[Brian Williams]

I know it is British, but what is it other than a L115A1.
http://www.defenceimagedatabase.mod.uk/fotoweb/Preview.fwx?position=170&archiveType=ImageFolder&sorting=ModifiedTimeAsc&search=&fileId=82009AFCAB28BB7B4818188E6EE0F5842527F21A9EA60BCB068E1C97D7AA43F0BA877BF55CF600ED1D3DB01BD3914663A4D1E1A7CC5D150BA4D1E1A7CC5D150BCC32D5C1A96E50B5513741741DE1AE2BA12A976DACE51EE4CC96205559FC6235261A446FA1EEB5DFE4946C9B6B32489635F7D81366A58E225047CA320D597944
http://www.defenceimagedatabase.mod.uk/FotoWeb/FWbin/preview.dll/45141267.jpg

[Jim Watson]

Looks like an AI
http://www.accuracyinternational.com/

[IronLance]

Now that is interesting.... that magazine looks a lot like the magazine used in my Ishy 2A1.

http://img328.imageshack.us/img328/927/ishymag0qm.jpg

[rbernie]

http://www.snipercentral.com/pm_sm.htm

[mete]

The Brits use an Accuracy International in 338Lapua for snipers.

[Mk VII]

the company made them in several configurations, and they were bought by Sweden as well.
The magazine is a special, and looks like it was made from fifty-cent tinplate.

[Zak Smith]

Yep, AI-ASM 338, folding stock ("2.0"). From the picture, it is indistinguishable from the AWM 300, but that is not used by Britain. The scope is the Schmidt & Bender.

The magazines look like this-- http://www.myweapons.nl/PP%20WG/Gallery/Rifles/Accuracy/AI%20Mag.jpg

The standard ones hold 5 rounds of 338 (or 300 in the same form factor, but different feed lips).

[hksw]

(Deleted. Attic's a little dusty.)

[Eightball]

It seems to be one of the many "red x in white box" series weapons that are so popular on forums nowadays...... :p

EDIT: Now that I have seen it, I'd bet it's an AI of some sort, with a fluted barrel and muzzle break/flash hider of some sort. Nice paint job on it, too.