Results in--2" barrel .38 Special velocity...Ported VS. Non-ported barrel

[Southern Shooter]

A month or so back I started a thread titled "useless gun??? .38 Special, 2" barrel...and PORTED". Some of you were interested in the results of chrono testing. See below the results.

(I posted this same information in the orginal thread. I apologize if that was not a correct thing to do. However, I just want to make sure that the information was not overlooked. Thanks.......)
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Ok, I took the Taurus 85 revolvers to the range this weekend. And, the results were surprising.
**********************************************************
Clear day. About 70 degrees. About 70 percent humidity. No wind.

3-shot strings

Master Chrony----Alpha Model set up at roughly 5 yards from muzzle
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Taurus 85 Ultralite non-ported

***White Winchester 130 grain FMJ***
Velocity
701.7
740.0
726.2

Average
722.63
-----------------------------------------------------
***Speer Gold Dot 135 grain +P Short Barrel***
Velocity
892.8
855.9
891.9

Average
880.2
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Taurus 85 steel ported

***White Winchester 130 grain FMJ***
Velocity
765.7
747.6
750.2

Average
754.5
-----------------------------------------------------
***Speer Gold Dot 135 grain +P Short Barrel***
Velocity
909.9
923.1
907.9

Average
913.63

Now, look at the numbers guys. The ported barrel .38 Special stomped my non-ported revolver. Why???

As far as the powder flash from the ports go...there are enough quality low flash self-defense ammos out there to deal with that concern. Honestly, I know that it was daylight, but I did not see any flash from the ports at all. Nor, did the other guys standing there watching the ports.

Whatever the reason...the ported barrel gun stays.

Thanks

 

[20nickels]

Did the porting help to control the gun at all? Did they reduce muzzle flip vs. the non-ported tube?

 

[351 WINCHESTER]

Assuming you were using the same ammo (same lot #), it doesn't make any sence.

 

[357-8-times]

Interesting that you have porting on the heavier gun?!

 

[Southern Shooter]

ammo lot and muzzle flip

The ammo came from the same boxes...I assume that would be the same lot.

Muzzle flip was hard to compare...one being an ultralite and the other steel.

Yes, the porting is on the heavier gun. It is for my wife...she needed all the advantage she could get...not good at dealing with recoil.

 

[Feanaro]

Have you measured the cylinder gap on both revolvers?

 

[Southern Shooter]

Barrel/cylinder gap

I have not measured the gap, yet. Will do so. Just eye-balling them there seems to be no difference...but I will put a gauge to them.

Even if the gap were wider slowing down velocity I am still guessing that there would be enough speed to cause reasonable expansion from Speer Gold Dot 135 Grain +P short barrel.

 

[Feanaro]

I'm simply curious as to how similar the gaps are. If they were close, it's an unexpected outcome. You would expect, all things being equal, the ported revolver to throw 'em out slower. Might not be the case though.

 

[sm]

Interesting indeed!

Thanks for doing this and do keep us updated on cylinder gap and anything else that comes up.

Just goes to show, firearms have their own quirks, and the only way to know, is to investigate and verify .

 

[mec]

These things happen. They don't always make sense

 

[Dan-O]

I guess my ported Taurus 85 Ultralight is a keeper as well.



If I remember correct, your ported one was done by Magnaport, is that correct? Mine came ported from the factory, and it just has the three dots on the top. Three on each side of the "sight". If I remember correctly, the Magnaport job has oval holes.

Thanks for doing the Chrono Testing.

 

[bhk]

It really pretty rare that two supposedly identical guns give the same velocity with the same ammo, even guns with no barrel/cylinder gap (i.e. autos or rifles). It just doesn't happen often.

The only way to really do this test to fire a single gun before and after porting. Then, and only then, can you assess the effect of porting on velocity. Who knows, maybe your ported gun would have averaged 50 fps more without the porting. We will never know.

 

[NG VI]

Maybe it's got slightly tighter or looser rifling? that's really interesting, and weird, and counter-intuitive.

 

[highorder]

I think the cylinder gap will tell the tale here. call it a hunch, but a scant few thousandths can easily account for the variation we have seen here.

 

[Joe the Redneck]

Look at the numbers again, and round them up or down, lets keep it simple.

Gun 1
Trial #1 702 - 740 difference of 38
Trial #2 856 - 893 difference of 37

Gun 2
Trial #3 748 - 765 difference of 17
Trial #4 908 - 923 difference of 15

So Gun number one is producuing a much greater spread in velocity than Gun number two.

So now we not only have to expalin how porting would make a bullet go faster, but also why it would create more consistant velocities.

May not be a porting issue, may just be the gun.

Either way, your ported gun is a fine example that even with a short barrel, it certainly doesn't kill velocity.

Joe

 

[Bones11b]

For me the interesting part is that there wasn't a great loss in velocity on the ported short barreled revolver. Many persons I have spoken to on the subject have been lead to believe that a ported short barrel revolver is useless due to the "fact" that you will suffer a great loss in velocity. Even if porting had caused velocity to drop 50fps it would still not negatively affect performance in my opinion. Thanks for the food for thought. Almost gives me a reason to pick up another short barreled revolver just so I can measure it before and after porting Not that I want or need another gun, this would strictly be for the good of science

 

[jfh]

I, too, would expect the (unexpected) velocity results to be primarily caused by differences in gaps. A second / related factor really also goes to how well the barrel and forcing cone are aligned with the cylinder, as well as forcing cone size.

As Bones11b pointed out, these velocity changes are not terribly significant in terms of "power"--and the expansion of hollow-point bullets at 2" barrel velocities is questionable except for the Gold Dot Short Barrel loads and the Hot Rod rounds by Buffalo Bore (which are not part of the consideration here for the shooter).

My own experiences with porting on Semi Autos suggest TANSTAAFL--you simply will get a velocity drop, but well-done porting minimizes that.

One tip: don't shoot lead bullets in a ported gun, unless you like tedious cleaning procedures.

If your wife has recoil / flinching problems, I would also consider reloading, and developing a round that replicates her carry round, then backing up the charge weight for her comfort. That can also be the start of a training / acclimation program for her.

Although one cannot build jacketed-bullet reloads as cheap as lead bullet reloads (here ruled out because of the porting), they still are money savers--typically, 50% to 75% or more over the cost of factory PD ammo.

Jim H.

 

[highorder]

FWIW, the 6 ports on the Taurus guns are easy to clean lead and carbon out of. I use a small bronze brush in a screwgun, or a small half-round file if necessary. Due care is always taken.

 

[Steve C]

There's quite a bit of variation in velocity from gun to gun with the same barrels and even within the same manufacturer. Apparently the porting doesn't contribute a significant enough reduction to overcome this variance.

 

[ChristopherG]

Here's a very speculative hypothesis, or WAG if you prefer:

Identical rounds in two guns, one heavier and one lighter, exert identical recoil or 'backpressure' on the launching platform; but the lighter gun recoils more--as anyone who has shot one of these ultralight snubs will attest. It responds to the 'backpressure' of recoil by moving farther back, and faster. So it absorbs more of the energy that would be moving the bullet forward at a given velocity.

Now, the physics classroom in my mind is a small and ill-equipped one, so I might be getting something obviously wrong (and the fact I've never heard of this hypothesis makes me think that's probably the case); but try this mental experiment:

Imagine that these identical rounds were being tested out of (1) a gun that had been integrally cast into an anvil, bolted to a 10-ton concrete block; and (2) a gun made of magically forged helio-scandiscat, a metallic compound of amazing strength and virtually zero mass. This virtual-zero weight gun is being fired by a brave, but weak-wristed, two pound garden gnome (foolishly emboldened by firing gun number 1).

I submit that this test would produce a significant difference in muzzle velocity as a result of the masses of gun (& shooter) and their reactions to the recoil/backpressure of the shot. And an older, wiser gnome.

But whether that difference is significant enough to observe in the real-world conditions described above, or in any comparison between practically shootable light and heavyweight guns in the same caliber, shooting the same ammunition? Don't know--never even heard it suggested.

 

[SaxonPig]

I would expect virtually no velocity loss due to porting because the ports are out near the muzzle. I think what you got was just standard deviation between two guns.

 

[SAWBONES]

Too many "experts" just have to pontificate about everything under the sun, including about how porting is inadvisable and undesirable on a defense or CCW gun.
I have porting (Hybra-Porting, done by Marc Morganti) on several .357 Ruger SP101 revolvers in varying barrel lengths, and there's no increase in blast, flash or blowback, but there's a definite and marked improvement in felt recoil and muzzle flip, with only a 2-3% drop in muzzle velocity over non-ported. A very good thing, as far as I'm concerned.

 

[kludge]

ChristopherG

Actually yes. There is always conservation of energy. If we assume the diameter of the base of the bullet is equal to the diameter of the case head, then the force from the expanding gasses will push both equally but in opposite directions. The sides of the case are not allowed to expand (much) so we ignore it and no energy is expended nor work is done there.

From there it's F=m*a , and since the gun is much heavier than the gun (for a 32 oz. gun and a 125gr bullet, 56 times heavier) it's acceleration won't be nearly as high as the bullet (duh).

So F=m(g)*a(g)=m(b)*a(b) and from there m(g)/m(b)=a(b)/a(g)=56, so the bullet accelerates 56 times as fast as the gun.

Now if we take a gun that's half the weight, 16 oz., it's easy to see that the acceleration of the bullet is now only 28 times that of the gun. Since the acceleration is reduced, the muzzle velocity will drop. Since conservation of energy must apply, the energy lost to the bullet (due to a lower muzzle velocity) must now transferred to the gun.

The other way to look at it - since the energy in the recoiling gun has increased, the energy in the bullet must have been reduced, and since E=(m*V^2)/2, and the mass of the bullet didn't change, the muzzle velocity must be lower.

In an extreme example, where the gun and the bullet are equal in weight, they will have the same acceleration and therefore the same speed (but going opposite directions) when the bullet leaves the barrel. In this case, both objects will now have the same amount of kinetic energy, and the bullet energy will be half what it would be in an infinitely massive gun.

 

[PawPaw]

I'm glad to see you posted the numbers. I've been looking for them.

For the record, guys, the Chrony was mine and I did the shooting while Southern Shooter watched the chrony and ran the numbers. I didn't feel any discernable difference in the recoil of the two revolvers, but I might have been jaded after touching off a bunch of heavy .30-06 loads I was testing. The recoil on those was invigorating.

Still it was nice to meet Southern Shooter and his son, and to help test the numbers on his revolvers. We talked a bit about the counter-intuitive numbers and discussed things like cylinder gap, forcing cone specs, and the general individual-ness of revolvers.

 

[Evyl Robot]

The first thought that comes to mind concerning the counter-intuitive numbers is exhaust systems on cars. I have considerable experience with what I like to call "rice-rodding" aka "sport tuning." With the smaller-displacement car engines, a little difference in exhaust pipe size makes a big difference. On a car that came with a 1-1/4" tube, bumping it up to 2" or 2-1/2" will make it breath nicely, and increase performance significantly. But, if you take it up to 3", usually you will encounter a performance loss, often making the car slower than it was with the restrictive, stock exhaust. I wonder if the ported barrel is showing an unexpected point in a performance curve like this. Could this be due to some type of venturi-style effect, or possibly a decrease in backpressure as the bullet accelerates down the non-ported section of the tube? Or, is it just a fluke due to a difference in cylinder gap, or rifling, or mass of the gun, or what? Who knows? It's not science until you can reliably duplicate results. Still, the initial experiment is very fascinating. Just my $.02.

./Michael