In late 2017 Iran released close range and high-resolution photos of their new (since 2016) Zolfaghar ballistic missile. Examination of those photos indicated that the body of Zolfaghar was not made of steel, like earlier models, but much lighter carbon fiber. That would account for the 40 percent increase in range claimed for this new version of an old missile. Zolfaghar appeared identical to the Fateh-313, which appeared in 2015 with a claimed range of 500 kilometers. It was initially believed that both Fateh-313 and Zolfaghar achieved their longer range by using larger and more efficient solid fuel rocket motors. Iran has been switching from liquid fueled rockets to solid fuel as quickly as they could but the technology is difficult to master. The United States began doing this in the late 1950s and many details of the problems involved in producing reliable and efficient solid fuel missiles had appeared in print over the years. But knowing the details of the exact chemical mixture and production techniques was less easily obtained. Solid fuel rocket motors are cheaper to maintain enable a missile to be made ready in less than 30 minutes compared to several hour for liquid fueled missiles like the SCUD. It was known that Iran has put a lot of effort into developing better solid fuel rocket motors. No one was paying much attention to what they were doing with carbon fiber materials.
Solid fuel rocket developments are more obvious. Meanwhile Iran began the switch from liquid fuel motors in in 2002 with the Fateh 110. This was a copy of the 1980s era Chinese DF-11 ballistic missile (range 300 kilometers, 800 kg warhead). Subsequent versions of Fateh followed the same development pattern the Chinese DF-11/15 went through years earlier. This included the use of GPS (American or Chinese) guidance in addition to the less accurate INS as a backup. For nuclear warheads either guidance system is accurate enough. For conventional warheads GPS is essential to avoid missing the target with the smaller explosive power of a conventional warhead.
The Fateh 110 is an 8.86 meter (27.5 foot), 3.5 ton rocket with a half-ton warhead. The first version had a range of 200 kilometers. By 2010 there had been to improved models, with ranges of 250 and 300 kilometers plus improvements in reliability and accuracy. The Fateh 110 was developed to replace the liquid fueled SCUD ballistic missiles Iran first obtained from North Korea in the 1980s. SCUD was developed in Russia using German World War II era V-2 missile experience. North Korea continued to supply Iran with ballistic missile technology and that evolved into the two countries trading solid fuel rocket motor and guidance system technology.
Iran appears to be adopting the same ballistic missile tactics China developed for shutting down Taiwanese air defenses during the first hours of a war. This involves using a massive number of short range ballistic missiles. Since 2009 China has maintained a force of at least 1,400 ballistic missiles aimed at Taiwan. That's up from 200 in 2000, 800 in 2004 and 1,300 in 2008. Most of these are DF-11 and DF-15 models. The DF11 (also known as the M11) has a range of 300-800 kilometer depending on warhead size and new rocket motor and flight control tech. The DF15 (M9) is basically a redesigned DF-11 that is more reliable and accurate. From the Chinese coast, to targets in Taiwan, it's about 200-300 kilometers across the Taiwan Straits. The distance from Iran to key targets in Saudi Arabia or other Arab oil states is about the same.
The Chinese missiles would use high explosive or cluster bomb warheads, and would basically be bombs that could not be stopped. Well, that's not exactly the case. Taiwan is investing in an anti-missile system that would negate a large number of the Chinese missiles and so are the Arab states within range of Iranian missiles. If used, perhaps 75 percent of the Iranian missiles would actually hit their target. The others would suffer failures in propulsion or guidance systems. Each missile is the equivalent of a half-ton or one ton aircraft bomb. Initially the Chinese missiles had primitive guidance systems, meaning that the warheads will usually hit up to 500 meters from the target. The Chinese equipped their missiles with several generations of GPS, tech, in response to advances in Taiwanese jamming technology. Guidance systems that are more difficult to jam are always being worked on. This technology has been much sought after by Chinese spies in the United States over the last few years.
In 2011 Iran claimed to have created an anti-ship missile, called the Khalij Fars, with a range of 300 kilometers based on the Fateh 110. What all this implies is that Iran is claiming to have developed a ballistic missile that can hit moving ships at sea. China has also claimed to have developed this technology (the DF-21D). But neither country has demonstrated their anti-ship ballistic missiles actually working. The problem is that there is no evidence that Iran has developed accurate and reliable guidance systems for these missiles and none of them have been used in combat.