I have picked up a SR-25 matching set upper and lower. I am looking to build it into a quality 800 to possibly 1000 yard gun, I am currently working my way through the sniper 101 videos on you tube. I am also new to long range shooting with plenty of AR-15 and pistol experience. My questions are what components should I use, I would like to find a knights barrel but haven't come across one yet, any trigger recommendations? How about rails Knights has some real nice ones.

I have a .308 AR and if I was building one today, I would seriously look at building it in 6.5 Creedmoor

for that distance you are talking about, it spanks any 30 caliber round, even 300 Winmag

I am in it too deep with all the ammo I have to change now

https://en.wikipedia.org/wiki/6.5mm_Creedmoor

I am going to assume you are completely new to LR shooting as you mentioned watching the Sniper101 videos.

As much as I love the 6.5mm rounds, if you are just starting out and learning the distance game I would suggest the .308. The .308 will be a better round to learn to shoot in the wind with. By the time you wear out a .308 barrel you'll should be squared away and will be that much better on the gun when you move up to the 6.5mm.

If you don't have much experience with bolt guns and are starting out with a large caliber gas gun, be patient. As you have probably read, the SR25/AR10 will not let you cheat the fundamentals. You must do everything right on every shot to get the precision you want with the gasser.

Buy a .308 1:10 twist Bartlien, 16-18" in length and have a good smith put it together then get in on a good LR class.

The more reading I am doing I realize that 1000 yards may not be very realistic especially in my AO. I want to start with the 308 for a few factors, 1. its a caliber I currently reload so I have several 5 gallon buckets of once fired brass 2. I already have the pre-ban SR-25 upper and lower 3. Its a good round for my AO, my range goes out to 200 Yards but will be extended to 400-500 yards soon. So the majority of my shooting will be 200-500 yards. However I plan on going up north to some longer ranges in the future I also plan on taking some long range shooting classes so this rifle will be my first real attempt at long range shooting. I appreciate any and all constructive advice, I am not on a strict budget per say but I won't dump money into it without a positive gain. I have to use this stripped upper and lower due to Connecticut's stupid laws so buying a complete rifle is not a option for me.

I'm jealous that you have a KAC receiver set! I'm going for an SR25ECC type build. Here's what I'm going with:

Upper:
Aero Precision M5 w/ BCG
CMMG 16.1 308 Barrel
KAC URX 3.1
Griffin Armament Flash-Comp Taper mount
PRI Gas Buster 7.62 CH
KAC 600m Sight Set
Aero rifle-length gas tube
odin adjustable gas block

Lower:
Aero M5 Lower w/ AR10 mag catch, Aero takedown/pivot pins, Aero bolt catch, DSG lower parts
Magpul FDE MIAD Rubberized Grip
CMC drop-in 2 stage trigger (2lb/2lb)
Aero M5 308 carbine stock set
Magpul ACS stock in FDE

I have a SR25 URX II take off if you're interested shoot me a PM.

If you have the money to spend, genuine Knight's parts are always available. Check Boltcarrier.com and Operation Parts for most ods and ends. I too am planning on an ECC build with a few slight modifications. Good luck finding a Knight's original barrel. I'm planning on using this 16" one from Rainier Arms that is very close to the Knight's ECC one Rainier Arms UltraMatch 16" .308 Barrel. Good luck with your build and happy hunting for parts.

Eric

i don't know if suppressors are legal there or not, but if you are looking for a knights mk11 mod 0 suppressor that has the push pin disconnect to the gas block, let me know.

Do not consider the 6.5 Creedmoor for your first AR-10 style rifle. Unless you are very experienced at hand-loading. I like the 6.5C, but only in bolt rifles.

There are plenty of quality SR-25 type components out there. Actual KAC parts are scarce though

1st lets start at 200 yards and work from there. Your SR25 in 308 will be much more forgiving and cheaper. Accuracy will be more work on your end than the 308 / SR25's part.
Then lets start at the 400 yard mark. Here you will notice even with higher magnification you are looking at targets that are very small even through scopes that have 14-16X magnification. These are my prefered magnifications.
Next lets do some steel plates at 600 yards (9-12") are my norm. these look like very little dots at 16X and take some concentration to say the least.

Now if you can do this regularly and hit them, I average about 8 out of 10 on a good morning not hung over and fed well, Ha Ha.. Then we can start talking about what the 6.5 Creedmoor can do for you.
Excellent cartridge that shoots flatter and a little faster but im not overly impressed with it just yet. I only have 300 rounds through my Ruger precision rifle in this calber. It is a hair more accurate than my M-1 A NM but only by about 1/8 MOA at the 200 yard mark.
Considering the ammo is 2X the cost im not overly impressed.    

Solid advice right here. I own a Knights ECC and prior to owning it, I had a rack grade Remington 700 as well as 5.56 precision based AR's that allowed me to work on the fundamentals.

What are you trying to accomplish with this rifle/build?  What are your priorities?

When most people get an SR25 receiver set, they are going for an accurate replication of the KAC product, but I notice that you seem to be interested in long-range shooting.

Both can be done, but getting actual KAC parts is going to be a little more difficult.

If you're wondering what direction SF is going with the SR25/M110, they are going 16" barrel, tighter twist, telescoping stock, Leupold Mk6, etc.

 
Thats a Mk8