OCW and or ladder test changes in powder and or components and MV question

[s3cr3tsqrrl]

I've done a lot of research and lots of shooting to develop a load for 2 308's and a 223 (all bolt guns). My goal is distance - 800+ yds for 308's and 600 + for 223. Shooting 168gr SMK's and 53gr and 69gr in 223. I'm an experienced shooter, new to reloading and work in LE.

My first question. If I find an optimal load that shoots well and am forced to change primer or brass or(comparable) powder. Can I just look for same/similar MV to have a good load?

After reading lots of Dan Newberry's info and info on ladder tests and OBT, it would seem?? That a change in a component would make little difference if I can duplicate MV? Or would acceleration and other factors make my theory incorrect.

I say all this due to the difficulty in finding components these days. And all the work I've put into finding a good load.

Second question. When working up a load I always shoot over a chronograph. Is it common to find loads or "nodes" with more consistent MV? I am seeing spreads of over a 100fps in some charge weights and as low as 6fps in others (5 shot groups). Is this common or is this mistakes made due to my inexperience?

Primarily using IMR 4064 in silver state armory brass with 210 M primers, fire forming and neck sizing only (only been through brass 2X). Just got some lapua brass for my other 308 but haven't shot it yet. Using a gempro 250 and what I think is a good routine for brass prep??

Thanks for any help and sorry for the excessive use of the word "and". <br />
<br />


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[rduckwor]

In my opinion, MV is an appropriate surrogate to determine the OCW load that works best.

Let's face it, aside from accuracy, what else can the average shooter measure?

Good Luck,

 

[roachm]

Tag for later.
You asked the exact question my shooting buddy and myself have been pondering the last week or so.
I guess our discussion stemmed from the likelihood of not obtaining our preferred powder.

My ? to him was can I switch powders (keeping everything else consistent) to a powder with a similar burn rate and expect to see similar results if I can duplicate the MV safely.

I plan to try this little experiment soon, but if anyone else out there has already done so, it would be great to hear your experience.

 

[Niles Coyote]

I’ll start with this first
“Second question. When working up a load I always shoot over a chronograph. Is it common to find loads or "nodes" with more consistent MV? I am seeing spreads of over a 100fps in some charge weights and as low as 6fps in others (5 shot groups). Is this common or is this mistakes made due to my inexperience?”

That is what I have seen also such as yesterday when I did a OCW on 70gr bergers in a 223.
From another post:
Fired over a magnetospeed 3 shots each
23.0g gave me 2842, sd= 25 es= 50
23.5g gave me 2933, sd= 1 es= 3
24.0g gave me 3019, sd= 27 es=55

I ran the numbers first then did a OCW and 23.5 was centered in the node. And other goods loads with other calibers/bullets/powders have nice stable numbers IME. So maybe we can stop shooting groups and just shoot over velocity checkers... lol, that was tongue in cheek in case tone is lost in text.

Now on your first question, “My first question. If I find an optimal load that shoots well and am forced to change primer or brass or(comparable) powder. Can I just look for same/similar MV to have a good load?”

I have not seen a difference moving from one primer to another unless it was a standard primer going to magnum or the reverse. On brass it gets tricky, internal volume matters. If two are similar then, yeah I have done it with little to no changes to powder charge. Such as using winchester brass and lapua in my 308s. The Winchester generally requires .2-.4 tenths more powder with 155-175 grain bullets... On the question of powder. I have not tried that but while finding a node with two different powders I have seen velocity differences of 20-50fps so I would say maybe...

 

[s3cr3tsqrrl]

I ran the numbers first then did a OCW and 23.5 was centered in the node. And other goods loads with other calibers/bullets/powders have nice stable numbers IME.

Thank you very much Niles, that is very helpful. I was scared the MV spread was due to my procedure. I assume when you say "I ran the numbers" in the above quote that you mean through "quick loads"? That's a luxury I don't have yet...

Thanks again

 

[Niles Coyote]

Thank you very much Niles, that is very helpful. I was scared the MV spread was due to my procedure. I assume when you say "I ran the numbers" in the above quote that you mean through "quick loads"? That's a luxury I don't have yet...

Thanks again

Nope, I fired them over a magnetospeed... I just don’t like doing both OCW and velocity checks at the same time. Others say the magentospeed doesn’t affect accuracy but I am not as convinced. The shot sample was three rounds each, just enough to give me an idea where I am at and also check for pressure on my brass.

 

[ss7]

Matching muzzle velocity may or may not work.
What you're really trying to achieve is a matched barrel time. Reducing the charge to offset for a reduced case volume may be OK, but changing the burn rate of the powder may have a significant change in barrel time with matched MV.
Changing printers have never affected my loads in my experience.

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[ss7]

Printers = primers

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