What is considered too fast for .308

[Darkside-Six]

I shoot 175 SMK's in a 24" Bartlien 1/10. When I broke my barrel in 2 years ago I did load development after 100 rounds and found a great load that gave me 2740fps. Gave me an SD of 3-5 and an ES of 10-14. I chronoed again after 300 and 400 and got very similar numbers. Now all of a sudden my exact same load is pushing 2795ish. Nothing has changed. Same 8lb jug of powder, same bullets, same primers, I anneal and use the exact same load process i always have. My SD and ES have risen a bit as well. The only thing I can think of is that my barrel finally sped up after about 500-600 rounds. I re-tweaked my load and dropped it by about .5 grains and am getting similar numbers as before but it's about 2750-2755. Not anywhere near blowing primers but I'm just curious how fast I can push these before I need to be concerned.


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[Rob01]

You are fine where you are at. My 20" with 178s is around 2700fps. With the factory Hornady 178 BTHP Superformance load in the 20" it is 2805fps. As long as you have good numbers and accuracy then leave it and shoot it.

 

[Marksman10x]

I'm getting about 2640 from a 20" with 175 smk's and a max load of varget. The barrel has about 200 rounds, so might speed up. This was basically at sea level.

 

[Pusher591]

I shoot 175 SMK's in a 24" Bartlien 1/10. When I broke my barrel in 2 years ago I did load development after 1000 rounds and found a great load that gave me 2740fps. Have me an SD of 3-5 and an ES of 10-14. I chronoed again after 300 and 400 and got very similar numbers. Now all of a sudden my exact same load is pushing 2795ish. Nothing has changed. Same 8lb jig of powder, same bullets, same primers, I anneal and use the exact same load process o always have. My SD and ES have risen a bit as well. The only thing I can think of is that my barrel finally sped up after about 500-600 rounds. I re-tweaked my load and dropped it by about .5 grains and am getting similar numbers as before but it's about 2750-2755. Not anywhere near blowing primers but I'm just curious how fast I can push these before I need to be concerned.


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Not sure how well or often you clean but a build up of powder or carbon/powder ring can create velocity jumps due to pressure.

 

[Darkside-Six]

Not sure how well or often you clean but a build up of powder or carbon/powder ring can create velocity jumps due to pressure.

I usually only clean when the accuracy starts to go. it had been almost a year and about 450 rounds since I cleaned it last. I gave it a really good cleaning and it was still fast. The only thing I can think of is that my barrel speed up.

 

[wapiti16b]

I'm getting 2740 fps from 168 g BERGER hybrids @ 5,000 ' elevation from a 20" 1n12 twist FN SPR with no signs of pressure . I'm using 8208XBR powder and notice reduced accuracy at around 300 rounds between cleaning , no loss in velocity just a slight increase in group size ( 1/2 moa to 3/4 moa ) . Velocity jump ? , what other factors have changed ? ambient temperature possibly ?, humidity ?
Regardless just shoot it and look for over pressure signs , if none are present enjoy , if it's a result of the barrel breaking in you have many rounds of enjoyment ahead of you !

 

[Greg Langelius *]

I don't know what's too fast, but I would suggest that if the velocity has changed by that much, it may pay to confirm/redevelop your load for accuracy. Accuracy nodes don't change just because the same load's velocity changed.

(Confirm = test the load with bracketed charges .2gr above and below it, to see if they might indicate better accuracy with an altered charge weight.)

Also, give the bore a good long soak with plain old Hoppe's #9 powder solvent. If there is a carbon ring, it may help. Carbon rings can be really stubborn, but if the velocity increase is due to pressure, it needs to be addressed.

Greg