What a Difference a Grain Makes

[Flatbush Harry]

I went to the range every day for the last 4 days and will go again today, in all likelihood. On Monday, I was looking to square away my Winny M70 EW in .30-06 for a possible upcoming hunt.

Just to warm up, I had brought a few of my standard M1 Garand match loads (47.0 gr of IMR4895 under a 168gr Sierra MatckKing with CCI BR2 primer) to see how the rifle would handle them and also get some sense of its 100-yard zero with a 168gr bullet. I was more than a little disappointed with my first 6 shots:

I happened to have a few remaining cartridges from a test session I had with my Savage 116 last year, so next I tried 5 shots with a slightly different load. The only difference in this load was 1.0 gr more of powder (total of 48.0gr), specifically IMR4895, which is my standard powder for my M1s:

This second group measured 0.6" ctc. Now I'll be working with several 168gr hunting bullets to find the best loads but I think, for a hunting rifle with no modifications but a scope, this Winny isn't too bad. I find the improvement from one grain of powder interesting and will be truing loads 1/2 gr heavier and lighter than this one to see if there's any difference.

BTW, these two groups were shot about 15 minutes apart after the barrel had cooled so I can't attribute the differences to just cold v. hot barrel.

FH

 

[71firebird400]

Re: What a Difference a Grain Makes

Nice work! Should make a stellar hunting rifle.

 

[spamassassian]

Re: What a Difference a Grain Makes

Very interesting! I'm still pretty new to hand loading, but so far I've noticed that even a few 10ths of a grain can make a difference, maybe 2/10 or 4/10 gr. can make or break a load.

Still trying to match the Federal GMM ammo/168 gr. Sierra HPBT... getting close.

 

[sirhrmechanic]

Re: What a Difference a Grain Makes

In handloading... a grain can make a massive difference.

Run the loads too fast, and you get patterns, not groups. Run too slow and the same applies with massive drop. This is why it's a good idea to test handloads upwards until accuracy drops off, then back off a bit. Lots of info on this in the handloaders section.

Great pictures showing a hot load vs. a slightly milder load that demonstrates accuracy vs. velocity. Thanks for posting.

Cheers,

Sirhr

 

[leadbullet]

Re: What a Difference a Grain Makes

looks like you found the sweet spot, congrats, the Garand are awesome.