In parts 1-3 Shawn has pretty much covered most of I would say.
Previously, I owned an Armalite AR10 model 10A4F and I replaced that with a LMT MWS which I quickly got rid of.
The Armalite was about $1500, and was a nice rifle. However with its 20 inch barrel, A2 stock, and longer then AR15 action, it make for a long almost awkward rifle. While it did deliver its guaranteed 1.5 MOA, it was neither the handy battle rifle I would have liked, nor a semi-auto precision rifle. So I replaced it with a LMT MWS. The MWS had some very nice features, but I had some issues with mine, and sold it quickly.
Now having tried the Colt 901, I much prefer the Colt over the previous two rifles I owned. The 901 is surprisingly soft shooting. That’s not to say that it doesn’t have recoil, but that it is a smooth impulse. Perhaps the M1 Garand might be a good comparison. The Armalite I owned was not that pleasant to shoot, and the MWS, while nice, was still a much sharper recoil impulse. When shooting the 901 off of a Harris bipod, the rifle recoils straight back, making it easy to watch my impacts through the NightForce 2.5-10×24 scope I was using. When shooting offhand with an Aimpoint T1, the 901 recoiled smoothly up and back, I want to say that the recoil impulse is smoother than shooting a M4 with M855. I don’t want to make some claim that the rifle has light recoil, but I find it extremely fun and easy to shoot.
I have noticed some people questioning the choice of the Vortex flash hider on the 901. I know it to be an excellent choice. 16 inch barreled 308s have a good deal of flash and blast depending on ammunition used. This pronged flash hider helped break up the flash and concussion from the shorter barrel, and makes the rifle much more pleasant for those around the shooter. While a pronged flash hider will ring(most noticeable when dry firing), it is not noticed when firing the rifle.
The 901 is not light, but in my opinion, it balances well. The Armalite rifle felt very nose heavy. The MWS, while similar weight, had most of its weight in its barrel, making the rifle far more awkward then the 901. The 901 handles very similarly to a MK18/CQBR with Daniel Defense RIS II and a suppressor. It is not light, but it feels far closer to that of a M4 then the MWS. I found the 901 easier to shoot well then the MWS.
On a side note, when I tried DAG surplus 308 in the LMT MWS, I could only get 6 inch groups at 100 yards with it. It got to the point where people were making fun of me with my performance with that rifle. This same ammo gives me 2.5 inch groups in the 901. So far, in my limited testing, the 901 seems less ammo sensitive then the MWS.
I spent much of the time shooting the rifle with a Magpul CTR stock, the VLTOR IMOD that came with it works very nicely as well.
The Colt 901 is an awesome rifle, but it is not perfect. So there are some things you should know before you buy one.
1. The 901 uses a non-standard height front sight, so it comes with a Troy micro rear sight. Standard AR15 rear BUIS will not work unless you use a rail mounted front sight on the monolithic top rail.
2. The area where the trigger pins are on the lower is reinforced. This means if you replaced the trigger, you will want to use the slightly longer trigger pins that come with the 901s trigger.
3. 5.56 PRI Gasbuster charging handles will not work with the 901 lower. It is unknown if the BCM gasbusting Gunfighter charging handles will work.
4. The 901 comes with “Colt Spec” .308 PMags. These Colt Spec mags have an over insertion prevention tab on them. I primarily ran the 901 with standard Magpul 308 Pmags and had no issues. When using the standard PMags, think just like using standard GI mags in an AR15, push into the mag well, then pull to make sure it is seated. The Colt Spec mags are nice, but not mandatory. With the upper removed, I found it was a non-issue.
5. The quad rail on the 901 is tall and narrow. I think that rail panels might not be a good choice for this rifle, but it does work well with ladder covers. I think that LaRue index clips were a little too slick for the 901. A Knights handstop and VFGs work well on the 901, but are lower from the bore then I am used too.(I mainly use the Daniel Defense RIS II rail).
6. The 901 is nose heavy, however it is not too different then a M4 with accessories, or a SBR with suppressor. I find it better balanced then many of the other .308 variants I have owned or used.
Please don’t read this list the wrong way, I HIGHLY recommend the 901. It is good to know these sort of things before you buy the rifle.
What I am looking forward to most is having an SBR 901. I am excited about having a 308 upper, and a short 5.56 upper in the same case, with a single .30 cal can I could run on both uppers.