Differences in Ammo accuracy

[KA1]

Hi guys, i went to zero my 6 Creed today and zeroed at 100 yds with Nosler 6 mm 90 gr AccuBond, i had half moa at 100 with 5 shot group, then I decided to try Hornady Black 105 BTHP and it was hitting 8 inches below aim.
I thought maybe it is hot barrel or something happened to the scope so decided to take another shot with the Nosler and yup dead center of aim.

could there be so much dufference or am I too new at this.

 

[JEFFPPC]

This is why you test. You did and have the answer. Never hurts to do a retest and verify. As a new guy reading and talking to others can help. But nothing beats trying things yourself. Remember lots of guys offer opinions on things they themselves be at did. Sorta like fake news.

 

[KMart]

could there be so much dufference or am I too new at this.

Yes

I once tested a Hornady against a Sierra bullet in 308. Can't remember the weight. Same everything except the bullet. The 2 bullets shot 6" apart at 100 yards.

it appears that you are shooting factory ammo. If you are, you changed everything. Brass, powder, primer, bullet brand, velocity and bullet weight.

 

[SSL]

I recently tried my first attempt at heavier (than I'm used to using) bullets in my .223. It is zeroed for 52-grain Hornady HPBT bullets and I started testing 68-grain Hornady HPBTs. Same powder (but lower weight, of course), cases, primers) at 100 yards. I started with a nice, tidy .32" group with the 52s that was well centered. Switching to the first load for the 68-grain bullets, the group, while quite nice for a first load test, was one inch low and nearly one and a half inches left. Switch back to the 52s and the group was right back where it belonged. Not the least unusual from my experience, though 8" does sound a bit excessive. As @KMart mentioned, you change every component with factory ammunition, so maybe that much difference is not necessarily a problem.

 

[Ned Ludd]

Due to differences in bullet weight, charge weight, seating depth, etc., comparing how the POI changes for different flavors of commercial ammunition may be like comparing apples to oranges. In fact, be cause the loads may be quite different, there is also barrel harmonics to consider, and how the launch angle of the barrel might affect POI for two different factory loads simply due the muzzle pointing higher or lower when each bullet exits the bore. Printing a groups 8" lower at 100 yd may seem like a lot, but the 2nd load has a bullet that weighs 15 grains more than the first. That means it probably has a lot slower velocity, and that the lighter, faster 90 gr bullet also shoots a bit flatter. Collectively, the difference doesn't seem shocking, even if it is a bit more than you'd ordinarily expect. As long as both loads group consistently around their own POI, I'd simply record the zeroes so I knew where to set the scope with each and not think much more about it.

 

[kvd]

I would say that accuracy is not at issue - just the POI - which can be expected for different bullet weights given no zero change. As long as both bullets group around one half MOA the knowledge of where the different points of impact are is useful.

 

[KA1]

Thanks guys,I appreciate everyone’s input.

 

[YEW PLUCKER]

Barrel harmonics is voodoo science. You never know where the tip of your barrel will be in space when it releases the bullet from a given load. That is why we test and retest, and zero and re-zero and continue to chase that perfect group.

 

[joshb]

Gosh....I can’t add anything! The posts above covered it all!

 

[M-61]

Due to differences in bullet weight, charge weight, seating depth, etc., comparing how the POI changes for different flavors of commercial ammunition may be like comparing apples to oranges.

Exactly
May as well change the rifles too.
Apples, oranges, and sheet rock