Savage .338 Lapua problems

[backcountryguide]

Need a couple pointers here to confirm my suspicions guys. So load development went great with the new Lapua brass and I settled on 90gr Retumbo and the 300gr Berger Elite. Groups were half moa or less out 1000. After I had 50 pieces fired I neck sized and reloaded. Went to check zero and first round hits a full 2 moa high at 100 yards. Went ahead and fired two more and the groups have now opened up to around 2.5 moa. All three of these rounds showed excessive pressure were as the virgin brass showed none. I stopped there and came home to mesure the once fired brass which was 2.725. These should have been trimmed before the second loadinng and I failed to do so. My question is do you guys believe this to be the problem? Im a little apprehensive to shoot the rest that I have loaded and think I'll just buy another batch and consider my self lucky. I didnt think the brass would stretch that much off one firing and this gun obviously has one hell of a tight chamber. What say you?

 

[ArchAngelCD]

Is your OAL longer than the factory ammo? Is the bullet hitting or close to the rifling?

I looked on the Berger bullet site and their load data lists a MAX charge for their 300gr bullet with Retumbo at 89.5gr. Berger lists a COAL of 3.681" for those loads. According to the article I read in the Aug 2014 Handloader the 338 Lapua is susceptible to high pressures even when within the limits of the load data. Your charge being slightly over the limits plus the other variables might have pushed the pressures too much.
338 Lapua Magnum | Berger BulletsBerger Bullets

The Handloader article is a good one, August 2014, #291, page 46.

 

[backcountryguide]

Arch I'm jumping 10 thou to the lands. I have the berger load data on hand but like I said this problem arose on the second firing. Should of seen these pressure indicators the first firing but the were not there

 

[canderson]

IMO the problem is the brass fits the chamber now. The virgin brass acted like a shock absorber when fired the first time. Some of the chamber pressure was used to make the brass conform to the chamber. I would pull the bullets and back off the load with the neck sized brass. This should get your pressure back down. Once you get the load shooting again with the neck sized brass you should be good to go. Another option is to full length size your brass. It will get it closer to the the same size as the virgin brass.

 

[desertbull]

Your neck tension is probably different on the second firing if you did not neck size the new brass before the first firing.

I have had better luck using the first firing to zero and fire form the brass to the chamber and start load development on the second firing.

 

[backcountryguide]

The brass was neck sized before the first loading. So nobody thinks the brass being to long is causing pressure issues?

 

[snowpro440]

To me the .338 lapua is sensitive to brass an a particular fit in a factory chamber , when setting up your full length die your brass needs to fit a little on the loose side an you might want to check it before you take that next step on every piece. Also when you fire it the case will grow in length every time. If not caught it will show over pressure signs and brass sticking and hard extraction, I had a hard time with my first lapua , then I moved on to a custom barrel and benchrest chamber with lapua brass and all my problems went away. good luck , Trim every time and full length size always for a factory chamber.

 

[backcountryguide]

Snowpro thanks for the insight. This is my first .338 so its been a bit of a learning curve. Full length and trim seems to be the best option and leave the neck sizer for the little stuff.

 

[MagnumManiac]

How does your neck sized brass 'feel' when you chamber it, is it tight, loose or have some feel when closing the bolt?
This is the easiest way to determine if your brass is too long for your chamber, or has excessive swelling from too high pressure. You must remember that the chamber may have as much as .040" in front of the neck over what the max brass dimension is. To determine this exactly would be to take a chamber cast and measure it.
How much does your neck expand on firing?
This can cause high pressures if it is too tight.
There are many variables that can cause problems pressure wise.

Cheers.
gun)

 

[backcountryguide]

I full length sized a few pieces and did a little more with the load. I worked up to 91gr Retumbo with the 300 grainer and shot two of the best groups Ive ever shot out of any rifle much less a thumper like this. Best was just under .25 at 105 yards the other flamer was just a hair over .25. Theses were 4 shot groups, one with virgin brass one with once fired so I think I will throw away my neck die and stick with the above load and practice for the .338 lapua. The groups were fired prone off an Atlas and a rear bag from Midway. Thanks to all that helped out it gave me some thinking to do about full length sizing and watching case length.