Energy loss from slide action/recoil?

[Carbonator]

How much bullet energy/fps is lost on a semi-auto/revolver from the slide action/recoil? In other words, how much difference in bullet velocity would there be between shooting a semi-auto/revolver, and the same load/round/bullet from a "fixed barrel? (suppose the barrel was welded into a non-movable object, like a 160 ton steel cube for simplicity)

 

[Preacherman]

You can get a good idea of this by comparing velocities from a fixed barrel (often used by ammo manufacturers to test their stuff) to those obtained from an actual carry gun. Typically, the fixed barrels will produce velocities 5% to 10% higher than those obtained from typical guns. (Of course, the manufacturers used to list the fixed-barrel velocities in their publicity claimes... Fortunately, they mostly use more common guns these days to obtain velocity figures - at least for handguns.)

 

[Redlg155]

As I understand things, recoil or weapon mass has zero to do with velocities. Othewise you could put a handgun in a vise and obtain higher velocities than you would just holding the handgun in your hand.

Revolver velocities are slightly lower due to cylinder gap allowing a bit of the gases to escape.

Semi autos will obtain a greater velocity because of the relatively sealed system. On a properly designed auto loader the bullet will have left the barrel prior to the system unlocking. Otherwise the pressure would make short work of the slide and create an unsafe condition.

I haven't seen a comparision of semi auto velocities vs similar fixed barrel velocities, such as 5" 1911 vs 5" Contender, but I would venture to guess velocities would be pretty close.


What strikes me as interesting is folks who have chronographed relatively light powder loads in revolvers vs full length rifles or carbines. I've heard of some reports where the rifle actually had a lower velocity than the handgun due to the powder burn being completed in the barrel and friction actually starting to slow the bullet down.

Good SHooting
Red

 

[Jim Watson]

Several years ago, one of the less conventional gun writers made clamps that would hold the action of an autoloading pistol closed. That way, he could fire the SAME ammo in the SAME barrel both fixed and functioning. Got higher velocity with the action unclamped and operating normally.

 

[JohnKSa]

If you can find some slo-mo footage of guns firing, you will notice that the bullet is gone before it's possible to detect significant movement in the firearm.

 

[P95Carry]

If you can find some slo-mo footage of guns firing, you will notice that the bullet is gone before it's possible to detect significant movement in the firearm.

Thx John ..... saves me having to type out exact same!!

Only real difference is in ''perceived'' recoil ... just that some energy is absorbed ''thru the system'' instead of translating to your hand!

 

[Carbonator]

So the energy used to move the slide reduces recoil only, and does not affect the bullet at all? In other words, the slide reduces recoil but doesn't affect bullet dynamics?

 

[JohnKSa]

Recoil is a product of physics. Something moves in one direction, things have to balance out.

The way to think of it is that a certain amount of energy is imparted to the gun as a result of recoil. There are lots of ways to absorb the recoil energy. The whole gun can move, the shooter and the gun can move, the stock/grip can flex, bend or break, a slide can move, the barrel can move, or any combination of what I've listed and more I've left out.

Don't think of recoil or the motion from recoil as something that is stealing energy from the bullet. It's a consequence of the bullet's motion, but it doesn't take away from the motion. It is the fact that the bullet DOES move away at a good clip that makes recoil happen in the first place.

Now, a gas-operated action is a bit different, but even that results in a heckuva lot smaller velocity loss than one might think.

 

[James Bondrock]

I am no physicist, but I don't see what the speed of the bullet has to do with recoil. Actually, it is the other way around: the recoil is affected by the speed of the bullet.

 

[BluesBear]

The reciprocal action of the slide on an semi-automatic firearm doesn't actually lessen the recoil but it does change the impulse of it.

On a 1911 for example there is a slight lessening of the recoil when the slide moves to the rear. Once the slide reached the rearmost position there is a little added recoil as sthe slide slams to a halt and the recoil spring pushed the slide forward while at the same time inparting a slight rearward thrust.

So while you would have the same amount of recoil in foot pounds from lets say 40oz revolver as you would in a 40oz semi-auto handgun shooting .45acp. The recoil impulse would be spread out over a longer duration on the semi and it would, to some people, feel "softer".

 

[Hal]

Revolver velocities are slightly lower due to cylinder gap allowing a bit of the gases to escape.

Red,
I see that theory mentioned quite often. On the surface, common sense would seem to support it. The strange thing though, is that time after time, the same ammunition fired from a revolver and a semi auto, having the same barrle lengths, almost always results in the revolver having marginally higher velocities.

How much bullet energy/fps is lost on a semi-auto/revolver from the slide action/recoil?

Carb,
On a locked breech like a 1911,,,none. The slide doesn't unlock until the bullet exits the barrel.

 

[ny32182]

I’m gonna go out on a limb here and say that autoloading pistols operate on the “for every action, there is an equal and opposite reaction†law of physics, meaning that the same amount of energy that is imparted on the bullet is also imparted on the gun. I’m also going to guess that before the bullet leaves the barrel, the entire gun/bullet is still one system, with no net energy transfer in or out. This would account for the lack of movement of the gun prior to the bullet leaving the barrel. If the gun started recoiling before the bullet was gone, accurate shooting would be impossible.

If anyone disagrees with the above, have at it, but I think its probably correct. Now, here is what I’ve been curious about for some time: exactly which part of the gun is the energy transferred to? Obviously, the slide cycles at some point, but how is energy transferred to the slide? The barrel moves a little bit, but does it move enough to throw the slide all the way open? Is energy transferred back down the barrel pushing the spent casing hard enough into the breachface to cycle the slide? This is what I assumed at first, but if this were the case, how could a failure to extract possibly occur?

Inquiring minds want to know.

-Nick

 

[antediluvianist]

it's a bit more complicated

."...So while you would have the same amount of recoil in foot pounds from lets say 40oz revolver as you would in a 40oz semi-auto handgun shooting .45acp. The recoil impulse would be spread out over a longer duration on the semi and it would, to some people, feel "softer"."

Yes , definitely the recoil impulse is spread out over a longer duration in the case of the semi. However, in a semi there is a problem. After the explosion of the cartridge, the slide and - for a short distance, the barrel that is locked to it -move backward and obviously have the same momentum, per conservation of momentum, as the bullet going forward ; the slide-barrel just move much more slowly (have less "v") since their combined mass is much bigger than the bullet's) . But when the slide hits the frame at the limit of its rearward motion, that momentum is absorbed by the frame, and the frame of the semi is only maybe 60% of the mass of the entire semi-auto pistol, so the "kick" at the point that the slide hits the frame is substantial. In the case of the revolver, however, the entire mass of the revolver absorbs the recoil.

Everything else being equal, the revolver will "kick" less than the semi, but the effect is lessened somewhat by the longer duration of the semi-auto's recoil.

 

[RecoilRob]

As mentioned by Hal, the revolver vs. auto comparisons often favor the revolver. This is really not strange because of the differences in measuring the barrel lengths.

The auto is measured from the base of the chamber while the revolver is meaured from the face of the cylinder. So, to be actually fair, the cylinder should be included in the barrel measurement when comparing to an auto.

If this is accounted for, the revolver should be slightly less, inch per inch, vs. the auto. But..... Different barrels on different guns make for different results. Sometimes the longer barrel doesn't perform as well as a shorter one for a whole host of reasons.

 

[P95Carry]

If the gun started recoiling before the bullet was gone, accurate shooting would be impossible.

ttbadboy ..... in fact the recoil movement DOES begin straight away!! However, the timeframe involved being obviously very short for the bullet to exit, plus the inertia of the guns weight to be overcome ... this is a minimal effect ... arguably tho increasing slightly for the longer barrels (and that perhaps in part negated or decreased by the extra barrel mass out front - longer moment).

However, for a given gun, ammo power factor and bullet weight etc . the thing is its early recoil rise should be consistent, and so it is allowed for when sights set. It is not ''noticed'' re accuracy.

To give a classic example ...... I used to shoot compo's with my 686 ... and I machined a heavy steel piece to slide on over the underlug and lock in place. After addition of that weight my POI changed by 6 whole inches down at 25 yds .... so I had to bring the sights up at the rear.

After that I had a better tamed gun with quicker target revovery. Proved the point to me.

 

[Carbonator]

Interesting RecoilRob

So the "functional" length of a Kahr 3 inch semiauto barrel is really only like 2", since the bullet is pushed forward and leaves only 2" of bullet travel before it leaves the barrel?

This would give any semiauto about a 1 inch "disadvantage" over a revolver with the same length barrel, correct? A semiauto 3 inch barrel approximately = a revolver 2 inch barrel (revolver flash gap not considered for simplicity)?

If I recall (from my limited memory), a revolver's flash gap will reduce fps by approx 50 fps. Reducing functional barrel length from 3" to 2" (as in an auto) reduces fps approx 100 fps (?), giving a slight edge to the revolver in terms of comparing an auto and revolver of same advertised barrel lengths.

 

[MoNsTeR]

Even if the barrel were mounted in a 160-ton steel cube, there would still be an equal and opposite reaction. It wouldn't move the cube very far, or raise its temperature very much, but the energy transfer would still take place. Remember, there's no such thing as an immovable object.

 

[Redlg155]

Hal,

Are you taking into account the measuring differences of revolvers vs semi autos as Recoilbob had mentioned?

Good Shooting
Red

 

[Archie]

Hummmmmmmm.... again.......

Okay. The effective barrel length is the distance from the base of the bullet chambered to the muzzle. Typically, revolvers have a bit of a barrel length edge in similar size guns.

The velocity "penalty" in semi-autos and revolvers has been argued for years. There have been tests run. One such test with revolvers (a revolver, anyway) used a single action something-or-other that was altered so the barrel could be screwed in and out to set the cylinder gap.

There have been a couple semi-auto tests wherein the slides were locked in one manner or other to make the pistol a locked breech manual repeater.

The over-all results are these: Both revolvers and semi's loose velocity in the normal operation of the device. (Large gasp of breath here, folks.) That is to say, both the barrel gap of the revolver, and the recoil of the semi-auto use up or waste some of the energy of the cartridge being used.

Which is more wasteful? This is the result my research: About 40 years of reading all these reports; sometimes interviewing the experimenters, and my own research into the matter.

There is more variation between two different handguns of the same type and caliber than between the two designs.

By the way, it does get heated sometimes. I remember talking to two different men, both known to me as knowledgeable and honest. In two separate conversations (happily some distance apart) they related to me the results of such testing. Both were convinced of the reliablity of their experiments and results. They were about 180 degrees out of phase and convinced the other (they knew each other) were full of processed bovine feed.

Want to do your own? Knock yourself out. But do at least three separate examples of each design and caliber. Here's the proceedure:

1. Obtain three different semi-automatic pistols in the same caliber. Determine barrel length by calculating distance from base of bullet while round is chambered to muzzle. If you have different type pistols, cut off the longer barrels to match the short one. (Better you should start with three different examples of the same model pistol. Three Government Models, three Browning HighPowers, three Glock 17s; that will save a lot of prep time.)

2. Obtain three different revolvers in the same caliber. Measure and record the cylinder gaps for all chambers of the cylinder. Using the length of barrel found for the auto pistols, cut off and crown the revolvers to the same funcitonal barrel length, base of bullet to muzzle. Install receiver mounted scopes or red dot sights so you don't shoot the chronograph.

3. Buy or load at least 138 rounds of ammo, all of the same type, manufacturer and lot number. If you load the ammo, load it all at the same time using the same components. You may want to load two lots, one at starting load levels, and one at maximal levels. If you are purchasing the ammo, go wild and buy target loads and full charge stuff, but maintain the lot number uniformity for each type.

4. Obtain a chronograph.

5. Find suitable range. Take a lunch.

6. Fire each handgun, noting the velocities attained. For revolvers, make sure each cylinder gets fired three times each. Five rounds per semi-auto. Repeat for the other load, if so inclined.
Break camp and go home.

7. Remove the barrels from the revolvers and alter the threads and barrel shoulder so the barrel will screw up against the front of the cylinder.

8. Devise a manner of locking the slides in place on the auto-pistols. I'm told a five inch "C" clamp will flex the slide enough to lock in place. I'd suggest some leather pads so the finish doesn't get screwed up. I've told a machinist's bench vice will also work, but it makes the pistol a little hard to shoot offhand.

9. Go back to range. Take a lunch and dinner.

10. Fire each handgun, noting the velocities attained. For revolvers, make sure each cylinder gets fired three times each. Five rounds per semi-auto. Please note that every time you shoot the revolvers, you will have to load the cylinder, cock the gun, fire, unscrew the barrel, rotate the cylinder and then screw the barrel back down. Every time you shoot the auto-pistols, you will have to charge the chamber, lock the slide in place, fire, unlock the slide and recharge the chamber.
Now you know why to take lunch and dinner. Take some Gatorade, too. You need to keep hydrated.
Repeat for the other load, if so inclined.
Break camp and go home.

11. Write findings. You should calculate average velocities for each type of ammunition for each of the sample guns prior to being altered. Then averages of the three revolvers and the three semi's. Then calculate the same averages for the "after" conditions. Then compare the averages between altered states of each of the samples and the revolver averages and the semi averages. This will show how much velocity change exists in each sample and the averages.

12. Repeat process with at least two other calibers. 22 long rifle is a good candidate, as is .45 ACP, .10mm, .357 Magnum and .38 Special. Properly, one wants to use low, medium and high pressure rounds.

13. Rebarrel the revolvers because they are going to be useless until you do. Probably re-finish the semis because they probably got scratched to heck despite the leather pads.

Let me know how this comes out, okay? I've been dying to do it but I can't afford to cut up that many guns just for curiousity. Maybe we could apply for a government education grant?

 

[Redlg155]

5. Find suitable range.

For your results to come out correctly you must use an indoor range where the temperature is controlled. You will get velocity fluctuations depending on the outside temperature.

That is to say, both the barrel gap of the revolver, and the recoil of the semi-auto use up or waste some of the energy of the cartridge being used.

Still..I'm finding it hard to understand how the recoil of a semi auto blowback or tilting breech design will waste energy being imparted on the bullet. Again..the bullet should clear the barrel prior to the action unlocking in a properly designed handgun.

It is a bit more understandable if we use semi auto rifles or gas operated weapons to explain a bit of velocity loss. These weapons do indeed use pressure from the system to operate the actions and gas typically enters the port prior to the bullet leaving the barrel.

Good SHooting
Red

 

[Jim K]

In a locked breech pistol of the recoil operated type, the barrel and slide remain locked together until the bullet leaves the barrel, even though recoil began at the same instant the bullet began moving. The purpose of the locking and unlocking mechanism (link, cam) is to keep the locking in place until the bullet exits.

Since there can be no bullet energy loss as long as the barrel and slide are locked together, there is no energy loss from recoil. And after the bullet exits the barrel nothing the gun does can affect it in any way.

Jim

 

[BluesBear]

You can't have it both ways

Stop. Take a deep breath. Think about it for a moment.

Why does a 6" pencil barrel S&W Model 10 have a higher front sight than a 2" S&W Model 10?

Why does a faster buller shoot LOWER than a slower one?

Now answer these questions and then tell me the gun doesn't move at all before the bullet leaves the barrel.

Yes the bullet leaves the barrel of a Semi-automatic pistol before the breech UNLOCKS, but not before the gun or at least part of it starts to move.

If the gun didn't move at all then the POI would be exactly the same for every shooter of the same gun.


Take a Thompson Center Contender, in a major caliber, with a scope. Have four people fire it at the same distance from a standing position.

Anyone want to take bets on whether or not all or any of the four shooters will have the same POI?


edited for spelling - I either need bigger keys or smaller fingers

 

[JohnKSa]

Bluesbear,

You're right that there is some small velocity loss due to gun movement (whatever form that takes), however, as you said, the velocity loss is so small that it's virtually impossible to measure.

Other quantities in the equation swamp it to the point that it's virtually a non-issue.

So, I would say that you're confusing the issue... ...with the truth.

In this case, being absolutely accurate is almost misleading.

Notice that I didn't say in my post that the gun doesn't move at all, only that there it's not really possible to detect the movement. As p95 pointed out, by increasing the weight of the gun, it's possible to change the recoil characteristics, thus changing the impact of the bullet on the target. This proves that the gun IS moving.

However, taking P95's example, let's look at how much movement it takes at the muzzle of a pistol to change the point of impact by 6" at 25 yards.

Assuming that the back of the gun stays still while the muzzle rises and that the sight radius is about 6", we find that the muzzle has to rise by 4 hundredths of an inch to change the impact by 6" at 25 yards.

So, while I acknowledge that you are correct (the math proves it), I stand by my original statement which discounts the small amount of movement(and therefore velocity loss) caused by recoil before the bullet leaves the bore.

 

[BluesBear]

John I wasn't disagreeing with anything YOU had said.

I had only posted about felt recoil. But since this is about velocity loss, It is in my learned opinion that IF there is any velocity actually lost by gun movement is would be immeasurable and immaterial.

The velocity spread from shot to shot would be vastly greater with even the best ammunition than anything lost due to recoiling mass.

The science of ballistics was once described by one of my professors as "repeatable inconsistancy".

 

[JohnKSa]

The science of ballistics was once described by one of my professors as "repeatable inconsistancy".

That's going into the files!

You know, if you did want to measure the velocity changes from recoil/slide motion, you might be able to do it with black-powder loads. I understand that the velocities from high quality black-powder ammunition are far more consistent than with smokeless...