303 British Brass Options?

The N540 powder is "Very versatile and Very temperature stable" which makes for an excellent hunting load. When used correctly with mild to midrange charge weights, the N540 will propel your choice of caliber down range with no issues. It is only when you load the N540 to near maximum charge weights that you run the risks of burning out the barrel, especially a .22-.25 caliber centerfire rifle barrel. 

(I personally know of an individual who junked a rifle barrel chambered for the .220 Swift using Varget. He wanted to duplicate the factory rated 4110 FPS of that bullet, and he burned the throat out in less than 750 firings using Varget.) 

 I use the N540 for my .243W,  .308W,  and .303B for the simple reasons of not having to switch to a different powder for the different calibers and I both hunt and target shoot. Keeping the charge weight to 39.5grns for the .303 results in very mild recoil with an averaged FPS of 2355 while still maintaining its accuracy. Using the same 39.5grns for the .308W and the averaged FPS is mere 2305.

The one and only issue I encountered using N540 for my .243W is when I chronographed a group of ten rounds that had been charged with 37.2grns of N540 which is 2.0grn below maximum charge weight. The averaged FPS was 3210 which is 140+ FPS faster than the printed data using the max charge weight.  Dropping the charge weight to the minimum of 35.0grns still produced numbers exceeding 2850 FPS.  I am using the 90grn OTM Scenar-L BTHP but decided to use the minimum charge weight of 35.5grns for the 90.0grn Sierra FMJ-BT and the averaged FPS stabilized at 2775 FPS. I have no doubt in my mind that had I kept shooting the rifle using the 37.2grns of N540 without doing my own load work up or, work down as my case implies, I would have burned that barrel out prematurely. My assumption is that if you were using N540 with your AR loads, you burned the barrel out by having near to max charge weights used. Again, just an assumption Geoff...

But many others who are accomplished mid and long range shooters found this out the hard way too, mostly in .308 Palma and F-Class match shooting, these guys are definitely not “pray and spray” types. 

Not the case.  I don’t shoot the AR at long ranges.  

As my post above said, I burned out two barrels on my AR shooting AA2520, which is a double based powder. It’s a simple fact that Nitroglycerin burns very hot. It was a mild load at modest velocity. 

My long range .308 load is Varget, a single based powder that is far more temp stable than any double based powders.  N540 is not very temp stable, long range shooters had to run a winter load a a summer load. This has been experimented on and well proven. 

I won’t be putting any double based powders thru my LE’s, I need the barrels to last.  Think of what Cordite did to LE barrels (which is a double based smokeless propellant). 

My long range .308 Varget loads are exactly mid range in the load tables, not “near max charge weights”.  I make it a point to stay away from max loads. 

But, don’t take my word for it, you can find out the hard way too..as many others beside me have. 

If you only shoot a few rounds a year, you won’t have to worry about it.