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All right guys, I will nail my flag to the mast with my colors showing for all to see.
I am in the begining stages of a projected build of a bolt rifle that may horrify some of the Grendel purists but satisfies my tinkering obsession.
There will never be a factory Grendel cartridge in my rifle so I decided the a chamber that wasn;t necessarily SAMMI would not be a detractor. The second factor in my thinking is that the Grendel brass is rare and expensive here where the Win 7.62x39 brass is plentiful and relatively affordable. I am no longer in the work force so these things are a consideration.
After a lot of drawing and bouncing ideas of a few learned shooters and tinkerers I have come up with what I call the 6.5 GM or 6.5 Grendel Max. It will involve a couple of preliminary steps but is easily doable for the similarily afflicted tinkerer.
My first step is hydro forming a case to use instead of the usual go, no-go guages for headspacing at barrel fitting time and to do this I will use a Forster Grendel Full Length Sizing die set in the press with a .05 spacer between the shell holder and the base of the die. The decapping stem is removed and with a Winchester 7.62x39 case inserted into the die and using an apropriate forcing mandrel a case is hydroformed as a Grendel Max, being .05 longer at the shoulder and shoulder neck junction. In the process the neck is reduced in length from the Grendel SAMMI length of .235 down to .22 for a neck length of 83.5% of bullet diameter which is the same percentage as the 300 Win Mag. Of course throating would allow the OAL of the loaded cartridge to be maximised for the mag length even if that was lenghtened to the rear marginally.
I know there is a volume loss using the reformed 7.62 case in the Grendel chamber but by lengthening it to the GM dimensions then that and more should be gained back and with the pressure advantages of the bolt rifle then I beleive a worthwhile gain can be made
I am in the sourcing process for a Mod 85 Zastava and a barrel and hope to geterdone over the winter. (Southern hemisphere winter) although those who indulge in these tinkering projects know how the time can get away from the planned completion dates.
Will stock it myself in one of the laminates I have made lately where I start with a 15mm (about 9/16) central core and do all the tapering of the forearm and mag well to wrist and butt section so that all the subsequent laminates are running paralell to the eventual outside surface of the stock. Just something a bit different but by not cutting through the outside laminates then I beleive a stronger and thinner stock can be made with the advantage of lighter weight. I will use NZ Beech for its colour, strength and toughness.
Anyway that is my intention so will sit back and see what the Horde think of the idea.
This is a pic of the 7.62x39 case with a straight necking to 6.5 as is chambered by some here in NZ alongside a Grendel case so you can see how much can be gained if the grendel neck shoulder junction is moved forward.
And my drawing of the Grendel and the Grendel Max
Von Gruff
I am in the begining stages of a projected build of a bolt rifle that may horrify some of the Grendel purists but satisfies my tinkering obsession.
There will never be a factory Grendel cartridge in my rifle so I decided the a chamber that wasn;t necessarily SAMMI would not be a detractor. The second factor in my thinking is that the Grendel brass is rare and expensive here where the Win 7.62x39 brass is plentiful and relatively affordable. I am no longer in the work force so these things are a consideration.
After a lot of drawing and bouncing ideas of a few learned shooters and tinkerers I have come up with what I call the 6.5 GM or 6.5 Grendel Max. It will involve a couple of preliminary steps but is easily doable for the similarily afflicted tinkerer.
My first step is hydro forming a case to use instead of the usual go, no-go guages for headspacing at barrel fitting time and to do this I will use a Forster Grendel Full Length Sizing die set in the press with a .05 spacer between the shell holder and the base of the die. The decapping stem is removed and with a Winchester 7.62x39 case inserted into the die and using an apropriate forcing mandrel a case is hydroformed as a Grendel Max, being .05 longer at the shoulder and shoulder neck junction. In the process the neck is reduced in length from the Grendel SAMMI length of .235 down to .22 for a neck length of 83.5% of bullet diameter which is the same percentage as the 300 Win Mag. Of course throating would allow the OAL of the loaded cartridge to be maximised for the mag length even if that was lenghtened to the rear marginally.
I know there is a volume loss using the reformed 7.62 case in the Grendel chamber but by lengthening it to the GM dimensions then that and more should be gained back and with the pressure advantages of the bolt rifle then I beleive a worthwhile gain can be made
I am in the sourcing process for a Mod 85 Zastava and a barrel and hope to geterdone over the winter. (Southern hemisphere winter) although those who indulge in these tinkering projects know how the time can get away from the planned completion dates.
Will stock it myself in one of the laminates I have made lately where I start with a 15mm (about 9/16) central core and do all the tapering of the forearm and mag well to wrist and butt section so that all the subsequent laminates are running paralell to the eventual outside surface of the stock. Just something a bit different but by not cutting through the outside laminates then I beleive a stronger and thinner stock can be made with the advantage of lighter weight. I will use NZ Beech for its colour, strength and toughness.
Anyway that is my intention so will sit back and see what the Horde think of the idea.
This is a pic of the 7.62x39 case with a straight necking to 6.5 as is chambered by some here in NZ alongside a Grendel case so you can see how much can be gained if the grendel neck shoulder junction is moved forward.
And my drawing of the Grendel and the Grendel Max
Von Gruff
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