Does Berger Make Jump Irrelevant?

[dustbag]

After I figure out my powder I always mess with seating to see what can happen. Here's an example


1/2" squares. Now if you put all 15 shots together it's still under 1/2" center to center POI even though seating depths vary. But the last group is pretty good on its own.

 

[FEENIX]

After I figure out my powder I always mess with seating to see what can happen.

That's a much better rule to adhere to. Know your powder and how to use it in your environment.

 

[Mikecr]

I thought seating depth was only critical for peak pressures and accuracy
when nearing the lands.

I believe that optimum seating is an abstract, unpredictable, and changing with different chambers even with same bullets.
The reason, I believe, is because seating directly causes 4 changes at once.
This is much like primer testing (another important abstract).

First I think coarse optimum seating is about matching optimum bullet-bore interface.
Second, fine barrel time
Third, pressure (also affecting time)
Fourth, neck tension (also affecting pressure and time)

Nodes that we TUNE are powder node (optimum burn), barrel node (exit timing), and system (weight/balance/rest/etc).
Prerequisites to tuning are case stability, primer/striking, and coarse seating.

As you depend on ever closer land relationships (raising starting pressure), you're accepting more sensitivity to that.
So the folks who choose to be against lands see loads collapse with erosion, and they chase lands.
The rest of us never need to chase lands.
There are some cartridges that highly reward high starting pressures. Usually small underbores.
Most hunting capacity cartridges do not need it, nor benefit from it in the long run.

 

[sjt18]

How do you test seating depth on a Weatherby with 3/4 of an inch freebore ?

There are tools you can buy then there's a redneck version that seems to work about as well. You can find the video on youtube by Ultimate Reloader showing it. Basically you take a stick that will fit your barrel without too much slop, close the bolt, then measure to the exit of the barrel. Then you loosely load a bullet into a case without powder and seat that bullet with your bolt into the chamber. Use the same stick and mark the end of the barrel. The difference is a close approximation of the real max length.

I'm not as good or precise as many of you guys. I'm not the best shot in the world. I'm looking for a good hunting load under 450 yds and usually under 200. My goal is to get a good accurate bullet which seems to be closer to max length on the things I've tried. Mostly I want to avoid being too close to the lands causing high pressure.