Quick question on OCW testing

[Bob 964]

Dan Newberry's instructions for OCW testing includes the following statement... "You will now look for the three groups which come the closest to hitting the same POI (point of impact) on the targets."

It is unclear whether the 3 groups are consecutive. In the examples he uses to illustrate, the loads are consecutive (e.g., 42.3, 42.6, 42.9).

Question: when doing an OCW test, are the three groups "which come closest to hitting the same POI" consecutive load groups, or just any three groups that hit the same POI?

Thanks.
Bob

 

[Hedge]

Re: Quick question on OCW testing

Consecutive. You're looking for a load band that will give you the same POI +/- your load increment. That would be the middle group of the three consecutive groups.

 

[725franky]

Re: Quick question on OCW testing

Yeah, what he said^^^^^^

The one thing I've always had a question about is why you have to allow the barrel to cool rather than just shoot straight through.

 

[Hedge]

Re: Quick question on OCW testing

Consistency in your test. Basically, you're doing an experiment where you do your best to minimize your variables. Barrel heat plays a significant part. By giving your barrel the same amount of cool down time between shots, you're minimizing the effect of heat on each shot. Kinda giving each bullet the same chance to perform.

 

[MitchAlsup]

Re: Quick question on OCW testing

Now, the interesting thing is:: once you have found the OCW node, the load ends up quite insensitive to barrel temperature. But you have to avoid this in order to find the OCW node.

 

[TexIndian]

Re: Quick question on OCW testing

It's important to remember the whole point of OCW or the Audette ladder - It's not about finding the smallest group, it's about finding the load where your POI will be least sensitive to variations in velocity (usually caused by changes in ambient conditions). OCW is based on Audette's work, and Audette was a military man looking for ammo that would hit its target no matter what conditions the soldiers found themselves in.

So yes, you're looking for consecutive groups. These are the groups where the POI stayed pretty much the same even though velocities were changing.

OCW is nothing more than an Audette ladder with three shots fired at each powder level. It seeks to avoid the influence of barrel heat, barrel fouling, shooter's subconscious influence or fatigue, etc. by changing the shooting order. Using the different points of aim makes it easier to keep track of which hole is which on the target but it can add another set of errors into the equation because the shooter has to shift his gun and body between every shot. And it adds the need for a convoluted measuring system.

HERE is an alternative way of doing the same thing as OCW. The shooter keeps track of which hole is which by using colored projectiles. But instead of the tedious measuring system, the nodes are obvious to the naked eye. It still uses the round-robin firing sequence like OCW but you aren't shifting your gun around 20 times during the test. (just like the other methods, you can use whatever distance you want)

It's a personal choice which method you use. They are all looking for the same result.

 

[Tripwire]

Re: Quick question on OCW testing

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 308_to_yuma</div><div class="ubbcode-body">Dan Newberry's instructions for OCW testing includes the following statement... "You will now look for the three groups which come the closest to hitting the same POI (point of impact) on the targets."

It is unclear whether the 3 groups are consecutive. In the examples he uses to illustrate, the loads are consecutive (e.g., 42.3, 42.6, 42.9).

Question: when doing an OCW test, are the three groups "which come closest to hitting the same POI" consecutive load groups, or just any three groups that hit the same POI?

Thanks.
Bob </div></div>

It should be self explainatory as the whole concept of OCW is finding a range of pressures that allow the exit of the bullet to happen when the barrel harmonics are having a minimal effect on the muzzle. This in itself would logically demand consecutive charge weights to achieve a "range".

You may not be aware but there's a way to talk to Mr. Newberry himself and get your questions addressed. He's a fairly common down to earth sort of dude, and easily answers to "Dan"....... Link

 

[Tripwire]

Re: Quick question on OCW testing

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MitchAlsup</div><div class="ubbcode-body">Now, the interesting thing is:: once you have found the OCW node, the load ends up quite insensitive to barrel temperature. But you have to avoid this in order to find the OCW node. </div></div>

Not quite.....

OCW will allow a high degree of insensitivity to <span style="font-style: italic">ambient</span> temperatures, but barrel heat is subjective. Some barrels handle heat much better than others, and I'll not go into the semantics of that as everyone should know it...but OCW is no better at fending off barrel heat than any other load development technique. OCW will even the playing field between a skinny barrel and a fat barrel with regard to harmonics, but barrel heat does what barrel heat is going to do.

Which is why it's smart to allow a cooling period to maintain some form of consistancy. When I test an OCW I simply do not allow the barrel to get over heated......

 

[Tripwire]

Re: Quick question on OCW testing

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: OldTex</div><div class="ubbcode-body">It's important to remember the whole point of OCW or the Audette ladder - It's not about finding the smallest group, it's about finding the load where your POI will be least sensitive to variations in velocity (usually caused by changes in ambient conditions). OCW is based on Audette's work, and Audette was a military man looking for ammo that would hit its target no matter what conditions the soldiers found themselves in.

So yes, you're looking for consecutive groups. These are the groups where the POI stayed pretty much the same even though velocities were changing.

OCW is nothing more than an Audette ladder with three shots fired at each powder level. It seeks to avoid the influence of barrel heat, barrel fouling, shooter's subconscious influence or fatigue, etc. by changing the shooting order. Using the different points of aim makes it easier to keep track of which hole is which on the target but it can add another set of errors into the equation because the shooter has to shift his gun and body between every shot. And it adds the need for a convoluted measuring system.

HERE is an alternative way of doing the same thing as OCW. The shooter keeps track of which hole is which by using colored projectiles. But instead of the tedious measuring system, the nodes are obvious to the naked eye. It still uses the round-robin firing sequence like OCW but you aren't shifting your gun around 20 times during the test. (just like the other methods, you can use whatever distance you want)

It's a personal choice which method you use. They are all looking for the same result. </div></div>

I believe if you sat down over lunch with Dan Newberry he would gladly tell you that OCW is certainly NOT based on Audette......if you doubt me then by all means follow the link above and ask him yourself.

OCW's main concern is addressing barrel harmonics, by actually SEEING the low side scatter nodes close up, the accuracy node spread across a range of pressures, and the upper side scatter node begin to open. You don't see that, that precisely, with a normally done ladder test.

Audette is an external function of velocity and BC over distance, and sees very little regarding barrel harmonics due to the broader increases in pressure. OCW is a function of barrel time, defined by very small increases in charge weight, and then seating depth. The method is not just another variation of Audette because the data obtained is much more refined and exact, and is mainly watching the physics of the shooting platform itself.

The inherent tolerance to conditional variance defaulted to the physics of a properly done OCW is just icing on the cake......

 

[Bob 964]

Re: Quick question on OCW testing

Thanks everyone for taking the time to respond and share your knowledge with me.
Bob