Riddle me this???

[jrebel]

Riddle me this.....

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. 

[Oh Mah]

The one with tighter group is not as good why?I guess the federal primers are worth the extra money.

[jrebel]

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. 

[BULLBLASTER]

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 

[jrebel]

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 

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.

[Oh Mah]

Yeah,This has been talked about a lot on other forums as well.The idea is that the Federal primers are better quality which equates to better control and that equals better accuracy tighter groups.They are more consistent than the others with the powder being used.Some times the other powders work better with other primers though  .

[Fl0und3rz]

It's possible that with five shot groups, you're seeing more noise than signal, I suppose.

https://whatis.techtarget.com/definition/law-of-large-numbers

[bobcat]

You need to shoot more groups in order to get a valid conclusion.

[Reidus]

barrel harmonics. SD dont mean much at all for grouping at 100yds. Lot of benchrest guns shoot bugholes at 100yds with terrible sd.

[jrebel]

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.   

[Reidus]

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

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.

[Reidus]

since a lot of the barrel vibration comes from the firing pin, wouldn't a harder or softer primer cause a difference in the harmonics?.....just a thought.

[jasnt]

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.   

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?

[j_h_nimrod]

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.   

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?

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.

[Biggerhammer]

I don’t think any big game animal is going to care which primer you use the results will be the same. It’s going to leave a mark!