Officers Model 38 - Inconsistent Velocity Stats???

[TheTinMan]

On Sunday I shot identical loads through three revolvers and was surprised that my Colt Officers Model 38 (6" barrel) was much less consistent statistically compared to two other pistols. One is a S&W Model 66-2 (.357 Mag chambers) with a 3" barrel. The other is a S&W Model 642 with a 1-7/8" (nominal) barrel.

66-2: Avg 656 Spread 56 Std Dev. 16.9

642: Avg 619 Spread 55 Std Dev 18.5

OM 38: Avg 701 Spread 75 Std Dev 24.9

Powder: Win 231 3.3 grains
Bullet: 148gr. Hornady HBWC
Primer: CCI Small Pistol #500

All cartridges were loaded at the same time in the same cases (once fired UMC). I load powder using trays and check every 5-10 rounds afterward for consistency when working up a new load like this.

My accuracy was better with the S&W 66-2 than the Colt but that doesn't mean much since I wasn't shooting off a rest. However, the extreme spread and standard deviation are very close for the two S&Ws despite the difference in barrel length while the same stats for the Officers Model are almost 50% higher.

Results were similar with a 3.1 grain load in terms of the two S&W revolvers producing very similar extreme spreads and standard deviations, with the longer barrel Colt being more inconsistent.

Is it possible this indicates a timing issue or something else I should look for?

I realize that the powder is taking up very little of the available case volume. Someone else suggested making sure that I point the gun upward after cocking it and lower gently toward the target to get more consistent powder placement in the case. However, why would that affect the 6" barreled gun more than the other two?

Could it be the clockwise rotation of the Colt's cylinder? (that's a joke BTW)

While I'm lost in the weeds, my Hornady manual shows a velocity of 750 fps for this load out of a 4" barrel. I expected a slightly higher velocity from my 6" barrel, not slower. I know that there are a lot of variables so am not sweating this much.

Thanks for your thoughts.

If you already saw my questions on another forum, forgive me. This forum seems to have more traffic and I'm still puzzled by these results.

 

[OKFC05]

I teach statistics, so help me out with some more vital information.

First, how many shots did you fire in the string to obtain the Avg and SD? In general SD for fewer than 10 shots are erratic, and 20 or more are needed for the small differences you are showing to be significant.

Secondly, are you positioning the powder the same in the cartridge for each shot? Powder to the front vs powder to the rear can make up to 100fps difference, particularly with 3.3gr in that large case. The longer barrel can be unconciously causing you to position the gun differently than the shorter barrels.

Basically, the results you have could either mean something (not necessarily what you think) or it could be statistical noise due to small samples. By the way, drop the meaningless part of SD after the decimal. Even a very good estimate of SD is plus/minus 4 or so.

I expected a slightly higher velocity from my 6" barrel, not slower

Welcome to the real world. Chrono owners find that to know what you have requires measuring your load in your gun, on that day. "Rules of thumb" on barrel length vs speed are statistical averages of large numbers of guns, or made by cutting the same barrel off progressively.

First thing you need to remember about statistics is that statistical averages applied to a sample of one have a confidence factor of ZERO.
It's like looking at table of avg life expectancy and predicting the day you are going to die: meaningless.

 

[TheTinMan]

Let me start by explaining my overall goal: I want a target load which is accurate in both the Model 66 and the Colt while still functional in the Model 642. My Hornady manual suggests that 800 fps is ideal with the 148gr HBWC; however, research here and elsewhere suggests that 800 fps probably should be a Maximum velocity - not necessarily an ideal.

Sample sizes for 3.3 grains Win 231:

66-2: 12 shots
642: 10 shots
OM 38: 11 shots

Same sample sizes for 3.1 grains of Win 231:

66-2: Avg 611 Spread 49 Std Dev. 13

642: Avg 593 Spread 60 Std Dev 15

OM 38: Avg 677 Spread 89 Std Dev 28

I know a little about the importance of sample size in statistics. However, I thought that two separate samples showing the same relationships might be more meaningful. Actually the differences in spread and std. deviation are greater with 3.1 grains than they were with 3.3 grains.

It is probable that I handle the two Smith & Wessons similarly but handle the Colt differently, both due to barrel length and grip shape. The Colt has an entirely different feel. Next time, I will make an effort to get the powder toward the rear each time and see if that makes a difference.

My concern was that the data might be pointing to a problem with timing or something else in the Colt. Frankly, I expected the 6" barrel to be more consistent - not less.

 

[Rule3]

How are you measuring/weighing you powder? You say you are using loading trays(which is good) but to be truly accurate each charge should be weighed. (yes, its a pain and maybe anal) but it will ensure that each charge is as close as humanly possible.

Perhaps test just one gun, say the Colt. Load 20 rounds and shoot just that gun, see what numbers you get.

 

[TheTinMan]

How are you measuring/weighing you powder? You say you are using loading trays(which is good) but to be truly accurate each charge should be weighed. (yes, its a pain and maybe anal) but it will ensure that each charge is as close as humanly possible.

Perhaps test just one gun, say the Colt. Load 20 rounds and shoot just that gun, see what numbers you get.

Hornady powder measure (with pistol insert)
RCBS 5-0-5 balance beam scale

I don't have any problem with being compulsive about consistency and/or accuracy. I trickle every charge when testing rifle rounds. However, I did spot check at least every 5 case loads. Plus the rounds in all 3 guns were loaded as a batch. Sure there's some inconsistency from one load to another, but it would be a freak accident if the Colt somehow got the most inconsistent charges in both charge weights.

20 round minimum it is.

 

[Alk8944]

TinMan,

OKFC05 males several excellent points, particularly about sample size. Too often shooters new to using a chronograph shoot 3-5 rounds and think the ES and SD mean something. Such a small sample doesn't even give an average velocity figure that means much. A sample of 20 rounds is minimal, and the larger the better. In reality, and for practical reasons, ignore ES and SD. The only thing that really means anything, and only if Kinetic Energy is important to the application, is the average velocity. Putting holes in paper all that means a thing is group size! Often loads that appear to be less consistent based on ES and SD will shoot better than ones showing "better" numbers.

You remark that you didn't expect the 6" Colt to give lower velocities than the shorter barrels, but the figures you posted show a higher velocity for the Colt, I don't understand.

There are many mechanical factors in revolvers which prevent making a direct comparison of velocity between guns based solely on barrel length. For example, I have an early 1950s .38-44 Outdoorsman with the standard 6 1/2" barrel. With the same load this gun is consistently no faster than several 4" guns I have, and even a 2 1/2" Model 19.

How you hold, or more correctly present the revolver for a shot string makes a large difference too. You have to be consistent. Next time you do any chronographing try this. For one string hold the gun muzzle down and lift the revolver to fire the shot without raising the barrel above level. Next, start muzzle straight up and lower the muzzle to fire the shot, being careful to never let it get below level. What you will find is the string fired with the powder in the back of the case (muzzle up) will give a significantly higher average velocity and lower ES and SD than the string fired with the powder in the front of the case (muzzle down). What you see is the result of what is known as position sensitivity. It is why bulky powders generally give better averages than dense powders.

And remember, the results you get are valid for that gun, that day, and under those conditions. Another test fired on a different day with everything being apparently identical may give you an average velocity 20-50 fps higher or lower that a sample fired on another day.

 

[Beans]

I have found that each gun is a study of reloading in its own right.

I have several guns in .45 ACP. I can get a average group out of almost any load I use in them, but to get a very good grouping I have to tailor a load for each handgun. Which includes different powders, primers bullet weights. A couple of them like 231, I have one that likes clays. Some of them really like the 200 Gr SWC, some of them like the 185 gr cast bullets and I have one that likes the 230 Gr Bullet. These are all S&W's

One good thing is the brand of cases doesn't seem to matter.

 

[ImprovedModel56Fan]

It's an interesting question, but it is highly unlikely that the answer is important. Guns more ore less have a purpose of hitting a target with a bullet, not a target velocity with a velocity. Within reasonable limits, I am pretty sure that the two are NOT demonstrably related. I'd have to go back and review the few data that I have, but I believe that I have plenty of counterexamples of the idea that lower SD of velocity means anything good (or bad).

The foregoing probably does NOT apply to bench rest shooting, and certainly not to long range rifle shooting, where velocity variation is actually quite important.

 

[TheTinMan]

Good Target!

Follow up:

Larger sample size of 35 shots showed an increase in the extreme spread to 102. Standard deviation close enough to be the same. I was very careful to raise the pistol barrel, cock it, and lower toward target the same way each time. Who knows if the powder is moving around in the case from shot to shot?

The important thing is that I'm getting better with the Colt Officers Model 38. The attached target shows a 5-shot group at 15 yards that measures 7/8" center-to-center. Yes, I stopped before the 6th round to avoid spoiling the group. Yes, this was my best target of the day. The 2nd best group was 6 shots in 2-1/4", so this is a fluke. I'll still keep it.

My conclusion from this discussion is that, with pistols, a chronograph is useful in determining whether or not your average velocity is close to published data and/or expectations. The other stats are close to meaningless AFAICT.

Even chronographing rifle loads (which I've done more of), the lowest standard deviation does not necessarily point to the most accurate load; however, standard deviation and extreme spread stats can point you in the direction of more likely accurate loads.

 

[Skip Sackett]

While I'm lost in the weeds, my Hornady manual shows a velocity of 750 fps for this load out of a 4" barrel. I expected a slightly higher velocity from my 6" barrel, not slower. I know that there are a lot of variables so am not sweating this much.

Gotta read the fine print Alk.

He is saying that the 6" barrel gave slower results than the manual says he should have gotten from a shorter, 4" barrel.

Tin, the truth is that every firearm is an individual, plain and simple, every one.

Personally, with W231/HP-38, I have had better results with loads towards the top of the data. Some claim that it is a fast powder and it very well may be but..... I have found that it works best when loaded towards the maximum side of things. Bullseye, not so much. If I was trying to build mouse f*** loads with a 148gr HBWC, I would use Bullseye WAY before I used HP-38/W231. Just me though.

FWIW

 

[TheTinMan]

Skip - my results tend to confirm yours in terms of the high end being more accurate with Winchester 231. The Hornady manual suggests best target loads with the 148gr HBWC and velocity around 800 fps. In MY PISTOL ON SUNDAY, 3.5 grains averaged 770 fps with a high of 820 and that produced the target I posted.

I'm using Win 231 for several reasons. It meters well for me. Also, I can use it for 9mm, .38 Special, and .45 ACP/Auto Rim. That covers a lot of my pistol reloading.

 

[Skip Sackett]

Tin, W231/HP-38 is a great powder and for the reasons you have mentioned in your post. That is one reason I recommend it to new loaders. It just takes one of the "things" out of the equation that can cause frustrations getting started.

Like anything that fits a lot of stuff, sometimes, it doesn't fit the best. In those instances, it is best to go to another powder. For tweaking in the Ol'Girl, maybe you will have to develop a "special" load for her that eeks out all of its potential. If you do, try the old standby of 2.7gr of Bullseye with that 148gr HBWC. I never have but all I hear is good about it.

I use a 158gr LSWC over 3.5gr of Bullseye in all of my 38/357 revolvers and it will shoot one hole groups out to 25 yards in just about all of them, the M637 may be the exception!

FWIW

 

[TheTinMan]

Skip - I am going to try 158gr SWC bullets as well. As everyone says, each gun is a unique entity with its own likes and dislikes. My Model 66 seems to love these 148gr HBWC bullets, but maybe the Colt will like the heavier SWC.

I already have 6 different powders on hand and really don't want to try any more unless I have to.

 

[Skip Sackett]

What other powders do you have then?

 

[Forrest r]

What you’re seeing is called inconsistent ignition. Chronographs are very useful in picking up on those kinds of problems with firearms. Put a new set of springs in the colt & you’ll see the SD & the ES #’s drop.

I use a chrony quite a bit to check for consistent ignition in different firearms. Living in NE Ohio & the long cold winters gives me time to really work on different firearms & wring out every last bit of accuracy out of them that I can. The cold brings out the worst in firearms and the different lubes that are used on the trigger groups/bolts/receivers/ firing pins/ECT. It’s pretty cool to work a firearm in & watch the accuracy increase as they get dialed in.

Here’s a little 22 rifle that I worked on a couple of years ago, a CZ LUX. I did some BBL work on it, polished the bolt & reshaped the firing pin & bought a new extra power striker spring. Did some trigger work on it & treated all the bolt/trigger group parts with moly. It shot decent averaging around ¼” group’s @25yds with low grade match ammo. After working on the rifle its groups shrunk by around 40%.

This is what the CZ LUX would typically do with 4 5shot group’s @25yds.

This is what the CZ LUX would easily do with 4 5shot groups after being worked on.

 

[TheTinMan]

Other pistol powders I have are Accurate #7 and VV 3N37, both intended for 9x23 Winchester and .357 Sig. Neither manufacturer shows load data for .38 Special for those powders with a similar bullet.

Forrest - I hear you loud and clear but am not about to attempt spring replacements in a 1937 Colt.

 

[Forrest r]

Well you took all the fun out of that one!!!

If you can’t raise the bridge than lower the river. Try a softer primer like federal or Remington or a mag primer with a softer cup. That should help the old colt out some.

 

[bmcgilvray]

The various Colt Officer's Model revolvers sure can shoot regardless of the velocity consistency. Here's a 10 shot, 10-yard best effort with a Officer's Model Match from 1957 using 148 grain HBWCs and 2.8 grains of Bulls-Eye. I've never chronographed loads fired from this revolver.

 

[TheTinMan]

You don' need no stinkin' chronograph!

That Target says it all.

 

[Forrest r]

Very nice shooting, I’m glad to see these old pistols can still shoot groups that can hold the 9-ring in the hands of experienced shooters using their favorite loads & cherry picked targets.