308Win, IMR4064, 155LS question

[jbell]

I am starting load development for a AW 308 Win. I am using Lapua brass, IMR 4064 and 155g Scenars. The IMR load data says a starting load is 43g @ 2602 FPS and max is 47.5 @ 2871 FPS being a compressed load. I usually try and stay away from compressed loads as a rule but would like to get some decent velocity out of the 155's. I decided to start a 44.5g and work up to 47g slowly to see where the accuracy came in and pressure began. I usually do this first work up with the bullets jammed 0.010" into the lands and then after finding the charge back the bullet off the lands. However I found a compressed load at my starting load of 44.5g. I was able to settle the powder by tapping the brass some so I could seat at the depth I wanted. If I didn't settle the powder I couldn't get the bullet seated deep enough. As I worked up to 45g I found I could no longer settle the powder enough to be able to seat to my depth (which I plan on seating the bullet deeper before I am done). So for now I am going to just start at a lower charge and work up to 44.8g and see what the velocity does.

What I am wanting to know is if anyone else has seen this or not with this load. My jam is 2.237" CBTO so I am seating to 2.247" CBTO or about 2.863" OAL. With the charge from 44.5g to 45g the powder is up in the shoulder getting very close to the neck. I am using the IMR 4064 as opposed to some of the other powders because I actually found some in stock.

Thank you in advance for any thoughts...

 

[jonbearman]

Use a drop tube and see if that helps. Is this dupont IMR or new manufactured stuff?

 

[dkhunt14]

I would try using a long drop tube and I bet the powder settles in better. Matt

 

[jbell]

Thank you both for the reply. Yes it is new mfg IMR, and I would use a drop tube but the only one I have is for 45cal so it is too big to work. I may order a drop tube that would fit, but I thought about that and just didn't have one. I should of mentioned it...

 

[rminut]

I bet the load data was made using Winchester brass. There can be quite a big difference in capacity when using those lincoln log powders. the tube will help but i doubt you will get close to 47gr.

 

[stool]

you are mis-using two terms..
OAL is overall length...of anything.
COAL is cartridge overall length...

i am guessing one of your numbers is ogive length of a loaded round.

What I am wanting to know is if anyone else has seen this or not with this load. My jam is 2.237" COAL so I am seating to 2.247" COAL or about 2.863" OAL. With the charge from 44.5g to 45g the powder is up in the shoulder getting very close to the neck. I am using the IMR 4064 as opposed to some of the other powders because I actually found some in stock.

Thank you in advance for any thoughts...

 

[jbell]

Stool,

Thanks I always thought OAL (over all length) was the length tip to tip and COAL was base to ogive. I guess they are the same. Ill fix the post...

 

[MrMajestic]

Do you find the crunching sound un-nerving? ;D Try a max load of 3031 behind the lighter bullets! As long as the bullets stay at the seated depth and pressure tested safe I don't get too concerned about compressed loads. JMHO

 

[jbell]

Oh the sound don't bother me at all. I cant seat my bullets to the correct depth. I was able to get the lighter charges to settle enough to seat my bullets where I want. But I cant get with in 2 grains of book max...

 

[fm1947]

155.5 Grain IMR 4064 40.0 2529 44.5 2800 103.2%
This is Berger data 44.5 is 103%

 

[boltman223]

I have an idea for another way to go at this. You could uni-throater from pacific tool and gauge and set the throat up so that you can seat the bullets out farther and have a little more room for powder.

The uni-throater is quite simple to use actually and can be done at home by hand.

 

[jbell]

fm1947, thank you for that info! I was thinking that the data on IMR's site may have been a bit off. I will report back after I chronograph my loads.

boltman, I appreciate the idea but I would rather not bother with altering the throat on my Accuracy International AW. I will change bullets or powder or both before I do that. But thank you for the idea.

 

[Bart B.]

jbell, are you looking for a load for those 155's to use in long range matches?

 

[gaboon]

I would like to see a 308 case fill with 47grs of 4064. I use 43.5grs and it just about fills the case.

 

[fm1947]

jbell, your welcome!, I'm waiting on a 308 barrel also from shilen, about 2 1/2 months now, I got a 1/13 twist, 26 inch, .334 neck, I bought some 4064 I couldn't find varget , but now I have both to work with. good luck, I start at lands.

 

[jbell]

Thank you all. I just bought this AW with a 308 barrel and will be ordering a 260 barrel for it soon. I just figure I will shoot the 308 barrel some too and cant find H4895, RL15, or Varget. I will be shooting steel out to 1200ish yards. There are not too many formal competitions up here in Maine, but I wish there were...

 

[Bart B.]

jbell, 1200 yards with decent accuracy may require a 30 inch barrel with 155's. They may need to leave the muzzle at least 2900 fps to remain stabilized and supersonic that far away.

Palma match rifles using 155's typically have 30 inch barrels and shoot 155's out around 3000 fps to be on the safe side of both pressure and bullet stability.

 

[gaboon]

Don't forget palma uses some serious hot loads too. Just too push the 155s to 3000fps.

 

[jbell]

Thank you for the info, but shooting past 1K isn't that big of a deal with the 308. I have done it several times before with other rifles. I know that the miss percentage goes up very fast once you get to about 950ish yards with the 308 on the size targets I shoot at (12"X 16" or 12" X 12"). I just have not used the IMR 4064 in a long time and was wandering why I could not get close to book max load with my combination. I usually use Varget or RL15 with a 175g SMK @ 2600 fps to shoot out to and slightly past 1K. I know they are subsonic by the time they get there (especially at 2500 feet below seal level DA, Maine can suck in the winter) but they handle the transonic state very well as do the 155 Scenar.

I was not really looking for a load to shoot at distance but rather if other have tried this combination of bullet, brass, and powder. What they found for velocity with having to reduce the load. I have found before that with a reduced charge but still a full case of powder you can attain the same velocity as you would with a higher charge due to the increase in pressure form the lack of space.

I decided to go ahead and reduce the charge and try it and see where the numbers are. Ill report back if I ever get to go shoot, I just got called into work again...

 

[boltman223]

2500 feet below sea level?