help reading results of OCW test

[scudzuki]

Last night I loaded up 3 of each increasing charges of H4350 behind Nosler Custom Comp 140 gr HPBTs seated .010" off the lands for my .260 Remington.
I had 50 cases prepped so I made 2 foulers and then 3 each starting at 39.6 grains and increasing .3 grains at a time to 44.1 grains.
Maybe I should have gone higher but I was already 2.1 grains over the Lee recommended max, which I know is a joke since I see reports of people running as much as 45 grains behind a 140 grain pill.
The guy I bought my barrel from said he had worked up a load with 139 Scenars in Remington brass and 44.2 grains of H4350 but that seems awful high.
I cleaned the barrel this morning before heading to the range, set up my targets at 150 yards, shot the 2 fowlers, and got to work.
The first 2 passes I let a little more time elapse between shots (say a minute) but I started running out of time so the last pass I moved along a little faster and the barrel stayed warm.

I watched for pressure signs on the loads above 43 grains and other than primers extruding into the giant firing pin hole in the stock Remington 700 bolt I did not see anything.

It was windy today with gusts above 15 MPH but I tried to time my shots. According to Strelok that could account for almost 2 inches of windage at 150 yards?

Maybe the wind totally blew my test, too, as I see a loose group right in the middle of what I interpret to be a node.

The results at 42.6 and 43.2 loof good but right in between at 42.9 is a load of dung.

Anybody have any insight into what's going on?

Joe

 

[mattsnuked]

Any velocities recorded? I've had barrels where 42gr were over pressured and others with 45gr. I hate OCW tests but others like them, if you think the wind was an issue I would look at verticle and less horizontal. That being said I would investigate 42-43gr range and get some multiple group averages.

 

[M1Amen]

I would definitely investigate that 42.6 load.

I actually do these in 6 round groups to allow myself a little more data. I would repeat everything in the 42-43 range, and make six rounds of each load this time. You may have pulled the shot just slightly, or you may have had a flyer. It happens, and this is why I take more than 3 rounds.

Also, go ahead and pull the test in to 100 yards for now. No need to go more than that until you are working on some of the finer points. The wind is likely not any concern for you at this range, but you can put some of those worries to rest by just bringing the target in to 100.

I would also go ahead and load up 4-6 groups of 3 rounds. One round of 42.3, one of 42.6 and one of 42.9. If you fire those, I bet they land within a minute of each other and you will confirm that you are indeed in a node.

 

[RyeDaddy]

42.6 would probably pull tighter if you seated deeper. 42.5-42.8 grains H4350 w/140's in the 260 is a near-universal load. The vertical stringing there is either parallax error or seating depth needs a tweak. I'd just run 42.6 again as is and see if the stringing doesn't go away when not on and off the rifle between shots.

OR.... Try 42.6-42.9 again when there's less wind. I would bet 42.8 would work as a OCW with some seating depth tweak.

 

[scudzuki]

Not parallax error, I dialed out any parallax.
The COL is 2.745 with the bullet .010 off the lands.
This throat is very shallow apparently.
Would I still benefit from seating the bullet deeper?

Joe

 

[RyeDaddy]

Only one way to know, unfortunately. Why not mess with seating depth a bit, say 0.005" longer and shorter? I think you've got the powder charge about right. In your next range trip you could do that AND try the same 42.6 again with more rounds and see what it looks like.

 

[scudzuki]

Absolutely.
Another excuse to head to the range

Joe