The lineage of the T44 traces back to the T20, a simple conversion of the M1 Rifle to fire fully automatic from a 20 round box magazine. After the development of the T65 Lightweight Rifle Cartridge, the T20 was modified to use this new round resulting in the T36. The T36 introduced a new recoil check, utilized the T25 Rifle magazine and reduced the barrel length to 22 inched. The T36 was further modified with a new muzzle stabilizer, the bolt stroke was reduced by the addition of a spacer in the receiver heel, and the stock and hand guard were modified to use a longer one piece hand guard and enclose more of the barrel and operating rod. A gas cut-off type gas system replaced the direct impingement gas system along with the stabilizer and magazine from the T31, and a reversion to the wider M1-type stock with its butt plate.
The initial gas port was set at 0.052", however testing showed that this gas port provided insufficient power to reliably operate the system. A gas port of 0.072" was eventually adopted.
Additional deficiencies encountered during Springfield's in-house test were:
- Magazines falling out during firing,
- Magazines failing to lift the last few rounds,
- Stabilizer struck by bullets,
- Rounds stubbed on feed ramps,
- Operating rods breaking at handle/tube joint, and
- The spacer used to shorten the bolt stoke loosening.
The following corrective actions were taken to resolve these problem prior to samples being sent to Aberdeen Proving Grounds (APG) for testing:
- The T47 five-prong stabilizer/flash hider fitted,
- Bullet ramps modified
- The follower modified to hold the rounds more vertically positioned.
At APG sample T44s were tested for accuracy, operation under normal and adverse conditions and for endurance. APG reported the following:
- Operating rod disengages during firing
- Bolt fails to lock back after last round
- Unsatisfactory ejection pattern (failure to consistently throw rounds forward)
- Unsatisfactory function under normal and adverse conditions
- Erosion of flash hider brush ring with subsequent failure of prong(s)
- Magazine springs taking a set
Springfield instituted the following corrective actions:
- The M1-style disassembly notch was filled in and a notch was cut in the middle of the outer operating rod track. The notch was occupied by a new tab added the the disconnector. This prevented the operating rod from disengaging from the receiver unless the disconnector was removed.
- The cause of the erratic ejection pattern was due to the ejected case not being hit by the knuckle of the operating rod due to poor timing. Increasing the gas port diameter to 0.075" corrected the timing issues.
- The unsatisfactory functioning was attributed to an under-power condition. The T20 had functioned satisfactorily at a cyclic rate of 800 rpm, and the T44 did not at 700 to 750 rpm, it was assumed that increasing the cyclic rate to 800 rpm would resolve the performance issued. Accordingly, the gas port was further opened up to 0.090", and this appeared to correct the problem in limited testing. Calculation on the maximum acceptable bolt velocity, however, limited the gas port size to 0.084". Further testing on the gas port size were postponed in order to investigate the feeding issued, see below.
- The feeding was still not reliable, so several changes were made: the magazine tube was lengthened 3/8 inch, with a new spring with 8 coils of 0.060 " wire and a free length of 12.8", the magazine catch pivot hole was moved forward 0.060", the front brow of the magazine tube was raised 0.060", and the length of the filler was increased 0.040" (shortening the bolt stroke).
- Spreading of the magazine feed lips and binding of rounds in the magazine were other issues in need of correction. The magazine ribs were deeped to bring the rounds closer together and keep the bullet stack properly staggered. The spreading magazine lips was not fixed but continuous gauging of the lip dimensions was instituted in order to continue testing.
Several rifles were required by APG for testing, so the most up-to-date rifles were sent. Upon their return the gas port size investigation resumed, and cyclic rates were extremely erratic and it was noted that the ejected case were fouled on the outside, and fouling increased with firing, there was evidence of extreme extraction force, and even with extreme extraction forces there was insufficient power for a complete cycle (failure to feed). The rifles were re-barreled with 0.075" gas port barrels. Springfield duplicated APG's normal and adverse condition tests, and while the result were not that good, the magazines gave so much trouble, it was decided that the magazine issue had to addressed before any meaningful information could be gathered on other reliability issues.
In June of 1952, the US Army Infantry Board (USAIB) at Fort Benning was scheduled to perform user trials of the T44 and as of March 1952 the T44 had the following deficiencies:
- Magazines were not all interchangeable due to the multiple variations in lengths and latch locations.
- The barrel was weak, several splitting along the splines
- The magazine latch was still not 100% reliable in retaining the magazine
- The operating rod weak and prone to breaking at the tube/handle joint
- The operating rod spring taking a set during operation
- The T47 five-prong flash hider eroded quickly
- The system not sufficiently reliable
The initial gas port was set at 0.052", however testing showed that this gas port provided insufficient power to reliably operate the system. A gas port of 0.072" was eventually adopted.
Additional deficiencies encountered during Springfield's in-house test were:
- Magazines falling out during firing,
- Magazines failing to lift the last few rounds,
- Stabilizer struck by bullets,
- Rounds stubbed on feed ramps,
- Operating rods breaking at handle/tube joint, and
- The spacer used to shorten the bolt stoke loosening.
The following corrective actions were taken to resolve these problem prior to samples being sent to Aberdeen Proving Grounds (APG) for testing:
- The T47 five-prong stabilizer/flash hider fitted,
- Bullet ramps modified
- The follower modified to hold the rounds more vertically positioned.
At APG sample T44s were tested for accuracy, operation under normal and adverse conditions and for endurance. APG reported the following:
- Operating rod disengages during firing
- Bolt fails to lock back after last round
- Unsatisfactory ejection pattern (failure to consistently throw rounds forward)
- Unsatisfactory function under normal and adverse conditions
- Erosion of flash hider brush ring with subsequent failure of prong(s)
- Magazine springs taking a set
Springfield instituted the following corrective actions:
- The M1-style disassembly notch was filled in and a notch was cut in the middle of the outer operating rod track. The notch was occupied by a new tab added the the disconnector. This prevented the operating rod from disengaging from the receiver unless the disconnector was removed.
- The cause of the erratic ejection pattern was due to the ejected case not being hit by the knuckle of the operating rod due to poor timing. Increasing the gas port diameter to 0.075" corrected the timing issues.
- The unsatisfactory functioning was attributed to an under-power condition. The T20 had functioned satisfactorily at a cyclic rate of 800 rpm, and the T44 did not at 700 to 750 rpm, it was assumed that increasing the cyclic rate to 800 rpm would resolve the performance issued. Accordingly, the gas port was further opened up to 0.090", and this appeared to correct the problem in limited testing. Calculation on the maximum acceptable bolt velocity, however, limited the gas port size to 0.084". Further testing on the gas port size were postponed in order to investigate the feeding issued, see below.
- The feeding was still not reliable, so several changes were made: the magazine tube was lengthened 3/8 inch, with a new spring with 8 coils of 0.060 " wire and a free length of 12.8", the magazine catch pivot hole was moved forward 0.060", the front brow of the magazine tube was raised 0.060", and the length of the filler was increased 0.040" (shortening the bolt stroke).
- Spreading of the magazine feed lips and binding of rounds in the magazine were other issues in need of correction. The magazine ribs were deeped to bring the rounds closer together and keep the bullet stack properly staggered. The spreading magazine lips was not fixed but continuous gauging of the lip dimensions was instituted in order to continue testing.
Several rifles were required by APG for testing, so the most up-to-date rifles were sent. Upon their return the gas port size investigation resumed, and cyclic rates were extremely erratic and it was noted that the ejected case were fouled on the outside, and fouling increased with firing, there was evidence of extreme extraction force, and even with extreme extraction forces there was insufficient power for a complete cycle (failure to feed). The rifles were re-barreled with 0.075" gas port barrels. Springfield duplicated APG's normal and adverse condition tests, and while the result were not that good, the magazines gave so much trouble, it was decided that the magazine issue had to addressed before any meaningful information could be gathered on other reliability issues.
In June of 1952, the US Army Infantry Board (USAIB) at Fort Benning was scheduled to perform user trials of the T44 and as of March 1952 the T44 had the following deficiencies:
- Magazines were not all interchangeable due to the multiple variations in lengths and latch locations.
- The barrel was weak, several splitting along the splines
- The magazine latch was still not 100% reliable in retaining the magazine
- The operating rod weak and prone to breaking at the tube/handle joint
- The operating rod spring taking a set during operation
- The T47 five-prong flash hider eroded quickly
- The system not sufficiently reliable
