How to chrony multiple types of cartridges?

[Dennis]

Hello,

I have a Ruger SP101 357 with 3 1/16" inch barrel and am interested in velocities of various factory ammunition from this particular revolver. I borrowed a Shooting Chrony model F-1 and the instruction manual says to use a minimum of 10 rounds to get a good statistical average. I have never chrony'd ammo before so I don't know what to expect. So here are some questions:

1. Do I really need to shoot 10 to get a good sense of the velocity of a cartridge? The main reason I ask is that some of the rounds I will be shooting cost over a $1 per round.

2. I plan to try out 7 different kinds of ammo - do I try them all at one sitting or do I shoot one type and then let the gun completely cool before testing the next cartridge?

I am not working up a load, these are all factory rounds. I just want to have a good sense of what kind of performance I can expect with the cartridge/revolver combination as this will be my main personal protection revolver.

Anything else I should consider?

Thanks.

 

[Rumrunner]

I use mine mostly to check new loads to make sure I didn't screw up. A lot of the time I only chronograph 3 shots in a load. If you know the factory stats, you can shoot 1 shot and if its close to those published you will get an idea what it's doing in your gun. If you were trying to get an idea so as maybe to figure down range trajectories etc, you would want to do more.

 

[Dennis]

Rumrunner,

Thanks for the input. I'm not too worried about trajectories at self defense distances.

 

[Bob Wright]

Ten shots is the best way to really determine the performance of any cartridge.

This is especially true for high performance ammunition. Some ammunition will clock very consistently, but most will vary a great deal.

Bob Wright

 

[Jimbo357mag]

Since you have a 5-shot gun why not use 5 and then if you have the time and money you could do it all over again and get a 10-shot average. After two or three loads I would also let the revolver cool some in between loading so you get a fairly equal temp during your process.

 

[s4s4u]

Do I really need to shoot 10 to get a good sense of the velocity of a cartridge?

Just 3 to 5 will do. With revolvers I usually run a cylinder through.

 

[rob-c]

Also to get consitant readings you have to make sure the bullet goes over the chrono in the same area as close as you can get it. And they work best with a overcast day(if your doing this outside)

 

[5of7]

As Jimbo said, why not shoot a cylinder full.
And while you are at it, shoot at a target so you can get a sense of the accuracy of a particular brand of ammo.
Also shooting at a down-rang target will assure that the bullets pass close to the same place over the screens with each shot.

But if all you want is to find the approximate velocity of ammo through your particular gun, then 3 will probably do.8)

 

[Dennis]

Thank you all for your valuable advice and suggestions. I will try to post my results as some may find them of interest.

I'll be testing 3 rounds from Buffalo Bore, 2 from Speer (including Gold Dot short barrel), 1 Remington and 1 Freedom Munitions - all 38 Special.

 

[Dennis]

I shot my rounds using the chrony and I would like to post the results, but I don't know what to do. I've attached photos before from Photobucket, but my results are in a PDF that was produced from a spreadsheet. Can I attach or otherwise post a PDF? The search feature did not help so I'm asking anyone if this can be done.

Thanks.

 

[Dennis]

Hopefully you can access this PDF if you are interested in the chrony results:

https://drive.google.com/file/d/0B_1ChZrbCL7eblZES1c5ZlZNMmM/view?usp=sharing

You will note some blanks where readings should be. I left these blank because I got some kind of error from the chrony. This was my first time ever using one so I'm sure my technique could use some improvement. In any case, I hope you can get a sense of the results with various ammo in my 3.06" SP101.

 

[Jimbo357mag]

The PDF file is great. Very consistent results. The Speer Lawman you shot was 11.8% under the factory estimated fps., wow. The others were not too out of line. That 150gr Buffalo Bore wadcutter at 961fps is interesting.

If you wanted to post a picture of something on your computer you can take a screen shot (print screen button) of anything on your computer and 'save' it in 'Windows Paint' and then post it as a picture file.

 

[Rumrunner]

Dennis,
Thanks for posting your results.

Jimbo,
Those 150 grain wadcutters shoot very well in my LCRx 3". Buffalo Bore lists them as a standard (non +P) load. Recoil is a little stout but not bad at all.

 

[Dennis]

The PDF file is great. Very consistent results. The Speer Lawman you shot was 11.8% under the factory estimated fps., wow. The others were not too out of line. That 150gr Buffalo Bore wadcutter at 961fps is interesting.

If you wanted to post a picture of something on your computer you can take a screen shot (print screen button) of anything on your computer and 'save' it in 'Windows Paint' and then post it as a picture file.

The Speer Lawman is factory tested with a 4" barrel so I expected to be a bit lower with a 3" barrel. However, the Remington load is also tested with a 4" barrel and it was just under 6% lower - go figure.

The 961 fps is a result posted on the Buffalo Bore website for this gun. I was hoping to get my velocities a little closer to it, but I am still satisfied with the performance in my gun. I'm sure it will still do it's job at 925 fps.

Thank you for your kind comments.

 

[Dennis]

Dennis,
Thanks for posting your results.

You are very welcome! It is good to contribute once in a while and not always be a "taker".

 

[nvbirdman]

Don't bother. Factory cartridges with the same bullet weight will vary less than 50fps. Even with different but similar weights you're only looking at a variation of about 150fps, and at self defense distances 150 won't make any difference at all.

 

[Jimbo357mag]

Don't bother. Factory cartridges with the same bullet weight will vary less than 50fps. Even with different but similar weights you're only looking at a variation of about 150fps, and at self defense distances 150 won't make any difference at all.

No offense but I don't know how you can say that. There are so many 38special and 38+P factory loads out there I am sure there is quite a bit of difference in them.

 

[cas6969]

Since there are several factors that can change your results from day to day, conditions to conditions, you'd be better off doing them all at once.

They may still not be correct, but at least they'll be relative.