It would be a duty weapon, yes. I work for a private company that has no restrictions, other than you must be qualified/certified to carry said weapon.
I prefer the collapsable stock, mostly because of body armor getting in the way of a longer stock. My shotgun is a youth model, if that helps. I've just seen females with really short arms struggle with long rifles- I just wanted to clarify that I wouldn't have that problem. LoL.
Prefer more of the M4 style. I've shot an H&K MP5 and wasn't really a fan, as I'd prefer a smaller, more long-range round vs a 9mm.
Holographic sights would be nice, along with a rail for a tac light.
I'm a big fan of S&W handguns, but I've never shot or handled one, AFAIK.
Ok so pretty specific list should make it much easier. To me you are looking for a 16" carbine, 6 position collapsible stock, maybe a quad rail...maybe not, a red dot sight of some sort, a weapon light, and a decent patrol sling.
For a duty weapon I would be looking for a complete rifle so 16" with a collapsible stock is not an issue as everyone makes multiple models in that configuration. Things to look at to narrow it down some and decisions you will have to make.
1) Gas System - 16" carbines are going to be available with two different gas systems. They will be available with either a carbine length gas system or a mid length gas system. The length of the gas system is determined by how far up the barrel the gas hole is drilled in the barrel. A carbine length system is the shortest at 7.5" and the mid length is well the one in the middle at 9.5" and a rifle length system is right around 12".
Gas system length is going to effect a couple of things.
a) First it is going to effect the force available to cycle the action and extract the spent casing from the chamber. It's a long discussion involving
port size, location, dwell time, extractor type, extractor wear, and reliability. Basically in the simplest terms the pressure at the gas port is different
for the two systems as the bullet passes the port. For a carbine it is right around 34,000 psi and for a mid length it's right around 27,000 psi.
Mil-spec M4's come with a carbine system and as I understand it the mid length system was developed to slow cyclic rate by allowing the bolt to
stay in battery longer. It also had the unintended effect of softening the recoil slightly....so slightly that I can barely even notice the difference. Also
due to the fact that there is less pressure in theory there should be less wear and tear on the bolt and the extractor. That being said I have a
Bushmaster 16" carbine with a carbine length gas system that has over 17,000 rounds down the barrel and it is still on the original extractor and bolt
go figure.
Choose the gas system length you want they should both be fine.
b) Second thing it determines is the sight radius, distance between the front and rear sights, on a rifle with a standard FSB (front sight base). Obviously
the longer the sight radius the more precise the sight picture and as the FSB is installed over the gas port a mid length would have the longer sight
radius. Since you are talking about a rifle with a rail and a red dot sight (RDS) you do not have to utilize a std FSB so again pick the gas system you
want.
2) Barrel Length - You are basically going to have two choices either a 16" barrel with a removable flash hider or a 14.5" barrel with a permanently attached
flash hider. The reason for that is BATF rules say that any rifle with a barrel length of less then 16" is a short barreled rifle and requires a lot of paperwork,
fingerprints, and a one time $200 tax stamp for you to own. How they get around that with a 14.5" barrel is by permanently attaching the flash hider to the barrel. If you feel that the 1.5" overall shorter barrel is worth it order a 14.5" but to me I like to be able to change the flash hider so I run a 16" barrel.
3) Barrel Twist - You may find as many as 3 different choices...those being 1/7 twist, 1/8 twist, and 1/9 twist. 1/8 will be the least common and 1/9 being the most common and 1/7 falling in the middle. I could type two pages of info about twist rate and just confuse the crap of of everybody but I'll try and do it easy and simple. Twist rate indicates the distance the bullet must travel to complete one full revolution, such as 1 turn in 7 inches (1/7 inches). A shorter distance indicates a "faster" twist, meaning that for a given velocity the projectile will be rotating at a higher spin rate. Higher spin rates are needed to stabilize longer bullets and longer bullets tend to be, but not always, the heavier bullets. For a duty weapon I would be looking for the twist rate that will fire accurately the longest/heaviest bullets I can find within reason. Generally this is going to be a 75 or 77 grain OTM type bullet and the only rate that can properly stabilize that size bullet consistently is a 1/7 twist rate. 1/7 will allow you to accurately shoot basically any bullet from 55 grain to 77 grain so anything from a plinking round to a very good self defense round.
4) Iron Sights - Do you want fixed sights or BUIS (back up iron sights). Me on a rifle that has an RDS I prefer fold down BUIS as it gives a nice clean view in the sight picture. I know lots of folks who run the standard FSB and a fixed rear sight and like it so it can work and work very well.
I'm sure there is more but I'm tired of typing.
Start with that and start to narrow down the field. Be prepared as a duty rifle like the one you are describing is going to easily reach $2000 whether you build it or buy it. I built this one and it came in just under $3000.
16" mid length 1/7 barrel, quad rail, weapon light, sling, RDS, BUIS, and 6 position collapsible stock.
