Well, considering the OP asked about M110's and SR25's, I'll just stick to that.
I recently was in the market for one and I looked at all the ones for sale and the ECC's and EMC's that were real M110's were actually trade in UPPERS from the military and came in grades 1-3; most of the grade 1's went fast and cost the most. The grade 3's still went for $6000 or so, not much different than the grade 1's, and all were trade in uppers mated to new civilian marked lowers. These were the FDE M110's with the rifle length FF rail and used the full adj. stock and the long suppressor that threads onto the gas block. I don't think it came with a scope because if it did it would have been the Leupold Mk4 2.5-10x, not the NF. Sounds like it may be one of these. If so, it's basically a used rifle with a nicer scope and max cost would have been around $8000. And it wasn't worth it then IMO.
They DO or DID sell a deployment kit that has everything minus the can and the thermal/NV stuff. It came/comes with a hardcase, several mags, books, targets, soft case or drag bag, covers for the scope, full cleaning kit, etc. It's also several thousand, I forget just how much but I wanna say $13,000.
I ended up getting a new civilian M110. It has the keymod handguard, they all do now, that or the m-lok. Originally planned on installing a FF rail, but that turned out to be not only more hassle than it was work, the keymod is actually an upgrade from the old URX system. A huge upgrade, and as good or better than the old FF systems. Anyway, it grew on me and I kinda like it now, in fact, I used one to build an SBR Grendel and outfitted my 20" Grendel with one so it's kinda like an AR version of the SR-25/M110 I have. It certainly is easier to build using them since they are one piece and basically yield a monolithic type upper. The KAC lower is superior to all others, period, end of discussion, be it AR15 or 10. Full ambi controls BUILT IN, not added on. While not necessary, certainly is nice. The trigger they come with is good enough I felt no need to change it out with a Geissele. Wish I'd known this years ago, since I use the LMT stock anyway, so they basically offered a better complete one I didn't have to build.
Anyway, the new M110 also uses a cut rifle barrel in 16 or 20 inch, and one is chrome lined but still cut rifled, the "combat" version. Nice. The 20" has the heaviest profile followed by the 16" medium and the 16" chrome lined lighter profile. It weighs about 2lbs. less than the 20". The ONLY differences between the military and civilian models is that the military lower says "M110" and the civilian one says "SR25". The military one comes with the inferior Magpul adj. stock but the superior (IMO) QD brake. The civilian one comes with the LMT SOPMOD stock and the flash hider. All come with the keymod or m-lok handguard. For $3800 or so shipped direct from KAC, I'd say that rifle was a great deal. Comes with a target, guaranteed to shoot sub-MOA (1MOA or less, mine was about .5, a bit larger). I can put whatever scope I want on it, so that's a plus and I plan on the USO 1.8-10x instead of the issue Mk4.
IF you buy a KAC rifle, I'd strongly suggest purchasing directly from KAC. If you are a veteran, military or police it's definitely worth it. I disagree about other rifles, I looked at them and even contacted some of them. Building a rifle like this isn't like building an AR, nothing is standard, so to get a GREAT rifle, you have to get one built ground up for it. That's the SR-25, all others are just copies of it really. Some better than others. The HK is nice, but not worth it IMO. They won't sell you the G28. FN is selling their Mk20 to civilians and it has similar requirements of the M110 and is the one SF is currently purchasing to replace their M110's. Mags are cheaper, but dealing with FN is a bitch. I still like the M110 better anyway. IF you have the money to just blow and really, really want a military type M110, call KAC and tell them you want the .mil version and are willing to pay the tens of thousands it will cost to get one. Then while on the phone, go ahead and get the clip on thermal and NV for several thousand more, then hang up and call up AAC, Silencer Shop or Ops Parts to get your hands on one of the older M110 reflex cans for another $2000 or so.
But if the factory $3800 SR25 doesn't float your boat, you can always build or buy another upper in the configuration and caliber you like later and still take advantage of the KAC lower and guts and possibly have two rifles, still for less than the cost of the deployment kit. Hell, you can build you own deployment kit for less. I got ten KAC mags and I think it came with the full blown cleaning kit and other stuff, so for what, $4800 shipped I had all but a case and drag bag. I ordered the appropriate KAC suppressor which fits the FH and is superior to the older reflex can, waiting on that still, and it currently sports a 3.2-17x USO and Atlas bipod, so it's no junk toy and still cost WAY less than 10k all said and done. Did I mention it's a NIB rifle too?
So personally, I'd get a new one for less and not look back. KAC has always made a fine rifle, one of the best, and has always used a fine cut rifle barrel. They've changed barrel supplies over the years, but always go with a good one. GAP was the only other one that offered a quality 7.62AR with a cut rifle 20"bbl. that I found.
That's about all I can say off the top of my head, but I'd go with a new one and just shy from the other one. Sounds too much like one of those graded trade ins.
