Wowzer! Didn't think that half a grain of powder would make that much difference

[CB11WYO]

So I rebarreled my 300 RUM to 7mm RM a bit over a year ago. At that time I worked up loads with Berger 180 VLDs and 66, 67, 68, 69, 70 grains of Retumbo. (whole grain increments, not half grain... that'll be important later... ) 68 seemed to be a clear winner (about 3/4 MOA) but since then it just hasn't shot as tight as I thought a custom rifle ought to.

Fast forward to this last weekend...

I decided to do a simple ladder test, just to see if I could squeeze anything more out of it. I loaded one round each of 67 thru 71.5 grains, in .5 gr increments this time , put out a target at 400 yards and went to work.

The results seemed pretty clear! (see pic) 67, 67.5, and 68 (shots 1, 2 & 3) went under 1" at 400 yards... I'd say there's a node there then. I was kinda excited to say the least. So to test it further I loaded up 3 rounds each of 67, 67.5 and 68 and went out to shoot for groups. 67 and 68 weren't anything special (maybe 3/4 MOA) but hey now look at 67.5! (see pic) 3 shots in under 3/4 INCH CTC at 400 yards! That's like .16 MOA!!!

Man I'm super excited and really hoping this ain't a fluke... had to go back to work this week but come this weekend I'll be out putting the 67.5 gr load through her paces at longer distances just to be sure! Looking like .5 grain might make some difference after all, really didn't think it would in a total charge of almost 70 grains of powder. It took a so-so hunting rifle and turned her into the best shooter in my safe pretty much.

 

[joshb]

Sounds like you have a shooter, there! Great news. I had a great day at the range, too. Ain't it FUN, when it all comes together? Josh.

 

[FeMan]

That's a pretty dramatic change and great results! My STW went from barely 3/4 MOA with 168 Bergers being the best I could do after complete load development to under 1/4 MOA when I changed from CCI Mag to WLRM primers.

 

[Dusty Stevens]

Were you using wind flags?

 

[TheOtherZilla]

Were you using wind flags?

He's in SW Wyoming. Wind flags just blow away... We have to use wind chains here..

 

[slm9s]

Lots of hope has been dashed after one great 3 shot group. I try to do at least 4 round groups with sporters or 5 round groups with heavy barrel rifles.

Hope it continues to shoot great for you!

 

[Brians356]

Lots of hope has been dashed after one great 3 shot group. I try to do at least 4 round groups with sporters or 5 round groups with heavy barrel rifles.

Hope it continues to shoot great for you!

Most forgiving of all are 1-shot groups. Those are what I hang on the braggin' board. 8)

 

[CB11WYO]

Lots of hope has been dashed after one great 3 shot group. I try to do at least 4 round groups with sporters or 5 round groups with heavy barrel rifles.

Hope it continues to shoot great for you!

Ohhhhh yes, don't worry it'll be tested thoroughly in the next couple weeks... but heck, that group could double in size and it'd still be better than it was shooting with my old load ha ha ;D

 

[grovey]

Lots of hope has been dashed after one great 3 shot group. I try to do at least 4 round groups with sporters or 5 round groups with heavy barrel rifles.

Hope it continues to shoot great for you!

Most forgiving of all are 1-shot groups. Those are what I hang on the braggin' board. 8)

+1

 

[Lapua40X]

That's some pretty tight grouping. I initially thought the caliper tips were not properly on the center points but a print out and independent measurement validated the data (and disproved my theory) so I apologize for having doubted you. Nice job ............

 

[cdparker]

Were you using wind flags?

He's in SW Wyoming. Wind flags just blow away... We have to use wind chains here..

Here in Alaska, I have a weather rock. It hangs on chunk of log chain. If the rock is swinging-it's windy. Wet means rain and white indicates snow. If the rock goes missing, I don't leave the house.