Virgin brass vs 1F brass Lapua

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Ogg2012

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In the process of fire forming my 308 Lapua brass, I came across a powder load that printed very well. After fire formed and processed, I attempted to duplicate the load. TOTALLY different results, groups were out to lunch. Was expecting that so no surprise there.

Just wondering if anyone has any experience of what needs to be done to get back to the node I was in? Considering the 1F brass is now formed and correct shoulder bump. The 1F cases now have more internal volume im sure. I don’t really want to burn through a bunch more components trying to get back if someone has had a similar experience.

The virgin brass load was 43GR benchmark with a 155gr VLD hunter.
 
Did you happen to have a chrony on the loads? Is the barrel brand new? cleanliness of barrel?

Cases won't provide much pressure change- it is dictated by the chamber.

How did you prep the new brass? Full size? Neck size only? Have you compared runout for the virgin/1F?

Nodes should somewhat follow the velocity, so if the barrel is speeding up (from new) or you are jumping further it could be affecting things. I haven't had the situation you are in, but I have had the situation where a load stops working and this is usually nothing to do with the load.
 
I didn’t chronograph the virgin brass loads unfortunately. Cleanliness was about the same. Maybe 10 round difference from a clean bore. Barrel is not new, 200 or 300 rounds through it. Brass was prepped with full size die, trimmed to same length, etc. Did not check runout. Rounds should have had the same neck tension as I prepped the virgin brass the same way I did the 1F. I anneal every time.

Only thing I can think of that would not be consistent between the virgin and 1F would be headspace which would change my jump and pressure. I’m thinking I will have to work my way down on the charge and work my way up closer to the lands.
 
If you chat with competitive FTR shooters, we all fireform our brass before worrying about settling on a final load... also, let the barrel season in (yours likely has).

Work up your load starting 0.4gr below to over where you are now in 0.1gr increments, and I am sure you will be back in tune next trip out.

Jerry
 
Mystic Precision said:
If you chat with competitive FTR shooters, we all fireform our brass before worrying about settling on a final load... also, let the barrel season in (yours likely has).

Work up your load starting 0.4gr below to over where you are now in 0.1gr increments, and I am sure you will be back in tune next trip out.

Jerry
Click to expand...

Very good advice.
Another thing to watch out for is leaving powder in your thrower for a few days. The change in humidity can make a huge difference depending on the powder and the humidity in your loading area. Bryan Litz had a good bit of info on this. The only other thought could be neck tension between the new brass and once fired.
 
You are probably on the wrong node. In choosing a load you should have at least two consecutive good groups with it - let say 42.0and 42.3 as an example that are good.

Lapua brass is notorious to have tight neck out of the box. Resizing and passing a mandrel is the way to go when first loading it and thereafter for uniformity.

Like Jerry wrote..fire formed brass should give you better result.
 
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