We had no issued carrier when I was in STA across two different platoons from 95-01, and I don't remember ever seeing one on the TO/E either. Hunting style bullet carriers on the belts or slings were around, depending on the shooter's preference. Also SAW pouches on the deuce gear were prevalent as well. Nobody I knew ran stock packs or anything else that attached to the rifle itself. Typically the sniper has a box in their pocket, and additional ammunition spread between the sniper and the spotter.
We would usually open the box along three sides of the perforations to have them readily available, but would leave them in the box like that and not loose. When we would go shoot competitions or works with the Brits, we would always be jealous of the guys with the DBMs.
Anything in addition was a self purchase as it was hard enough to get money to pay for fuel to truck to the field (rule was if it was less than 20 miles to the training area, we hiked), much less get anything special from open purchase. A typical sniper would drop a minimum of $1000 on their own gear for everything from mountain rucks to GPS devices to web gear and water purifiers. Ghillie suits were entirely self purchase and built as well, mostly using bulk burlap from garden centers. DRMO shopping was our favorite pastime as well just to save us a few bucks. Our scope covers were usually an old sock with a knot tied in the end and a slit down the side. There's a reason we always said STA stood for "Steal, Take and Acquire" because that's the only way we could get anything. Gear adrift is a gift. The 90's were some harsh years for DoD budgets, and the Corps was in the habit of always giving back money to Congress that we didn't spend too.
With our weapons issue we would have the rifle, leather sling, brass punch rods with jag and brushes, double oil bottle, camel hair brush, lens cleaning compound and paper, and that's about it. Nothing's too good for the Marine Corps, and nothing is what we got!