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ES/SD vs group size

emslife1

Hi guys,

I am new to the forum, but have been able to use a lot of discussions to figure out issues. I have tried doing a google search, but could not find the answer to my question.

I just bought a new chronograph to dial in my reloading skills. I have read that going off just group size is not a definitive of reloading practices, so I got the magneto sporter to see how well I am doing.

I was able to get single digit numbers for SD/ES on some of the loads but the groups were still bigger than an inch. The work up was based on the accuracy tech work up using the chronograph first, and then going back to check group sizes.

What causes single digit numbers and open groups?
 
What kind of rifle (factory? Custom? Cartridge?) and distance are you testing at?

How long have you been shooting this particular rifle? How long in general?

For the time being I'll end with: what's the smallest group (how many rounds?) you've ever shot with it at this same distance?

Those two questions of yours (what causes single digits <and> open groups?) have vexed us all for many, many years. Nailing down which may be affecting your results is (one of the reasons) why this forum exists.
 
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.
 
If you are shooting a factory rifle and barrel with no accuracy tuning other than load development it can be a trial. All you can do is optimize what your weapon can deliver and save pennies for custom barrel, bedding job, trigger, etc.. Also optimize your bench, bipod, or sling technique as that is half (or more) of the equation in the beginning.
 
Sample size can be one reason. Plenty of guys using a lab radar over the course of a match and a days shooting have interesting stories with respect to what the numbers mean and how they should influence decisions.
There are plenty of threads here from the 1k BR guys that talk about the loads indicating the lowest numbers not being the load that shoots the smallest group at distance.
It could also be you have good ignition and burn through primer and powder choice, hence good ES/SD numbers but a poor seating depth choice so the bullet exit is at a point in the barrel vibration which varies shot to shot as barrel harmonics are influenced by more than just consistent FPS of the projectile.
While changing seating depth might change the numbers you could well end up with a better balance of the two. i.e. high single digit/low double digit numbers but small groups and a better over all agg.
 
emslife1 said:
Hi guys,

I am new to the forum, but have been able to use a lot of discussions to figure out issues. I have tried doing a google search, but could not find the answer to my question.

I just bought a new chronograph to dial in my reloading skills. I have read that going off just group size is not a definitive of reloading practices, so I got the magneto sporter to see how well I am doing.

I was able to get single digit numbers for SD/ES on some of the loads but the groups were still bigger than an inch. The work up was based on the accuracy tech work up using the chronograph first, and then going back to check group sizes.

What causes single digit numbers and open groups?
Click to expand...

You might try working with the seating depth. A few years ago I shot 30 rounds with 6 different seating depths. I fired 1 shot each from group 1 through 6 and then started over again. These are 168 grain .308s at 100 yards off a bench. The velocity is only about 2,560 - 2,570 fps. This load also shot 4 out of 5 under 1/2" and the 5th at total 5/8" at 215 yards the same day. Some bullets are more sensitive to seating depth, some rifles prefer one bullet to another and some like certain powders and velocities.
Shot.jpg
 
spclark said:
What kind of rifle (factory? Custom? Cartridge?) and distance are you testing at?

How long have you been shooting this particular rifle? How long in general?

For the time being I'll end with: what's the smallest group (how many rounds?) you've ever shot with it at this same distance?

Those two questions of yours (what causes single digits <and> open groups?) have vexed us all for many, many years. Nailing down which may be affecting your results is (one of the reasons) why this forum exists.
Click to expand...

I am shooting a Remington 700 in 243 win. Just got the rifle, so I am new with it. I am using a 95 grain SST, CCI BR2 primers, H4831, and hornady brass with everything prepped. Also used Lees Dies. Nothing has been done to the rifle itself. I do all my workups at 100 yards.

I have been reloading for over a year without the use of a chronograph. My first rifle was a savage 10 in 308 win, and no modifications done to it. I was able to get sub .5 inch moa groups at 100 yards, and shoot it out to 1000 yards using premium components. I never used a chronograph then. My rifle is currently getting a custom fitted barrel by phoenix custom rifles, so ill be reworking it up when I get it back.

I shoot off of a lead sled to eliminate as much error as possible.
 
Es/Sd matters to a point. You cant load ammo with an es of 50 fps and expect good groups at distance, although they may shoot small at 100. But once you get under 20 fps ES, ES becomes irreverent. Example, load 1 with 18 es vs load 2 with 3 es. Say they both shoot excellent at 100. The load with 18 es may very well shoot smaller at 600 or 1000 than the load with 3 es. Or it may not. You have to shoot at those extended ranges to know. If your talking short range, the ES really doesnt matter.
 
emslife1 said:
I am shooting a Remington 700 in 243 win. Just got the rifle, so I am new with it. I am using a 95 grain SST, CCI BR2 primers, H4831, and hornady brass with everything prepped. Also used Lees Dies. Nothing has been done to the rifle itself. I do all my workups at 100 yards.

I have been reloading for over a year without the use of a chronograph. My first rifle was a savage 10 in 308 win, and no modifications done to it. I was able to get sub .5 inch moa groups at 100 yards, and shoot it out to 1000 yards using premium components. I never used a chronograph then. My rifle is currently getting a custom fitted barrel by phoenix custom rifles, so ill be reworking it up when I get it back.

I shoot off of a lead sled to eliminate as much error as possible.
Click to expand...
That was excellent for a stock .308 rifle. Hopefully the new one will be a tack driver.
 
I saw a 6ppc pound tiny groups with an ES that would make your jaw drop. I have shot loads at 600 that had terrible ES and tight vertical and on the flip side, watched single digit ES put up big vertical.
I can't seem to find the post by Alex Wheeler but if you search ''positive compensation" on this site or the same by Bill Calfee, you will find your answer.
 
Barrel harmonics are the key to small groups. Powder charge and seating depth are used to find that accuracy node.

Low sd's insure that velocities are consistent. This shows up in vertical dispersion at longer ranges.

Low sds without the coresponding barrel harmonics won't get you there

You can lower your sds with accurate powder charges and consistent neck tension
 
T-shooter said:
You might try working with the seating depth. A few years ago I shot 30 rounds with 6 different seating depths. I fired 1 shot each from group 1 through 6 and then started over again. These are 168 grain .308s at 100 yards off a bench. The velocity is only about 2,560 - 2,570 fps. This load also shot 4 out of 5 under 1/2" and the 5th at total 5/8" at 215 yards the same day. Some bullets are more sensitive to seating depth, some rifles prefer one bullet to another and some like certain powders and velocities.
Shot.jpg
Click to expand...




I think my next step will be to play with the seating depth for three of the best charges with the best SD/ES to see what kind of groups I can get. If I am already seated close to the Lands, and seat the projectile further away, wont that increase the overall pressures, and alter the SD/ES? If thats the case, then I can pick the best rounds with lower FPS so that I dont over do it with pressure.

So much that goes into precision reloading haha. Its almost an obsession. Thanks for all the replies guys. Will update everyone on my findings.
 
emslife1 said:
I think my next step will be to play with the seating depth for three of the best charges with the best SD/ES to see what kind of groups I can get. If I am already seated close to the Lands, and seat the projectile further away, wont that increase the overall pressures, and alter the SD/ES? If thats the case, then I can pick the best rounds with lower FPS so that I dont over do it with pressure.

So much that goes into precision reloading haha. Its almost an obsession. Thanks for all the replies guys. Will update everyone on my findings.
Click to expand...
It shouldn't increase the pressure, usually being too close to the lands is what does it. I guess going too far back would diminish the case capacity a little. The best way is to just try it. Maybe in .005" increments. If you find a sweet spot, go back and try .002" each way. Don't trust 3 round groups when getting close. 5 is better and to verify anything, do 10.
 
In the past you have done good group sizes without a chronograph. Then you attempted to use the chronograph to workup good groups and it hasn't worked for you. At this point I would suggest that you work up your groups without the chronograph and after you have good groups use the chronograph to get the information on the loads velocity. As it is you are chasing the numbers to find accuracy when you should get accuracy first and then chase the numbers without affecting your accuracy.
 
emslife1 said:
Hi guys,

I am new to the forum, but have been able to use a lot of discussions to figure out issues. I have tried doing a google search, but could not find the answer to my question.

I just bought a new chronograph to dial in my reloading skills. I have read that going off just group size is not a definitive of reloading practices, so I got the magneto sporter to see how well I am doing.

I was able to get single digit numbers for SD/ES on some of the loads but the groups were still bigger than an inch. The work up was based on the accuracy tech work up using the chronograph first, and then going back to check group sizes.

What causes single digit numbers and open groups?
Click to expand...
I hope you didn't try to shoot groups with the magneto attached. That changes barrel harmonics. Matt
 
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