Just got a upper and lower set and trying to build a 10.5 SBR. Just submitted a Form1 so I got time to think and search for deals. My goal is light weight and accuracy. I decide to go with a geissele SD 3G trigger and all other parts are in pending. Please give me some good suggestions and maybe deals that going on can save me some money. Especially on the trigger. Thanks for all the suggestion ahead!!!!

I really like my Aero Precision/Ballistic Advantage 10.5 w/FSB. Check both sites as they have deals posted quite often. I got my new/unused SSA-E for a smoking deal from the EE.

I really like my Rainier Arms Select 10.5" barrel. Well made, accurate, great fit and finish, chambered in 5.56, nice medium profile, etc.

Only downside that I can recall since building it, is I'd take a chrome lined barrel over stainless for my purposes. Next time.

I'd suggest a caliber meant for a barrel that short like the blackout.  With 5.56 you'll have half the powder burning outside the weapon.  If you want a fireball, a serious concussion, and pissed-off folks next to you at the range then go 5.56, but if you want all that mitigated in a piece meant to be short the 300bo is the way to go.

To that point, look for a linear compensator.  Makes shooting a 10.5 barrel much more tolerable.

My 10.5 is enjoyable to shoot, much better than my 3-gun rig with its brake.

I doubt you can shoot 300BO for less than $.14/round.

FIFY

I think someone built a 12" FAL.  The velocity on it was less than 7.62x39 at 16 inch.  But the pressure has not reached peak yet = blast and concussion beyond tolerable level

check out the blowout deal KAK has going on, if your undecided on caliber they have 10.5 blackout pistol gas , or an 11 inch 5.56.  both melonite coated..

What was the caliber you submitted on your form1? I hope you did not put multi. I thought that was grounds for rejection, but this may have changed.
I have a 10.3" SBR, 5.56, and I think its a blast to shoot. I need to swap in an H or H2 buffer to slow it down some. I am using a 51T Brakeout, and it does throw alot of muzzle flash, which is something I am going to have to correct before acquiring NV.

Did you put down 10.3? or 10.5? for your barrel length? 10.3 would have opened up a couple more possibilities for you in the realm of barrel selection, but Im not sure if the ATF would throw you to the wolves for that. Havent been down that road.

I'd figure out the purpose of the weapon first of all, then go from there. Obviously the rifle wont be used for long range applications, but will be effective to 300 yards without question. Is it a carbine class gun? Just a range toy? Home defense? Safe queen?
Answer this question and then go from there IMO.

I personally and trying to go clone route with a CQBR blockII clone. It needs a lot of parts to get clone approved, but right now the platform is doing well for me. Just shoulder the rifle the way it is supposed to be shouldered and recoil shouldnt be an issue at all. That being said, I've never fired a .300 BO before, so I wouldnt have the subjective knowledge to compare the two in terms of felt recoil. Do you have other AR's? What calibers are they???
I would say keep them standardized unless you're bored, can afford all the ammo, or just primarily a collector and not an avid shooter. Nothing wrong with any of those, but may influence the build process.

In terms of saving the scratch, Primary arms usually has sales of 15% off triggers every few months. Since this is one of the easier mods to a rifle, just wait one of those out. As far as the other parts are concerned, Buy once, cry once. I've learned this the hard way. Its difficult to be patient to wait on that right part to come along, but they're out there. keep an eye on the EE here once you get your parts selection solid. Might find something come over that you cant pass up.

Oh and BTW, I got my form 1 back in 66 days. Mailed in late may, had the stamp back in July. My wife's was mailed same day, it came back a month after mine. Hope yours comes back that quick. Good luck with the build!

Get a lightweight barrel with a gas port sized for the ammo you want to shoot. I like Wolf for blasting, some don't. But if your gas port is only sized for 5.56 then it limits your ammo choices.

I bought a Radical Firearms 10.5" barrel for a cheap truck gun I built. I have been VERY impressed with it. Pretty dang accurate out to 2-250 yards.