Here, too.
I noted that at least a couple of us mentioned the .303 Brit on your "Favorite 3 rounds" thread.
Of the rifle cartridges I shoot and reload for regularly, this one's my favorite. I have an all mil-spec No. 4 Mk I, which shoots just fine, although the barrel is pitted in places.
I also have a highly customized, elegantly stocked No. 4 that looks like an old Jeffery- or Rigby-style Lee-Metford, at least until you see the peep sight. The metal was polished and dehorned (where needed) and then deeply blued. It's got a banded front sight with hood, a functional and nicely blued 5-rd magazine, a Talley barrel band swivel ala the classic British big game rifle (it looks, at first glance, like the rifle carried by Kilmer early in The Ghost & The Darkness, except on mine the wood is darker). And this one's a shooter! With certain handloads (some 180gn Sierras) it's almost MOA at 100yds - iron sights. Even with factory loads it's pretty tight. It likes PMC's 180gn (GameKing bullets), and the Federal 180gn load too. Lately I've been loading up the 215gn Woodleigh Weldcores. Still looking for the right loads with these, but I had some decent groups at the last range outting. The best with the 215 grainers shot into about 1 1/2 inches, using 41gns of IMR 4320 (YMMV). I'm sure it can do better. I've got some of the 174gn Hornady's but just haven't had time to work up loads for these.
If you don't already have it, I highly recommend Stephen Redgwell's
"Shooting The 303 British". Great reloading data for a wide range of bullet weights, among other useful information. He has a very nice .303 website, but I don't have the URL handy.
As to your final question about Gibbs, I've got a Gibbs "Extreme Carbine" in .303 which I've posted about before. It's basically a "carbine-ized" No. 4 MkI, with an electrolus (sp?) nickel finish.
I restocked it with walnut stocks from Boyd's, as the "sporterized" military stocks it came with were for-sh*t. The buttstock was way too short, and the forend was too long (unnecessary weight). But once it was wearing the new stocks (with 1 inch recoil pad), and after it was correctly bedded, it's been nothing but a pleasure to shoot. Very good groups at 100 yds with both mil-spec ammo and the "hunting" type ammo mentioned before - especially given its short 20 inch barrel, which includes the muzzle brake. Athough loud, the brake does dampen recoil. At a regional gun show I found a heavily-cosmolined but otherwise "new" looking 10 round Lee-Enfield No.4 mag. No problems with feeding or jams so far.
Right now the carbine's away for more stock work - having 3 Pachmyr flush-mount swivels put in (for use with my 3-point Ching sling
). Some posters here have asked for pictures. Once I get it back, I'll try to oblige.
Hope this helps.