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This is why I restricted the build to ideally no more than 10,10mm/.400 diameter bullet maximum so the case still retains a shoulder to head space from. It would be interesting to build a couple of dummy rounds at the upper limit to see how they turn out.

If you want the fun of making a new cartridge then go ahead.

However from reading this and other posts on the subject of subsonic fullbore rounds there seems to be a bit of mystery about it which I cannot fathom.

For example a 308 win with a 230 gn 311284 over 4gns of N 320 will give you heavy and slow, this can be done with any 30-32 cal centrefire cartridge without chambering to blackwhisperout or whatever is flavour of the month is.

My project will not be used for subsonic rounds and is as much about putting the donor action to good use and building a rifle suitable for reduced load use at short distances with the ability to shoot to 2-300 yards if the opportunity arises (Obviously not on the majority of MoD ranges)

It wasn't your original post I was referring to David.

dromia wrote:For example a 308 win with a 230 gn 311284 over 4gns of N 320 will give you heavy and slow, this can be done with any 30-32 cal centrefire cartridge without chambering to blackwhisperout or whatever is flavour of the month is.

I'm looking at using .308 Win with a heavy jacketed bullet out to maybe 2-300yds but still subsonic, so I guess I'll need slightly heavier charge than that.

My aim is to duplicate or at least come close to the Lapua 7.62x51mm Subsonic round used by certain black rectangle units.

ovenpaa wrote:

Chapuis wrote:Ovenpaa you have really started something now. Having seen the picture of your dummy rounds I couldn't resist and made up a dummy using a 280 grain cast bullet pushed into a .308w case forming a 9.3x51mm wildcat. The big fat flat nosed bullet with a huge meplat in the dumpy case is just sexy.
I wouldn't know if such a round would offer any real advantage over any existing cartridges such as a 9.3x62 Mauser or even if such a cartridge would be ballistically feasible but it certainly gets my interest.

Chapuis, any chance of a picture I would build a couple of dummy rounds for myself however the largest suitable bullets I have are 9mm/.355

I would be embarrassed to post it as I haven't been able to completely close up the case neck as I've had to bodge it rather, using just what dies I had available. Unfortunately my 9.3x74r dies are to deep for the 51mm case to enter sufficiently for me to close the neck properly around the bullet in a nice neat fashion so I have a secondary bulge.

Incidentally I've done a little bit of a search on the internet and it looks like others have had a similar idea before but haven't pursued it. Also 8x51 using .322" bullets has been thought of previously.

If anyone has a couple of spare 9,3mm or 10,0mm jacketed and or cast bullets I would be happy to try and stuff them in the end of a .308 case to get an idea of proportion and the antics required to form the brass. Personally I have a feeling it might be easier to just go straight to fire forming using a pistol powder and then use a modified Forster bush die to neck size to the correct size.

The Russians built a 9mm centerfire SMG a while ago that was supposed to be able to defeat all current body armour at up to 400m whilst being silent. I'll see if I can dig out a link.

This is it, oomans. The Czechs have something similar that we once had our paws on. It made an excellent dogbuster.

http://en.wikipedia.org/wiki/VSS_Vintorez

ovenpaa wrote:If anyone has a couple of spare 9,3mm or 10,0mm jacketed and or cast bullets I would be happy to try and stuff them in the end of a .308 case to get an idea of proportion and the antics required to form the brass. Personally I have a feeling it might be easier to just go straight to fire forming using a pistol powder and then use a modified Forster bush die to neck size to the correct size.

David,
I looked at this a while ago while I was contemplating rebarrelling the Ishy to something bigger. I discounted the .40/10mm bullets after reading about the 400 Whelen and trying to neck the 308 up to 10mm - not pretty!

From what I've read 37 cal is about the biggest you can go while retaining a effective shoulder in a 308 case. In the end, before I pasted the Ishy to you, I decided that if I was going to do it then 358 Win would be the way to go.

BTW I also experimented with 9mm bullets in a 308 case.

Edit: 375 Scoville 30-06 necked up to .375


Another couple to consider is the 450 Bushmaster or 458 SOCOM.