284 Win - jump and jam

Get or give advice on equipment, reloading and other technical issues.

Moderator: Mod

Message
Author
PeteFox
Posts: 598
Joined: Tue Oct 16, 2018 5:20 pm
Location: 7321 Tas.

284 Win - jump and jam

#1 Postby PeteFox » Mon Jun 20, 2022 2:17 pm

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

Strahan 19-06-22 core data.jpg


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
You do not have the required permissions to view the files attached to this post.

KHGS
Posts: 934
Joined: Thu Oct 20, 2005 12:46 am
Location: Cowra NSW

Re: 284 Win - jump and jam

#2 Postby KHGS » Mon Jun 20, 2022 2:49 pm

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.

willow
Posts: 567
Joined: Sat Aug 15, 2015 9:51 pm

Re: 284 Win - jump and jam

#3 Postby willow » Mon Jun 20, 2022 7:50 pm

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/

Tim L
Posts: 876
Joined: Mon May 19, 2014 7:11 pm
Location: Townsville

Re: 284 Win - jump and jam

#4 Postby Tim L » Mon Jun 20, 2022 9:09 pm

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.

saum2
Posts: 1046
Joined: Fri Jun 13, 2008 12:22 am

Re: 284 Win - jump and jam

#5 Postby saum2 » Tue Jun 21, 2022 8:59 am

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


Return to “Equipment & Technical”

Who is online

Users browsing this forum: No registered users and 46 guests