OAL or OCW first?

[fremont]

I've always used OCW with varying charge weights with a constant OAL (usually the longer of SAAMI max or .020" off the lands), but I was listening to the Modern Day Sniper podcast and their guest (can't remember his name) made an effective argument for using a constant (safe) charge weight with varying distances off the lands, e.g., start at .030" and go back to, say, .150".

Anybody tried both and have a clear favorite?

 

[mwkelso]

I've tried both.
Using a chronograph, OCW worked faster. Without a chronograph, CBTO was more effective.
@Mikecr makes a great argument in favor of CBTO before OCW, and has the science to back it in his explanations. That is where I learned the nitty gritty details of CBTO.
They both work though, in my opinion.
Brian Litz also makes arguments in favor of both. His most recent interview he did changed it all though. He was heavily in favor of CBTO: after finding his max charge, backing off .x grains, then proceeding with CBTO testing.

 

[Mikecr]

Begin with FULL SEATING TESTING (your coarse adjustment).
Good time to test primers too.
Then move on to powder testing (your fine adjustment).
Then seating tweaking (group shaping).
Then neck tension(sizing length) last (finest adjustment).

Tuning in this is powder and neck tension. The rest are prerequisites for optimum accuracy.

 

[rsmithsr]

anything before wasting time and money on ocw

 

[Mikecr]

OCW functions to provide a forgiving load, -not most accurate.
You need ladder testing (some form of) for accuracy.

 

[fremont]

Begin with FULL SEATING TESTING

Mikecr, I don't know what this means.

 

[elf]

Mikecr, I don't know what this means.

Mikecr is a gunsmith and frequent scribe on this site. I begin all load testing with a moderate powder charge, and bullet right at kiss and then move in by .005" . When I am satisfied with that, I fine tune the charge .05 grs. at a time.

 

[mwkelso]

Mikecr, I don't know what this means.

When I'm working a load starting with CBTO, I start at lands jam (0.00" jump) and work backwards in 0.010" increments.
Depending on what bullet you're using, there are cases where you don't need to start at the lands. I use the Nosler ABLR for a couple cartridges, which most often like to jump about 0.050" or more. I start at a 0.040" jump and work back from there with those ones. Others like the partition, I know they like to be up close. So I start at the lands with those.

 

[bill123]

Begin with FULL SEATING TESTING (your coarse adjustment).
Good time to test primers too.
Then move on to powder testing (your fine adjustment).
Then seating tweaking (group shaping).
Then neck tension(sizing length) last (finest adjustment).

Tuning in this is powder and neck tension. The rest are prerequisites for optimum accuracy.

Mike, How do you integrate primer testing into this?

 

[Mikecr]

Mikecr, I don't know what this means.

A LINK: https://www.longrangehunting.com/th...-from-berger-vld-bullets-in-your-rifle.40204/
Works with any & all bullets(not just Berger).

I'm not a gunsmith or scientist,,
If I'm different, it's that I'm of average intelligence and consider the notions of mobs(any) with skepticism.
This, because collective intelligence drops with numbers, so group judgement(mob thinking) is nearly always wrong.

 

[BountyHunter]

If you are using a magazine, seating bullets at the lands is a waste of time, money and barrel. Seat at max coal for the magazine and work back from there. Makes no sense to develop a load for a magazine gun IF you cannot load the magazine.

 

[Mikecr]

Mike, How do you integrate primer testing into this?

You don't tune with primer swapping. You search out consistency in ignition.
You can find this, with primer swapping (and/or striking adjustments), at the same reduced load testing used for seating testing, which can be done while fire forming your cases to stable (another prereq for powder testing).

Where the mob is failing is in their notion that all adjustments are tuning. They are not.
You don't have to shoot tight grouping to see which primer is most consistent, or which CBTO is producing tighter grouping than others.
You don't have to be, and should not be, anywhere near tune with prerequisite adjustments. Otherwise, you'll be adding [coming/leaving into/out of] tune to the abstracts.

Many just pull some seating out of their butts and go right to powder testing. Then, while in powder tune, they screw that all up with prereq adjustments. This, often leading them to believe they just happened to choose the right seating, and the right primer, from the git go. But really, what are the odds of that?
Sometimes they're lucky. Sometimes tune with what ever else they did is good enough. A lot of us are not so lucky though, and would always wonder what best really would be.

 

[bill123]

You don't tune with primer swapping. You search out consistency in ignition.
You can find this, with primer swapping (and/or striking adjustments), at the same reduced load testing used for seating testing, which can be done while fire forming your cases to stable (another prereq for powder testing).

Where the mob is failing is in their notion that all adjustments are tuning. They are not.
You don't have to shoot tight grouping to see which primer is most consistent, or which CBTO is producing tighter grouping than others.

So are you simply looking for low SD/ES w/ primer testing?

 

[Mikecr]

So are you simply looking for low SD/ES w/ primer testing?

Yes. That's what I look at.

This is an area in need of great investigations.
We know nearly nothing of primers and their optimum striking needs. And there is also no predicting of ignition qualities from one over another, so it's trial & error for us.
But it might be less abstract than it seems. It may be possible for developed standards, and a logical testing process.

This is anecdotal, but something I would like to revisit someday:
I entered a local 200yd accuracy contest. It's for hunters, get in line, shoot once at a 1" bullseye at 200yds (off sand bags), if you hit it you get back in line. The bullseye goes to a 1/2" dot after round 6. The last guy hitting wins. At round 10, it's closest to centered, in the event that remaining shooters are not going to miss.
There is a line, instead of multiple tables, to force cold bore shooting at differing rates.
When you've prepared for this, you're ready for hunting season no doubt.

I've won & lost it, and showed up one year more prepared than usual.
Centered the first few rounds, as expected. But then threw a shot a full 1/2" outside the bullseye. Well that was it for that, went to my range to figure out what happened. Something major must have gone wrong, but it shot perfect and would not repeat. A month later It did it to me again at the range, then again within the week. I had tore the gun down looking at everything with nothing found. Primer seating was never in question because I measure every primer seated at 2thou crush -every single round. I've never had primers themselves fail. Then luckily, I had a misfire. That's when I found that the firing pin was intermittently slipping in it's cocking piece (not much, no markings of this).

So now I had to figure out how to restore the firing pin setting to optimum.
Off to the range with a handful of tools, testing released firing pin protrusion from boltface through a range of increments. 3sht grouping for each setting. With this, grouping opened and closed and reopened just like tuning. That's because I was shooting from a tuned load. I was not tuning, but coming in/out of tune, with the same primers I had established as lowest in SD for the same powder I had tuned with.
I have no idea how,, but not only had I restored my prior performance, I also found even better performance.
Better than I would ever have found otherwise. One particular setting was beyond denial as best.
I ended up installing a bushing in the cocking piece to permanently force this setting.

It was a PIA to take the bolt completely apart so many times..
I wonder though if there might be an optimum striker setting that is unique to each primer brand.
Maybe when we're swapping primers, we're finding a primer whose optimum striking is nearest what our gun happens to provide. After all, they all fire just fine, there is nothing 'better' about one over another, but chances are that one still provides better results than another.
This is where we need a scientist (like Harold Vaughn) to measure impact momentum, force, speed, and results -per brand. There might even be a way to normalize with a powder doping.
I also use BAT actions, with reversible trigger hangers to affect this, along with primer changes. Trial & error..