@ JR86:
No, friend, no problem with the rifle, nor with the dreaded "headspace". What you are looking at is combination of a slightly-large chamber (better for combat) and SAAMI-spec ammunition. This bulge in the casing would be less if you had been using proper MilSpec ammo, but nobody makes it for public sale any longer.
SAAMI is the Sporting Arms and Ammunition Manufacturers' Institute. It is an industry group, American of course, which sets the standards for manufacture of sporting ammunition. Being American, of course, they don't bother to read the BRITISH specifications for the .303 cartridge. The attitude seems to be, "The Brits might have invented it, but what the hell do THEY know?" So they set their own "standards" which do not agree with the standards of the people who INVENTED the stuff...... and all the makers adhere to the SAAMI spec, even though most of them made huge amounts of .303 ammo to the MILITARY spec at one time or another. Currently, you will find ALL American ammunition made to this spec. The fact that the American spec does not fit the British rifle just means that the Brits don't know how to make their own rifles.
Or, at least, it SEEMS like that is the case. Some of us have been through this for 50 years and more and STILL can't fathom the reasoning.
So that's the PROBLEM.
You need a SOLUTION.
Head down to your local Dollar Store and get a $1 packet of pony-tail ties. I got some a couple of weeks ago and they were 500 for $1 and they were TACTICAL. Must have been: they are BLACK!
You get a fresh box of ammo and you head to the range with your pony-tail ties in your pocket. On the firing-line, take a minute to slip a pony-tail tie onto each .303 cartridge, sliding it down until it is JUST above the Rim of the cartridge. You do this ONLY on the first time you fire a particular casing. Now you start shooting.
The pony-tail tie pushes the cartridge BACK against the bolt-face and holds it there, reducing effective "headspace" to zero.
It also CENTRALIZES the cartridge in the chamber of the rifle. Your casings should come out expanded EVENLY radially and now headspacing on the SHOULDER (as with a rimless cartridge) because they are now FIREFORMED to YOUR chamber. From now on, you reload these casings, neck-sizing only..... and your groups, believe it or not, will shrink like hemorrhoids hit with Prep-H.
This treatment with the pony-tail ties or with O-rings has been popularised by forum contributor Big Ed and so generally are termed "Ed's Famous O-Rings". I am Scots by ancestry and so always am looking for a cheaper way to do something: I changed his O-rings (wha' cost MONEY, laddie!) to pony-tail ties.... which are much cheaper.
The idea sounds dumb.... but it WORKS. Ed reports 32 reloads out of a box of .303 brass and that is NOTHING to sneeze at. Normally, full-length sizing, American .303 brass will give you about 3 loadings..... and the brass is HALF the cost of your ammo. You can further stretch the life of your (expensive) brass by loading down a bit, as you already are doing. And you can make your brass last halfway to forever by combining techniques (Ed's O-rings plus neck-sizing) with the famous C.E. Harris UNIVERSAL LOAD. This is 13 (thirteen) grains of Red Dot shotgun powder behind a 180-grain CAST (heavy emphasis on CAST) bullet. This gives you about 1800 ft/sec, accuracy about 2 MOA in many rifles, tighter in some, a cost-per-shot of 10 cents (including a gas-check) and an effective range for gopher-shooting of better than 200 yards. This is friend BUFFDOG's gopher-sniping load out to 300, but he is a better shot than most (including myself).
Most important of all: enjoy!
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Border Scot Recipe for a Hot Beef Sandwich:
"First thing, laddie, nip 'cross the Border, stayin' clear o' the March Warden an his gang o' murdrin' Sassenachs, an' steal a dozen ca'tle........"
