The river receded, the deer finally wandered far enough away for me to ignore, and the bench was put to use. The Chrony and the targets gave me some interesting feedback on 6 different bullets, all on top of the factory charge of powder.
The rifle used is a CZ550 American that I put a Nikon Buckmaster 3-9x40 BDC scope on, in CZ factory rings. Single set trigger, which I did use after the first round; alternating between each load. 25" barrel.
The factory powder charge averaged 59.1gr, with a high of 59.5gr, and a low of 58.8gr. They used an extruded powder that appears to have been slightly compressed under the 286gr solid. As all the other bullets were slightly shorter, both overall and below the cannelure on those with one, I believe the powder was not compressed with any of the replacement bullets. None of these showed any pressure signs after firing.
On the day of shooting, temp was about 73*-74*. (Broke my thermometer not too long ago and haven't replaced it yet). Breeze was out of the south at 3-5mph, roughly 90* R-L. Took the time to walk to the target after every round and marking the target, giving the barrel time to cool between shots (3-5 minutes between).
Shot from the bench with my rest screwed up to allow a fairly vertical posture; very similar to shooting off the sticks, but sitting.
After the comments on getting lower than listed velocities, I was mildly surprised to find my readings to be above the velocity shown on the box. As I have spent a lot of time to eliminate lighting issues that can cause discrepancies, and have checked other loads against friend's chronographs, I think these are reasonably accurate findings.
The factory Nosler 286gr Solids had the highest average velocity at 2554fps, and also the lowest spread at only 8fps. 5 rounds gave me a "huntable" group just over 2" (largest group of the day). They also had a POI roughly 1" right of everything else.
The 286gr Partitions had the lowest average velocity at 2505fps, with the spread at 16fps. Slightly better group at 1.77".
The 285gr Norma Oryx averaged 2524fps, with the same spread as the Partition. And no surprise, to me anyway, printed at the same POI with a group size of 1.95". Based on trials of these two bullets in other calibers, I expected these to be interchangeable.
The PPU 270gr SP averaged 2557fps, right there with the 286gr Solid, but an inch higher POI, directly above everything else. This bullet played nicely with the rifle and had a 1.28" group with 3 cloverleafed.
Apparently, this combination really matched well with the 286gr Woodleigh PP/SN. Seated to a COL of 3.163", the 5 rounds averaged 2525fps, the worst spread at 23fps, but the best group at 1.05".
And the last bullet, a Hornady 286gr SP, averaged 2513fps and produced a 1.55" group. Only have a partial box of these, so this load was really just for fun.
With this outcome, I've pulled another 10 and replaced 5 with Woodleighs and 5 with the 270gr PPU to see if a 2nd round yields the same results.
The day of shooting I was slogging through a little mud and trickling water to reach my backstop. The 2nd round has been delayed as we had another storm roll through that evening and the next couple days, and my shooting range looked like this on the 23rd-
Might get back to the range in another day or so if duties as State Commissioner for Babe Ruth/Cal Ripken don't get in the way; as the month of July gets pretty busy with baseball tournaments. Warmer temps and no more rain have made it possible to get to the backstop without waders again. Looks like this tonight-
Quite frustrating. But fortunately, it allowed me to confirm a number of other loads that had been developed prior to August last year. After 30+ years of good service, the Chrony has been officially retired.
