6gt
- Thread starter Dthomas3523
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Could be caused by your headspace, if it’s just an ejector mark, unaccompanied by heavy bolt lift. Cases growing .008 means your headspace is prolly something like .006-.007 over a go gauge, which is fine (cause you’re only going to bump .002-.003 back from that), but leaves enough room for the case to get a running start at the bolt face and leave a mark from the ejector.
Alpha brass is 001 under my go gauge. If it's growing 008, and prob not fully formed due to first firing, likely 009 for true headspace, that chambers out of spec, however it's workable. You'll be fine future firings, I'd strip your bolt down and just bump enough for free bolt fall.
I had mine chambered 002 past go, get 003 growth on virgin. Bumping 001 over virgin. Once you get to the point of needing a new barrel, you could run into a situation with your brass........if the smith cuts the barrel proper, you'll need to bump all your brass back quite a ways. Or you can send him one your sized cases and tell him to use it as a go gauge but 002 deeper. However, that chamber will once again be out of spec.
I had mine chambered 002 past go, get 003 growth on virgin. Bumping 001 over virgin. Once you get to the point of needing a new barrel, you could run into a situation with your brass........if the smith cuts the barrel proper, you'll need to bump all your brass back quite a ways. Or you can send him one your sized cases and tell him to use it as a go gauge but 002 deeper. However, that chamber will once again be out of spec.
He’s still within spec, though, technically - SAAMI allows .010 for chamber dimensions (1.3607-1.3707 at the datum). Shorter headspace is arguably a little better, but once his brass matches his chamber, he’s good to go. Probably goodness not running hotter stuff, though - Hornady factory stuff might show more issues, especially with the tight bore and longer headspace.
You’re spot on about having the smith who cuts the next barrel match fired brass minus a couple thousandths, just to save brass wear.
My jgs gauges in gt and creed are 005 apart, go VS no-go. 007-008 seems excessive.
Sounds like your cases are stretching a fucking lot. 8 thou ain’t nothing lol.
That said, 32gn of Varget or 36gn of H4350 sounds about right and shouldn’t blow shit up.
It takes 2-3 firings to really fire form brass… I’d just stay on the lower end of charges until your brass settles in before you push it.
That said, 32gn of Varget or 36gn of H4350 sounds about right and shouldn’t blow shit up.
It takes 2-3 firings to really fire form brass… I’d just stay on the lower end of charges until your brass settles in before you push it.
Forgive me, but I want to understand (and learn). I thought bumping the shoulders back .002" means from the chamber dimension? That is, your sizing die is fixed, and it should be bumping all brass back to the same measurement, regardless of whether or how much the brass has fire formed? This gives your brass some .002" clearance to chamber but be as tight as possible to be snug up against the chamber. That is, as large as possible but no chambering difficulties to slow you down when chambering a new round on the clock, even if the chamber is a little dirty or it is dusty out and you are on the clock.
Maybe I do not understand this reloading process, or maybe I do not understand what you are saying.
I do not understand why bumping back .002 should ever result in being .008 shorter (I assume you are talking about the shoulder here, still).
Could you please explain this to me simply? Do not be afraid to talk down to me. I will not get offended. I really want to understand what you are writing. Thank you.
I read that as what he's saying is that he's trying/planning to bump .002, but it isn't clear what he should use as the reference dimension that equals his chamber (because his brass hasn't grown consistently on first firing, which is typical - it usually takes 2-3 firings before it all uniformly matches the chamber). Once his brass is consistent, he can bump .002 from the nominal case length, and be good to go each time.
The bit about being .008 longer - he's comparing his longest fired brass to a brand new case (which is typically .001-.002 shorter than the minimum chamber dimension in the cartridge spec). His chamber has to be at least as long as his longest fired case - so using that as the reference, and making sure all the brass is at least .002 shorter than the longest fired case is a good way to start. But he's not talking about bumping them .008 shorter (that'd severely shorten the lifespan of those cases if done regularly).
That said... While getting dies set, or simply through negligence, it's possible sometimes to over-bump a case by that much... ask me how I know... LOL. So, accidents do happen.
Precisely. I'm using a comparator on the case shoulder.
The factory brass that I measured was about 1.407" (this is clearly just a reference measurement relevant to my measuring system only). I don't have any more new brass to measure to double-check this.
Most once-fired brass is in the 1.413"-1.414" range, with a couple of cases at 1.415" and a few at 1.412"
I have set the die to bump to 1.413"
I'm still seeing the occasional ejector mark with 1x fired brass loads, which should only have a headspace of 0.002" or so. I don't think it's high pressure based on the powder charge and velocities (I'm in the velocity range other people are getting from short barrels with dasher/BR and even ARC cases). Although I ack that the .236" bore might be fucking me here
I have seen other people saying "this just happens" with Alpha brass sometimes due to the surface finish, or brass hardness not fireforming and gripping chamber walls well. I am looking to see if others have similar experience.
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