User:Sarf/EM1

The EM-1, also known as the "Thorpe rifle", was an experimental British assault rifle. It was tested against the rival in-house design, the EM-2, but although the EM-1 was favourably received, the EM-2 was selected as the more fully developed design, and one which was easier for the RSAF to produce with the machinery that they had at the time.

It shared its compact bullpup layout and unit magnification optical sight with the EM-2, and like that rifle it used the experimental, intermediate powered, but highly efficient .280 British ("two-eight-oh") round, which was designed to replace the venerable .303 ("three-oh-three") round.

Background
The EM-1 was part of the same initiative, to produce a modern "Infantry Personal Weapon" (IPW) for the British army, that produced the briefly-adopted EM-2 or Rifle Number 9 Mark 1.

The design process started with the military tactical requirements for range and lethality - the requirements led to the design of the optimum ammunition in the form of the .280" round, and once that had been perfected a suitable weapon could be by designed for it which could replace all of the exisiting SMLE battle rifles, the Bren magazine-fed light machine-gun, and the Sten sub-machine gun.

The Royal Small Arms Factory (RSAF) at Enfield started working on four designs of which two generally similar designs known as the EM-1 and the EM-2 (the "EM" standing for Experimental Model) came to the fore. The EM-3 (designed by Major Eric Hall) and EM-4 (designer unknown) did not proceed beyond the drawing board. The nomenclature was made official on January 6, 1948. Both were unofficially named after the lead designers in each team and were known as the Thorpe rifle and the Janson rifle respectively. A fifth design was commisioned from the BSA company, who built prototypes of a more conventional rifle using the same 7mm round, the BSA 28P.

Both EM-1 and EM-2 used 20-round magazines with "stripper" reloads (as opposed to box magazines), included simple conical optical sights for fast aiming, and had a carrying handle built into the top. They could fire semi-automatic or fully automatic. The two designs were very similar looking, but were internally very different in design and construction, with no parts in common other than the sights, though the barrel forging appears to have been a shared component with the EM-2. The EM-1 used steel plate pressings for simpler manufacture.

The EM-2 was eventually selected as the best design, and was adopted as the British Army's new rifle on April 25, 1951. It appears that the development of the EM-1 was started somewhat later than that of the EM-2, and it never caught up.

Design Faults
It appears that the development of the EM-1 was started somewhat later than that of the EM-2, and it never caught up. Under test, some teething faults became apparent.

The rifle was also simple to strip, but re-assembly of the weapon in its prototype state was said to require "great care" when inserting the long recoil spring, and also when inserting the the bolt into the bolt carrier, as the ejector had to be held in.

If the piston failed to return fully forward, it could be pushed into place by the cocking handle (forward assist). However if the piston bounced at the forward end of its stroke, it could not be pushed forward and the only way to clear would be to eject the unfired round and re-cock.

A worse fault was that the hammer-cocking mechanism could jam against the piston rod - this would require a strip and re-assembly to clear.