38/357 Chrono Data and Observations

[Peter M. Eick]

I was out Chrono-ing again. 10 ft to chrono, 20 shots per string, 89f, 72% humidity, elevation of 79 ft.


The 357 Magnum used was a 1939 Registered Magnum. 6.5" barrel.
Starline brass, cci550 primer, 13.5x2400, 158 grn Lasercast. 1173 mean 34 sd
CBC brass, cci550 primer, 13.5x2400, 158 grn Lasercast. 1234 mean, 30 sd.
Remington brass, cci550 primer, 13.5x2400, 158 grn Lasercast 1217 mean, 36 sd.

Observation. Brass matters for velocity. Even though the range is not large (60 fps) there is a striking difference in over all speed even though the sd was not greatly different.

Starline brass, cci550 primer, 4.6 grns of Trailboss, 158 grn lasercast. 744 mean, 32 sd.
Starline brass, cci550 primer, 4.4 grns of Trailboss, 158 grn lasercast. 752 mean, 33 sd.
Starline brass, cci550 primer, 4.6 grns of Trailboss, 158 grn lasercast. 737 mean, 31 sd.

Observation, weird how more powder does not help in this case. Maybe within the tolerance of error, but need to run a larger ladder test.


The 38 special is a 1939 38/44 Outdoorsman, 6.5" barrel.
Starline brass, cci500 primer, 4.0 grns of Trailboss, 158 grn lasercast, 707 mean, 29 sd.
Starline brass, cci500 primer, 4.2 grns of Univ Clays, 158 grn lasercast, 843 mean, 54 sd.
Starline brass, cci500 primer, 3.7 grns of AA2, 158 grn lasercast, 813 mean, 21 sd.
Starline brass, cci500 primer, 3.5 grns of Titegroup, 158 grn lasercast, 849mean, 19 sd.
Starline brass, cci500 primer, 4.4 grns of Univ Clays, 158 grn lasercast, 902mean, 55 sd.
Starline brass, cci500 primer, 4.6 grns of Unique, 158 grn lasercast, 933 mean, 30 sd.


Observation. 4.0 grns is pretty mild with trailboss. I think I will work up to a bit more for a ladder test. Universal has a lot more sd then unique but both are worse then Titegroup. Trailboss, unique and AA2 were the most accurate. Its surprising what 2/10's of a grain of Universal will do to the velocities.


Now this same load 4.4 grns of Universal, starline brass, cci500 primer, 158 grn lasercast in both guns.

Registered 870 mean 23 sd.
Outdoorsman 887 mean 28 sd.

Observation is that they were a lot closer then I would have expected. I guess the difference between shoot a 38 in a 357 is not that much.

Last comment, a +P FBI 158 does 862 out of the outdoorsman and winchester 158 normal pressure does 742 out of the outdoorsman. Amazing how mild these are compared to standard book reloads.

Any additional observations?

 

[NailGun]

Very good info. Thank You for posting

 

[Grump]

On what I presume to be your .38 Special load using Trail Boss, you did 4.6, then 4.4, then back to 4.6 grains????

I suspect a typo here...

Edited for MY TYPo

 

[Ben Shepherd]

I've seen that on occasion.

You start out with a bottom end load, and don't start gaining speed until you've upped the powder charge better than a full grain. Then they settle down and velocity and powder charges become linear.

Does make you wonder though, doesn't it?

Thanks for posting your work.

 

[Peter M. Eick]

No, the 4.6 the second time is not a typo. I was surprised at the change in velocity so I took another box of 50 and shot another 20 rounds worth over the chrono to verify the results.

I have decided that I am going to try and take the chrono to the range every time I go and just start collecting data on every gun and every load. Thus I will just try and post the data as it comes available. At times I don't think there is enough just basic load data and chrono results on the board, so I decided I can do something about that.

Next week I was going to do some 357 Maximum loads and 10mm work.

 

[Ben Shepherd]

If you're going to get persnickety here, and it sounds like you are:

Remember to tip the barrel up between shots to avoid any powder position issues.

 

[DBR]

If you want typical, real world results, shoot the first shot of each cylinder outside the chrono and then take the next five without favoring muzzle up or muzzle down.

It is also informative to take five or six shots muzzle up and then repeat muzzle down. This shows the worst case position sensitivity . I have found it varies greatly from one powder to another even though the unbiased average velocities are similar.

In a defensive situation the first and possibly only shot is most likely to be from a muzzle down start. This gives the worst possible velocity and maybe ballistic performance.

From short barreled revolvers using premium ammo I typically see 5% to 10% velocity differences depending on muzzle up vs muzzle down.

 

[Peter M. Eick]

At one time I would have gone to the effort to tilt the barrel, but I have given up on that. What my goal is to test the system. That means everything from the primer to the ability of me to hold the gun on target and everything in between.

I don't normally weight every charge and I don't normally tilt the barrel. Thus the 20 round string gets a good sample of the whole system. I view it the same way I view using just one chamber in the cylinder for chrono work verses all 6. You get more consistent data but what does that tell you about the whole system.

For this reason, I just load them up like I normally would and shoot my 20 like I normally would. This gives me 5 shots as spares in case I go too fast for the chrono and then I can use another gun for the other 25. I can then pull out another box of 50 and target check the ammo.

Thanks for the advice though.

 

[kludge]

Peter, why the 550 primers on such a low pressure .357 load?

Thanks for posting this, I've been thinking about getting some Trail Boss so I can teach my wife to shoot the 357.

P.S. should these loads have a disclaimer? I found the following at IMRpowder.com --

IMR HANDGUN DATA

TRAIL BOSS

NEVER Exceed the Loads Listed Here

STARTING LOADS MAXIMUM LOADS
POWDER GRS. VEL. PRESSURE GRS. VEL. PRESSURE

357 MAGNUM
Case: Winchester Twist: 1:18.75"
Barrel: 10" Trim: 1.285" Primer: Winchester SPM

---------------------------------------------------
Bullet: 158 GR. LRNFP Dia. .358" COL: 1.610"
Trail Boss 3.2 754 16,500 CUP 4.2 865 20,400 CUP

Might this explain the higher velocity at the 4.4gr load?

 

[Peter M. Eick]

The first question you answered yourself. If you read the data from IMRpowder, note they say a winchester SPM primer. Note that is a small pistol MAGNUM primer.

The second question goes to the pressure and velocity levels. Note I am using a 6.5" barrel, not a 10" barrel so we have some differences there. But how come I can only get 752 FPS with 4.4 grns when they are getting 865 with 4.2 grns?

If you compare the same 6.5" 38 special data to imrpowder.com then you see that we are a lot closer. 707 for me at 4.0 grns vs. 804 for 4.2 grns and a 7.7" barrel.

I believe that the 13,700 psi for the 38 special load is "close" to the actual pressures I could obtain, but given my results I am highly skeptical of the 20,400 psi for the 357 magnum load.


Should this information have a disclaimer? Well if I was exceeding the published velocities I would have, but since I am below the published velocities (given some adjustment for barrel length), I chose not to. There was a nice article in Handloader magazine about a year ago that pushed the concept of velocity is a better judge of pressure then other techniques. Basically you load up till you get the booked velocity and use other pressure detection methods as a secondary check instead of visa-versa. This is the technique I am following.