After handling and firing M91/30s for many years, I've come to prefer them over the carbines. Despite it's length, I find them handy and surprisingly well balanced. The longer barrel cuts down on muzzle blast flash and concussive noise quite a bit. I can fire my 91/30 without hearing protection and it is not overbearing. The carbines? Not recommended!! Also the longer 91/30 gives a bit better velocity for increased penetration and terminal effect and also has a longer sighting radius for better shooting. They also recoil somewhat less do to the increased mass.
But, the carbines are a hoot and people love to see the big fireballs they make at the range! But for combat make mine the full size rifle, even if it is a longer weapon for sure.
Now look, I'm not trying to see the Mosin is the best combat rifle for 2017. Obviously it's far from it. BUT, with the proper technique and experience and a rifle that is set up properly, they can still do the job.
People complain of sticky bolts. Well there are fixes for that, no it is NOT how all Mosins are and it is NOT how they should be, usually it is a result of different factors like storage and wear.
Then some claim you have to remove the Mosin from the shoulder to reload a cartridge. Phooey! You don't!! It is just awkward for a while when you first learn to work the bolt from the shoulder, it becomes second nature and one can work the bolt nearly as fast as a Mauser with some practice.
And stripper clips? Many have issues with these. But with proper milsurp clips, not junk Chinese repros, and the right technique it can be fast smooth and effective. Knowing how to set up the clips to prevent rim lock will keep it from happening even on rifles with worn interrupters, of which I've had a few.
Remedial actions takes some getting used to as there are a couple major stoppages that can occur when mishandling rounds during reloading, but they can be overcome.
The guns are generally not as accurate as modern rifles and they don't need to be. They are BATTLE RIFLES, they are generally accurate enough to defeat exposed personnel out to 400-500 meters and beyond and are effective on area targets much further out. The round is still considered to be very powerful and effective with high penetration properties.
In short, they are not as ergonomic or simply nice as a Mauser or Lee Enfield, but they do work and work well IF you know how to run one. A Mosin was my first rifle and in the past decade I have learned to run it properly. They have their flaws and I would never trade one over my PTR-91 if I was going into a battle, but honest to god I wouldn't feel unarmed with one if it's all I had, and I'd much rather have one over many other guns in that situation.
Keep in mind Mosins are still used in many global conflicts to this day. Images and videos from places like Syria, Iraq, Afghanistan, Ukraine, and tons of other places show them being used alongside modern assault rifles and other weapons. For a guerrilla style shoot and scoot type ersatz sniping weapon, they are perfectly adequate and the ammunition is abundant in that part of the world and they will continue to be useful and ultimately effective weapons in low level conflicts for years to come. In the US they aren't as cheap as they used to be but you can still find very good deals on them at gun shows and yard sales etc., same for the ammo. They are very solid and durable rifles that will do the job of defense or hunting.