Testing for "initial" OAL

[GSSP]

Take a cartridge you're not familiar with, pull up all the data available and pick a bullet, powder, case and primer combo. Determine the OAL when seated to just touch the lands. It fits in the mag with room to spare. You're gong to run a ladder, followed by a few groups within the nodes that looked good. Then a seating depth test followed by a primer test to determine which gives the best numbers.

Before any of this what do you like as a place to seat the bullet?

1. In
2. Touching
3. Out a little
4. Out a lot
5. Run a OAL test with various OAL to determine an "initial" best, before you even run your ladder? If so, give some details please.

Alan

Remember, this is a cartridge you're not familiar with.

 

[Terry]

You said...You're gong to run a ladder, followed by a few groups within the nodes that looked good. Then a seating depth test followed by a primer test to determine which gives the best numbers.

Based on your criteria you could start in the lands. This will develop maximum pressure for the load tested. As you reduce contact pressure will drop. This may require upping the powder charge a little.

 

[GSSP]

This is a hunting rifle, pure and simple. I've been running ladders for several decades and occasionally I hear someone say they run a seating depth test first, before they start the ladder, to find the "initial" sweet spot. So, I figured I see if anyone had anything to say about that.

I usually start .005" off and either go in and/or out depending on if it's a target or hunting rifle.

For the record, it's a 257 R on a very custom Pre 64 M70. 115 BT, IMR 4350, CCI 200 and Nosler +p, new unfired brass.

Alan

 

[mikecr]

You can run Berger's seating depth test from any charge. So it makes sense to do this 1st, and/or while fireforming.
With best seating of this, your ladders won't look so bad to pick through.
After all else, all that's left is fine tweaking of seating to shape grouping.

IMO, it's a mistake to haphazardly choose an abstract seating from which to base the powder testing.
After all, whatever you choose like this could be the very worst in seating, and consider what the worst in seating does to an otherwise great load. Not gonna make finding best load any easier, that's for sure.

This applies to normal cartridges, and not those known to need jam for pressure nodes.

 

[GSSP]

Mike,

Tried it this morning. I had about 12 new Nosler 257 Rob +P cases that had slightly buggered necks right out of the box so I loaded them up with "starting" loads before running a ladder. I shot 3-shot groups of .005", .045", .085" and .125" off the lands before starting the ladder. Good test. .005" was the worst (8") and it was a toss up between .045" (3.5") and .125" (3"). Glad I ran it. I ran the ladder with .045" off, had 10 nice shots @ 303 yds in zero wind and nodes at #'s 4/5 and 9/10 with .3 gr increments of IMR 4350 and 115 gr BT from a VERY custom 257 Roberts. This rifle is known for being very finicky and I've now found another load for it that will be cheap to shoot (blemished Nosler's) and easy on the barrel and cases.

Alan

 

[mikecr]

It makes sense, right?
If you had just chosen 5thou off to run your ladder(with no particular reason) then resolving best powder from ~2.5moa(8") could have been a lot tougher than from ~1moa(3") to begin.
Now you can shape your grouping tight with fine seating adjustment within 5thou either way from .045". Something there will be better or worse, and there should be a window there to center.