wider spreads but tighter groups?

tahunua001 · October 7, 2014, 11:15 PM

hello all,
I recently switched from an RCBS balance beam scale to a charge master automatic scale/measure combo. I've noticed a strange phenomenon since I made this switch. my standard deviation and extreme spreads have been much larger than with my old setup but my average groups have been much tighter than with my old setup.

anyone have similar instances? possible explanations?

Bart B. · October 8, 2014, 06:27 AM

Are you referring to velocity?

If so, then something else changed. It's not charge weights. You may not be holding the rifle as consistantly against your shoulder. That alone can make a 4X difference in the numbers.

tahunua001 · October 8, 2014, 09:58 PM

I chrono from a lead sled. and yes, extreme spreads in velocity, are up, groups are smaller, interestingly enough.

bfoosh006 · October 9, 2014, 08:26 AM

You have just seen why I don't put to much merit in SD and ES figures....

I have noticed the same thing over the decades... in both factory and reloaded ammo.

IMHO, there are just to many variables in reloading and shooting for Low ES and SD to have any truly meaningful effect on overall accuracy.... I would think how clean your barrel is would matter more.

green_MTman · October 9, 2014, 09:35 AM

what is meant by standard deviation and extreme spreads.if groups are tight than whats the problem.you may mean flyers.so you mean that before you got a flyer every 20th shot but groups were bigger.now you have smaller groups but a flyer every 12th shot.

if this is the case,i mean 2 inch groups at 100 is fine for hunting out to 300 yds and reliability being crucial in the field your old shots may have been more practical.

im still not sure what your post means

TATER · October 9, 2014, 04:47 PM

Just a stab in the Dark.. Could you be controlling the runout better now for some strange reason ?

Metal god · October 10, 2014, 09:16 AM

Have you double checked your digital scale to your beam scale or check weights yet . I've seen with my own loads that a .3gr difference does not change much but can just a tad . What does smaller groups mean 2" to 1" / 1" to .5" / .9 to .7 ?? . I would not put to much into ES - SD unless the rifle is locked into a machine rest or let to freely recoil . Any inconsistent hold on the rifle can and will change your ES-SD

October 7, 2014, 11:15 PM	#1
tahunua001 Senior Member Join Date: July 21, 2011 Location: Idaho Posts: 7,839	wider spreads but tighter groups? hello all, I recently switched from an RCBS balance beam scale to a charge master automatic scale/measure combo. I've noticed a strange phenomenon since I made this switch. my standard deviation and extreme spreads have been much larger than with my old setup but my average groups have been much tighter than with my old setup. anyone have similar instances? possible explanations? __________________ ignore my complete lack of capitalization. I still have no problem correcting your grammar. I never said half the stuff people said I did-Albert Einstein You can't believe everything you read on the internet-Benjamin Franklin

October 8, 2014, 09:58 PM	#3
tahunua001 Senior Member Join Date: July 21, 2011 Location: Idaho Posts: 7,839	I chrono from a lead sled. and yes, extreme spreads in velocity, are up, groups are smaller, interestingly enough. __________________ ignore my complete lack of capitalization. I still have no problem correcting your grammar. I never said half the stuff people said I did-Albert Einstein You can't believe everything you read on the internet-Benjamin Franklin

October 10, 2014, 09:16 AM	#7
Metal god Senior Member Join Date: April 10, 2012 Location: San Diego CA Posts: 6,876	Have you double checked your digital scale to your beam scale or check weights yet . I've seen with my own loads that a .3gr difference does not change much but can just a tad . What does smaller groups mean 2" to 1" / 1" to .5" / .9 to .7 ?? . I would not put to much into ES - SD unless the rifle is locked into a machine rest or let to freely recoil . Any inconsistent hold on the rifle can and will change your ES-SD __________________ If Jesus had a gun , he'd probably still be alive ! I almost always write my posts regardless of content in a jovial manor and intent . If that's not how you took it , please try again .

October 8, 2014, 06:27 AM	#2
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	Are you referring to velocity? If so, then something else changed. It's not charge weights. You may not be holding the rifle as consistantly against your shoulder. That alone can make a 4X difference in the numbers.

October 9, 2014, 08:26 AM	#4
bfoosh006 Senior Member Join Date: February 17, 2009 Posts: 1,089	You have just seen why I don't put to much merit in SD and ES figures.... I have noticed the same thing over the decades... in both factory and reloaded ammo. IMHO, there are just to many variables in reloading and shooting for Low ES and SD to have any truly meaningful effect on overall accuracy.... I would think how clean your barrel is would matter more.

October 9, 2014, 09:35 AM	#5
green_MTman Senior Member Join Date: March 27, 2014 Location: southeastern Vermont,USA Posts: 325	what is meant by standard deviation and extreme spreads.if groups are tight than whats the problem.you may mean flyers.so you mean that before you got a flyer every 20th shot but groups were bigger.now you have smaller groups but a flyer every 12th shot. if this is the case,i mean 2 inch groups at 100 is fine for hunting out to 300 yds and reliability being crucial in the field your old shots may have been more practical. im still not sure what your post means

October 9, 2014, 04:47 PM	#6
TATER Senior Member Join Date: November 19, 2002 Location: Mississippi Posts: 963	Just a stab in the Dark.. Could you be controlling the runout better now for some strange reason ?