And didn't the IRA make do with an assortment of civilian weapons and captured military weapons, along with a hearty amount of what we would now call IEDs?
I think they had a bit more than that. From their friends in America and libya strange bedfellows.
To continue and escalate their armed campaign, the IRA needed to be better equipped, which meant securing modern small arms. In previous campaigns weapons had been secured before hostilities commenced via raids on British Army and even Irish Army weapons depots. In the 1969–1971 period this was no longer feasible. By 1972, the IRA had large quantities of modern small arms, particularly Armalite rifles, manufactured and purchased in the United States. The AR-18 rifle in particular was found to be very well suited to the Provisionals' purposes as its small size and folding stock meant that it was easy to conceal. Moreover, it was capable of rapid fire and fired a high velocity round which provided great "stopping power"
The IRA's main gun runner in the USA was George Harrison, an IRA veteran, resident in New York since 1938. Harrison bought guns for the IRA from a Corsican arms dealer named George de Meo, who had connections in organised crime. Joe Cahill acted as the contact between NORAID and Harrison. In 1971, the Royal Ulster Constabulary (RUC) had already seized 700 modern weapons from the IRA, including 2 tonnes of high explosive and 157,000 rounds of ammunition, most of which were US made.
Gaddafi later helped provide the IRA with the weaponry they needed to wage an armed campaign which lasted more than 30 years and claimed more than 1,000 lives.
The Eksund was carrying around 1,000 AK-47 machine guns, a million rounds of ammunition, more than 50 ground-to-air missiles and two tonnes of the powerful Czech-made explosive, Semtex.