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New virgin brass vs new factory ammo vs 1x fired brass
- Reloading Depot
- 6 Replies
When I take measurements of virgin brass, there tends to be substantial variations in their head space, case length and even with the thickness of the case walls. . . particularly from one lot to another. You have cases that are mass produced to within a range of tolerances to fit a range of factory chambers that are constructed to within the SAAMI range of tolerances. In addition to that, I find virgin cases are often just trimmed to length with a square cut (no chamfering or deburring), which certainly has effects on a bullets bearing surface and affecting performance. If one is one is not addressing these issues of virgin brass, one can expect to not have as good performance as one can get with well prepped reloaded brass.
High quality brass, like Lapua, will pretty uniform compared to some other brands, having less of these issues, but still there issues like a case headspace that just doesn't fit well in a particular chamber. I happened to try some virgin Alpha brass for the first time in my .308. Measuring the various dimensions, they were very very consistent, but the case mouths were cut square so I chamfered and deburred them. Upon loading them up to fireform using my favorite precision load, it performed outstanding where the whole batch was chronoed and I got an SD of 6.2 with an ES of 29 and the result on target was great too (like 5 shot groups between .350 and .500). That's as good as I do with my Lapua brass that has been fully fire formed and processed.
I've always been of the school that one can do "some" load development with virgin brass. But they're not fully ready until fire formed and fully prepped to include annealing so that the cases are as uniform from case to case as possible. Along with all this, it's also very important to have very accurate powder weights in these cases for consistencies sake.
Factory cartridges shooting sub MOA consistently isn't really that hard to get if one has a quality barrel. And it can be harder to achieve with factory ammo with a pencil barrel compared to good sporter barrel. So, there are various factors involved.
On more than one occasion I've taken factory ammo (like Federal Premium match grade, as they call it) and taken half a box of the cartridges apart, measured them (like seating depths) and the powder weights. On each occasion the factory cartridges has substantial variances that not only showed up on the targets, but also on the chronograph. Having taken half of them apart and reloading them using the same bullet and powder (weighed the total weight and divided the weight by the number of cartridges to make each cartridge have the same powder weight). Before doing the total weight, I recorded the powder weight of each cartridge and yup, there was what I'd call significant differences. When I reseated the bullets, I also seated them to the same seating depth as the average of the from the factory seated cartridges. The last time I did this was March of this year with Fed Premium 175 SMK's. The factory cartridges produced an SD of 13.3 and an ES of 43 with a group of .655 MOA and the reloaded cartridges produced an SD of 8.6 and an ES of 25 with a group of .491 MOA (this is from an RPR with a 26" Krieger heavy barrel). Average velocity was only 4 fps difference. Though these were only 10 shot of factory ammo and 10 of the redone cartridges, on other earlier occasions I saw the same kind of thing.
I think the biggest factor one is going to find with factory ammo is the particular company's quality control. And along with that, like when evaluating when one's load development, one can get lucky and happen to get a real good results from a small number of rounds fired, but firing more becomes hard to reproduce the results.
.008 to .012 short on headspace is a lot and may take several firings to get them fully fire formed . . . especially if they're not annealed properly. In my limited experience, that amount and variance would certainly produce poor results.
Precision Rifles.....show em!!
- By Bigrederic
- Bolt Action Rifles
- 5732 Replies
Been shooting this one allot lately... H&W 308 with Impact action and CRB barrel.
PortaJohn
- By Darryle
- The Bear Pit
- 137983 Replies
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