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Help! Extreme spread and standard deviation loads

bowhunthard said:
The furthest I've shot it so far was 350 yds., the groups averaged from 0.5" - just under an inch.
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Click to expand...

Unless you're a competitive BR or F-Class shooter, I wouldn't be too concerned with ES. ES becomes more important as you shoot longer ranges and as long as your load is grouping well to whatever range you're shooting you should be good to go. If you start seeing significant vertical dispersion at longer ranges then you could have an ES problem. But I would not go solely by the numbers an electronic device is telling me, especially one of the cheaper ones that most of us use.
 
yeah i tend to put mine farther than closer... through my experience, if you have the chrony closer to your barrel, it will get screwed up by the gas/particles escaping the muzzle blast force could also be the culprit.
 
I usually put mine @ about 12 to 15' from the muzzle, but I've never replaced the batteries so far. Guess I'll have to do that.

Thanks alot for the help.
 
First off, I don't personally do a whole lot of shooting beyond 200 yards because like you, my range is limited. So take this all for what it is worth. I just like to try to get my es and sd down as low as possible. I also have a chrony and I believe it to be fairly accurate. But as stated above, you have to get it out far enough from the muzzle to get good readings. Mine is at 21 feet. I have tested it in all sorts of light conditions with a few loads and the ones that are best always read very close (within 3-10 fps from one day to the next, and es/sd will not change even that much) I have found that if the temp/pressure/humidity are close, it gets the same readings regardless of lighting, given enough light. This would suggest that atmospheric conditions are actually changing the MV, not that the chrony is off. in low light/late afternoon watch for error readings. if you get an error reading in a string or within a few minutes of shooting, then the numbers might be suspect. but cloud cover or lack of, has not caused me a problem. I always use the diffusers too. Yours may differ. as far as getting it down, same lot of brass, good brass (not remington in my opinion), trimmed to within .002", charged within +/-.1 grains, seated to within .005", and finding your sweet spot for seating depth. beyond those factors if the deviation/spread sucks and your groups are good out to 200, try another powder if you think you will shoot very long distance with the load at some point. Every rifle likes something a little different in my experience with a lot of rifles, and I don't believe there is a magic powder that gets these numbers down for all rifles in a given caliber. I have one 6.5-284 that loves RL17 and I get ES and SD numbers under 5fps consistently with one load, same load in the other rifle gets SDs over 25. Not sure if this helps much, but I think it is all sound advice, and I know it to be my experience.
 
Lot of good info mentioned, but nobody said anything about primers yet and they have a fairly significant effect on ES and SD. You might try a different type of primers.
If the rifle is older a weakened main spring can also be a cause of high ES and SD.
 
dodgefan said:
Lot of good info mentioned, but nobody said anything about primers yet and they have a fairly significant effect on ES and SD. You might try a different type of primers.
If the rifle is older a weakened main spring can also be a cause of high ES and SD.
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Not sure how I missed that. With large rifle loads I always use either WLR, Fed 215 or GM210M. I use a different standard for the way I choose, but at any rate, these I see as known goods. GM210M for anything less than 45 grains, WLR between 45 and 50 and 215 for over 50. You have to have consistent ignition of course. This works for me.
 
In my many years of highpower competitive shooting, I've talked with lots of national champions, record setters and such folks who shoot the most accurate box magazine rifles in the world. Some of them have rifles and ammo that put benchrest rifles to shame aas far as accuracy's concerned.

Two things that usually cause high muzzle velocity spreads; primers and firing pin springs.

If the firing pin spring is too weak, it won't smack the primer hard enough to make its compound detonate (burn really, really fast) with the same repeatable amount of heat. Firing pin springs do weaken over time, even when they're uncocked in the rifle. Replace them every two or three years. And using a stronger one that what is factory specs is usually a good idea for uniform primer performance. As these springs weaken and primers are no longer popping uniformly, the powder charge won't burn consistantly. Velocity spread increases and average muzzle velocity for a given barrel and powder lot and charge weight goes down.

A couple of folks have tested large rifle primers in modified .17 Rem cases with a BB seated but no powder used. Shooting the BB's through a chronograph and using the velocity average is the indicator. Primers with the lowest average velocity produced the lowest muzzle velocity spreads and best accuracy when shooting bullets. Magnum primers were the worst. Which is probably why I got best SD and accuracy with the mildest large rifle primer with my 30 caliber magnums as well as .308 Win. ammo. RWS 5341 primers....expensive, but they really did do wonders. Wolf large rifle primers are popular these days with those shooting the best scores.

Exact powder charge weight's not all it's cranked up to be. When a bunch of us did some testing for a many-hundred thousand round batch of .308 Win. match ammo using new Winchester cases, Fed. 210M primers and metered IMR4895 (3/10ths grain spread), mild lots of primers produced sub 3-inch test groups at 600 yards. Not too shabby in my opinioin. Note that benchresters typically meter their charges instead of weighing them for matches up to 300 yards.

Ones technique in testing ammo shooting their rifle as it rests atop somthing on a bench may well impact their muzzle velocity readings. I've seen a few people get near 100 fps spread in average velocity shooting the same rifle and ammo. It's all in how hard they held the .308 Win. against their shoulder.
 
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Thats good info Bart. Thanks! I will bookmark this page and keep it in mind. Always interested in someone with hard info. The logic makes a lot of sense, but I still say that in my experience my best ES and SD numbers were with Fed 215s, now I got something to experiment with. Not my thread but I sure do appreciate it. I knew that many of the recent best scores were coming with wolf LR primers, had no idea why. just figured they were most consistent right now.
 
bowhunthard said:
The furthest I've shot it so far was 350 yds., the groups averaged from 0.5" - just under an inch.
Click to expand...
Click to expand...
You're not happy with 1/4 MOA? Have you determined how accurate your chrony is yet? Seems to me the first thing I would do is rule out the possibility of instrument error before I started started burning up a 300 RUM barrel on a wild goose chase looking for a better ES that an inaccurate chrony will never give you.

Just my opinion :rolleyes:
 
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