Keeping watch on weapons and those who use them

America's military manpower goes from strength to strength, whatever the state of its weaponry (see above). The All-Volunteer Force has been advancing on both fronts - quantity and quality - for two-and-a-half years. The last fiscal year was the best since the volunteer program began in 1973, according to the Pentagon. The current one (1982) promises to be better, notably because of the increased level of re-enlistments. Even the National Guard and reserve forces, which had been set back when the bulge of Vietnam era enlistments ran out, are being replenished at faster rates.

No, the Navy has not suddenly solved the once headlined shortage of thousands of petty officers, those who know the score and get things done. Instant experience has not been invented. But improvement is on the way as retention rates rise and experience accumulates. This year the Navy is retaining 81 percent of those eligible in contrast with 73 percent last year.

It is easy - and no doubt correct - to say that more Americans are choosing the uniform because of fewer civilian opportunities at a time of high unemployment. Also they can hardly fail to be tempted by the recent substantial hikes in military pay.

But a less tangible factor cannot be dismissed: a sense of heightened appreciation for those in military service. Things have changed since the Vietnam aftermath when those who served were often wrongly discredited along with their government's policies. As long as nations must maintain armed forces , those who maintain them must be honored.

Not everything is coming up roses. The present encouraging figures of enlistment - with more high school graduates and better test scores - arrive shortly after a study warning of racial imbalance in the military. Recruiting may grow more difficult with the end of recession and the shrinking of the target group of young Americans. The number of 18-year-olds is expected to fall 19 percent by 1990.

But right now, says a Pentagon manpower official, ''we're in absolutely great shape.'' A salute, please, to the volunteers who are keeping the All-Volunteer Force on the march.