Federal Premium 7.62 more accurate than 308 and hand loads: Need help

[Kevin1]

Rifle: Savage 10FP with B&C Medalist A2 stock
Shooting at 100 yards (I know for load dev, farther distance is preferred)
175 SMK used for all factory ammo and reloads

For the first time, I tried the Federal Premium in 7.62 (GM762M2). I’m a little confused and need some help understanding the way my rifle shoots these different type of ammo.
The groups you see with Federal 308 (GM308M2) are typical out of my rifle. I usually get a flyer that opens up the grouping to around 1”.
I’m doing some load development with IMR 4064/175SMK/Winchester brass and 42 grain seems to give the best results. I did get a couple of flyers on the first and last shot, but overall it’s more accurate than the factory ammo GM308M2.

Here’s where I get confused.
The Federal Premium in 7.62 (GM762M2) looks to produce better groups compared to both the GM308M2 and my hand loads. The last shot with GM762M2, is one shot perfectly in the center (surely some luck there)

So here’s the question:
I was about to swap my factory barrel because of some of the flyers I’m getting with hand loads and GM308M2. But after seeing the awesome groupings I get with GM762M2, I figured out there must something I need to do differently in reloading my rounds. Any ideas?


Here’s the pics of the groups. The last shot with GM762M2, is one shot perfectly in the center.

 

[hahco]

when I see horizontal spread like some of those groups on my targets, it's usually because my gun isn't sitting rock solid in the bag. The slightest horizontal movement of the crosshairs to one side or the other as the trigger breaks can cause that. I would actually say that it looks like the IMR 4064 load has a lot of potential! FWIW, my Savage 10PC (although it is in a factory accustock), does 5 shots in 3/4" at that range when everything goes right. swapping to a better barrel very well may net you some tighter groups overall.

 

[flylo]

I can't answer your question but you sure made me feel better as I just bought 44 boxes of Fed 168 gr prem match & 50 boxes of 175 gr prem match. I'm new at LR shooting & plan on handloading but always heard Fed prem match were the best factory ammo. Thanks! ;-)

 

[Kevin1]

I understood that for both loads (GM762M2 and GM308M2), Federal is using IMR 4064 powder.

Does anyone knows if the charge and seating depth is different between these 2 loads?

 

[winxp_man]

The 762 is loaded with a harder mil-spec primer and is best suited for semi-automatic rifles. The cases are also built to military visual specifications to show the iris/annealing mark on the case neck. The 762 is loaded to the 308 specifications but with cosmetic differences to the case.

 

[weshowe]

Kevin1,

I've had similar results with 4064. You're shooting position may be part of the problem, but I can't really address that without seeing you shoot.
Reloads: open the neck using a proper .308 mandrel AS A SEPARATE OPERATION. This makes the mouth coencentric and has the same neck tension on each case. Using this method groups shrink considerably. It's extra work, but worth it.
Try a 175 grain SMK over 44.0 grains of Varget, a Lapua case, and a Federal 210M primer loaded to a OAL of 2.800". If that doesn't shoot nothing will.
Finding what shoots is half the fun...;-)

Good luck in your endeavor.

Wes