300 win mag load question?

[Greyfox]

I would initially work on the originsl load that gave you the half inch group, and try to replicate everything including brass, particularly if it was new and unfired. Given its a new rifle, I'd give it a thorough check, and also your rest, form, etc. I just went through a similar situation to yours with my buddy and it turned out it was a loose screw on forearm mount on his Caldwell rest causing his groups to open. I wouldn't rule out " a bad day".

 

[West Bay Wader]

Did your neck sizing die have the full expander in it? Most come with 2 different pieces to hold the decapping pin - a small one and one 1thou under bullet diameter. Use the larger one which will size the neck internal just under the bullet diameter and should give you consistent neck tension.

I have had a similar problem when I went to shoot some brass for the 2nd time but I sized with a bushing die and no expander ball. There was enough difference in neck thickness to give me problems with inconsistent neck tension. It was Norma brass and I did not need to neck turn for my chamber and just didn't check it. All of my ladder work looked like it was for nothing - in fact nothing shot very well. Then I figured it out. I didn't have to worry about it with Lapua brass (or not significantly).

 

[AP218]

I double checked everything and I couldnt find any loose screws or bolts. I will give it a cleaning and see if it helps. I also loaded up a few rounds is some more new brass so maybe I can narrow down if it's something I'm doing with my resizing die.

Thanks for all of the good advice.

 

[AP218]

Also I think somebody asked about what rest I use. I have been using sand bags under the front and rear.

 

[AP218]

Shot some today after cleaning and the help of a led sled type rest and my groups tightened back up. My original load that shot good still did not preform like the first time I tried it. Maybe the first time was just like. I did find a few other loads that grouped prett good though.

 

[280 Man]

Glad to hear your groups tightened back up...

 

[Marble]

It's always nice to get a load figured out and have the gun shoot well.

Congrats!! Now go shoot some more!

 

[AP218]

My groups are pretty good but I'm gonna working on its some more to try and avoid a fe flyers.