Velocity Extremes -

[38SPL HV]

What extreme spread (ES) and standard deviation (SD) do you find adequate in your 38 Spl / 357 Magnum loads? I usually test factory ammo for their ES/SD and attempt to better these with my handloads…which in 38 Spl +P isn't too hard to do. I usually aim for ES below 50 and SD below 15…I also find that the higher I run my loads within published data the tighter my ES/SD become…i.e. powders which I obtained lowest spreads in 38 Spl +P using 158 gr cast are Power Pistol, BE-86 (best accuracy) and W231. In 357 Mag with 158 gr and 170 gr +/- Keith's in upper mid range velocities, N340 has given me the tightest spreads and best overall accuracy.

Please tell me your experiences.

 

[ArchAngelCD]

Sorry, I really never thought about that. Of course the lower the better but I just never thought to set limits on my reloads. (maybe I should lol)

 

[stansdds]

I also prefer loads with smaller extreme spreads in velocity. 50 fps is about all I will tolerate for an ES.

 

[rockquarry]

While ES and SD numbers can have a small bearing on accuracy at the distances most of us shoot, they are indications of consistency only. Many other factors affect accuracy at least as much or more. Benchrested group sizes fired at a reasonable distance, 25 yards and certainly no less, will tell you far more about a good load.

It's possible to develop a very accurate load that has low ES and SD numbers, but don't assume that will happen. If the ES and SD numbers are really wild and disparate, the load probably will shoot poorly, but that's an extreme example.

If your goal is low numbers with accuracy a secondary objective, try a compressed load of slow burning powder in a bottleneck rifle cartridge. You'll be amazed at the low numbers, many of them the same. The load may be accurate, but there's just as good a chance that it won't be.

I think ES and SD numbers may become more meaingful for accuracy at very long range, but as one factor only, though I've never verified this.

 

[Krogen]

While ES and SD numbers can have a small bearing on accuracy at the distances most of us shoot, they are indications of consistency only. Many other factors affect accuracy at least as much or more. Benchrested group sizes fired at a reasonable distance, 25 yards and certainly no less, will tell you far more about a good load.

It's possible to develop a very accurate load that has low ES and SD numbers, but don't assume that will happen. If the ES and SD numbers are really wild and disparate, the load probably will shoot poorly, but that's an extreme example.

If your goal is low numbers with accuracy a secondary objective, try a compressed load of slow burning powder in a bottleneck rifle cartridge. You'll be amazed at the low numbers, many of them the same. The load may be accurate, but there's just as good a chance that it won't be.

I think ES and SD numbers may become more meaingful for accuracy at very long range, but as one factor only, though I've never verified this.

Well stated rockquarry! Velocity ES and SD are "indicators" but certainly not the be-all and end-all. However I've seen muzzle velocity variations make a difference in an extreme case. Testing 22 Long Rifle at long distances - 200 meters - shows that it matters. You're lobbing bullets a long distance and it does matter. I have put rounds on paper at 200 m while monitoring muzzle velocity with a LabRadar. Vertical stringing correlates directly to high and low muzzle velocity. In some cases, I see a 1 1/2" wide group go 8" high. All directly correlated to muzzle velocity variation. Yes, this is an extreme case. A slow, stubby bullet at long range. Under typical conditions and velocities, for typical rounds, ES and SD are indicators.

 

[Ivan the Butcher]

I large bore Black Powder cartridges, it has been found that an average grouping load a 50 or 100 yards, might have a smaller group (not just MOA, but group size) at 200 yards and continue this MOA further out! All the ballistic books claim this is impossible! Don't believe everything you read! (If you ever watched an arrow in flight, you have seen the same thing!) Some loads need a while to settle down.

I my smoke less long range loadings, It hasn't been this dramatic. I have a couple loadings that have the same group size (not smaller) at 100 & two or three hundred yards. My 338 Lapua magnum has a load that is 1/2" at 200 and the same at 300 (300 gr SMK over Hodgdon Retumbo). I only use the chronograph to establish the velocity for trajectory figuring purposes. This combination hits cigarette pack sized targets at 500 yards very consistently.

Ivan

 

[H Richard]

Back before I had a Chronograph I loaded per loading manuals. I developed loads around the desired velocity but varied the loading, seating depth, and crimp until I got the most accurate load. I had no idea how fast they were going, just the est. from the manual. All I cared about was how accurate the load was.

When I got a chronograph I concentrated on long range rifle loading's, but worked them up the same way as I had pistol, trickled in the load, varied the OAL, varied the crimp. When I got a accurate load I would then chronograph it so I knew the velocity and could figure the drop at various distances. I didn't know the SD of ES until then. And sometimes it would be a very low number and sometimes it wouldn't be.

 

[rockquarry]

Back before I had a Chronograph I loaded per loading manuals. I developed loads around the desired velocity but varied the loading, seating depth, and crimp until I got the most accurate load. I had no idea how fast they were going, just the est. from the manual. All I cared about was how accurate the load was.

When I got a chronograph I concentrated on long range rifle loading's, but worked them up the same way as I had pistol, trickled in the load, varied the OAL, varied the crimp. When I got a accurate load I would then chronograph it so I knew the velocity and could figure the drop at various distances. I didn't know the SD of ES until then. And sometimes it would be a very low number and sometimes it wouldn't be.

Many don't seem to be aware of this. Lots of (flawed) "conventional wisdom" gets so much Internet coverage that it becomes dogmatic truth. I don't know how many shoot benchrested groups to determine the accuracy of a load, but it appears to be a very small number from reading numerous posts.

 

[Nevada Ed]

One would think that a lower ES would be the best, but

Depending on the type powder & the amounts used per a certain fps

I have had loads with a ES over 150, that out shoot some test loads that
are in the 20, 40 & 80 ES

at many of my outings with test loads on powders, OAL, and bullet weights.

Some bullets get down to just two or three powders that work the best
in the accuracy department, if you want a low ES & small groups.

However my my 9mm's and 38 snub nose can drive me crazy, getting this and I have learned that you don't always end up with a low ES load
that wins in the accuracy department.

I have two loads that are very accurate in my C9 3.5" 9mm pistol, but
I can only load them for myself, being IMR4227 and Trail Boss powder
that is not listed for a 9mm loading and may cause a "Squib" in a strangers, pistol.
One has a ES of 11, while the other is in the high 100's.

I have found that a high or low ES in not my result of accuracy in 90% of my range trips
but rather my grip and trigger control.

 

[rockquarry]

One would think that a lower ES would be the best, but

Depending on the type powder & the amounts used per a certain fps

I have had loads with a ES over 150, that out shoot some test loads that
are in the 20, 40 & 80 ES

at many of my outings with test loads on powders, OAL, and bullet weights.

Some bullets get down to just two or three powders that work the best
in the accuracy department, if you want a low ES & small groups.

However my my 9mm's and 38 snub nose can drive me crazy, getting this and I have learned that you don't always end up with a low ES load
that wins in the accuracy department.

I have two loads that are very accurate in my C9 3.5" 9mm pistol, but
I can only load them for myself, being IMR4227 and Trail Boss powder
that is not listed for a 9mm loading and may cause a "Squib" in a strangers, pistol.
One has a ES of 11, while the other is in the high 100's.

I have found that a high or low ES in not my result of accuracy in 90% of my range trips
but rather my grip and trigger control.

Well stated, Nevada Ed.