The same powder for the 6" barrel 2.75 lb gun is 6.66 ft lbs recoil. (This formula used 1.5 times the speed of the bullet as the speed of the gas.)
.

Your "formula" is baloney.

These are my 686's. The 2.5" recoils more than the 4", which recoils more than the 6", which recoils more than the 7". No formula, just the facts.

I also have a couple of SBH Rugers with different barrel lengths, 1911s with different barrel lengths, Freedom Arms Mod 97s in .357 with different barrel lengths, MR 73s with different barrel lengths, Model 29s with different barrel lengths, Model 27s with different barrel lengths and a couple others I cannot remember offhand. The shorter barreled gun ALWAYS recoils noticeably more.

686s.jpg
 
Interesting answers indeed:

Myself I have done a little testing/shooting with firearms that have interchangeable bbl.'s/bbl shrouds along with using either bbl nuts or comps on the same setups.
DiDmnFO.jpg

I've shot a lot of different bullets/loads in those dw's, anything from mild 38spl's to wild 357's. I've tested all the bbl.'s/shrouds pictured above with the standard bbl nut's and the comps. I've also tested different torques on both looking for accuracy along with testing different bbl gaps. It's nothing to go to the range with 300/400 rounds of a test load and bring several different bbl.'s/bbl shrouds/bbl nuts/comps and do a lot of testing. Been doing this for 10+ years.

I have also owned 586's in the past (same time/taking both to the range on the same day for several years) with 4" and 6" bbl.'s (non ported).

Don't know a lot about the longer ported l-frame revolvers but I do own/shoot a 586 l-comp & I'm glad that comps there with some of the loads I've ran down the tube.
5vi2mrE.jpg

IMHO:
At the end of the day the extra weight of the longer bbl is a huge plus. Having the port or comp is a huge plus. Yes you will easily be able to tell the difference between a 6" bbl'd 686 and a 4" bbl'd 686 (non ported) even with light 38spl wc target loads. The porting is an added plus.

There's a member here MCB that will hopefully chime in. Can't remember but I thought he was using 38s&w's in a long bbl.'s heavy n-frame for different shooting events.
 
Your "formula" is baloney.

These are my 686's. The 2.5" recoils more than the 4", which recoils more than the 6", which recoils more than the 7". No formula, just the facts.

I also have a couple of SBH Rugers with different barrel lengths, 1911s with different barrel lengths, Freedom Arms Mod 97s in .357 with different barrel lengths, MR 73s with different barrel lengths, Model 29s with different barrel lengths, Model 27s with different barrel lengths and a couple others I cannot remember offhand. The shorter barreled gun ALWAYS recoils noticeably more.

View attachment 898516

Recoil is merely physical force generated by the mass and velocity of the projectile. A shorter Barrel may result in a firearm which weighs less and is less able to reduce felt recoil, but a longer barrel which provides a higher velocity of the projectile will result in a greater recoil force.
 
Recoil is merely physical force generated by the mass and velocity of the projectile.

No it is not.

Tip, consider why muzzle brakes work.

A shorter Barrel may result in a firearm which weighs less and is less able to reduce felt recoil, but a longer barrel which provides a higher velocity of the projectile will result in a greater recoil force.

Wrong.
 
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I am about to ramble... :D

Recoil is simply the change in momentum or impulse defined as Mass times Velocity (since we assume everything starts stationary and the masses don't change). The mass is both the mass of the bullet and the mass of the propellant gases. The velocity of the bullet is easy to measure. The velocity of the propellant gases is dynamic and is faster than the muzzle velocity of the bullet initially and diminishes rapidly as the pressure drops after the bullet leaves the barrel. It is typically estimated as an average for recoil calculations. Exact measurements are typically done on ballistic pendulums or recoil force measurement systems.

The impulse number is a fast and easy number for comparing different loads in the same or similar weight firearms. It is commonly used in practical shooting sports. In that context it is usually called Power Factor (has unique units), though they typical ignore the additional recoil from propellant for simplicity and expediency in a match where it has to be measured quickly.

From a human factors point of view the change in momentum or impulse is not great. For that it is common to calculate free recoil energy. This is the kinetic energy the weapon would have if allowed to recoil with no constraints (ie hands holding it etc). Though this is a theoretical number and the shooter never truly experience it since they are holding onto the firearm it is a good way to quantify the recoil event. The free recoil energy takes into account the weight of the firearm and although a heavier gun does not reduce the impulse it does slow recoil velocities and thus reduces the recoil energy. This is the primary reason 357 Mag in an air-weight J-frame is a very unpleasant experience and yet that exact same load in a 6-inch full size steel revolver can be rather pleasant in comparison (despite the velocity increase that may occur due to the longer barrel). The military uses free recoil energy as the metric for soldiers in training. Depending on the free recoil energy level of the weapon being used a soldier is only allowed to fire a prescribe number of rounds in train per day.

https://bisonballistics.com/calculators/recoil

This is a nice free recoil calculator that allows you to select pistol, rifle, shotgun to make a more accurate estimate of the propellant velocity. Plug in you data and you can see how it changes free-recoil energy. There are lots of these calculators out there some will give you a lot more data if you want.

Finally and probably most importantly felt-recoil or perceived recoil is the total experience the shooter experiences and this included the recoil impulse and/or free recoil energy but it also includes things like muzzle blast and flash, possibly a semi-auto action cycling, the fit of the gun to the shooter and the shooter's own tolerances to and experiences with recoil. It is easy to calculate momentum changes and free recoil energy but it is very hard to capture the recoil experience in a way that can be communicated to another shooter easily.

OP I think the 4-inch gun will have slightly more recoil than the 6-inch ported gun when fired with the same ammo but it will be a modest increase in most cases. As several other posters have said the recoil difference is going to be minor and it will still be a very pleasant gun to shoot. In someways it might be more pleasant, though the 4-inch gun will have slightly more recoil but the lack of porting might reduce some muzzle blast making it a more pleasant experience. Either way I think the differences with low recoil 38 Special will be almost imperceptible and you will enjoy shooting the new gun as much as your current.
 
I have short and long and ported and non-ported barrels. A 5" barrel is a good compromise between 4" and 6" on an L-frame. I think it has ideal proportions. A 6" is better proportioned on the N-frame. The grip size and style also affects proportion. Ports are nice for competition-style shooting, but not so good for shooting in confined areas or from close retention positions. The short barrels handle quicker, but aren't as steady on alignment and have a short sight radius, though this latter factor is irrelevant with reflex sights. The longer barrels handle slower but are steadier. A 6" full-underlug or an 8.x" half-lug barrel start to get a little unwieldy, not to mention harder to holster and carry.
 
I have a Smith and Wesson 686 with a 6" Power Port barrel and it is a pleasure to shoot.

Low recoil .38 special is delightful out of K- or L-frame revolvers with 4" barrels.

I'd add that the ports probably aren't doing much of anything with such a low-pressure, low-gas-volume load. Ports and compensators, when properly designed, are seemingly magical in that the more powerful/violent the round being fired, the more they work to hold the muzzle flat. Of course, there's no actual magic involved, just Newton's third law. Ports and comps use the propellant gasses by redirecting them... they become rockets pushing down on the barrel (assuming they are exhausting upwards). If you don't feed them much gas, the rockets don't have much thrust.

.38 target loads are generally going to use small charges of fast powder. Those are great for generating low recoil, precisely because they don't generate much gas. That means they aren't "feeding" the ports enough gas to do anything meaningful. Those ports might be really doing something with full-power .357 ammo, but they're not doing much at all with .38 special low-recoil rounds. You won't miss them a bit.
 
Jeez, dude, all I did was crunch some numbers with the common formulas used to calculate recoil force.

https://en.wikipedia.org/wiki/Recoil

There's no need to go psycho over it.

I didn't see anything wrong with your math other than leaving out the effects propellant gases and that would have made both values a bit higher and the difference slightly greater using the classic estimations for gas velocity. The velocities and weights seem about right. Not sure most shooter could feel that small of difference. It less than 2% with those numbers. I suspect the deference in experienced recoil would have more to do with muzzle blast in the four inch gun than the actual recoil impulse.
 
I am about to ramble... :D

Recoil is simply the change in momentum or impulse defined as Mass times Velocity (since we assume everything starts stationary and the masses don't change). The mass is both the mass of the bullet and the mass of the propellant gases. The velocity of the bullet is easy to measure. The velocity of the propellant gases is dynamic and is faster than the muzzle velocity of the bullet initially and diminishes rapidly as the pressure drops after the bullet leaves the barrel. It is typically estimated as an average for recoil calculations. Exact measurements are typically done on ballistic pendulums or recoil force measurement systems.
.

The velocity of the gas exiting the barrel is substantially higher out of short barrels than longer barrels. We know this as the pressures are substantially higher within the first few inches of bullet travel. Pressure drops dramatically as the bullet travels down the barrel.

The formula you reference treats the velocity of the burned charge as a constant. Observation proves that to be incorrect.
 
Adding the weight of the powder would add an nearly equal amount of force to the calculated recoil of each gun, so I did not feel it was necessary. The longer barrel would still have a calculated force slightly greater than the short barrel.... (This formula used 1.5 times the speed of the bullet as the speed of the gas.).... Most formulas that calculate recoil use the same gas velocity value for all calculations, like I did when using 1.5X in my formula.

I tend to think gas velocity is, to some degree, a function of the pressure at the moment of muzzle exit. Do you think that's true?
 
I tend to think gas velocity is, to some degree, a function of the pressure at the moment of muzzle exit. Do you think that's true?

Yes. And I agree with wagonburner that a problem with the current formula is that it treats the gas velocity all the same even if we're using different barrel lengths or different powders which will produce different gas pressures and gas speeds.

Unfortunately, we don't know more realistic numbers to plug into the formula. These are the numbers we have (1.25, 1.5, 1.75, 2000, 4000, 4700) and we're stuck with them, like it or not.

SAAMI uses the 1.25, 1.5, 1.75 numbers. But there's a bit of guesswork as to which apply best. It is a recognized concern when doing recoil calculations. But, as said, these are the numbers we have to work with.
 
The velocity of the gas exiting the barrel is substantially higher out of short barrels than longer barrels. We know this as the pressures are substantially higher within the first few inches of bullet travel. Pressure drops dramatically as the bullet travels down the barrel.

The formula you reference treats the velocity of the burned charge as a constant. Observation proves that to be incorrect.

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.
 
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