MAYADEEN, Syria Rebels who have laid siege to a Syrian army base near Mayadeen in southeastern Syria have made mortar attacks a regular part of their routine.

Machine shops operated by rebel sympathizers now are turning out dozens of rockets that rebel forces use to pummel Syrian government positions from a distance – a capability that until recently belonged only to forces loyal to President Bashar Assad.

During their recent assault on an artillery base near Mayadeen, rebels belonging to the Jabhat al-Nusra faction raced forward in a captured tank – a wild sight to anyone who has spent the last year tracking rebel groups whose personal weapons often are nothing more than shotguns and aging hunting rifles.

In the past few months, rebels have gained access to heavy weapons that they previously could only dream of – rockets, mortars, cannons and tanks, even portable surface-to-air missiles that in recent days they used to down Syrian aircraft. At the Bab al-Hawa border crossing with Turkey on Thursday, about two dozen armored personnel carriers and tanks of various vintage were on display, evidence of recent rebel captures.

Many of the weapons come from Syrian government warehouses on bases that the rebels have overrun or from the rebels’ own shops.

“We’ve fired this five times today,” a rebel using the nom de guerre Abu Omar said as he showed off a mortar tube the rebels had constructed using the barrel of a Syrian army armored vehicle they had destroyed nearby. “We started using these about three months ago.”

“When we capture weapons from the government, we study them and copy them,” Abu Omar said. “We also learn how to make things from the Internet.”

For its part, the Syrian military also is using increasingly heavy munitions, particularly bombs dropped from jets and helicopters, a development that as much as anything is responsible for the enormous surge of refugees and displaced people that international aid organizations have reported in recent weeks. Millions of Syrians who once felt relatively safe in their homes as they waited out government shelling now have fled in the face of airstrikes that can bring down multistory buildings.

The result, ironically enough, has been a drop in civilian casualties in recent weeks, compared with highs over the summer, as people flee rather than risk being buried in the rubble.

The increase in weaponry has changed the dynamic of the conflict here, helping to even the two sides and spurring a rebel push that has seen several government bases overrun in recent weeks. U.S. officials have noted the rebel successes in explaining why they have continued to decline to provide weapons.

U.S. Ambassador to Syria Robert Ford, at a forum in Washington on Thursday, said that the recent gains made by Syrian rebels “are absolutely real. That said, there is no sign right now of any kind of political deal to be worked out between the opposition groups and the regime. Which means the fighting is going to go on.”

“Arms are not a strategy. Arms are a tactic. We think that a military solution is not the best way for Syria,” Ford said.

The rebels’ ability for the first time in the conflict to use weapons such as rockets and mortars may be more significant to the rebel advance than the few instances when they’ve downed Syrian government aircraft with shoulder-fired surface-to-air missiles. Indeed, rebels besieging an artillery base inside Mayadeen had deployed a pair of anti-aircraft missiles, waiting to ambush a helicopter that had been flying in supplies for the besieged soldiers daily. In the end, though, the helicopter didn’t show, and the rebels took the base after the 150 Syrian soldiers abandoned it under fire after days of rebel bombardment.

Rebels stress that their homemade weaponry is far more accurate now than it was just a few months ago, when rebels admitted rockets they made often misfired wildly.

“We tested the rockets before we used them, and they are 90 percent accurate,” said a weapons manufacturer who uses the nom de guerre Abu Ammar, who does his work in the same machine shop he’d used before the war to manufacture baking equipment.

“We know the rockets are effective because we heard the soldiers talking about them on the radio after we began using them,” said a rebel commander who was visiting Abu Ammar’s shop and who declined to give his name.

Abu Ammar said that he had learned to manufacture the rockets from manuals obtained by the rebel military council in Deir al-Zour, the province in which Mayadeen is located. “They are Qassem rockets,” he said, referring to a type of rocket widely used by Palestinian militants in the Gaza Strip to attack targets inside Israel.

Perhaps underscoring their effectiveness, the factory in which Abu Ammar works was targeted by an airstrike minutes after he gave journalists a tour.