Got an Alpha Chrony the other day, and finally had a chance to take it out to the range this weekend.

I can not believe that I waited this long to grab one of these! It will really be a help in finding the correct aim point at longer ranges (varmint hunting). I do have a question for some more expirenced chrony users out there.

My .223 loads (both the 55gr and 60 gr) both have a standard deviation of 36 fps. Now that is a lot better than the off the shelf stuff I had laying around, but my .308 deer load had a SD of 19.

What is "acceptable"? I mean is a change of 36 FPS noticable enough to change the point of aim?

outstanding, and welcome to the club.

now, be prepared, you'll probably shoot it!


36fps, from high to low, or +-36?

i have had some loads and rifles that shoot teens, but 36, if it's grouping well, is excellent

jeffe

A standard deviation of 36 fps means that the average round will be withing 36 +- of the average velocity.

And yes, I imagine I will shoot the thing one day. Just hope I won't for a while. That and I made sure to turn in the warrenty card!

NEJack,
Enjoy the chrony. It's the handloader's best friend.

Regarding SD, be aware that some chronys will spit out an SD for as little as 3 shots, but it really takes 10 or more shots to calculate a mathematically meaningful SD. I'd suggest you simply ignore the SD for those 3 shot or 5 shot strings.

Assuming there are at least 10 data points, I like to think in terms of SD as a percentage of velocity. For example, my snubnose might be lucky to have an SD that is 1.5% of velocity, my lever gun is hard pressed to do better than an SD that is 1% of velocity, but a good high velocity rifle load should easily have an SD of less than 1% of velocity, and 1/2 of 1% is a realistic goal (most chronys are only accurate to 1/2 of 1%, anyway).

That 36 fps SD would be about 1.2% (guessing a 3000 fps velocity) while the 19 fps SD would be about 0.7% (guessing a 2700 fps veocity). The 308 SD is pretty decent, but the 223 could use some work -- assuming we are talking about 10 shot strings, and not 3 shot or 5 shot.

You won't notice the POI difference at a 100 yards but might at longer ranges. 1000 yard shooters go to a lot of trouble to minimize their SD. The SD is a measure of variation, and less variation is better. +/- one SD would include something like 67% of your shots, while +/- three SD would include something like 97% of your shots (I'm going from memory so my numbers could be off a little).

Things to investigate on the 223 -- primer, crimp, distance to lands, neck tension, and throwing a consistent powder charge -- particularly anything that effects ignition.

SD is not a cure-all for reloading, but it is a good indicator for ignition. For example, SD can help you decide which brand and type of primers is best for your load. Ditto for evaluating crimping and neck tension.

Some people will tell you that SD doesn't matter. That is probably because they are going by a 3-shot or 5-shot SD.

I took my readings from 30 shot groups for the .223's and a 15 shot group from the .308. Just wanted to make sure.

The comment on iginition possibly being the problem has got me thinking again. I currently use CCI SR primers for the .223, and have been thinking of going to a mag primer to see if it helps (I am using AA2460 and AA2230 ball powders). It was one of those things that came to mind after I loaded 700 rounds for my pdog trip, but now that is done I might have to try a box of mag primers to see.

Also, last year I started using a light crimp on my .308. Seemed to improve accuracy a bit, but thinking about it I can see how that would affect ignition also.

Everyone with a Chrony STOP!!

Replace those wires with wood dowel's, only cost a dime per 3' and you can make 4 per stick.

Hit a wire, and 95% your gizmo is ruined.

Second: Get a 1/8 or 1/4" pc of plexiglass and cover that membrane face before unburned powder particles eat holes thru it.

Those and shooting the things are NOT covered by their warranty.

Neither is hitting the face with a b/p patch.

Been there, done that, and borrowed another and damned if a mutual buddy didn't hit a wire on that one. So I'm out two and don't have one at all.

From my experience, nah, ain't gonna say it again!!!

Best of luck folks!!

George

Another little bit of advice, watch shooting anything with a sabot through one. Had a friend put his chrono down with a sabot from a deer slug. Congrats on getting the chrono, makes a world of difference having one.

NEJack, Congratulations on the chrony! Now your loading will move to a new and higher plane. On the SD's bottom line is they indicate uniformity of the internal ballistics. Meaning the ignition, consistancy of charge and evenness of burn, among a few things coming to mind. For long range varnmint look for single digit or low teens. The flash hole diameters and bullet pull will be an area to look to for consistancy, as well as weighing cases and measuring bullets for their diameter as well. Your bores might like .2238 bullets or .2242? Time and experimentation will tell. Enjoy the toy.

Congrats on the new hardware!! You're gonna love it!! Pair it with some ballistic software and you're set. Sighting in has never been easier.

Last winter I signed up for a coyote hunt. I wanted my Swift sighted in dead nutz at 300 yards. I chrono'ed the load and ran the ballistic program. I did the sight-in at 25 yards. When I posted the target at 300 yards and shot, the group centered up EXACTLY where the program said it would. INCREDIBLE!! Those two items are priceless.

One thing I did learn about my loads before it got destroyed.

Had to adjust my thinking and loading quite a bit.

Sure was educational and I do intend to replace it with a good one from some other brand that don't set in front of the bullet with the whole system.

That's the part I think is wrongly built. Otherwise, the price and quality were ok. Easy to use too. But, did get a lot of missed and wrong readings when they should have and most did register.

Once you get into it, you'll learn a lot.

George

The Chrony has helped already.

Over Memorial Day weekend, some friends and I went to western Nebraska for a pdog shoot. Couldn't understand why my AR was not making shots at ranges I knew it was capable of. Looking at the speed data, and running it through the Point Blank program (nifty freebee BTW), I figured out that those 55gr bullets lost a lot more speed at 250+ yard ranges than I thought.

A buddy of mine is helping me build and pexiglass "cage" to protect the eyes, and I don't use a black powder so that should be ok.

I've got a chronagraph and learned a few years ago that the easiest way to become disapointed with your reloading is to get a chrony and a bore scope.

Hey Peg:

Sure changes your ideas and opinions about what you knew for a fact, don't it??

George

I can understand the need for a chronograph in putting together dangerous game loads where velocity and bullet penetration is the key to killing power BUT the loads never seem to be the most accurate ones. I've always tried to make my rifles as accurate as I can and it is never (for me anyway) at the top end where the accurate load is. Alot of my magnum calibers do work best at the top side of the loading ladder but then I will shoot the load over the chrony and low and behold the velocity just doesn't make it as advertized. I hunt very little dangerous game so years ago if I didn't think I had enough gun to get the job done I would just step up in caliber. I like my rifles to shoot where I'm looking. Not to get off subject but never look down the bore of your favorite rifle with a bore scope unless you are ready to re-barrel! JMO