308win load trouble @ 300 rds down the tube

[eric32]

Well today at the range i was shooting ammo that was loaded about 1 month or so ago for a match that i never made it to. i just got a new S3 10-50-60 got it zeroed and started hitting some steel 8 inch plates at 300 yards. So i started shooting with my magneto speed and off the bat noticed my load was running a bit fast than the last two range trips.

Load that i frist developed

20 FPS ES for 10 rounds

41 gr IMR4064
Win Brass
FL sized with a LEE die
.334 loaded neck
WIN WLR primer
2.980 COAL
2502-2522FPS

208amax

28" CBI barrel


now it seems to be running in the 2530-2570 with a ES of 50FPS.

I will also add that the barrel after this outting has hit 295rd down the tube.

What could be the issue that would cause this all the sudden?

 

[thefitter]

Temp?

 

[Kermit in Va.]

Could it be a temp change ???


Kermit

 

[eric32]

it was 40-50 degree when i frist got the load

now its 70's why did the ES jump up so much?

 

[bigedp51]

How was your ammo cleaned before you reloaded it, I think it was here that it was mentioned that cleaning with stainless steel media "super clean" necks would cause the bullets to bond to the inside of the case necks over time.

Just wondering, this was said by the dirty neck clan. :

 

[eric32]

I just tossed in some walnut media for a couple of hours i dont believe in super clean brass due harder seating after never saw a accuracy difference with a sonic cleaner vs Walnut media

 

[jlow]

it was 40-50 degree when i frist got the load

now its 70's why did the ES jump up so much?

I think depending on how wide your sweet spot is and how close you were to the edge of that spot, the increase in temperature could push you out of it and affect both your ES and group size. This is why when you do an OCW and choose your load, you usually don’t pick a location too close to the edge especially if it was run on a cooler day.

 

[BlackEagle]

If you're shooting heavy bullets you may be compressing the powder enough that the bullets may be getting pushed out a little. They may be getting pushed far enough that they're into the lands.

 

[eric32]

If you're shooting heavy bullets you may be compressing the powder enough that the bullets may be getting pushed out a little. They may be getting pushed far enough that they're into the lands.

they are already in the lands .10 thou but when i seat the load i don't hear any crunching of the powder

 

[MrMajestic]

It is not untypical for a barrel to speed up after/during break-in and the round count could vary. Sounds like this may have happen and pushed you out of tune. JMHO

 

[eric32]

It is not untypical for a barrel to speed up after/during break-in and the round count could vary. Sounds like this may have happen and pushed you out of tune. JMHO

So what do i do??

Do i drop powder charge to get back into the 2500-2520 FPS range?

Or do i just go to a higher node??

 

[ShootDots]

There is ONE possibility I can think of... You did not mention the style (B/T or VLD) nor the weight. However, judging from the speed you might be shooting a 185-190gr bullet. If that is the case 41.0grs charge of IMR 4064 is approaching or is at the top of the pressure scale for that projectile and powder. IMR 4064 is VERY temp sensitive as well as >>> and this may be your answer>>>VERY barometric pressure sensitive. If you shot on a clear crisp day and then shot on a warmer HUMID day>> you are going to have some rather surprising events. When you push temp / barometric sensitive powders to the limit, almost any "atmospheric" change of any appreciable degree will cause those kinds of "exceptions" that you do not expect... Like I said, this ONLY may be the culprit. Down here in Houston, Texas we have LARGE temp / barometric pressure swings and I have learned from experience.

 

[eric32]

There is ONE possibility I can think of... You did not mention the style (B/T or VLD) nor the weight. However, judging from the speed you might be shooting a 185-190gr bullet. If that is the case 41.0grs charge of IMR 4064 is approaching or is at the top of the pressure scale for that projectile and powder. IMR 4064 is VERY temp sensitive as well as >>> and this may be your answer>>>VERY barometric pressure sensitive. If you shot on a clear crisp day and then shot on a warmer HUMID day>> you are going to have some rather surprising events. When you push temp / barometric sensitive powders to the limit, almost any "atmospheric" change of any appreciable degree will cause those kinds of "exceptions" that you do not expect... Like I said, this ONLY may be the culprit. Down here in Houston, Texas we have LARGE temp / barometric pressure swings and I have learned from experience.

darn my bad i am shooting the 208 amax, but i think you might be on to something but now i have to see if anyone want to trade 8lbs of 4064 for some varget. i have a load with BR2 primers and Varget with a 10 shot ES of 6

 

[ShootDots]

You will find that during the COOL to COLD months where there is a high pressure system (low humidity) IMR 4064 works GREAT... But start heading towards a humid summer and you need an "extreme" powder... Varget or even RL-15 would be my lick AND in that order... I hope this helps..

 

[eric32]

yea helps a whole lot thanks i never thought of RL-15 of being temp insensitive ?

 

[witnessing]

Mine does the same thing with the same load . Brass is r-p. Poi shifts up or down one inch at100 yards.

 

[MrMajestic]

Try some H414. Not "Extreme" but it is slower and finer so you can get enough in a long-seated .308 Winchester. I shot it in a long throated Remington 788 with the 208 A-Max and Palma cases. Very accurate and good velocities from its 20" 10tw tube. IMR 4064 may be a little fast for that heavy weight however use to be the "go-to" powder for the 150-168 class bullets. Do you have Quick Load? If so run the #'s with H414 and you will be pleasantly surprised.

To answer your earlier question, yes adjust your powder charge to get you back in tune.

 

[ShootDots]

Eric. you can pick up a "can / bottle" of RL-15 and right on the label it says "consistent at all temperatures".. It is "fairly" temp stable>>>not as good as Varget or 8208>>>But nonetheless pretty good. It is also "dirty" so the "hotter" you run it, the cleaner it will burn... However, it will NEVER be as clean as Varget or ANY of the VV powders!

 

[cmillard]

you didn't by chance shoot your cold bore through the chrony screens did you? I usually send a couple down range first before I send them through the screens. that will throw things off otherwise

 

[bigedp51]

yea helps a whole lot thanks i never thought of RL-15 of being temp insensitive ?

The military stopped loading the special long range ball 7.62 with RL-15 due to heat related high pressure problems in Iraq and Afghanistan. This ammunition is now loaded with IMR4064 so RL-15 is NOT a extreme powder.

Cartridge, Caliber 7.62mm Special Ball, Long Range, MK 316 MOD 0 (United States): A 175-grain 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 grains)