OzFclass

G'day
the image attached is from some load testing with a .284Win
- all five shot groups
- new Lapua brass necked up from 6.5
- Moly coated 183 Sierra
- all loads at 0.010" jump
- 2209 powder, GM 210 primers



The ES is fairly tight at 51.3 gn, but convention says I should be looking in the area where the curve is flattest - around 50 gn but I think the ES is too wide.
The OBT for this barrel is 51.7gn - also a bit too much ES there.
All groups for this test were fairly ordinary at 0.5" to 1" which I put down to the ) .010" jump?. I have only used hybrids before so I am looking for input as to how/where to proceed from here.
What sort of increments should I make in the jump - starting point?
Comments welcome
Pete

My barrel shows a preference for jump with mollied 183 SMK bullets. 3 shot groups at 100 yds were best from .006" to .015" jump, this was at 22 degrees C, Groups were slightly enlarged one hole from .006" to .012" with vertically strung groups from .012" into the lands to .006 jump. I have suspended testing for the time being, too damn cold, I prefer to do my load development at around 22/26 degrees. The quest continues, but with promising results.
Keith H.

Looks like a narrow node to me Pete - your load data at 51.3gr looks good, but 51.1 and 51.5 the ES/SD open up again. I've never shot the Sierra 183gr, but I know Rod D and Albert Van Wyk have got them working, and they shoot them as good as anything else I've seen. With that particular bullet I'd be inclined to start with a jam and work back in 5 thou increments into jump territory to see if your group sizes shrink.

Here is an article from the lead designer:
https://sierrabullets.wordpress.com/201 ... matchking/

In 308, I'm finding the mollied Sierras like a 6-8 thou jam.
On the SAUM with 283s mollied I had an SD over 5 shots of 2.7 with a 5 thou jam but opted for the better group with an SD of 13.2. at 15thou jump.
I figure an SD is subject to more error in measurement than a ruler on the target face.

What Tim said, either .005-.010 jam or .006 jump works for me in 284 or SAUM