Seating depth challenge?

[Okanogan]

I thought this recent post on the Precision Rifle Blog was interesting enough to be worth sharing on the forum:

https://precisionrifleblog.com/2020/04/15/18-shot-bullet-jump-challenge/

There are a couple of other related posts on the blog regarding bullet jump that are also pretty interesting. I've followed the blog for several years now and particularly like the recent focus on reloading.

 

[Jud96]

I found all of their recent articles on seating depth to be extremely interesting and it has convinced me to change my mind on seating depth. I know I will be doing things differently when it comes to load development and seating depth. I have always heard and been told to jump bullets 0.005-0.050 off the lands. That basically has been the rule to follow for as long as I have been reloading. This evidence though really has me believing in it and I'm excited to see how this works for me.

 

[cape cove]

@Jud96 I always felt that way also until I rebarreled my 7/08 and couldn't get the accuracy I wanted. To make a long story short I done the Berger seating depth test all the way to .140 off the lands and found the accuracy I was looking for at .120 off the lands. Since then when I do a ladder test concerning seating depth I got to .140 off if I can.

 

[AZShooter]

It is worth pointing out that the 105 Berger they tested is a hybrid which typically is not that finicky as to seating depth. There were some minor changes in ES with the 6 x 47 and almost identical results with the 6 BRA with a wide range of seating depths, no surprises there.....


Glad to see they tried the 115 DTAC which is not a hybrid. This tells me there is a smaller window of performance based on seating depth.

For me this just confirms that I will continue to shoot hybrids when ever possible.

 

[Buck Fever]

I think it is very interesting but if you are shooting .338 instead of 6mm, it is hard to think the jump that works best for them will work best for you.

I dont want to burn up too much of my barrel life trying to figure it out so I can only hope that someone else generates the data.

 

[Jud96]

I think it is very interesting but if you are shooting .338 instead of 6mm, it is hard to think the jump that works best for them will work best for you.

I dont want to burn up too much of my barrel life trying to figure it out so I can only hope that someone else generates the data.

You don't have to burn up your barrel. These guys did extensive testing to back up their claims and prove it so people would believe them and not blow them off for working outside the norm. It really would only take like 20 shots to do a seating depth test. That's firing two rounds each in .010 increments from 0.020 off to 0.120 off. Shoot the shots at separate aiming points on a grid pattern. Map the point of impacts and pick the seating depths that have the same or very close point of impact to one another. This will find the "sweet spot" that will shoot good across a wide range of seating depths. If you're shooting a .338 magnum, your throat could erode several thousandths in just a box of hot reloads. Instead of chasing the lands every 50-100 shots because you're close to the lands and not in the seating depth node, you can find a wide node that will allow the bullets to have .010-.030 differences in length but still shoot good and have consistent point of impact.