An Odd Characteristic of the SMLE

[Bruce_in_Oz]

I was always intrigued by full-bore shooters who used a SMLE or No4 for some distances and a P-14 for others: similar length barrels, generally the SAME sighting units.

I heard various stories about different rifles shooting "better groups" at oddly divergent ranges.

As Peter noted, once the bullet has left the muzzle, the barrel has NO more effect on it. (Irregular muzzle-blast dispersion aside). So, given that EVERYBODY was using the same, bog-standard Mk7 ammo, what, if anything, could be happening? (Apart from 20th Century Voodoo)

The waves that are generated in a barrel from the moment the trigger is pulled to the point of departure are immensely complex. The wave patterns are multi-mode: vertical, horizontal, axial and torsional; all at the same time. It is variations in these, from shot to shot, that cause the most grief after the ultimate insult of a dodgy crown. This is why proper bedding is supposed to produce CONSISTENCY in the wave patterns from shot to shot as it CANNOT eliminate them. If the muzzle is pointing up a squillionth of a degree EVERY time a bullet departs, that is consistency and you just go with it. What you end up with is a set of behaviours that suit your ammo. That is why, every time you fiddle with your ammo, either by changing brands of factory fodder or the balance of components in "home-brew" that you end up back at the range to re-zero.

Mk3* SMLEs and No4s were build around Mk7 ammo, end of story. (Lets just gloss over the odd allowance for Mk 6 ammo in the throating of SMLEs for a minute). If you "free-float" a No4, it MIGHT shoot with a handload that you come up with eventually, but it is almost impossible that it will both group the same AND to the same point of impact with said Mk7 ball. If you wind a Lithgow heavy barrel into your SMLE action, it will NOT perform the same as the original barrel. After you have cheerfully removed a lot of wood and deleted sundry bedding gizmos that were used on the standard barrel, one could hardly expect it to. It may be better; it may be not. Most of any improvement will possibly come from the simple fact that said heavy barrel is (hopefully) NEW and has not yet had its throat burned out by cordite or its crown blasted away. As for the interesting practice of opening out the muzzle hole in the nosecap with a hand-held rat-tail file and bashing in a bit of rubber hose as a "bearing"...........

Back in the days before Oz lost its sense of humour about such things, I worked on a lot of M-14 / M1A rifles. One regular job was to give them the AMTU match rifle treatment (minus the NM barrel, of course). This worked well in MOST cases. However, the improved groups were generally NOT terribly close to the original MPI. Re-zero and carry on! One chap insisted on having his “free floated”, i.e., there was no “pull-down’ of the barrel by the cap behind the gas cylinder. This rifle shot F4 and M80 ball all over the place; but with hot-loaded 125gn Speers, it was a screamer.