Optimum Charge Weight (OCW) method and bullet seating depth?

[MCMXI]

Has anyone here used the OCW method along with adjusting bullet seating depth either during or after the OCW process? I have a question about the order or procedure that you use to find the BEST load for your particular rifle, bullet and powder of choice.

If you've used the OCW method and found the BEST load with the same bullet seating depth for ALL loads, is changing the bullet seating depth from 0.005" off the lands to 0.040" off the lands in say 0.005" increments going to change the average POI significantly? Is adjusting the bullet seating depth "merely" a way to reduce the group size for what WAS and is STILL the BEST load? I hope my question(s) make sense.

Here's a link that I should have included at the start.

http://www.clik.to/optimalchargeweight

Thanks.

 

[USSR]

1858,

I don't use the OCW method. My starting point is COAL, based on either chamber length (long actions - .010 to .015 off lands) or magazine length (short actions and autoloaders). I then go looking for a certain range of velocity, and play with the charge weight until I find the sweet spot near the optimal velocity. Finding an accurate but underpowered load does not trip my trigger.

Don

 

[MCMXI]

Don, thanks for the reply. So you don't experiment with bullet seating depth once you've set the COL based on the chamber and throat of a particular rifle? Once you've got the velocity that you want, is your criteria for "the sweet spot" based on group size alone since I'm assuming that your velocity doesn't change much as you adjust the charge over a narrow range?

Finding an accurate but underpowered load does not trip my trigger.

I'm with you on that! I know you've been actively involved in long-range shooting matches for years and this is something that I'll be starting soon so muzzle velocity is VERY important.

 

[Kernel]

Interesting. I didn't even know what the OCW method was until I saw this post and Googled it. Lots of food for thought.....

http://optimalchargeweight.embarqspace.com/#/ocwinstructions/4529817134

Not that this answers your question, but based on my readings one of the primary advantages of the OCW method is it minimizes the need for finding an optimal COAL.

 

[USSR]

So you don't experiment with bullet seating depth once you've set the COL based on the chamber and throat of a particular rifle?

Nope. The less jump the better. I just make sure I stay atleast .010" off the lands due to variations in bullet ogive locations.

Don

 

[kelbro]

I have used the OCW method on several rifles and had great luck with it. On the few occasions where I then experimented with seating depth variations, it just tightened the groups up a little.

 

[MCMXI]

Kernal, I think it's a fascinating approach but it's not as straightforward as it seems. A monkey can collect data ... interpreting the data is the difficult thing ... I'm still in the monkey phase!!

Don, thanks ... I know you've been on the cutting edge for a while so I respect your opinion and appreciate your thoughts on this. As I mentioned, I'm seating my bullets so that they're 0.020" off the lands at the moment but would like to get them a little closer if it helps reduce the group sizes without adversely affecting anything else.

kelbro, ok ... now we're getting somewhere. Bullet seating depth affects case pressure and case pressure affects velocity and barrel vibration, but how much? In other words, does the amount of powder, assuming cases with "equal" volume, far outweigh (no pun intended) the effect of 0.005" changes in bullet seating depth? This OCW could get complicated and expensive if I load 30 rounds (six different loads) with the bullet seated at x", then another 30 rounds (same six different loads) with the bullet seated at x-0.005", then another 30 with the bullet seated at x+0.050", then x-0.010" and x+0.010", and so on.

 

[Walkalong]

OCW - whatever W

Pick a bullet and powder. Pick an O.A.L.. (I like .010 to .020 off the lands if possible-.030ish into the lands on my bench gun) Pick a start charge.

Test it. Bump it .1 to .2 grains at a time and keep going up. You will find a sweet spot. If you keep going, you will find another sweet spot. If you reach the max recommended charge or see pressure signs before you find another sweet spot, stop. The last sweet spot you find before reaching a dangerous level is your fastest accurate charge. Any sweet spot under that is fine too. It all depends on what you are after. Most target shooters and varmint shooters want their bullets in flight as short a time as possible. For a nice target load at 100 yards at the range, any sweet spot will do, and brass will last longer.
A.C.

 

[adobewalls]

If I remember correctly, bullet seating depth changes are measured by shooting groups at 300 yards, after you have found your OCW for the powder.

To me that implies its only for fine tuning a promising load.

Might be worthwhile if your shooting competition or just curious; but for hunting and plinking, its probably overkill.

 

[USSR]

Pick a bullet and powder. Pick an O.A.L.. (I like .010 to .020 off the lands if possible-.030ish into the lands on my bench gun) Pick a start charge.

Test it. Bump it .1 to .2 grains at a time and keep going up. You will find a sweet spot. If you keep going, you will find another sweet spot. If you reach the max recommended charge or see pressure signs before you find another sweet spot, stop. The last sweet spot you find before reaching a dangerous level is your fastest accurate charge. Any sweet spot under that is fine too. It all depends on what you are after. Most target shooters and varmint shooters want their bullets in flight as short a time as possible. For a nice target load at 100 yards at the range, any sweet spot will do, and brass will last longer.

+1.

Don

 

[MCMXI]

Walkalong and Don, the process that you describe is what I've done for years but this anecdote by Dan Newberry (OCW author) intrigued me ...

"A group fired with my 30-06 at 335 yards consisted of loads all charged with 57.5 grains of H4350 pushing Sierra 165 grain Gamekings. One shot used a Remington brass case with CCI 200 primer, another used a Winchester case with that same primer, and the last load in the three shot group used a Winchester nickel case with a CCI BR primer. All three shots of this mis-matched trio came in at 2/3 MOA at 335 yards. (Update, I've since repeated this test for a five shot group consisting of two Remington cased loads, two Winchester nickel cased loads, and one brass cased Winchester load. Again with CCI BR and CCI 200 primers--again, the group broke 2/3 MOA. A point of interest, the Remington cases weighed ten grains more than the Winchesters. But that wasn't enough difference to take the group outside MOA due to the pressure tolerance of the OCW load). By the way, if all brass and primers are kept uniform with this load, it is about a 1/3 MOA performer (1 inch) at 300 yards, so I'm not saying that uniforming brass doesn't help--it obviously does. It's just that an OCW load is much more tolerant of pressure altering component changes."

This goes against everything I thought I knew about reloading. Since my intention is to shoot tactical long-range matches using the same load, and I have no way of knowing what the atmospheric conditions will be the day of the match, a pressure tolerant load sounds like a great idea to me. Also, the Lapua (.308 Win) and W-W Super (.300 Win Mag) brass that I'm using varies by something like 2 to 3 grains at the most so it sure would be nice not having to keep weighing the cases every time.

adobewalls, thanks ... I went through the OCW pages again and noticed the author's comment "After you have positively identified the OCW, you can then adjust the seating depth to fine tune the load for ultimate accuracy. After doing so, you can be assured the final load recipe will be a consistent, solid performer."

Anyway, thanks for your comments ... I appreciate the effort.

 

[USSR]

1858,

I've known Dan for years. He used to be a regular poster at SnipersHide.com. He's a good guy, even though we disagree on the value of his load development methods. Seems to me, the proponents of OCW are heavy koolaid drinkers. You know, like global warming theorists and Savage worshippers.

Don

 

[30Cal]

There are a lot more powerful tools out there, such as Design of Experiments or Taguchi Design, that enable you to vary all sorts of stuff at the same time while still pulling meaningful results. Properly done, they'll give you outstanding results in short order, but it's a fairly complicated subject.

A buddy of mine wrote this:
http://www.zouaves.org/agr/Working_up_a_match_load_using_DOE.pdf

 

[kelbro]

kelbro, ok ... now we're getting somewhere. Bullet seating depth affects case pressure and case pressure affects velocity and barrel vibration, but how much? In other words, does the amount of powder, assuming cases with "equal" volume, far outweigh (no pun intended) the effect of 0.005" changes in bullet seating depth? This OCW could get complicated and expensive if I load 30 rounds (six different loads) with the bullet seated at x", then another 30 rounds (same six different loads) with the bullet seated at x-0.005", then another 30 with the bullet seated at x+0.050", then x-0.010" and x+0.010", and so on.

When you find a true OCW load, slight variations in seating depth do not have that much of an effect. Same with switching from Federal primers to Remington primers. Nobody ever said that these are 'perfect' loads. In my experience, they are just good repeatable, acceptable loads.

Seems to me, the proponents of OCW are heavy koolaid drinkers. You know, like global warming theorists and Savage worshippers.

I live in the AZ desert and a NY'er wants to talk about global warming And don't go dissin' my Salvages I'm a lefty and don't have too many choices

I was in a cab today in Rotterdam,NL today and the Turkish cab driver told me that now with Obama in office, the world prospects are looking up. Talk about Koolaid! CNN reports (over here) repeatedly say that "all of America" (that's us) is so excited about Obama and our hopes are renewed.

 

[USSR]

I was in a cab today in Rotterdam,NL today and the Turkish cab driver told me that now with Obama in office, the world prospects are looking up. Talk about Koolaid! CNN reports (over here) repeatedly say that "all of America" (that's us) is so excited about Obama and our hopes are renewed.

kelbro,

That's the International OCW (Obama Changes the World).

Don

 

[Walkalong]

only at the price of our freedom, no biggie, right?