I will start this with the disclaimer that if you do this job, I didn't tell you to! If it goes horribly wrong, please don't say I said it would work. This is not for the weak at heart. Taking a grinder to a $1500 rifle that hasn't even been fired yet, was the hardest part to get over. In the end , it turned out extremely well.
Unless you are going to get a rail that stops before the front sight base, I would go with a low profile gas block. The R3 comes with a railed gas block and it won't fit under the Samson rail. Actually, it most likely won't fit under any rail. So, you would have to cut it down or replace it. The FSB that I cut down was easier to do IMHO. I took my time and was very careful not to damage the rest of the gun. As a precaution, I removed the gas tube. If you go fast, one slip and the upper is going to be toast. The tools I used were big in comparision to the job. A double wheel bench grinder, handheld angle grinder, hacksaw and some files. Make sure that you clean out the hole in the gas block before reassembly as well. Particles of dust or filings can cause havoc with the cycling. As for driving out the taper pins and putting on another gas block, I prefered the pinned in one. At least you won't have to fiddle with the gas system. This could cause a lot of headaches if it is not set up properly. The set screws can work loose, but those taper pins ain't going anywhere.
In the end, I would say the R2 is better to do this with. It you want a flip up gas block sight, then go with the R3. The less you mess with the gas system the better.
Again, YMMV.
Hoddie.
I don't think I would have the guts to take a saw to one, the result is very sweet.
