The W48 was 846 mm long and weighed 58 kg; it could be fitted in a 155 mm M-45 AFAP (artillery fired atomic projectile) and used in a more standard 155 mm howitzer. The fission warhead was a linear implosion type, consisting of a long cylinder of subcritical mass which is compressed and shaped by explosive into a supercritical sphere. The W48 yielded just 72 tons TNT equivalent.
The Mk-54 Davy Crockett was designed to be fired from the M-388 recoilless rifle. Weighing only 23 kg, the warhead in its casing was 400 mm by 273 mm. It was first tested in October 1958 as part of Operation Hardtack and yielded 10 tons, but later developments increased that to 1 kt.
So lightweight warheads have been available for a long time in the West, so it is entirely possible that India may have a suitable <60Kg design using the simpler gun or linear implosion type.
The Mk-54 Davy Crockett was designed to be fired from the M-388 recoilless rifle. Weighing only 23 kg, the warhead in its casing was 400 mm by 273 mm. It was first tested in October 1958 as part of Operation Hardtack and yielded 10 tons, but later developments increased that to 1 kt.
So lightweight warheads have been available for a long time in the West, so it is entirely possible that India may have a suitable <60Kg design using the simpler gun or linear implosion type.