Hornady .257 120gr HP

The Hornady 25 caliber 120gr HP has been discontinued for some time. I have half a box from a long time ago and picked up a new box online a little while back. Judging from the boxes the box I recently acquired is an older bullet. I’m planning on using them in my 257 Roberts AI, I used one of the newer (partial box) bullets to find my seating depth in the rifle. The measurement with the comparator for the bullet touching the lands was 3.538”, so I seated it at 3.528”, .010” off the lands, the die micrometer was set at .572. I misplaced that box of bullets so grabbed a few of the older (full box) bullets to load a test load. I seated them with the same seating die setting as the other, and something looked wrong. I measured these rounds and they were 3.535”. Now I was curious and took another bullet from the full box and found the lands in the rifle with it. Touching the lands with that bullet was 3.535”. I adjusted the seating die micrometer in .010 and got those bullets seated .010” off the lands, measuring 3.525” with the comparator. So now I have one round at 3.528”, micrometer at .572, and four rounds at 3.525”, micrometer at .562, all 5 are .010” off the lands. There definitely was changes made to the bullet through the years, and I’m hoping there won’t be a big change in loading from one to the other.


JTD

I doubt that in a X57 family case .013 will make a significant difference in the pressures unless you are at max loads. The actual case intrusion mat be less owing to the larger dia being longer on the new bullet .
That doesn't sound like what I meant to say.
If the full dia is longer on the new version, the bearing length and ogive , the nose will be shorter and will result in a shorter bullet overall . Then the length at the same OAL will occupy less case space . The base of the new bullet is probably very close to the same place as the old bullets . Target HPs can exaggerate this .

I had definitely thought exactly what you are saying. I left them loaded the way they are because I have loaded one each of 46.5gr. 47.0gr. 47.5gr. 48.0gr. And 48.5gr of RL 19. At this point I’m just looking for my max powder charge with this bullet powder combo, and get a general idea of velocity before I start actual load development. I feel it will be fine for this test.

I hope that after I find my load with the one bullet that I will not have to deviate from it much when I start using the other bullet.


JTD

I always measure that in each new lot of bullets and write the number on the inside of the box lid. They often vary some, although not by that much. You approach your setup much the same way I do.

I have noticed minor differences in bullets at times, but what really got me was these were noticeable to the naked eye, my shitty eyes! Here is a picture, I don’t know if it will show the difference in shape well enough for you guys to see.

https://uploads.tapatalk-cdn.com/202...0af5cf564c.jpg


JTD

That displays exactly what I was trying to say .