OCW with 12.7x99

[big5ifty]

The is my second attempt at an OCW test for this rifle.

This was shot prone, which is also the first time for me shooting this rifle prone.

Lapua brass, CCI 35 primers, N570 and Peregrine 750 Gliders. Distance 199 meters.

I kept the powder interval at 0.5%.

I fired 4 shots per string, one for each charge weight on successive targets. Ten minutes elapsed between each string.

The patches near the bottom cover the holes made by other shooters on the line cross-firing onto my target.

I'm calling the first target the scatter node. The fourth target is exactly 1.5% away in charge weight, and will be the load going forward.

 What is notable is that the first four shots are all the lowest shots on each target. It took me those four shots to get a consistent shoulder position in the center of the butt, instead of against the top half of the butt. I believe that is why each of the four shots all printed lower.

My previous attempt at an OCW test was off the bench, from an unstable position, and demonstrated to me very clearly that any     instability in the shooting position is greatly magnified on the target.

[Tripodmvr]

I am quite sure that Quick Load can save you plenty of very expensive components to get you closer to a more precise load.

[big5ifty]

I use the software to get to a starting point, like I used GRT to select the powder type.

From there, I prefer not rely on the software to tell me what's best, I need to see it on the target.

My best confirmation of any load is to repeat the test and get the same result.

This method has proven repeatable in my other target rifles.

I'm not against learning anything new, I will try find out how other people use the software for selecting optimum loads.

I'll see how this works for me in the upcoming one mile shoot.

[big5ifty]

I'm trying a different powder, and without changing anything in GRT, the predicted velocities are coming out to around 10 fps of actual.

I've adjusted the powder charge to where the BT and OBT are 1/100 th of a millisecond apart in the program.

That was data from an OCW test I ran, that showed a possible accuracy node at 243.5 grains. Which is at the very top end of the load data, the next node down should be 236.5 according to my OCW test.

The predicted node in the software is at 237.0, which is very close to what I see on paper already.

I loaded up 4 rounds at 237, and then four rounds each at 0.5% either side of it.

Looking forward to seeing the result.

[big5ifty]

The rifle is printing four shots on one moa, group size is 1.25 moa. That load is at 238.1 .

If anyone is shooting a 29" or 30" barrel in their 12.7x99, try N570 powder. You get a more complete powder burn with less powder in that barrel length, which greatly reduces the concussion of the muzzle blast burning the excess powder outside the barrel. Just pay attention to the case fill, N570 doesn't fill as well as 24N41.

Vihtavuori have updated their load data to use N570.