BigBlack wrote:

No paticular rifle in mind with my above statement. I was merely thinking out loud and looking for opinions and thoughts on something that was mulling around between my ears. I am however working on my .243 using 100gr Game Kings right now.

OCW method link

Read the above web page to understand OCW.

I will do an example for the 100 Gr Game King using IMR 4064 since that was the powder Sierra suggested for a hunting load and I like its performance in many calibers... Select a reasonable OAL and keep it the same for all bullets. Sierra says 2.650" so use that to start.

Max load is 36.2 grains. Newberry says to reduce charge by 10% and make three sighting bullets at that level and 2%plus 2%

That would be 32.6, 33.2 and 33.9 grains. These will be used to get the bullets on paper and see how much a change affects the point of impact.

The first test set is 2% more than the hottest sighter or 34.6 grains. Make at least three of rounds at each test level. (5 may be better if you think you might screw something up!)

The subsequent test levels are 1% greater powder charge each until you cross the maximum suggested charge. In this case the levels are:

#1 34.6 gr
#2 34.9gr
#3 35.3gr
#4 35.6gr
#5 36.0 gr
#6 36.3 gr

Since it takes six levels to exceed the maximum charge you will need six separate aiming targets and a sighting target at at least 100 yards. You will not care if the impacts are centered only that you have a clear aiming point that you can get a repeatable sight picture on every time. The Sight-in Targets with the orange 1" squares work well for this at 9x or above. But so does a 10" paper plate with a 1" square drawn on it with a Sharpie like Newberry uses...

Shoot one round from each level at its own target. Do not shoot all of level one then all of level two all of level three etc. You should vary the order that you shoot the 18 rounds,(1-6,1-6,1-6) (1-6,6-1,1-6) round robin or even random order to factor any change in shooting conditions, shooter or rifle. Just make sure that all the loads from level 1 end up on the level 1 target and the loads from level two all are on that target... If any signs of pressure(flattened primers, hard bolt lift and extraction etc) appear do not continue to go to a higher level! (duh!)

When you are finished you will have six three shot groups on six targets. Make a triangle out of the three shots and mark the center of the triangle. Discount any called "flyers" and re shoot another bullet (which is why I said to load more than three) Measure the distance from the center of the triangle to the center of your aiming point in verticle and horizontal distance. (This is why I like the gridded sight in targets)

You should see that the point of impact walks across the target as you increase the powder charge. What you are searching for is three levels in a row that have very nearly the same Point of Impact.(POI) You are not tuning for really tight groups at this time, only checking the POI.

For the sake of discussion since I have not done this load I will make up some POI's.


#1 34.6 gr - -2", left1"
#2 34.9gr - -0.5", left 3/4"
#3 35.3gr - +1.5" left 1/4"
#4 35.6gr - +1.6"left 1/4
#5 36.0 gr - +1.6" left 1/4 "
#6 36.3 gr - +2.0" Right 1/2"


In this made up example the, three loads of levels 3,4,5 had very nearly the same POI. In this case the OCW would be 35.6 grains. This means you could load up 35.3 to 36.0 grains of powder and still hit the same spot.

The final test is to back the target up to 300 yards or whatever your longest likely shot is and shoot a three shot group with the OCW weight and a three shot group with the loads of 35.3,35.6 and 36.0grains. Both groups should have the same POI. at this time then you go back and tweak the OAL to get optimum accuracy. If you and your gun are able to shoot MOA... this load will too.


I made an Excel spreadsheet to do these calculations but do not know how to post it here.

nosler manual says most accurate load tested with a* eg imr3031 33.0grns
winch 760 38grns bla bla bla this has always seemed a good place to start as someone else has done the work for us.seems a shame not to use the books suggestions as a starting point. I always check any load by using at least 2 or 3 books or website loads so I dont cock it up.