Hey all!   Thrilled to be here.   Going to be building my first AR and I skipped ahead straight to an ar 308

I only ordered my stripped receiver so far and have been slowly modifying and confirming different parts I will be using.  I will be relying very heavily on this forum and others to build the rifle to meet all of my needs.  I am 100% open to suggestion from the group here on my build!

My biggest goals:

    -  I want to lower recoil at (almost) all costs.   I would like to be able to have as little recoil as possible to increase my accuracy and speed on longer range shots.  I also want my wife to be able to shoot the gun and have some fun with it.   I know they don't kick like the old 308 hunting rifles I learned on but I have the ability to customize the gun and I would love to take advantage of it.  The adjustable gas block seems like a no brainer here from what I've read.  Also a few people seem to say the lightweight BCG and buffer would be in my favor but I got confused when I saw people say the same thing about a heavy buffer...

    -  Mid to long range accuracy.  I feel like it goes without saying that everyone wants an accurate rifle....   I'm not talking sniper or competition build but i'd like to be conscious of this during the build.

    -  Versatility.  Basically going to be my only AR platform for a few years.  If shtf it's coming with me.  Of course I have other options that would make the trip but this would be top dog when it comes down to it.  I also want to be able to have fun at the range and be able to hunt if needed.

What barrel and gas length?

Large frame ARs can be quite finicky when mix and matching parts.

I understand and admire your desire to build it from scratch, but from a logistical/financial/mechanical standpoint I would strongly suggest your first large frame AR either come complete, or buy a complete upper to snap on to your lower..

PSA has great value and performance on the upper kits they sell assembled, and back with thier warrenty.

Just my .02, but there are alot of large frame AR gurus on here who know alot more than me.. I only own one, an Armalite Super SASS in 260 Rem, which I seldom shoot due to the bouts of depression I get whenever I lose a piece of Lapua brass..

 
You are right with adjustable gasblock then. You'll let precisely as much as needed gas to cycle the action reliably.

In my opinion lower mass BCG and buffer _might_ lead to premature bolt opening (before bullet left barrel) depending on gas length of the barrel. With buffer mass it is easier (and cheaper) to experiment then with BCG - just remove all weights from the buffer on your complete build and test fire it to see if accuracy affected. That's what I've done on my 308 build - kept original BCG but removed weights from buffer. So far so good - but I have to adjust gas block when I switch from 147 grain military surplus to 168gr match ammo now.

Not being smartass here, but physics laws tells you how recoil can be mitigated - heavy rifle, low impulse cartringe. streaming barrel exhaust backward so rifle will move forward. Since you plan to hunt with it - you don't want to build benchrest cannot either.

So, things to get rifle you're looking for in terms of lower recoil and good accuracy still able to use for hunting,  I can suggest are :
- 6.5 Creedmoor caliber with barrel length 20" or 22" (24" is recomended lenght, as far as I remember). Cartridge has lower impulse comparing to 308, flatter trajectory, ammo price of 6.5CM match grade is on par with 308 match grade.
- Adjustable gasblock
- Matching upper/lower
- Rifle length gas system ( the farther gas port, the later bolt will start opening, the less overgassed system you'll get)
- Muzzle brake
- Standard mass BCG and buffer (still can tinker with buffer mass later)
- Good trigger ( plenty options nowadays, to me LaRue triggers works the best, but I can't say I tried alot of them )

as far as barrel length goes I was thinking 18"    is that long enough with these goals in mind?  I ordered an aero precision m5 lower so I'm committed there.

There are fundamentally four different ways to reduce felt recoil.

1) Direct muzzle blast back towards the shooter. This reduces absolute recoil force up to 85%. The key is to get a very effective muzzle brake, like the PA hyper tap, and then to direct as much gas into the brake as possible by turning the adjustable gas block all the way down. To turn the gas block down, you need to reduce energy needed for cycling..which can be done using low mass BCG + buffer, and lower spring tension. The mass of BCG and buffer are added together here.

2) You can increase mass of the gun. This reduces velocity of the gun during recoil although the recoil force is the same.

3) You can increase mass of the BCG, which changes the recoil impulse by reducing the primary recoil impulse and increasing the secondary recoil impulse. The total recoil force is the same (compared to adding the mass elsewhere).

4) Shoot lighter loads.

Method 2 and 3 work together, but method 1 and 3 work against each other. IMO method 1 is the best normally because it doesn't involve adding weight. For an AR10 however, i would rather have higher recoil and a tamer sound. It's really better suited to less rapid shooting like hunting and long range target.

Search for my old post on "the physics of recoil reduction" to get a more thorough answer



Use a modern free float handguard. Accuracy will be mostly in the barrel, ammunition, and scope selection.



AR10 is honestly not as versatile as the AR15 platform.
A short barreled 300 blk would be much more versatile between hunting and SD purposes.
308 has a lot more recoil and noise than 5.56. If you use a MB like i suggested above to reduce recoil, the blast will be quite loud making it an anti social gun, and a good way to cause permanent hearing damage if you ever have to rely on it for SD without hearing pro. I wouldn't recommend going any shorter than 16" in your barrel.

Thank you for the response.  I understand the 5.56 is more versatile and clearly way less recoil.  For me I would rather build the 308 first mainly because the round is hard to argue with.  Range, somewhat affordable/available, and stopping power.  I have friends with 300 blackouts and they race each other to the shop for ammo and never want to practice.  The range is no where near the same as well...


My metaphor here is that I am trying to get the most miles per gallon as possible out of my pickup truck. Yes it's big and bulky but there is a reason we need them.

I will check out the post you recommended.  This is somewhere i feel like people go 2 ways on.

My lightweight DPMS G2 has soft recoil compared to a M&P10 that a customer brought in for upgrades, with a small difference in weight.
Brake, light BCG and adjustable gas are key.
L.A.R.B. buffer bumper helps too.
I did these, minus the LW BCG, to his rifle and it was much better.
My Aero M5 has all of these features and is a real teddy bear to shoot.

This is good news.  I think the LW BCG seems like a nice option.  What setup did you go with?   I'm currently working on my list for the lower.  I was going to order a lower parts kit and buffer tube soon.  Really want to start hammering out the details.  There is just so much available these days its damn near overwhelming.

I plan on running an 18" barrel.  Is Criterion worth the extra money?  It seems that I can get it with rifle length or mid length gas ports.  The aero barrel comes with rifle length.

Welcome

Show us pics of your build once complete

I feel like I was already sold on the Criterion but now I'm completely sold on the Criterion!!   Thank you for the feedback!

My next "is it worth it" question.   I'm looking at the Aero bolt carrier groups.  Is nickel boron worth the extra money over phosphate and nitrite?   I personally don't mind spending money if there is a point, I do not want to spend money just because something is pretty.

Another random question....    If I order the aero LPK without FCG and separately order the ALG Act trigger.   Do I need any other parts to complete the FCG ?

With that selection the lower will be complete. You'll have all the lower parts (minus the trigger) in that kit and your ALG trigger will complete the lower.

Many Thanks!

I took a little pause on this build with a few other things going on.  It's time for me to order my buffer kit and stock.   Do you think the standard aero m5 buffer kit will be fine for this application?