Replication of Federal GMM in .308

At the suggestion of Unclenick, I re-tested 42.7, 42.8, and 42.9 gr IMR 4064, 175 gr SMK, in .308 to see if the point of impact changed within this accuracy node.

This time I tested at 100 yards, on a calm sunny 60 degree day (today). I also made sure I tested with the same barrel temp by shooting 1 round per minute, then taking 5 min off, for every single group. I shot a 4 shot group, 3 times, for each powder charge.

Again, each charge was sub moa, today with the 42.7, and 42.8 Grain charges, I had a couple nice cloverleaf groups (about 3/8 MOA).

Anyway, the Point of impact change was minimal. I used the same targets , same spot of aim etc.
The 42.7 and 42.9 gr groups had almost exactly the same center of groups relative to point of aim. 42.8 was about 1/4-1/2" higher on average, but it seems likely that was something I did.

Anyway, the main point here of this entire thread is this: You can duplicate the results of Federal GMM using the same components and same powder charge. (At least with respect to the 175 gr smk .308)

However, you may be able to get better results like I did where I got the same accuracy with an additional 110ish fps.

I guess that's one reason why we handload right?
 
Congrats , nice to see you have success . I was never able to duplicate Fed gmm . I only have one target I took a picture of shooting GMM and it was only 3 shots @ 100yds

guns167.jpg


I've never really been able to get 175gr smk to shoot that good . I can get them to shoot 1/2 moa but nothing like that pic above . I will add that SMK's although shoot great , are not my most used 308 bullet . That is the 178gr A-max and most recently the 168gr BTHP . How ever my best load using the smk was not with 4064 but with 40.7gr IMR 4895 . it is/was a bit slow at only 2510fps if memory serves but real accurate .

I have a 500ct of 175gr TMK's I'm working up a load with right now using AR comp . I just started trying both of those components but hoping this will be a good combo . I've heard from a few guys claiming AR-comp is as good as Varget if not better . Only time will tell if that's the case .
 
That brass has no problem if it isn't being pushed too hard. Also, a recent read of the Norma manual revealed they occasionally make some of Federal's brass for them, but they use an alloy with a little more copper, so it may also be a matter of what lot you got.

Congrats on your success with this project.

Metal God,

I just got 500 of the TMK's to mess with, too. The TMK are secant ogive bullets, so they're going to be more sensitive to optimal seating depth and to cartridge runout than the tangent ogive SMK's. Sierra has mentioned the same thing Berger did: that they sometimes prefer to be seated into the lands for best performance because of the secant ogive.
 
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