Chrony'd my first loads

[DragonFire]

Okay, I finally got out the chronograph I received for Christmas and and clocked a few rounds through it. Though I think I know the basics of it, I don't think I really know much more than that.

I was using a 10mm revolver where the rounds were loaded with 200gr WestCoast plated RNFP over 8.6 gr of HS6. The velocities were between 1065 and 1079 (I don't have the figures in front of me, but the Chrony (gama model I think) spit out high, low and average velocity and SD. (I only shot a couple of strings of 5 shots so the results aren't very reliable yet)

Iwas pleased with the velocity, and didn't think the range was that bad. While I know what Standard Deviation means, and know I want a small one, I have no idea what's a good SD and what's too large.

I also don't know what to do if the SD is too large. I also load on a Dillon press. It does the seating, crimping and throws the powder charge, so is there that much that I can control to improve things?

Assuming all I need to know can't be summed up in the limited space here, can someone point me to a source of information on how to get the most out of chronographing my loads?


BTW: I used my .22 cal pistol to set up the chrony, figuring it was easier and cheaper than using the 10mm. Maybe I shouldn't be, but I was surprised that the .22 Remington ammo I used had an extreme spread of almost 200 fps. I thought factory ammo would be much more consistent than that.

 

[sumpnz]

One point on the statistics from your chrono. When I was testing some loads worked up for me by my FFL he explained that his previous chronograph (had to be replace after getting shot) calculated SD for him, but the formula used was for large (>30) sample sizes. He typically uses 5 round samples for initial testing of loads and found that the SD was way off as a result. When he replaced that chronograph he just got a low end one that simply displayed the velocity. He wrote the numbers down and then entered them in a spreadsheet that uses the correct formulas for SD and other statisical data.

As far as what SD is too large, I can't really answer that question. It all depends on what you want the ammo to accomplish (plinking, deer hunting, varminting, match level target shooting, etc). Obviously, plinking ammo will be able to tolerate a higher SD than varminting or match grade target ammo.

I'm very far from an expert in handloading, but I do know that one way to reduce SD is to use a powder that very nearly, if not actually fills the case to capacity without exceeding pressure limits for your weapon. If the powder can slosh around in the case it will not burn as evenly and consistantly as it otherwise would. That, and of course, measuring your powder charge very carefully to ensure consistancy from shot to shot will help. Measure 20-30 consecutive charges being thrown by your press to see if it is giving consistant amounts. Once it is established that it is then you should probably measure every 10 or so charges to ensure that the amount being thrown is not changing.

.22lr ammo is notoriously inconsistant. Unless you buy match grade ammo you will probably find similar results with most .22lr ammo, especially the bulk packs. If done right, your hand loads should beat the pants off any factory load for accuracy and consistancy. Of course you can't reload any rimfire cartridge, so you're stuck with factory loads there.

 

[Bullet]

Consistency is the key to loading. I own a chronograph too. I hardly use it. Lately I am wanting to find the speed of some 38+Ps because their supposed to expand best at 1,000 FPS. My chronograph will be able to tell me when my loads reach this speed. If your going for group size then your target will tell you this not your chronograph. Somewhere I read that groupsize and SD don't always go hand in hand but chronographs will give you an idea of speeds. Have fun loading.

 

[popbang]

The SD for my plinking loads tends to be in the 20's, although some loads go as high as 30's. My carry loads are in the high teens or low twenties. My hunting loads seem to be more consistant than more moderate loads. So, in the end I like anything below thirty for a SD.

 

[Handgunr]

I think that trying to shoot for SD numbers in the 20 to 30 range as an average, is pretty realistic.
Depending on what I shooting over my chrono, I've had numbers as high as 50, and as low as 5 or 6 with light wadcutter loads.

Low SD numbers also don't necessarily equate to great accuracy, but they give you the knowledge that your loads are consistent.
Usually, this relates to an accurate load, but like I said, not always.

Keeping an eye on your handloads and being as meticulous as possible in their construction, more often than not, produces pretty low numbers.

High SD numbers indicating wide variations in velocity create miniscule differences on bullet exit points. During barrel vibration, or oscelation, these exits occur at different muzzle oscelation points, and although the differences are very tiny, they show far more on target.
Each barrel has a "sweet spot" (aka barrel "ring") or favorable frequency range in relation to the velocity of a round fired in it.
If the velocity of the cartridge you just loaded falls within this "favored range" of the barrel, usually great accuracy is had.

My 2 cents,

Take care,
Bob