The conversion is easy, no metal cutting required though you will need to drill a few rivets out. Get a good bit for when you do that, or start with a small bit then work your way up. It's really not much more work than removing the trigger assembly, then putting the new trigger assembly in the right place. A couple of notes on it...
* If you want the bolt hold open, you will need to grind/cut a notch in it for the safety to pass through. Alternatively, Carolina Shooters Supply (who is EXCELLENT to deal with) sells pre-cut BHO's for $15. That will save you a ton of headache. For me, I had to re-do the install a zillion times because the notch wasn't the right size/shape and I had to keep making it bigger.
* Using the "shepherd's crook" spring to hold stuff in place is a hassle, spend the $7 or $8 on the axis pin retaining plate and it's a snap to get it all back together again.
* Don't forget to order the pistol grip screw, and you may also need to get the nut for it too, depending on if the trigger guard you get (some have the nut built-in).
Going for the SBS is possible. Depending on how short you go, you may need to get a shortened piston (machine shop or gunsmith can install that for you) and shorten the gas tube and perhaps relocate the gas block. I'm not 100% sure how that would go, but I know that the folks selling SBSs built on Saigas (like Tromix) are asking a pretty big dollar amount for them.
Re: ghost rings... the choices aren't great. There's the Kreb's set (
http://store.carolinashooterssupply....-Custom/Detail) for $99. It's a barrel clamp design for the front, and no tritium. It uses an AR front post, so you can get a fiber front post, a colored plastic one, or a tritium one (
http://www.brownells.com/.aspx/pid=2...ONT-POST-SIGHT $60). The only other choice is the Tromix tritium HK style ghost ring (
http://store.carolinashooterssupply....ight-HK/Detail $120), which I *think* requires welding for the rear sight. Whatever you do, do NOT mount a rail or sights to the dust cover, you might as well not have them since the dust cover is loose. Unfortunately, the "Texas Dog Leg" mount doesn't fit the Saiga 12, because it mounts on the rear leaf sight and the Saiga 12 doesn't have the rear leaf sight.
If you put sights on, you have 3 approaches for the rear: weld to the gas tube/receiver/etc., mount on a rail, or install in the leaf sight's dovetail. The Krebs ghost ring kit uses the dovetail, it is the most "no modifications needed" choice out there.
Your options for getting a rail on the top of a Saiga 12 are:
* Something that clamps onto the side mount - I just got one from Kalinka Optics (
http://kalinkaoptics.com/mounts/ak-v...ck-finish.html $52) and it is excellent.
* The Ultimak rails that mount on top of the gas tube using the rear sight dovetail to hold a nut and the front sight bead's hole (or a new one tapped in the gas block), Carolina Shooters Supply has two models for $99 each, depending on how your gun is set up.
* A quad rail handgaurd; some of the tri-rails have an optional 4th rail. The quad rail may very well cover the leaf spring area or block you from installing a sight there, so if the sight you want uses it but you still want the rails (and you will for HD, for a vertical foregrip and a light), get the tri-rail.
If you want to also shoot birdshot, you'll possibly end up having to get a new gas plug, but it all depends on how yours does. It's luck of the draw if it functions well with the bulk pack stuff (depending mostly on how many gas ports you get and their size), though the higher velocity birdshot (1200+ FPS like Winchester AA Sporting Clays, Remington Express Long Range, and Remington Nitro - my favorite) cycles them pretty fine with the factory gas plug... but they are 50% more expensive ($7.50/box vs. $5/box) so the $20 gas plug looks like a bargain after one trip to the range.
So... the config that I'd recommend for you would be:
* Krebs ghost rings - $99
* Tritium AR front post - $60
* Tri-rail - $100 (you can get a cheap polymer HG/rail for half this price)
* Vertical foregrip (optional)
* Light (optional)
* Gas plug (as needed) - $20
* Trigger kit - $60
* Polymer pistol grip - $10
* Pistol grip screw - $5
* Folding Warsaw-length stock ("Warsaw length" is shorter than "NATO length", because Eastern Europeans are a bit shorter and wear lots of thick winter clothes for much of the year) or adapter + M4 stock; to save money, just use the fixed Warsaw length polymer AK stock at first, if you need to - $20
* Axis pin retaining plate - $8
* Pre-modified BHO or Krebs Safety with notch (optional... you don't need the BHO for HD at all, it's really only useful for the skeet range where they require open breech all the time)... it's not a "last round bolt hold open" which would actually be useful for HD...
* Oversized charging handle (optional)
* 2 12 round SGM stick mags or 1 20 round MD Arms drum (clear or smoke cover to check round count) - the Pro Mags have a bad reputation, both for sticks and drums - $80 - $100 total
Prices are off the top of my head...
So you'd be looking at $462 plus the purchase price of the gun (roughly $550 from Classic Arms, last I checked), after S/H you are looking at around $1,020 - $1,050 if you do the work yourself. The work is less than an hour from start to finish even if you've never done it before, it's a quick project. Expensive? Not in comparison to a lot of decent S/A shotguns on the market (Benelli, Beretta). Compared to the typical S/A HD shotgun out there (Mossberg 590, Remington 1187, etc.), yes. Compared to the typical P/A HD shotgun? Very much so. But to make it a fair comparison, it's not too much more than a decent pistol, especially if you cut a few corners (omit the ghost rings, fixed stock, polymer rails). Just doing the conversion to PG will set you back about $100 total, put down $100 more for magazines/drums, and you are looking at under $800 for a reliable (though unrefined) S/A shotgun with amazing capacity.
But... what you get are two things. First, you get the proven AK action. There's a reason why you don't see many S/A shotguns in the HD/LE roles, and it boils down to "trust issues". Imagine if the world of pistol were such that the only semi auto pistols people would trust their lives to were HKs and $3,000 1911s, and everyone else was packing a revolver? That's the world of shotguns. Sad, eh?
The other advantage to the S12 is the magazine. You can store the gun and ammo separately for safety, but be ready with a quick rock 'n lock and bolt charge. You can reload in a fraction of the time compared to any other shotgun, even though they tend to not like being loaded on a closed bolt depending on mag design unless you download by one round. Best of all, for the HD role, the 20 round drum is simply unbeatable. The only limitation with the drum is that you must use 2 3/4" shells (no 3" shells). No big deal... I've fired 3" Super X magnum #00 buck and 3" magnum slugs through mine, and I'd much rather have 2 3/4" shells with a bit lower recoil to let me put follow up shots on target faster. I know the "how many rounds onboard" topic is hot... having 2 - 3 times as many rounds available without a reload (and a reload in a fraction of the speed) is a game changer. I hope that I *never* see a situation in which 20 rounds of #00, #1, or 1 oz slugs is needed, but if I ever encounter that scenario, I'd prefer to have the S12 and a drum than a duck gun and a box of shells in my pocket.
J.Ja