Optimal Charge Weight load development - Voodoo?

[Wiking-76]

I'm currently working with this method and it works better than traditional ladder-testing.
http://optimalchargeweight.embarqspace.com/#/ocw-instructions/4529817134

But there's something I don't quite understand...

Quote:
11. After you have fired the sighters and confirmed that there are no pressure signs (hard bolt lift, flattened primers, etc.) you allow the barrel to cool for an adequate amount of time (use common sense--the hotter it is outside, the longer it will need to cool) you will then fire your first shot from the first group of the graduated charges. You fire this shot at target number 1.

12. Allow the barrel to cool, then fire a shot from the second graduation at target number 2. Wait for cooling of the barrel, then fire a shot from the third graduation at target number 3. Continue this "round robin" sequence until you have been through all of the targets three times. At this point you will have a three shot group on each of the targets.
End of Quote

What's the deal behind shooting this "round robin-sequence", instead of simply firing f.e. three-shot groups (of load X) on each target?

Is there someone out there who can explain this to me?

Regards

 

[Macmathews]

It places the error factor from barrel heat/harmonics over all groups fired instead of each graduated group being fired from a hotter and hotter barrel.. Eg - waiting any realistic amount of time between shots and on shot 21 your barrel will be hotter than on shot 4.
It also keeps any other margin of error spread between all groups. Like wind or eye fatigue

Btw - I am having great success with this currently. Shooting 1.5 inch groups at 300 yards , I don't think my shooting ability is any better than that.

Kyle

 

[One-Eyed Jack]

The cleanliness of the barrel changes as you progress, cleaner at the start and dirtier at the end. The round-robin method is a way to even out the effects of a dirty barrel, otherwise target 1 would have three nearly clean bore shots and the last target would have three shots with the dirtiest barrel. This assumes you start with a clean rifle, but some people don't clean their barrels often (example, they use moly or BN coated bullets).

 

[NoFail]

Yeah what these guys said. I didn't do round robin at first. When I started round robin things actually did get better. I mean the groups came out more defined and easier to "read", if you will. I wasted a lot of time and money before doing it all the right way as instructed by the OCW guru.

 

[jwp6114]

Used this method to produce consistent 2" groups @ 600 yds in good conditions. 243AI

 

[Pinecone]

From the Test Example page of the site:

This is basically a "round robin" system of grouping each charge, which precludes disadvantaging late groups due to fouling, or heat build up.

 

[Sniper260]

Sounds like that may get confusing with shot placement of each shot. Are you color coating your bullets? I've heard that works good, but I'm too afraid to use a sharpie on my bullets and send them down the barrel. I've had good luck with my ladder testing at 300 yards.

 

[Macmathews]

Sounds like that may get confusing with shot placement of each shot. Are you color coating your bullets? I've heard that works good, but I'm too afraid to use a sharpie on my bullets and send them down the barrel. I've had good luck with my ladder testing at 300 yards.

Its no important where each shot lands. Only the groups center if you will.
As long as you grab the right charged bullet and shot the right group each time. Individual shots mean nothing

Kyle

 

[doc76251]

Somethings to consider when using the OCW load technique

1. DO NOT shoot your aiming point! Even at 100 yards if you poke a hole just off center of your aiming point you will start to "spread" the group in that direction. In general I will load an additional 5 rounds from the "middle" charge weight and zero the rifle with them. Then I dial on about 3MOA or a Mil and begin the round robin.

2. Use a Sharpie on the PRIMERS not the boolets to color code them for charge weight.

3. Give yourself enough target to shoot at. As the powder charge changes you will see the rounds group in different areas in relation to the aiming point.

4. As above the round robin method removes a lot of mechanical variables. It will also mitigate the personal variables. Some folks are jumpy for the first few rounds and then smooth out. Others get progressively worse as the recoil sensitivity sets in. This is also why you plot each shot after you take it so that you (in the comfort of home) can analyze your groups.

Doing OCW is not hard but with just a bit more effort you can gather some serious data which is what you are really after. That can net you some outstanding loads that if chosen properly will give you the same POI across a wide band of temperatures.

Cheers,

Doc

 

[Wiking-76]

Thanks a lot for the answers, guys.
...no Voodoo at all ;-)

Regards,

 

[Deadshot2]

Sounds like that may get confusing with shot placement of each shot. Are you color coating your bullets? I've heard that works good, but I'm too afraid to use a sharpie on my bullets and send them down the barrel. I've had good luck with my ladder testing at 300 yards.

I just use a target with 5) 3" stick on target spots on them. I number them with an "El-Marko" with numbers large enough to read. Cartridges are then segregated in my ammo block in numbered groups. Bullet from group one to target one, then #2 to target #2, etc. After shooting #5, go take a "pause for the cause", let barrel cool, run a bore snake down the tube, whatever, and then repeat. I shoot all my OCW tests in groups of 5 and "round robin".

Once I started doing that I was able to get far better results when I returned with a box of ammo all loaded to the "Optimum weight".

 

[AKsarben]

Older thread but I have to ask. How well does this work for loading for a .308 AR-10? I have shot a 5 shot group out of a AK-47 .308 caliber that, using factory ammo, was pretty impressive given the firearm.

My latest bunch of tests on a new LR 308 *DPMS 16" bbl. using IMR8208 XBR showed me that the minimum load grouped very well compared to those mid way through, or toward the top end where I notice slight pressure signs like extractor swipes.