The SMLE is just a bad choice of rifle for your intended use. Ammo difficult to find in most places, and very expensive. Plus, due to fact that the locking lugs are located on the rear of the bolt, these rifles grow headspace as they are shot. Don't believe me? Well, the British military issued field kits with replacement heads for the bolts, to be used as the headspace got bigger and bigger. The replacement heads are numbered #2 through #4, getting larger in the series.
Many of the surplus SMLE's you find today have excess headspace and need the bolt heads replaced. It use to be easy to find #2 and #3 heads at gunshows. But now you have to look really hard for a #2, and I haven't seen a #3 or #4 in many years.
The 1916 Spanish mausers that have been converted to 7.62 are also a poor choice. First off, they are among the weakest of the mauser designs, being based on the 1893 mausers not the 98 mausers.. Second, they were designed to shoot the relatively mild 7mm mauser round, not the hotter 7.62 Nato rounds. Like it or not, they will grow headspace. And finally, you will note that they have not been converted to .308 Winchester. (Note, the barrel has 7.62 stamped on it.) The .308 Winchester is a commercial hunting round, generating 66,000 psi! The 93 rifles was designed to handle the 7mm mauser at 42,000 psi. You do the math.
And by the way, even a bolt action shtf rifle should be a quality rifle, not a junker. You gonna stake your life on a junker military surp rifle?
A far better rifle than the SMLE or 1916 mauser would be used Marlin 336, in VGC, with a quality synthetic stock, in .30-30, with two spare parts kits.
And even better, would be to find a sporterized 03A3 Springfield, in .30-06, which still has the original receiver sight on it (these can be found for as little as $250 to $275 at large gunshows), and put an old military stock back on it, or a good synthetic. It was built as a true battle rifle, and is strong as a tank. It may even be possible to buy a good quality .308 chamber insert and install it with red loctite. You could then shoot both 7.62 Nato or .308 Winchester in it. Most of the times, these cartridges feed fine from the .30-06 internal magazine, but if they don't, then there are many ways to alter the magazine to take care of this.
I would never consider the Ishapore (made in India in the 1960s) SMLE in 7.62 Nato. It does not have a receiver sight, should not be regularly fired with .308 Winchester in it, and worst of all, despite the large capacity magazine, alot of them have feeding problems. It will not take standard SMLE mags, you so have to find after-market, thin sheet metal mags, many of which are very poorly made. They were made by India as as a stop-gap military rifle, until they could get up to speed with semi-auto battle rifles.
Hope this helps. Don't waste your time buying worn out junk. It never pays.