Post by: jrebel on June 11, 2018, 02:30:59 PM
Two loads....both the exact same with exception of primers. Two five shot groups per load (one chono'd with V3 hanging off the barrel and 5 without for grouping). Both had identical FPS
Remington 9 1/2 primers: SD 5 (excellent), FPS 3065, 180 grain accubond. 1.5" group w/o chrono hanging on barrel
Federal 215's: SD 7 (Excellent but not as good as above), 180 grain accubond. .75" group w/o chrono hanging on barrel.
Why double the group with a better SD and exact same FPS??? I was shooting off a Caldwell Fire Controll so have a hard time believing it was me and the fundamentals.
Post by: Oh Mah on June 11, 2018, 02:41:57 PM
Post by: jrebel on June 11, 2018, 02:45:36 PM
The one with tighter group is not as good why?
I love that 5 shot group......nothing wrong at all. I just find it weird that that group was with the Federal 215's which has a higher S/D and the Remeington 9 1/2's won't group as well with a lower S/D.
You would think with the S/D's being very close and FPS being identical that they would group the same....but the Remington 9 1/2's don't group as well.
Post by: BULLBLASTER on June 11, 2018, 02:46:11 PM
Post by: jrebel on June 11, 2018, 02:48:05 PM
In this case it seems like it works better with the 215 primers for that particular combination. Who knows why, and who really cares. Use the 215 and be happy or repeat the test to see if the results are consistent :twocents:
The results with the 215's are repeatable. I was just trying the Remington's because I could.......I agree the Federal's are the winners. I just thought it was weird.
Post by: Oh Mah on June 11, 2018, 02:49:08 PM
Post by: Fl0und3rz on June 11, 2018, 02:58:30 PM
https://whatis.techtarget.com/definition/law-of-large-numbers
Post by: bobcat on June 11, 2018, 03:03:07 PM
Post by: Reidus on June 11, 2018, 03:12:39 PM
Post by: jrebel on June 11, 2018, 03:17:29 PM
barrel harmonics. SD dont mean much at all for grouping at 100yds. Lot of benchrest guns shoot bugholes at 100yds with terrible sd.
Just because I find it fascinating.....why would the primer change the harmonics? I have never seen this before so again....I just find it fascinating so thought I would share and see if any had any thoughts.
Post by: Reidus on June 11, 2018, 03:29:28 PM
barrel harmonics. SD dont mean much at all for grouping at 100yds. Lot of benchrest guns shoot bugholes at 100yds with terrible sd.
Just because I find it fascinating.....why would the primer change the harmonics? I have never seen this before so again....I just find it fascinating so thought I would share and see if any had any thoughts.
Different pressure curve :dunno:
I was shooting 300wsm with wlr primers with good accuracy and not that great of sd. tried fed 210s and sd dropped dramatically with good accuracy. I dont recall the velocity being much different but its been a while. Kind of like what makes a barrel a hummer and allows it to shoot through wind better than other barrels. Its pretty interesting stuff.
Post by: Reidus on June 11, 2018, 03:31:44 PM
Post by: jasnt on June 11, 2018, 03:38:29 PM
it wouldn’t change harmonics. It’s more likely you need more rounds for each group (10 shot)to show you they are both group the same at 100. Stretch it out farther and you will see a slight improvement with the lower sd. Chances are YOU just had a better group with that primer and the primer change had little to do with it. How consistent is your cheek weld?barrel harmonics. SD dont mean much at all for grouping at 100yds. Lot of benchrest guns shoot bugholes at 100yds with terrible sd.
Just because I find it fascinating.....why would the primer change the harmonics? I have never seen this before so again....I just find it fascinating so thought I would share and see if any had any thoughts.
Post by: j_h_nimrod on June 11, 2018, 07:11:31 PM
it wouldn’t change harmonics. It’s more likely you need more rounds for each group (10 shot)to show you they are both group the same at 100. Stretch it out farther and you will see a slight improvement with the lower sd. Chances are YOU just had a better group with that primer and the primer change had little to do with it. How consistent is your cheek weld?barrel harmonics. SD dont mean much at all for grouping at 100yds. Lot of benchrest guns shoot bugholes at 100yds with terrible sd.
Just because I find it fascinating.....why would the primer change the harmonics? I have never seen this before so again....I just find it fascinating so thought I would share and see if any had any thoughts.
That is correct in theory, but incorrect in application. The primer will not necessarily change the harmonics of a rifle, but the difference in the primer cup thickness, combustion heat, pressure curve, etc. will effect overall accuracy. I have had some loads over the years with abysmal SDs that shot very well and other loads with very good SDs that did not group for crap. It is all voodoo...
He did state it was a repeatable issue and that this was not the only target showing issues.
Post by: Biggerhammer on June 12, 2018, 08:13:51 PM