Completely confused - new scope, loads and bad groups

[Nosler06]

Well just finished sighting in my 1971 Browning BLR .308. This rifle used to have a 3x Leupold fixed power scope and had great groups of smaller than 2 inch square 100yds 4 or 5 shots. I have replaced the scope with a new Leupold Vari II 3x9 scope. The ammo is reloads of .308 Nosler 165gr Partition bullets, CCI200 primers, and 42.5gr IMR 4895 powder. I believe this rifle had better groups with IMR 4350 powder. The IMR 4350 powder from what I have been told is not recommended for the .308 cal. I am trying to figure out why the grouping is not as tight as before with this scope replacement. I am not sure what I am missing here. I have gone as far back to check powder weights on 3 different scales to be sure something is not going wrong at that point. Would love to here any suggestions.

 

[mmattockx]

So, you changed the scope and tried a new load and are wondering why the groups aren't as good as with a different scope and load?


Mark

 

[Nosler06]

Sorry, I will clarify a little. The load data supplied for the IMR 4895 powder was used when the old scope was on the rifle. I should have asked two different questions. I wondered also if someone knew of a reason the IMR 4350 powder should not be used in the .308. I have had great success with the IMR 4350 powder in my 30-06.

 

[Stevebot-7]

Are you able to try shooting some of the old ammo with the new scope, or try shooting the new ammo with the old scope put back on? That's really the only diagnostic advice I can give. I don't know enough voodoo to get into discussing the differences between the two powders.

 

[Ganderite]

Different loads get different results.

Load the 4895 in 0.5 increments and see if one works better. Also, 4350 would work just fine. Try it. 45 to 49 gr.

 

[rodregier]

Loose mount has opened up more than a few groups too. Mount to receiver, scope to mount fasteners "tight"? Scope not slipping in the rings? Scope body not contacting the barrel or receiver?

If you're still scratching your head, try some factory ammunition as a diagnostic tool.

 

[bushwhacker]

I recently tried reloading some .308 with 4350 and found the recommended load required compressing the powder with the bullet. Not a maximum load by any means. I dumped the powder and went with 4064. May have not been a problem, but I didn't want to take a chance. The 4350 works fine in a 30-06, but it has more case capacity.

 

[bubba300]

Is the powder you are using from the same lot or can,that will change group sizes sometimes.