6.5-284 Norma + Scenar 136-L + H4831sc Load Verification

[sawacs]

Would you guys mind giving me a math check on my load data?

I am trying to figure out a safe starting load for my 6.5-284 Norma 24" CBI 1/8 twist barrel using the Lapua 136-L Scenar bullets.

Here is the situation..

My particular chamber will allow me to seat the 136's to 3.068" COAL which is touching the lands.

Lapua's data shows a COAL with the 136's of 3.110"

Berger sent me data for the 136's with a COAL of 3.180" which I cannot achieve due to a shorter throat.

Here is the data from Berger for the Lapua 136-L's using H4831sc which is the powder I am using.

Bullet: Scenar 136-L
Powder: H4831sc
COAL:3.180"
Start charge: 49.0gr 2657fps
Max Charge:54.2gr 2936fps

Just for reference, Nosler shows the following data for a 140 grain bullet

Powder: H4831sc
COAL: 2.980"
Start charge: 45.0gr 2601fps
Max charge:49.0gr 2769fps

My question is where to start with the charges if my seating depth is 3.058" COAL or .010 off the lands?

Would I be on the safe side starting with 49.0gr of 4831sc based on a seating COAL of 3.058"? I am fairly certain I would be okay starting with 49.0gr but it is always nice to hear opinions from others.

Advice would be appreciated!
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[Capt RB]

Use the nosler start charge at your coal! Run a ladder with .3grain increase. In 15 shots you will have a load map for your gun My 308 has heavy bolt lift smoked primers with craters the moon is envious of at 43grns of varget. Look around and you see guys running the same 175grn bullet with 45+grns of varget with the same brass.

 

[Greyfox]

At your COAL you will be fine starting starting at 49gr with H4831sc. I suspect you will end up with a charge weight with 140gr bullets in the 51.5-53gr range using LR primers.

 

[sawacs]

Thank you both for the replies!

For now, I plan on sticking with the 136-L's especially considering the gun has never been test fired: built and head spaced it myself back in 2010 which is the reason I am being overly cautious with the loading.

After I get the 4831sc and the 136-L's tuned, I plan on moving over to the Retumbo then on to 140's.

Cheers!

 

[Trnelson]

I agree 49.0 of H4831sc is safe place to start. Take small steps up, considering your COAL. I treat that 136g scenar just like the 139g. In my 6.5/06 they both hit maximum safe pressure prior to 52.4g with H4831sc.
Very consistent bullet for steel and paper, but don't waste your time trying to hunt with them. Both behave in a similar fashion as a FMJ

 

[sawacs]

I would be very happy if I can find a good accuracy node at 51.0gr or under. Velocity is not overly important but accuracy is.

Thanks