OCW Load Workup In 308 With 155gr Nosler Custom Competition
I have been reloading for a number of years now, but typically my load development consists of checking a quality loading manual, loading up a series of charges between the minimum and maximum charge in half grain increments and then shooting for groups. I tend to pick the best group, preferably towards the upper end of the velocity range. I don't have to have the fastest velocities, as I don't want to worry too much about over pressure or barrel life, but I want decent velocity for better ballistics and terminal performance for hunting rounds.
Recently I have been trying to be more deliberate about my precision rifle shooting, such as attending a couple long range matches. I posted recently about the Cheyenne Precision Rifle Match that I attended. Shortly after that, I picked up a 1000 count box of Nosler Custom Competition 155 grain bullets for a decent price from a local Sportsman's Warehouse. The price was low enough that I couldn't pass them up. While they don't have the highest ballistic coefficient, the number isn't too bad and they can be launched a little faster than the 178 grain A-Maxes that I have been using.
Plugging some numbers into JBM Ballistics shows that the 178 A-Max will likely be a little more resistant to wind, but the 155 Nosler CC should keep pace with a decent drop.
I decided to try a method of load workup called Optimal Charge Weight Load Development, or OCW for short. Now many of you may be familiar with this, but it was developed by Dan Newberry. You can click on his name to go to his website and read the full description of how to perform an OCW test. The following is a version of it I used based on the website and a combination of forum posts and videos that I have watched about the subject.
As a warning: All load data present here is used for reference only. Never assume that any load that is safe in one rifle is safe in yours! Consult the proper reloading manuals and work up loads by backing off of maximum loads by at least 10%.
Now let's get into the actual load work. I am starting with once-fired Remington 308 Winchester brass. I received a fair amount of this brass for free and can't turn down a deal like that. All of the brass was sized, tumbled, trimmed and the primer pockets were cleaned. Each was primed with a CCI Large Rifle primer and I used Varget powder for this test.
Looking at the Nosler reloading book, they listed a maximum charge of 46.5 grains of Varget and a cartridge length of 2.8"
I started out loading up one round each at 90%, 92% and 94%. These three loads are for sighting in and checking for pressure signs. I then loaded up three rounds each from 95% to 101% in 1% increments. These rounds are to be fired for groups, while still watching pressure signs. Each load was marked with a sharpie to make sure that I could keep them separate and look at pressure signs after the fact if necessary.
The idea of the OCW test is to look at the center of each group and look for consistency between the groups. Refer to Dan Newberry's website above for a complete explanation of the process. The idea is that the groups will tend to move around your point of aim as the charges change. You want to find a range of loads that have a similar impact point. That consistency is a good match for your particular rifle and should be more resistant to variations in the reloading process. Once that range of loads is located, you can experiment with the middle of that range.
One disadvantage of developing a load in Colorado in the beginning of February is of course the weather. Fortunately the range I belong to has enclosed range houses for the 100 yard ranges. As you can see in the picture at the top of the post, there was snow on the ground and the temperature was about 20 degrees.
One concern with the temperature is of course that loads that I test now may have higher pressures and perform differently in warmer weather. Varget is one of Hodgdon's extreme series powders, so it is more temperature resistant than some, but it is not immune to temperature changes. I will of course need to be cautious of some of the warmer loads as I approach warmer weather this summer.
When I got to the range I found it empty. I set up the target I had prepared and set up my chronograph. For the load testing I shot the first three rounds into the center point of aim. I then fired one round from each load into the corresponding target circle from 95% to 101% checking for pressure signs each shot. I was able to make it through each of the rounds without noticeable pressure signs. I let the barrel cool, then shot each load again, this time working from the top down. Once those were done, I let the barrel cool, then shot again from the lowest to highest.
By shooting the test in a round robin format I hopefully remove some of the variables of the barrel heating and spread out any shooter errors that may occur. While I may have been able to shoot some better groups firing three at a time, this will hopefully give a more accurate picture of how the loads truly perform.
While not the best photo, the target above is the result of the OCW test. Ignore the bottom left circle, that was a group from another rifle. Another range member that I had previously met at a local long range match showed up towards the end of my test and let me try out his rifle.
I used the target above to calculate group sizes in Ontarget. Though those numbers are difficult to see in the photo, the important thing to look at is the relative location of the groups. What stood out to me is the 45.1, 45.6 and 46.0 grain loads. These are each centered to the left of the aiming point and at about the 9:30 position.
By specifically concentrating on the middle of that load range, the 45.6 grain loading, I should be able to find a tolerant load. That group was .771" and had an average velocity of 2,880 fps.
My next step will be to load up some more rounds with 45.6 grains and varying seating depths. I will load up enough for multiple five rounds groups to give me a better idea of the velocity and group potential. Stay tuned for an update....
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| At the range for the OCW workup |
Plugging some numbers into JBM Ballistics shows that the 178 A-Max will likely be a little more resistant to wind, but the 155 Nosler CC should keep pace with a decent drop.
I decided to try a method of load workup called Optimal Charge Weight Load Development, or OCW for short. Now many of you may be familiar with this, but it was developed by Dan Newberry. You can click on his name to go to his website and read the full description of how to perform an OCW test. The following is a version of it I used based on the website and a combination of forum posts and videos that I have watched about the subject.
As a warning: All load data present here is used for reference only. Never assume that any load that is safe in one rifle is safe in yours! Consult the proper reloading manuals and work up loads by backing off of maximum loads by at least 10%.
Now let's get into the actual load work. I am starting with once-fired Remington 308 Winchester brass. I received a fair amount of this brass for free and can't turn down a deal like that. All of the brass was sized, tumbled, trimmed and the primer pockets were cleaned. Each was primed with a CCI Large Rifle primer and I used Varget powder for this test.
Looking at the Nosler reloading book, they listed a maximum charge of 46.5 grains of Varget and a cartridge length of 2.8"I started out loading up one round each at 90%, 92% and 94%. These three loads are for sighting in and checking for pressure signs. I then loaded up three rounds each from 95% to 101% in 1% increments. These rounds are to be fired for groups, while still watching pressure signs. Each load was marked with a sharpie to make sure that I could keep them separate and look at pressure signs after the fact if necessary.
The idea of the OCW test is to look at the center of each group and look for consistency between the groups. Refer to Dan Newberry's website above for a complete explanation of the process. The idea is that the groups will tend to move around your point of aim as the charges change. You want to find a range of loads that have a similar impact point. That consistency is a good match for your particular rifle and should be more resistant to variations in the reloading process. Once that range of loads is located, you can experiment with the middle of that range.
One disadvantage of developing a load in Colorado in the beginning of February is of course the weather. Fortunately the range I belong to has enclosed range houses for the 100 yard ranges. As you can see in the picture at the top of the post, there was snow on the ground and the temperature was about 20 degrees.
One concern with the temperature is of course that loads that I test now may have higher pressures and perform differently in warmer weather. Varget is one of Hodgdon's extreme series powders, so it is more temperature resistant than some, but it is not immune to temperature changes. I will of course need to be cautious of some of the warmer loads as I approach warmer weather this summer. When I got to the range I found it empty. I set up the target I had prepared and set up my chronograph. For the load testing I shot the first three rounds into the center point of aim. I then fired one round from each load into the corresponding target circle from 95% to 101% checking for pressure signs each shot. I was able to make it through each of the rounds without noticeable pressure signs. I let the barrel cool, then shot each load again, this time working from the top down. Once those were done, I let the barrel cool, then shot again from the lowest to highest.
By shooting the test in a round robin format I hopefully remove some of the variables of the barrel heating and spread out any shooter errors that may occur. While I may have been able to shoot some better groups firing three at a time, this will hopefully give a more accurate picture of how the loads truly perform.
I used the target above to calculate group sizes in Ontarget. Though those numbers are difficult to see in the photo, the important thing to look at is the relative location of the groups. What stood out to me is the 45.1, 45.6 and 46.0 grain loads. These are each centered to the left of the aiming point and at about the 9:30 position.
By specifically concentrating on the middle of that load range, the 45.6 grain loading, I should be able to find a tolerant load. That group was .771" and had an average velocity of 2,880 fps.
My next step will be to load up some more rounds with 45.6 grains and varying seating depths. I will load up enough for multiple five rounds groups to give me a better idea of the velocity and group potential. Stay tuned for an update....
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