90's military sci-fi book series: rifle firing "flechette" rounds, grenade launchers as a standard weapon

Question

I've been trying to identify several series of military sci-fi that I read in the early 90's. I've had more luck remembering details of some than others.

For this particular series, the only details I can remember involve the standard troop weapon. It was a rifle that fired "flechette" rounds (as they were called in the books). Ammunition for the rifle was a solid block (plastic, I believe.) When fired, the mechanism in the weapon shaves slivers (flechettes) off of the solid block and launches them at an extremely high rate of fire.

Also, IIRC, the standard weapon also had grenade launchers that launched small spherical contact fragmentation grenades.

The characters were human, and the war/combat was the focus of the books, not a sidebar. The main characters were soldiers in the unit that was the focus of the overarching plot of the series. Futuristic, planet-side, not on Earth. It's likely the series took place on multiple planets.

I remember a scene with a unit commander ensconced in a mobile command center while planning a battle, in which he opted to ignore the computer's weather forecast and asked a farm-boy trooper for his opinion on what the weather would do that night (rain by dawn). Although, I'm not 100% certain that this is from the same books as all that's been mentioned before. I could be mixing my series on this detail.

Answer 1

The plastic block ammo sounds a lot like Old Man's War (2005) by John Scalzi. Check out the links and the book cover, it might ring a bell.

From Goodreads:

John Perry did two things on his 75th birthday. First he visited his wife's grave. Then he joined the army.

The good news is that humanity finally made it into interstellar space. The bad news is that planets fit to live on are scarce-- and alien races willing to fight us for them are common. So: we fight. To defend Earth, and to stake our own claim to planetary real estate. Far from Earth, the war has been going on for decades: brutal, bloody, unyielding.

Earth itself is a backwater. The bulk of humanity's resources are in the hands of the Colonial Defense Force. Everybody knows that when you reach retirement age, you can join the CDF. They don't want young people; they want people who carry the knowledge and skills of decades of living. You'll be taken off Earth and never allowed to return. You'll serve two years at the front. And if you survive, you'll be given a generous homestead stake of your own, on one of our hard-won colony planets.

John Perry is taking that deal. He has only the vaguest idea what to expect. Because the actual fight, light-years from home, is far, far harder than he can imagine--and what he will become is far stranger.

Answer 2

The weapons don't match but asking a farm boy trooper for an opinion sounds like it could be a book in the Hammer's Slammers (1979 onwards) series by David Drake.

From Goodreads:

When a planetary government faces threats from guerillas, insurgents or terrorists, the men they hire are Hammer's Slammers - known throughout the galaxy for their cold, ruthless ferocity, their ability to defeat overwhelming forces, and their willingness to go up against impossible odds.

Answer 3

As I recall this is identical to a weapon Eisenhorn used. Been too long (books were published between 2001 and 2004) but with the inclusion of the grenade launcher and the description of the weapon, it is exactly as I remember it from the book.

Editor's summary:

Inquisitor Gregor Eisenhorn is an Imperial inquisitor, one of the tireless defenders of humanity. With his warband he scourges the galaxy, walking in the shadows of darkness in order to root out heresy. When that heresy is found to infiltrate the hierarchy of the Imperium and the Inquisition itself, Eisenhorn must rely on himself alone to deal with it – even if it means making deals with the enemy and compromising everything he has ever believed in.