There is a difference but, unless you know original design intent, you don’t know why the Swiss cut their chambers a little longer. Maybe it is was due to grease clearance, mud clearance, or something else.
But I am not worried due to the number of 303 British, 308 cartridges that I have fired with greased bullets and greased cases.
The Royal Society has the right idea: Their motto is to “accept nothing on authority.†Knowledge is to be based on observations/tests in the physical world, and if authority conflicts with these observations, then authority is wrong. There has always been a continuing fight against dogma created by authority figures.
Based on my observations greased bullets, greased cases do not raise pressures. Grease does not pinch the bullet in the case neck, and I believe it is because as pressure builds in a case the neck starts expanding from behind the bullet, rolling forward toward the case mouth until the bullet is released. This has the effect of moving the grease, grease may be “incompressible†but it is not immovable.
I fired over 1000 rounds of greased 303 British and I greased the heck out of 308 Cavim. I had a case of the stuff, maybe 1500 rounds, currently the brass fills two complete 50 caliber ammunition cans. I wanted to fire the stuff in my FAL, I did not want the cases to stretch, so I put ammunition in plastic bags, dropped in tablespoons worth (actually fingerdips) of Casteroil stick wax in the bags and shook the stuff. Stick wax was a bad idea. Stick wax
http://www.freemansupply.com/CastrolIloformStic.htm is tenacious stuff, it is meant to stick to saw blades as they cut through metal or ceramic. Casteroil stick wax is very thick and did not apply smoothly. After shaking in a bag, I had huge clumps of stick wax all over the ammunition. When I loaded and fired the stuff a mist of stick wax formed in the air. The rifle was coated, my clothes were coated, my glasses were coated, and the stuff does not wash off in plain water. But something interesting happened. I was able to open the gas system in my FAL by more than a couple of clicks and still have reliable function. For those who don’t have a FAL, you adjust the cycling by bleeding off gas until the bolt is no longer held by the follower. Then you add a click or two. I was able to verify that lubricated ammunition reduced breech friction significantly, and by increasing the gas bleed, made the rifle cycle smoother and with less banging and slamming.
Still, the plume of stick wax was objectionable and I ended up wiping down the cases. I left stick wax on, but not in the thick, clumpy quantities. The cases were covered from head to toe with a thin coating of stick wax, and I shot them that way. Shot them in bolt rifles, M1a’s, FAL’s, anything of mine that was in 308.
Since I don’t have copper fouling problems with modern jacketed bullets I don’t have to grease my bullets, but I lubricate my cases and have not encountered any pressure issues. I have shot out two barrels on one M1a, another on another, shot out match 308 barrels, one AR15 barrel, no problems.
Those who have the energy to go page by page from every Arms and the Man at Google books, such as I, will find that pre WW1, greasing bullets was the norm. Shooters are bragging about the accuracy, about shooting 3000, 7000 greased rounds without bore fouling or cleaning. There are actually pictures of greasing devices, for clubs! However I notice a tension in the articles of shooters: while they don’t see evidence of harm in their own rifles and ammunition, yet rifles are blowing up and behind the scenes the Ordnance Department must be claiming the blow up’s are due to grease. Not until 1918 does the Army actually put out a statement in print that Army rifles do not blow up more frequently than any other rifle and when an 03 blows up, it is due to shooter stupidity. Incidentally, this is after the production of single heat treat receivers is discontinued. No one outside of the Ordnance Department is aware of the dangerously defective rifles the Army is manufacturing, issuing and selling, and the Army is not telling.