help tell me about this rifle

[muffett.2008]

If it's the groove, by the time the bullet gets to the end of the barrel, it would just fall out, if it was the lands, pressure would increase in the thin end of the barrel.
Methinks this is a furphy.

[Bruce_in_Oz]

Early SMLEs had their bores lapped to produce a taper in the rifling. This was first done with the initial 1000 trials rifles.

This taper was at the MUZZLE end and meant that the bore diameter was enlarged (at the muzzle) from 0.3025"-0.3045" to 0.304"- 0.306".

This was all tied in with trying to raise the muzzle velocity to that of the "long" Lee Enfield. Note that we are talking about the Mk6 round-nosed bullet here.

Apparently, full details are in the "specifications". If anyone has a copy of the Spec. data for the Mk1 SMLE, it will all be in there.

A lot of this is tied in with the comparative trialling of the L.E. rifle and the "new" Short rifle. The L.E. had a long leade, much longer than probably necessary for even the old Mk6 type round nosed bullets. It was also much more gently tapered than one sees on later SMLE barrels.

However, SMLE barrels continued to be throated to accept the Mk6 bullet LONG after that projectile had passed from frontline service. However the rifling in later SMLE barrel starts more abruptly than the earlier Lee Enfields.

What I suspect they were trying to do by tapering the muzzle end, was to reduce the friction of the bullet on the lands and thus raise the muzzle velocity. The only problem was that once the very hard jacket had engaged the rifling at the rear, it was hardly likely to keep expanding as it traveled up the bore, especially as the pressure DECREASES as the bullet travels forward.

In the trials of 1902, it was also found that "max" bullets 0.312" dia. shot better than "min" 0.301" dia. bullets. Not only that, but barrels made to the "low" limit, shot better than those of "high" diameter limit (Surprise, surprise!!). Finally, rifles with a "short" leade AND a square-faced muzzle, shot a "figure of merit" TWICE as good as "conventional" barrels. That last one is no news to anyone who has shot target or bench-rest rifle in the last fifty years, but it was a major discovery in 1902.

The upshot of all this was that the bore was eventually left parallel (within manufacturing tolerances) but the GROOVES continued to be tapered. This tapering was eventually dropped in 1917.

You can imagine the ludicrous amount of time and precision workmanship involved in TAPER lapping the grooves without affecting the lands. If this were being done on barrels cut to length, it would also have been nearly impossible to avoid uneven belling of the muzzle as the lapping slug ran out. These days, match barrels are lapped BEFORE trimming, profiling, chambering, and crowning. They are also lapped to ensure almost perfect parallelism, NOT taper, especially outwards taper at the muzzle.