It seems there is much more written about IRA gunrunning from the United States, weapons being given by Gaddafi’s Libya, EOKA, etc. down to the exact weapons and quantities, but not comparable documentation about Loyalist gunrunning operations. Where did the UVF, UDA/UFF, RHC, etc. acquire arms in that era?
A common feature of community events in Northern Ireland, especially those in working class areas was the 'show of strength' in which the local paramilitary unit would show off their weapons to the local residents. Paramilitaries would pose for photographs, fly flags or even fire shots off, the aim of which was to reinforce to the locals that they had either the ability to defend them or to carry the war to the other side.
Loyalists in particular, with a culture much more focused on large scale community events like marching season carried out a great many shows of strength and showed off a wide range of weapons. Pistols, rifles, submachine guns and shotguns but often lacked the heavier weapons the IRA would present. While both the UDA/UFF and the UVF did have access to RPGs they were too valuable to risk and they were kept hidden. GPMGs like the M60, HMGs like the DSHK and anti-materiel rifles like the Barrett were all out of reach of the Loyalists.
When the conflict began both Republicans and Loyalists were badly armed, though neither as much as they like you to believe. The gun battles that erupted in Belfast during the riots before the arrival of the British army in August 1969 were mostly fought between the IRA and RUC, with Loyalist snipers coming to prominence after the RUCs withdrawal to wait for the army. In the immediate aftermath the IRA began to refill its stocks with old arms of old battles, mainly held by IRA members that had fallen out of the organisation. The Loyalists also began to dig out old arms, primarily those imported during the Home Rule Crisis before WW1 but they also had a notable advantage in privately owned firearms, as the government was more likely to give Protestant gun clubs approval than Catholic ones, additionally they could also access the firearms held in the homes of members of the Ulster Special Constabulary.
The IRA immediately began to look for better and more modern weapons with which they could combat the newly arrived soldiers and quickly they were far better equipped than their Loyalist rivals to which the Loyalists, panicked by this took a leaf out of the IRAs book and began to raid army bases for guns. This was primarily led by the UVF and it is strongly believed that many of the raids were inside jobs but they netted plentiful arms for the Loyalists, though it was painfully dwarfed by the sheer amount of arms the IRA was getting it hands on from the US and later the first wave of weapons from Libya.
Loyalists also gathered arms from all angles, buying them from criminals or even across the sectarian divide and even famously the stealing of some guns from an Official IRA arms dump, an event that led to a stand off when the Officials kidnapped three Protestants and demanded the guns return. The whole fiasco ended somewhat amicably when the leader of the UVF, Gusty Spence called the Belfast Officials' leader, Joe McCann and negotiated their release though the guns were apparently not returned.
Weapons of the Ulster Defence Regiment were extensively used by a loyalist group known as the Glennane Gang, a coalition of loyalists and active duty police and soldiers, both UDR and regular army. The group was active in the North Armagh area of Northern Ireland, a predominantly Protestant region bordering the IRA stronghold of South Armagh. The region saw some of the most brutal sectarian killings in the conflict with weapons lifted from UDR stocks, or brought by UDR members being major contributors. One such weapon, a Stirling submachine gun, UF57A30490, was used in the murder of 11 Catholic civilians. Weapons that had disappeared from Glennane barracks would be found even in Belfast, in the stocks of the UDA, a sign of the increasing role of rural loyalist units as quartermasters for the urban units.
The first major attempt by Loyalists to import weapons in 1972, ended in a major disaster as the arms dealer they had made contact with was a British agent. There were continued attempts with varying levels of success, Loyalists found allies in Canada just as the IRA found allies in the US. The Canadian route saw several modern weapons imported, but it was eventually stifled by Canadian police in the late 80s. Unlike the IRA who found a great pile of international allies, fellow separatist movements, leftists and anti-colonialists, Loyalists struggled and often found themselves making contacts with groups in great disrepute to the say the least. On one such occasion the UVF was approached by Dutch Neo-Nazis to carry out bombings of synagogues in the UK in return for money or arms, a request that was turned down. The Loyalists did however find some allies in the enemies of the IRAs allies. They made some overtures to the Apartheid government of South Africa, who was battling the irstwhile ally of the IRA, ANC. The member they sent, Brian Nelson, was identified by the South Africans as a British agent and broke contact but did not tell the UDA who had sent him. A much more profitable alliance came from, somewhat ironically the Maronite Catholics of Lebanon, the militias of whom where battling the much more close IRA ally, the Palestinian Liberation Organisation.
In 1988 the combined Loyalist factions of the UDA, UVF and Ulster Resistance, a paramilitary founded by Ian Paisley and the Democratic Unionist Party, launched a joint attempt to import a large shipment of modern weapons. The importation was funded by a bank robbery performed the UVF and UDA, the money then carried by well-to-do Protestants to Switzerland and used to pay an arms dealer for 206 Vz.58 rifles (a Czechoslovak assault rifle that looks similar to kalashnikov pattern rifles), 94 Browning pistols, 4 RPG-7 launchers with 62 rockets, 450 grenades and 30,000 rounds of ammunition. The arms were successfully brought into Northern Ireland and split between the three organisations but immediately met with disaster. The UDA was intercepted immediately and its whole share captured. The bulk of the UVFs share was captured not long after in Belfast and later in the year a small portion of the UR share was captured in North Armagh.
The UVF attempted to import another large shipment in 1993, of over 300 rifles, 50 pistols, 500 grenades and 60,000 rounds of ammunition, which was intercepted and captured in a joint British-Polish operation. This was to be last major hurrah of Loyalist arms importation.