Some questions regarding .38 Special Chrono results

[Oyeboten]

My brand spankin' new "Item Number 852429 Competition Electronics ProChrono Digital Chronograph" I'd Ordered from 'Midway' last week, arrived...so...now some figures:



Revolver today, is my lightly modified, daily carry, Model 10-6 S&W, 3 Inch Barrel, as seen here -





Strings of six, fired from 10 yards.


Me-Load - 158 Grain, Lead, Hollow-Nose, Semi-Wad-Cutter Bullet, Remington Primer, 20.7 Grains early 1960s "DUPONT" 3 F, .040 Home-made Grease-Wad, good Crimp...max OAL to still fit -



FPS as



770
770
770
770
770
770


Yes...every darned Round got the same FPS reading, and I even tried other rounds making different readings in-between them, to double-check.


Next -


Me-Load - 158 Grain, Lead, Hollow-Nose, Semi-Wad-Cutter Bullet, Remington Primer, 20.7 Grains new Bottle "GOEX" 3 F, .040 Home-made Grease-Wad, good Crimp...


FPS as



670
670
670
670
670
670


And, yes, I tried other rounds in-between to double check....


Next -


Commercial 'FAMAE' Brand, 1970s vintage, .38 Special, made in 'Chile' or someplace, 158 Grain Round Nose Lead, unknown Primer, unknown Propellent -


FPS as


751
792
768
778
804
750



Next -


Me-Load - 158 Grain, 'Waffle-Sided', Lead, Hollow-Nose, Semi-Wad-Cutter Bullet, Remington Primer, .040 Home-Made Grease Wad, consistent/approx 15.75 Grains of "777", good Crimp.


FPS as


722
751
786
773
807
767


Kind of inconsistent...


Maybe the "777" does not like Grease Wads?


I'd appreciate any insight into why my meticulously prepared 'BP' loads appear to be so wonderfully consistant...


While my "777" Load was not consisent?


1970s Ammunition from 'Chile'...who knows...


What do you think?

 

[qajaq59]

I think you must have the best powder measure ever made!!!

If you hadn't tested the other ammo I'd have thought that the chrono had a glitch, but......?

I'll have to watch this thread to see if someone can explain that one.

 

[BADUNAME37]

I find it hard to believe, however I have no reason NOT to believe you!

It must be a combination of just the right components, perfect measuring of powder and just the right load for the gun!

 

[Walkalong]

You sure you hit "next" when checking the FPS.

Remarkable. I have never chronoed black powder, so I have no clue.

 

[fecmech]

I'm no expert but from my reading I'm pretty sure black powder loads are generally more consistent in velocity. The Black powder cartridge rifle guys have some super consistent long range loads. The .38 spl case is originally a black powder case, smokeless powder leaves much extra room in the case.

 

[RidgwayCO]

I've heard that BP was consistent, but that's surprising...

Just for additional info, how far away from the muzzle was the chronograph placed?

 

[Oyeboten]

Chronograph was 10 Yards from the Muzzle...


Target, was an old 10 Meter Air Rifle one, tiny Bulls Eye, set a couple feet behind the Chronograph.

I wanted a consistent Bullet Path centered over the sensers, and pretty well kept it.



Chronograph was on a Folding Table, and, I shot from a kneeling position.


In seeing the BP readings being the same FPS each shot, I paused, and shot a 'FAMAE' Round, just to see, and it gave it's own different reading...so, I'd do two or three BP, then a 'FAMAE' just to be sure the Chronograph was not stuck.


BP Powder Measure was a 1950s' Lyman' 1.3 cc 'scoop', used same way each time from a small Bowl of Powder.


The '777' I made my own Scoop...used same way each time.


Once all done, I did a few extra of the two different BP rounds, and, got same readings as previous.


Sure was fun...


A nice beginning!


Possibly, the '777' prefers 'light' compression...where, I'd given it no compression at all....merely Charging the Cases so the Powder, and Grease Wafer, ended up where I intended the Bullet Base to be.


Next try, with '777', I will use 'Alox' Tumble-Lube, no Grease Wafer, slightly larger Charge, light compression....and see what that does.

 

[jfh]

I'm a bit sceptical, but I suppose it's not impossible.

First of all, are you sure you read more than one shot during the BP sequences? I cannot speak to the exact command functions off the top of my head--but I can say that if you did not do the store, then it may be you are simply re-reading the same round set, or merely the same round.

Did you hit 'store' at the end of each sequence? Does the display show a new string set (of numbers) being entered? When you cycled through the result, did it show "round 1, 2," etc? I'll re-read my manual again, about the setup sequences, to see if there is a tip there.

One last tip: check the formatting of your output--I have mine set up for one-tenth fps readings, and that, to me, makes more sense.

Otherwise, I am not qualified to talk about BP results--but if it turns out these measurements are accurate, then a big congratulations on your (BP) reloading skill is in order, Oeyboten.

Jim H.

 

[Oyeboten]

Hi jfh,



Well...I did everything the same for each group...

The two BP groups had entirely consistent FPS...the two other groups did not have consistent FPS.


I deleted after each Group...and, fired other, different single rounds in with the two respective BP loading strings, once I was seeing the same FPS appearing for the BP round group being tested, and, the different ('777', or, 'FAMAE' ) rounds gave their own different FPS.


Curious, huh?

 

[jfh]

Yes, it is curious--like I say, I have no sense of BP loading--i.e., maybe loads are consistent, whatever--but I simply can't wrap my mind around six shots being that consistent.

That's why I wonder about the commands you used to store / delete / recall (?) the strings. I haven't looked at my instructions recently, so I'll come back with the specific questions later about command usage.

About your recording technique: For all shots, did you simply write down the number you saw on the screen, as you made each shot? Or, did you store them and then recall them, hitting "next"--did the screen show, for example, a "1" and a "6" somewhere along the bottom, IIRC?

Otherwise--if I get curious about BP 38 Specials, I'm going to subcontract my loading to you.

Jim H.

 

[bluewater]

"Chronograph was 10 Yards from the Muzzle..."

Good shooting from 30 feet!

 

[LJH]

Huh? 10 yards seems ok to me.

I have never seen a string that consistent. Congrats!

 

[atblis]

I think if you assume a normal distribution and a reasonable SD (like 10 maybe), you're into a series of events that are rather improbable.

I get a 1 in 122,000,000,000,000,000,000 chance of observing that series of 12 shots (but I got a C- in stochastics so...).

Assumptions
Normal distribution
Mean is velocity observed
SD of 10
+- 0.5 fps to obtain that reading on the Chronograph

Basically, no freaking way.

 

[Oyeboten]

I'll try again soon...