Load development for 140 AccuBonds

[Irish]

Hi all

I have been working up a load for the 140 Gr AB in my Remington 700 using H4831SC. As I am kind of new to this I was wondering if someone might explain why the following is happening.

57 Gr of powder gave me a 3 1/2 group at 100 yards. The Group was 4 inches left of aim point
58 Gr of powder gave me a 2/34 inch group at same distance but the point of impact had moved to within 2 inches of aim point
58.5 Gr = 2 inch group and the aim point and point of impact were similar.

Why is the point of impact changing depending on the powder charge. If it was changing on the elevation plane I could understand it but on the windage plane it has me puzzled.

It seems to me that the higher the load the tighter the group so I'm now going to try 59 Grs behind the 140 AB. However all data I have read says this it the max load for the 140 gr projectile. Is that the case or could I go higher. I am not getting any pressure signs at all at present.

By the way at the same time as above 56 Gr of powder behind a 150 gr Norma Onyx gave me 1 inch group with a point of impact that was 3 inches high but on for windage.

Thanks in advance for what is probably a very simple explanation

Hugh

 

[JD338]

What caliber are you shooting?

JD338

 

[Irish]

sorry ......told you i was new...........270 cal

 

[JD338]

sorry ......told you i was new...........270 cal

No worries.

Which 270? :?
I assume 270 Win but maybe you are loading light for a 270 Weatherby or 270 WSM.

JD338

 

[Irish]

Yes 270 win . Not many of the other kind in Ireland

Hugh

 

[tjen]

Every barrel has harmanics or vibration patterns. Changing the amount of powder changes the timing as to when the bullet exits the barrel and where the barrel is in its vibration pattern. It could be up down left right ect... We generaly think the heavier the charge the faster the bullet so it should not drop as much and be higher. But it could be any where do to vibration/ timing. After loading up to Max charge for your gun you can then very the OCL to match these loads to your gun for the tightest group size.
With leverguns and their cartridges having cannelured bullets verying the charge is most ofton the only option to tune in more accurate loads.

 

[Antelope_Sniper]

If you want a real trip, try changing primers with that load. Try CCI 200, and then try Winchester Large Rifle Magnum primers. In my experience, by just changing the primer these loads will shoot 12 inches apart. That's why group size is all that matters. You can always move your point of impact.