The roll of navel gunfire can again be heard all over town, and this time it's Agriculture Secretary John R. Block who's in the cross fire.

The battle, dating to the early days of the Reagan administration, pits two camps of navel orange growers against each other. The issue is a federal order that determines how much fruit can be sold each week.

The latest round began in January when, at about the time that freezing temperatures devastated the orange crop in Florida, Block announced that he was suspending the weekly "pro-rate" rules that governed the amount of navels that California and Arizona growers could sell at retail.

Some growers feared that the sky would fall without the traditional control over supply and, indirectly, price. But shipments since Block's order have been down about 5 percent. Prices to farmers in California have actually fallen about 10 percent.

So, in keeping with Block's belief that the best agriculture is one free of government mucking, the suspension has continued.

Now his critics have realigned their guns and again are taking aim at the order.

A grower lobby, dominated by the big Sunkist cooperative and represented by Reagan campaign press aide Jim Lake, has met with Block twice in the last two weeks, trying to get him to reverse himself. And members of Congress, who earlier banned the Office of Management and Budget from any further tinkering with agricultural marketing orders, have been urging the White House to overrule the secretary.

"Yes," Lake said yesterday, "some members have gone to the White House, urging that somebody get to Block and get him to do the right thing . . . . He said in January he would change if conditions warranted, and the growers think that a reversal now is in order."

An aide to Block said that the situation is under weekly review, but that "everyone has been surprised at how well the market has worked without the pro rate in effect."

From the other side, fearing that Block was about to slip on a well-placed peel, California grower Carl A. Pescosolido, a leading critic of the pro-rate system, orchestrated a full-page advertisement in yesterday's Washington Post, urging President Reagan to back Block's position.

"I am aware of a number of visits and phone calls to the secretary, trying to get him to reverse himself," Pescosolido said. "My objective is to preserve the current situation, but I became alarmed when I began to realize all that lobbying was going on. I heard there was more than a small likelihood that the decision would be reversed within two days. Thus, the letter."

Pescosolido, who has one of the largest orange-growing businesses in the world, said that since Feb. 1, when Block's order took effect, the market for oranges "has been more profitable than would have occurred in the regulated market."

"Our prices are down but we are shipping more," he said, "so our net revenue is up."

Since Reagan took office in 1981 vowing to reduce regulation, the Great Navel War has been one of the tartest philosophical skirmishes in town. It has divided Reagan supporters and put big oil companies that grow navels at at odds: Shell opposes the order, while Tenneco wants it.

The marketing orders that regulate the growing and handling of more than three dozen farm specialty crops have been a centerpiece of the dispute. After reviewing the orders, the administration ruled that it no longer would support those that prevented farmers from growing certain crops.

Pescosolido, who enlisted in the battle after news reports in 1981 told of massive amounts of navel oranges being destroyed because the pro rate banned their sale, says he thinks that the free-market ideas espoused by Reagan and Block will prevail when the smoke has settled.

"All I want is to be allowed to get out there in the market and take my risks," Pescosolido said yesterday. "Our crop is about average this year, but the market has been very capable of absorbing every orange grown in California . . . . Consumer prices will be trending downward in the next few weeks. Everyone wins."