Hi there to all following this thread. Grampa Grump from Oz here. Have just bought a 308MXLR (2008), but have yet to take delivery due to firearms ownership requirements. STOP PRESS :- As I write, a text has just come in advising that my "Permit to Acquire" has been approved by SA Police Firearms Branch



. Now I have to wait till the weekend to take delivery as my local dealer is out of town this week

.
I've been following this thread for a while with great interest, in anticipation of this new (to me) rifle. Dies, projectiles and 100 brass were included in the deal and I intend to "roll my own" from the outset. I have measured the brass and it is
1.528" HS (Hornady HS Comparator) consistently over ten randomly selected cases. Length and rim diameter are equally consistent at 1.910" and .501" respectively. Obviously I don't know the HS dimension of the rifle as yet and the method of fire forming is where my questions lie. Adam from RPP in post #1 outlined his preferred method which is what I have used in the past, however here is another method I have used for undersized brass. To make 257 Roberts cases from 7 x 57 brass I simply necked down, checked neck thickness and fire formed. This worked OK but the case bodies were not concentric after firing due to loose chamber fit. A friend suggested sizing down the neck not quite to the shoulder leaving a "false" shoulder to headspace on. Cases were then sized so the the bolt closed with only the slightest drag on closing. After firing the cases ejected freely, were concentric and no adverse signs noticed. This allows fire forming at normal cartridge C.O.A.L. Would this method work with my 308 ME. I have experimented by expanding the necks of a couple of reject cases (off centre flash hole) using a 21/64'' drill bit for a mandrel on my drill press as a "proof of concept''
test. This works OK (tried a few 30/30 cases too) but the attrition on the brass is about 25%,mainly from necks folding in at the mouth. I'm thinking of using a .338 expander button in my loading press to solve this issue. I feel that the neck damage issue was caused by misalignment and inaccurate tapering of my "mandrel" with a bench grinder; n.b. remember "experiment" and "proof of concept". Drill bit was used blunt end first and not spinning when pushed into the necks!
Would this method be OK to use in the marlin having due regard for less camming action than the bolt on the .257 and would the size up then down cause more than tolerable stretch compared to fire forming without the rigmarole? Some load info for fire forming would be appreciated as well.
Sorry about the long winded ramble, regards,
Chris (aka "Grumps")



PS I have H4895, H4198, Varget, 8208XBR and Trail Boss powders and 125,150 and 160 grain projectiles available.
PPS For JACKTW and fellow "Gremlin" experimenters the cases are Hornady
lot.# 4150715. Hope the info is of help to you. (where are your bullets Jack?)

