Group size vs ES

I have heard several different reasons offered that could be behind this phenomenon...one thing I can say for certain...I have absolutely seen it and I was confounded. Many moons ago I barreled up one of the first rifles I ever did. It was an absolute tack driver. It was just a 308 on a 700 with a trigger, an H.S. Precision stock and some glass bedding. I was shooting reloaded Lake City 58 brass and it was pretty well hardened up after 32 years...at that time one of my buddies had been messing around with a chronograph.
This rifle would put every shot touching at 100 yards off a bench, but ES was well in the 50-60's, sometimes higher.
I accidentally stumbled onto some info in a reloading book about annealing brass cases and tried it. Next trip to the range the rifle shoot single digits and my buddy was going crazy...we concluded that the only thing I did different was anneal the cases. They sized easy and the bullets felt like a feather compared to seating before, problem was the group opened up to like 1 1/2" or so.
I don't know, but I think some powders must like the bullet to be seated tightly. Which these were...the expander ball actually chirped and the handle had to be bumped pretty good when the case was withdrawn from the size die.

OhYtD said:

I have heard several different reasons offered that could be behind this phenomenon...one thing I can say for certain...I have absolutely seen it and I was confounded. Many moons ago I barreled up one of the first rifles I ever did. It was an absolute tack driver. It was just a 308 on a 700 with a trigger, an H.S. Precision stock and some glass bedding. I was shooting reloaded Lake City 58 brass and it was pretty well hardened up after 32 years...at that time one of my buddies had been messing around with a chronograph.
This rifle would put every shot touching at 100 yards off a bench, but ES was well in the 50-60's, sometimes higher.
I accidentally stumbled onto some info in a reloading book about annealing brass cases and tried it. Next trip to the range the rifle shoot single digits and my buddy was going crazy...we concluded that the only thing I did different was anneal the cases. They sized easy and the bullets felt like a feather compared to seating before, problem was the group opened up to like 1 1/2" or so.
I don't know, but I think some powders must like the bullet to be seated tightly. Which these were...the expander ball actually chirped and the handle had to be bumped pretty good when the case was withdrawn from the size die.

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It could be the powder but I would retest seating depth with the annealled necks. With the reduced neck tension I would guess the bullet no longer liking the initial pressure spike and changing the amount of jump could bring it back into line

That's why I went to a magneto speed. Mine was doing the same thing. Heck it gave me readings of over 3600 with 115's out of my Weatherby. Big spreads even made me look like a dummy when I posted the speeds on here.

WildRose said:

If your group size is good, your chrony is probably off.

If your ES is minimal your vertical dispersion should be minimal.

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Excellent reply. I have a 6.5X47 all custom with a 7.2 standard deviation. .219 agg on 10 shots @100 Lots of homework but it pays off.

Results published in Modern Advancements in Long Range Shooting Vol 2, tend to suggest that annealing will probably not solve a ES/SD problem. I haven't noticed much improvement myself when using my Annie induction set up though others have reported different individual experiences as noted above.

If you're happy with group size, I would suggest holding COAL/ seating depth and trying slightly higher/ lower powder weight and/ or primer combinations that produce roughly similar velocities. I have noticed across a variety of calibers that varying these parameters up/ down can result in a moderate change in ES/SD. If I thought I had really bad ES/SDs I would try a different powder and try initially to match velocity to the accurate load. The above approach is roughly similar to what I believe Adam MacDonald of Autotrickler fame suggested in one of his early blog posts.

I have only owned a Magnetospeed and a Labradar so I can't really offer much insight into reliability of the classic units. If the option exists to borrow another chrono and see if you get similar results then that would be an easy choice for a load that already groups well.

I don't know if 65 FPS difference would have necessarily show much vertical dispersion at 300 yards. Maybe there was some other factor that inadvertently compensated for a lower/higher point of impact with your 3 round group? (I.e., stud recoiling against a sandbag, etc.). I usually Try to keep ES under 20 and don't really freak out about it until it exceeds 40 FPS. But, I'm only shooting out to 400 yards. If I can hold to less than 1/2 MOA vertical dispersion at that distance, I'm happy. You may not be. Anyway, you might want to bite the bullet and go with 5 shot groups for purposes of testing. I don't blame you for not wanting to burn the powder and take the kicks but it may be more informative to do so. Sometimes I just compromise and shoot 4-shot groups!

YZ-80 said:

I don't know if 65 FPS difference would have necessarily show much vertical dispersion at 300 yards. Maybe there was some other factor that inadvertently compensated for a lower/higher point of impact with your 3 round group? (I.e., stud recoiling against a sandbag, etc.). I usually Try to keep ES under 20 and don't really freak out about it until it exceeds 40 FPS. But, I'm only shooting out to 400 yards. If I can hold to less than 1/2 MOA vertical dispersion at that distance, I'm happy. You may not be. Anyway, you might want to bite the bullet and go with 5 shot groups for purposes of testing. I don't blame you for not wanting to burn the powder and take the kicks but it may be more informative to do so. Sometimes I just compromise and shoot 4-shot groups!

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I've got about .3 moa vertical @ 300. I'm just trying to keep barrel life as long as I possibly can with 3 shot groups. It's a sendero contour barrel, which would be my personal lower limit on barrel diameter in that cartridge. It builds plenty of heat in just 3 rounds.

djfergus said:

I've got about .3 moa vertical @ 300. I'm just trying to keep barrel life as long as I possibly can with 3 shot groups. It's a sendero contour barrel, which would be my personal lower limit on barrel diameter in that cartridge. It builds plenty of heat in just 3 rounds.

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Oh, I get it. Don't blame ya!

Shadowwalker said:

Excellent reply. I have a 6.5X47 all custom with a 7.2 standard deviation. .219 agg on 10 shots @100 Lots of homework but it pays off.

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The key to controlling vertical within the loaded round is a very low SD.

djfergus said:

It's a pro chrono. It's been questionable before in the evening while sitting in the shade.

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My chrono likes sunny blue skies.

I see a lot of shooters trying to achieve a super gun. Super guns are super by design not accident.
For what it's worth...I spent 50 years shooting serious benchrest in rimfire, centerfire and airgun. Have worked for a major arms mfger in R&D for years plus a long personal tenure along side Ed Shilen when he made real barrels and everyone In the shop was a serious shooter. In fact I was there in N.Y. when we made our first buttoned bbl and have the first target ever shot with a Shilen barrel. I am a former world champion in benchrest.
This is a really tough game where everything counts. If you seek the Grail you will find extreme accuracy is a multi layered exercise in absolute perfection. The one who reduces the variables the most, all other things being equal will win. History dictates and supports this.
Not only does the ctg have to be purpose driven, the bbl maker has to have serious credentials, the action has to be designed correct, the chamber has to be a work of art as does the crown. The brass, primers and projectiles must be historically accurate and flawless. Winners win because they know something you do not. Look at what they are using. They are not using it because it doesn't work.
The bedding, chamber and crown must be done by a master not your local smith. You find these guys in the benchrest field. You must embrace their knowledge and methods or you will get beat by someone who does.
They also shoot the smallest groups on the planet so must know how to acheive tiny groups. Learn from them.
Loading becomes an art form in exact repeatability to acheive low SD here.
You will find Accuracy is always found in the details.
Thiis sport requires severe dedication and effort and an open mind.
It also helps if you learn how to really shoot. The best made gun in the world is useless unless you learn how to shoot it and the best shooter in the world will lose with a poorly made gun.
Wind and it's affect on projectiles are a science unto it's self and takes years to understand and predict.

gator378 said:

My chrono likes sunny blue skies.

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Yes, mine does also. What makes me suspicious it that about a year ago, I shot three rounds into one hole @ 100 yards with a 300 winmag over this chrono about the same time of evening, at the same shooting location and I had about 60 fps spread showing on the chrono. I supected it was lying that day also. Was just a little sliver of sun above the horizon that evening.

Y

Shadowwalker said:

I see a lot of shooters trying to achieve a super gun. Super guns are super by design not accident.
For what it's worth...I spent 50 years shooting serious benchrest in rimfire, centerfire and airgun. Have worked for a major arms mfger in R&D for years plus a long personal tenure along side Ed Shilen when he made real barrels and everyone In the shop was a serious shooter. In fact I was there in N.Y. when we made our first buttoned bbl and have the first target ever shot with a Shilen barrel. I am a former world champion in benchrest.
This is a really tough game where everything counts. If you seek the Grail you will find extreme accuracy is a multi layered exercise in absolute perfection. The one who reduces the variables the most, all other things being equal will win. History dictates and supports this.
Not only does the ctg have to be purpose driven, the bbl maker has to have serious credentials, the action has to be designed correct, the chamber has to be a work of art as does the crown. The brass, primers and projectiles must be historically accurate and flawless. Winners win because they know something you do not. Look at what they are using. They are not using it because it doesn't work.
The bedding, chamber and crown must be done by a master not your local smith. You find these guys in the benchrest field. They do however shoot the smallest groups on the planet so must know how to acheive tiny groups.
Loading becomes an art form in exact repeatability to acheive low SD here.
You will find Accuracy is always found in the details.
Takes sport requires severe dedication and effort.
It also helps if you learn how to shoot. The best made gun in the world is useless you learn how to shoot it and the best shooter in the world will lose with a poorly made gun.
Wind and it's affect on projectiles are a science unto it's self and takes years to understand and predict.

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All good sound advice. I don't have any desire to compete. I usually set up my hunting rifles to shoot 5/8 moa or less with e.s. around 10 fps or less. They serve my purpose if I can get them to do that. I have two rifles that will do better than that and the cold bore shot is dead on. I'm working on making this one the same as the other two if possible.

djfergus said:

Y

All good sound advice. I don't have any desire to compete. I usually set up my hunting rifles to shoot 5/8 moa or less with e.s. around 10 fps or less. They serve my purpose if I can get them to do that. I have two rifles that will do better than that and the cold bore shot is dead on. I'm working on making this one the same as the other two if possible.

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djfergus said:

Y

All good sound advice. I don't have any desire to compete. I usually set up my hunting rifles to shoot 5/8 moa or less with e.s. around 10 fps or less. They serve my purpose if I can get them to do that. I have two rifles that will do better than that and the cold bore shot is dead on. I'm working on making this one the same as the other two if possible.

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It does not mean that you have to become a competiive shooter. The object no matter what the chosen displine is to have the projectile hit where the crosshairs are. My point is that there are methods available to shooters to achieve ive Nervanaavailable to all shooters to make it all come together.