Barrel throat erosion and accuracy.

[mikecr]

I'm not suggesting that there is anything wrong with OCW, incremental, ladder, wave, or any other powder development. But for the past ~35yrs I've noticed folks treating seating/CBTO as though a fine adjustment wiggled about after load development. And this is the folks who do any testing at all, and not just set the COAL to book or magazine fit..

OCW does not account for seating until afterwards(as a fine adjustment), and from any seating we had happen to pull from our butts to begin.
But seating adjustments can have the single largest affect to results. Do a full test, Berger's or similar, and you'll see how bad it can get from seating. You might consider amidst the ugly in it what further load development at that seating would look like. Could you really find the best powder load there?

I'm pretty sure most people never determine best seating. They find best powder, and then significant seating adjustments collapse their load results. This leaving them to think they're at best seating(like they magically guessed up front the right CBTO).
When folks never actually develop & shoot with best seating, no matter how well the results, their results are not best. And then some of these folks are the ones claiming twice realistic barrel life -because they can't see best has past -because they never seen best to begin.
I'm not talking about shooters in 100-300 IBS. They consistently detect accurate barrel life. But underbore cartridges are all about peak pressure, and to reach it their seating is very limited. No full blown seating testing there. You're not gonna see a competitive 6PPC shooting 50thou OTL, right? Maybe ~5thou OTL, but their probably testing/adjusting ITL or soft seating or jamming. They're shaping grouping that is mostly set by their pressure node(powder).
I'm talking about distant shooters with a lot more seating options.
I think they can benefit with the understanding that they don't have to continually measure and chase land relationships.

 

[jlow]

Mikecr – I’ve read your post a few times. I understand that you feel strongly that seating depth optimization should be done prior to powder weight adjustments. However, you say “Do a full test, Berger’s or similar, and you’ll see how bad it can get from seating”. I can certainly believe this, but I am sure someone will come in and say the same about how bad it could get from different powder weight test with fixed seating. So I am not sure what that proves except both are important.

Let’s assume that both sides agree that regardless of how you approach this i.e. powder optimization first or seating depth optimization first, that there is an optimal setting. The question is how is it different how you get there? The rationale being, it may not matter?

Speaking from personal experience I know I feel more confident going the powder optimization first because the OCW method allows me to find it relatively quickly i.e. I don’t need to be lucky to hit the exact powder weight in my search but look overall for that POI movement or in this case lack of movement to find the sweet spot area. If I was going to do the same thing now going the seating depth optimization, I honestly don’t know a few things that makes me wonder how to move forward. For example, is there such a thing as a sweet spot for seating depth? I presume so. If yes, how wide is this sweet spot i.e. how easy is it to detect? This is key as of course we potentially have a wide distance to test.

 

[dmoran]

jlow & Mike -

Sorry if I sound pessimist here, but much to those scenario's can only be factually proven individually, and to each ones own unique scenario's, demands, and bullet choice. Do to all the obvious variables from one persons scenario to another's, is where generalization resultants would only deem righteous to some and could be totally wrong and damaging for others.
There is a lot of different opinions and expectations amongst us all......
What one might find as acceptable accuracy and calls it great, might not fit the desires of another.

With that said, I've tried both ways and myself find the charge to be the most critical aspect to find first, that effects all other tuning abruptly and more significantly. Also in my experience, if we are not in a good charge zone, vertical can plague seating tests.

Personally I start by finding the charge zones (via ladder test), then I move on to finding the best seating zones, then I go back and refine both from there found zones to find the optimal charge and optimal seating depth.
After pin-pointing both the optimal charge and seating, I then proceed to fine-tune the load by neck tension adjustments and variations of brass prep (primarily the necks).
Donovan

 

[jlow]

You are basically doing what I am doing but I am curious at to Mikecr’s strong opinion in the other direction. Not married to my current methods and so interested in hearing what he has to say.

I guess proofs are always difficult, and I have give my rationale as to why I start with powder weight optimization, but I would like to at least hear some convincing rationale why seating depth optimization is a better place to start.

Also I am sure many are in the same boat as me which is they went by the charge weight optimization route first and have found decent accuracy nodes and would be reluctant to spend more barrel life going the other route again unless there was a convincing argument.

 

[bill123]

jlow & Mike -

Sorry if I sound pessimist here, but much to those scenario's can only be factually proven individually, and to each ones own unique scenario's, demands, and bullet choice. Do to all the obvious variables from one persons scenario to another's, is where generalization resultants would only deem righteous to some and could be totally wrong and damaging for others.
There is a lot of different opinions and expectations amongst us all......
What one might find as acceptable accuracy and calls it great, might not fit the desires of another.

With that said, I've tried both ways and myself find the charge to be the most critical aspect to find first, that effects all other tuning abruptly and more significantly. Also in my experience, if we are not in a good charge zone, vertical can plague seating tests.

Personally I start by finding the charge zones (via ladder test), then I move on to finding the best seating zones, then I go back and refine both from there found zones to find the optimal charge and optimal seating depth.
After pin-pointing both the optimal charge and seating, I then proceed to fine-tune the load by neck tension adjustments and variations of brass prep (primarily the necks).
Donovan

After doing that, will you adjust seating depth as throat erodes?

 

[dmoran]

Bill -

I've actually seen both ways. Where to say in one barrel and bullet choice, seating is not effected by erosion much at all. But in another barrel with other bullet choices, "chasing the rifling" is needed.
Examples I have had:
- with a 6PPC of mine with 66/68's if I am not chasing advancement, grouping and aggregate suffer
- in two 6Dasher barrels from 105/107's, same as above with the 6PPC
- in 5 other 6Dasher barrels, I hardly see any effect of seating to erosion
My 2-Cents
Donovan

 

[bill123]

Bill -

I've actually seen both ways. Where to say in one barrel and bullet choice, seating is not effected by erosion much at all. But in another barrel with other bullet choices, "chasing the rifling" is needed.
Examples I have had:
- with a 6PPC of mine with 66/68's if I am not chasing advancement, grouping and aggregate suffer
- in two 6Dasher barrels from 105/107's, same as above with the 6PPC
- in 5 other 6Dasher barrels, I hardly see any effect of seating to erosion
My 2-Cents
Donovan

Thanks!