How fast is too fast for 308?

[turnerdye1]

Bergara HMR in 308 w/ 20" barrel

Bullet - Hornady 178gr ELD Match
Powder - CFE223
Primer - CCI
Case - LC
COAL - 2.80

Loads from 46-48 grains in .5gr increments.

Velocity (I apologize for the spacing. I cant get ti figured out on here)
Loads Shot 1- Shot 2 -Shot 3- Shot 4- Shot 5---Average-- SD Group Size Pressure Signs
46---- 2709 ---2656--- 2694---2627--2593------ 2655----47.6
46.5---2741--- 2764--- 2778-- 2793--2823----- 2779---- 30.8
47 ----2816----2799---2833---2785---2828------2812---- 20.1 **Best**--- Very slight primer cratering
47.5--2857----2856---2854----2863---2870----- 2860--- 6.5 ---------------- Extractor marks and primer cratering
48--- No Shoot Pressure Signs

All these groups shot right around 1MOA at 100yards. I left my tape measure at home so I don't have exact measurements. The 47.0gr load shot at probably .5-.75" and was by far the best.

From what I've read a lot of people aim for 2600-2700fps is this bullet weight range. Is there any reason for that or is 2800 good to go as long as the pressure signs are minimal?

These were shot at 100 yards. I have access to 1100 at my family farm which will be the max for this gun.

 

[sloughfoot]

Test again in the full heat of summer. You might change your mind.

 

[ckcollins2003]

I would choose a different powder if I were you. You are getting a big variance in speeds except for the one that you are receiving pressure signs from.

My loads are hot... over 2900 fps with 155's, but I'm not showing any signs of over pressure and I have a SD of 9. Consistency is key to getting good groups at long ranges. I have had a lot of loads shoot under .5 moa at 100 yards with big deviation like that, but once you get out to longer ranges they always open up a lot and are somewhat unpredictable. Make sure neck tension is consistent, brass is consistent, bullet weight is consistent, and find a load that you are comfortable with that also shoots good. Play around with seating depth to help out with SD also.

 

[bigedp51]

• Cartridge, Caliber 7.62mm Special Ball, Long Range, MK 316 MOD 0 (United States): A 175-grain (11.3 g) round specifically designed for long-range sniping consisting of Sierra MatchKing Hollow Point Boat Tail projectiles, Federal Cartridge Company match cartridge cases and Gold Medal Match primers. The Propellant has been verified as IMR 4064 (per NSN 1305-01-567-6944 and Federal Cartridge Company Contract/Order Number N0016408DJN28 and has a charge weight per the specs of 41.745-grain (2.7 g).[SUP][22][/SUP]

 

[turnerdye1]

Test again in the full heat of summer. You might change your mind.

What will I be looking for? Do velocities increase that much with temperature?

I would choose a different powder if I were you. You are getting a big variance in speeds except for the one that you are receiving pressure signs from.

My loads are hot... over 2900 fps with 155's, but I'm not showing any signs of over pressure and I have a SD of 9. Consistency is key to getting good groups at long ranges. I have had a lot of loads shoot under .5 moa at 100 yards with big deviation like that, but once you get out to longer ranges they always open up a lot and are somewhat unpredictable. Make sure neck tension is consistent, brass is consistent, bullet weight is consistent, and find a load that you are comfortable with that also shoots good. Play around with seating depth to help out with SD also.

Yeah I've read that people have had good luck with CFE223 in 308 so I wanted to test it since I have 16lbs for 223. All my 223 loads are just plinker/training rounds anyways. I may just switch to Varget for 308 since its a little more temperature stable.



I am going to northern Indiana in the middle of January and may just load up some rounds with Varget for a 200 yard ladder test and then go from there. This is my first precision bolt gun so I'm still getting the feel for it.