If by "Universal die" you mean Lee you will have to turn down the decapping pin ...easy enough,just chuck it in a drill and put the file or sandpaper to it.
Yes, simples! If a fancier (read: more bling and higher price) solution is desired, Sinclair makes a universal decapper with two sizes of pin, and I'm sure K&M, 21st Century Reloading and others do too. I have a Sinclair example and it's decapped many thousands of small flash-hole cases as I prefer doing this as a separate operation to clean primer pockets out before cleaning the rest of the case and resizing.
Life is getting complicated thanks to all the small-primer brass options (some with large flash-holes; some small) in traditionally large primer / large flash-hole cartridge models - eg 308 Win, 260 Rem, 243 Win - but here are those that
should be both small primer and flash-hole:
220 Russian (and derivatives, primarily PPCs)
BR Remington / Norma and anything derived from this brass
6.5X47mm Lapua (only made by Lapua and that's its spec)
In addition, there are the pic-n-mix models with 'traditionally' large primer / large flash-hole but where special match versions with small versions of both features have been developed primarily to reduce MV ES/SDs:
308 Win Lapua 'Palma', the first such modern variant was introduced maybe 10 years ago at the request of the US Palma teams to replace standard Lapua large primer cases and was made publicly available by Lapua almost immediately thereafter. (However, Lapua wasn't the first as Remington produced thin-walled small primer / flash-hole special UBBR 308 cases for re-forming into BR variants a couple of generations ago.)
6.5mm Grendel - originally designed as a prototype military number by Bill Alexander (Alexander Arms) with small primer and I assume large flash-hole in this role, but when further developed jointly with Lapua for civilian use the small flash-hole was chosen and was the only type originally available under both Alexander Arms and Lapua headstamps. Since then, large primer variants have appeared as have small primer / large flash-hole (eg PPU).
6.5mm Creedmoor - originally introduced by Hornady as a large primer number, likewise picked up by others in the same form. When Lapua introduced its Creedmoor brass a couple of years ago it was solely in small primer / flash-hole form. More recently some of the new case manufacturers have produced it in up to three forms (large everything; small everything; small primer + large flash-hole).
Traditional large primer designs mostly based on the 308 Win case such as 243 Win and 260 Rem now with small primer options from Peterson and others. As with the Creedmoor, some companies have adopted this form with the matching small flash-hole; others with small primer and large flash-hole.
The two sizes are nominally:
1.5mm (0.059") diameter
2mm (0.079") diameter
All large primer cases use the latter and so do many non-boutique small primer designs (222 Rem 'familiy'), 22 Hornet, 17 Rem, 204 Ruger, 6.8mm Rem SPC (which can be either size primer depending on manufacturer) and so on.
The small flash-hole is an essential part of the mix in the ongoing quest to improve cartridge performance consistency especially minimising ES/SD values. Experiments have shown that the PPCs and BRs see poorer performance if their flash-holes are reamed or drilled out larger, 0.070" being a primary boundary - hit that and everything (ES/SD and groups) suffer.
There are downsides, especially when cartridges reach the size where their charges are in the mid 30s (grains) and above, some powders in some ambient conditions having unreliable ignition. 308 Win size cartridges are reckoned to be at the top end for both items being small .... and some people believe they and their charges are actually too large for this form of case. Certainly, they are unsuitable for military use and hunting in very low temperatures.
Irrespective of such arguments, prepare for some (and further) confusion. Small primer case variants are now on a handloaders' bandwagon and manufacturers, especially the smaller newer ones, are keen to capitalise on this and increase sales overall.
