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> Fireforming new brass
Fireforming new brass
@ 07:31 am (GMT) |
David KoppGreetings all,I've started fire forming new Lapua brass for a Tikka 6.5 SE. I started with low charge using Varget @ 38-39 grains. Best average was 39 grains @ 2680 4es-2sd. With a fed 210 primer, I notice all primers were protruding slightly. If my memory serves me this means the brass hasn't formed exactly to the chamber. If this is a ok I'll continue with this load and increase pressures 2nd time around. My 2nd thought was increasing the power to where the primer gets pushed back into the case but making sure I'm not close to maximum charge. I'm guessing 2900-3000fps would be the goal. It's a 95 grain max, set at 70mm oal. The intended use will be coyotes or smaller. This is my first time fire forming new brass. |
Replies
@ 09:04 am (GMT) |
Nathan FosterRe: Fireforming new brassHi David, I don't really like to answer this sort of thing via a forum as there could be something amiss or there could be some error of communication either in your description to me or vice versa. It can also mislead other readers if they misinterpret info. Better to have the gun on the bench for this sort of thing. In any case, will try to cover all bases.If the primer is protruding at the center only, then this is simply a result of the firing pin hole in the bolt face being very large, allowing the primer to flow back into the pin hole. This is not generally a cause of concern unless the gap is very large / material being sandwiched etc. If the primer is shifting back just a little bit then yes, just load a bit hotter to get a full fire form. If the whole primer is flowing back and is visually noticeable, it may be a cause for concern. It may just be that the cases are minimum spec versus a max spec chamber, but if its highly noticeable, it may indicate excessive head space. One possible cause (does not pertain to you) is the occasional discrepency between U.S brass versus CIP spec chambers. This does happen from time to time (9.3x62 a good example / same issues as you are experiencing). But as you have indicated, you are using Lapua brass which is generally a very good fit in a Tikka chamber. Yet another cause, is the use of an undersized (less than minimum case spec) full length die. If the cases are run through such a die, it may alter tolerances. Of the more dire possibilities, excessive head space can occur as a result of lug set back (hot loads) from a previous owner or excessive lug lapping. An oversized out of spec chamber is of course yet another possibility. Try the hotter FF load. Hopefully everything will be fine. But if the protrusion is dramatic, it might be useful to have the chamber checked with go and no go gauges. OK, hope that covers everything. |
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@ 12:03 pm (GMT) |
David KoppRe: Fireforming new brassThank you very much Nathan for the quick reply. I've hand loaded for a number of years but still consider myself a novice.I purchased the rifle from new and started with factory nosler and reloaded them. I never pushed my handloads to cause a excessive headspace, I don't believe. I have always worked up to your recommended velocities with care. This rifle was my first DYI using your books. I understand about primer center protruding my remington 308 does this slightly. Primer protrusion is not dramatic, its very little. I researched load data and hodgdon had the lowest start weight compared to speer that started at 40 grains. Which, made me think not enough powder charge, but I thought to post this and gain some advice. I'll work up in .5 grain increments from 40 grains and see if I can reach 2900fps. Much respect to our founder and members. Cheers, David |
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