Help with 260 Rem Load Developement

[IAHNTR]

Need a little help form my LRH Friends

Doing load development on my brothers 260 Rem 700 that was a 308 and we put a 260 take off barrel on.

Looking for a little advice on where to go from here. I've attached a few graphs showing what we have done so far.

Powder is IMR 4350 in 0.2 grain increments with Nosler 120 Ballistic tips loaded to 0.010" off the lands. I don't think we've achieved max pressure yet, but getting close.

Ladder test shot at 500 yards and speeds from Magnetospeed. Ladder was done with Magneto on to gather velocities at the same time.

I'm initially thinking of doing a seating depth test in the 45.0 and 46.1 grain areas, but that's why I'm here.

Thanks for helping.

 

[MarkA]

I was never able to get accurate ladder results with magneto on barrel, IMO the minor shifts in the bayonet due to recoil over period of shots will move poi around too much for ladder testing.

 

[gohring3006]

Your data is pretty much useless with the Magnetospeed on.
Unless you are going to leave it on permanently.

 

[IAHNTR]

All I've read (a lot) says the magneto changes POI, but group size is the same. At 500 it changed POI ~3.25 moa high.

We were also following a testing procedure that was highlighted by 6.5 guys and is done on the premise that you use the speeds rather than where the bullets print on paper. It's done this way to completely eliminate shooter error. You could essentially shoot them into a pile of dirt and get the same info. And, since my brother doesn't shoot a whole lot, we thought this would help eliminate his discrepancies.

Where the flatter spots on the velocity graph show up are where the "nodes" would be if doing a regular ladder. We shot 3 at each charge weight to get a good velocity average, see the ES on those charge weights and be able to average the 3 (instead of 1) for the basic ladder.

We just combined 2 different load development methods together.

Thanks for the input.

 

[gohring3006]

Shifts in the Magnetospeed will change the location of Nodes and Antinodes.

 

[RockyMtnMT]

With the info that you have I think I would load the 46g load and go do some group testing without the Magspeed.

Steve

 

[LRSickle]

I'm thinking 46.1gr. I'd like to see that same test without the MagnetoSpeed though.

 

[FURMAN]

The only thing I care about when running a ladder test is vertical impact on target at extended distances. I am looking for little to no vertical change across at least a .5 grain change. After I find the node I load more of it to check for repeat-ability then start playing with seating depth. Ditch the magspeed, run the ladder, and show us some pics.

 

[IAHNTR]

The only thing I care about when running a ladder test is vertical impact on target at extended distances. I am looking for little to no vertical change across at least a .5 grain change. After I find the node I load more of it to check for repeat-ability then start playing with seating depth. Ditch the magspeed, run the ladder, and show us some pics.

Sounds good. Need to shoot further than 500 though. More like 800.