338 Lapua Mag Problems

I purchased a 110 BA in 338 Lapua Mag and started reloading for it after I shot some Hornady 250 gr. HPBT with no problems. The first reload was fine, but the primers were flattened.
250 gr. Siera Spitzer Boattail
90 gr. Hodgdon Retumbo
Winchester WLRM
Lapua Brass
The second reload had the same problem with the primers being flattened. Along with that, 2 out of 5 of these didn't go off the first time that they were struck by the firing pin.
225 gr. Nosler Accubond
82 gr. Alliant RL-19
Winchester WLRM
Lapua Brass
Both reloads used the minimum powder charges or very close to it. I am really curious as to what might have caused this, any help would be greatly appreciated!

flattened primers are not always a sure sign of pressure,and are you sure the fireing pin struck the primer on those 2 shots.you could be having the same problem a lot of us are having with the accutrigger.

I would say it's possibly a combination of over sizing your brass, and not enough powder charge.

If you're over sizing your brass, and bumping the shoulder back too far, you may not be hitting proper headspace with your brass, i.e. the brass is too far forward in the chamber, and not up against the bolt face hard enough for the firing pin to get a good strike on the primer.

Also, you're running a minimum powder charge, which if coupled with the above scenario, can allow the primer to start to back out of the primer pocket during initial combustion, since the brass is sitting forward off the bolt face. Then as the pressure comes up enough to set the brass back against the bolt face, it has to drive the primer back into the primer pocket, causing it to flatten.

I would try playing with your sizing die, start with the die several turns higher in your press than you've had it, and size one, then test chamber it in the rifle. Keep doing that and slowly turning the die down in the press until you can just close the bolt with a slight resistance. Lock the die ring here and size a batch that way.

As far as powder charge goes, especially with the very large case cartridges, I start my ladder testing at the half way mark between the "min" and the "max" charge in the table, and work my way up from there. It's been my experience that large cases and slow powders don't even start to shoot good until you get up near the "max" area anyway.

Thank you both for getting back so quickly, everything was very helpful. I saw the indentation on the primer from the firing pin on both. I haven't noticed anything that I would consider a problem with the accutrigger except for very minor creep. What kind of problems are you experiencing with your accutrigger?
The scenerio with the minimun powder charge is what I was thinking, but a second opinion is always helpful. I have done a fair amount of reloading for my .308 and .243, but I thought it better to be safe and start lower because the powder charge is roughly double compared to my .308 and .243. The next time that I sit down to reload I will go over everything again and play with my sizing die and the powder charge.
Do you think that a different primer would be helpful to try, I usually use Federal Gold Medal and I have had great success with them.

some people,me included have problems not pulling straight back on the trigger,causing what sounds like a misfire.from my experience with my 110ba 338 anything less than a 250 grain bullet is a waste of time and powder.the 1:9 twist actually preffer s the 300 grain pills.as far as powder i get excellent results with retumbo.

I don't have any experience with the 338 Lapua. I have also had great success with the Fed match primers. I use them in my 243, 6.5x284, 22-250, and 308. None of these use near as much powder as the 338 L though. You may find you need a hotter primer for the larger powder charges, but I would wait until you run the charges up the scale, as combustion is bound to get more efficient as you go up.

Are you getting sooty cases now? I would imagine you're not getting a good gas seal around the neck now?