Interesting Observation.

[Dead Eye Dick]

Shooting my RPR. Previously loaded 20 rounds of 6.5 CM for a Kimber Hunter. Did not work out so well so I dropped the project. The bullet used was a 130 grain Berger. Since I had never tried them in the RPR, I thought I would give the 130 grain Bergers a try.

The RPR shoots 143 Hornady ELD-X’s and Berger 144 hybrids almost equally well, getting some pretty good groups even for this oldster. They get easily around a half inch for three shots. However, the 130 Berger’s put three shots in 2 inches. Same powder, same primer and OAL.

Not a problem, I am happy with the Hornady 143’s and the Bergers. Just thought it was wild that one firearm would go from a tack driver to a shotgun with a change of bullets. (And later in the day, shooting at 500 and 600 silhouettes, it was spot on with the 144 Bergers. )

 

[straightshooter1]

Shooting my RPR. Previously loaded 20 rounds of 6.5 CM for a Kimber Hunter. Did not work out so well so I dropped the project. The bullet used was a 130 grain Berger. Since I had never tried them in the RPR, I thought I would give the 130 grain Bergers a try.

The RPR shoots 143 Hornady ELD-X’s and Berger 144 hybrids almost equally well, getting some pretty good groups even for this oldster. They get easily around a half inch for three shots. However, the 130 Berger’s put three shots in 2 inches. Same powder, same primer and OAL.

Not a problem, I am happy with the Hornady 143’s and the Bergers. Just thought it was wild that one firearm would go from a tack driver to a shotgun with a change of bullets. (And later in the day, shooting at 500 and 600 silhouettes, it was spot on with the 144 Bergers. )

Your observation is soooooo, common!

ANY piece of a cartridge that's changed (e.g. bullet, powder, primer, COAL, CBTO, etc) will have an effect on the precision one will see on paper. The fact that the 130 gr Berger is 13-14 grs ligher than those other bullets means that the difference in weight alone changes the pressure dynamics being applied to the bullet. Also, that 130 gr Berger has a different BTO than than those other bullets and when loaded to the same OAL the distance to the lands is very different, which often makes a significant difference in the way the bullet will perform.

When you switch to a bullet with that big a difference, you need to rework your load, changing the amount of powder your charging the cases with and even the seating depth where your OAL will be different.

Now you know.

 

[Dead Eye Dick]

Your observation is soooooo, common!

ANY piece of a cartridge that's changed (e.g. bullet, powder, primer, COAL, CBTO, etc) will have an effect on the precision one will see on paper. The fact that the 130 gr Berger is 13-14 grs ligher than those other bullets means that the difference in weight alone changes the pressure dynamics being applied to the bullet. Also, that 130 gr Berger has a different BTO than than those other bullets and when loaded to the same OAL the distance to the lands is very different, which often makes a significant difference in the way the bullet will perform.

When you switch to a bullet with that big a difference, you need to rework your load, changing the amount of powder your charging the cases with and even the seating depth where your OAL will be different.

Now you know.

First Point, please don’t be offended. You made Good points all.

Excepting the reworking of the OAL, this was a completely different loading, optimized for the bullet weight. I had previously seen major differences in point of aim when switching from 7mm 140 grain Sierra Match Kings and Speer 145 SBT’s out of a 15 inch barreled XP-100 so knew there would be differences. However, I marvelled at the groups differece in size. Just thought this was an interesting observation. That the difference would be so great from an individual rifle that has shown excellent grouping with a variety of bullets and loads was unexpected.

Another point of interest, this particular rifle shoots the 144 Berger and the 143 Hornady very closely to the same point of aim. I can use them interchangeably. Of course the powder charge is different for each bullet (one half grain less for the Berger.). Going to the same charge that the Hornady shoots well, opens up the group considerably. Further experimentation with Sierra Match Kings (140 Grain) demonstrated that with Serra’s recommended landings (again working up from the basic load to near maximum) demonstrated quite a bit more velocity but the accuracy was quite as good.

So, the rifle is happy with a hunting bullet and a match bullet. However, sometimes it is good to try new things.

 

[nn8734]

It would have been interesting if that 130 Berger load was plug and play with <= .5 MOA performance.

The 130s are good bullets. I haven’t started reloading yet for my 6.5 cmoor but the Federal Gold Medal Match stuff w/the 130 AR Hybrids performs very well in mine.