308 AR

Putting together an aero precision M5 set (https://swfa.com/catalog/product/view/id/178864/).  Wanting to make sure I am on the right train of thought. 

I purchased a LPK for the M5 from aero minus the fire control and pistol grip.   I have a barrel already from a buddy who bought a Ballistics Advantage 308 barrel then switched to creedmoor before firing the first shot.

On the rest of the build...... my impression/knowledge is that the only 308 specific parts I'll need to finish will be -

• Buffer
• Buffer spring
• BCG
• Charging handle
• Ejection port cover

The other parts can be from the AR15 platform/size

• pistol grip
• handguard
• fire control/trigger
• handguard
• buffer tube
• stock
• gas block
• gas tube

Anything I got screwy here? 

Handguard will need to be .308 handguard.  The barrel nuts and barrel extension are much larger. 

I just ordered a Aero M5 set on their presidents day sale one with the fitted handguard.  Have plans to do similar.  On my Mega MATEN set you could use a AR-15 tube, buffer and spring.  Not sure on the Aero either, when mine arrives I plan to try the AR-15 tube and see if it works or not as I have several laying around. 

I really wanted to do a lightweight upper and lower, but the Aero is only 6 ozs heavier than the 2A armament with the handguard I would have chose with it.  More than twice the price for 6 ozs was to hard to swallow. 

I would do a 308 trigger, not an AR15 trigger, you can get bumpfires due to higher recoil. Timney makes AR10 triggers, I use those.

But people do use AR15 triggers in AR10s. Maybe you get lucky and get a full auto with no stamp.

I'd rather be on the safe side.  I noticed a few triggers marked AR10 so I will look for one of those rather than take a chance

I was mistaken on the spring and buffer.  I was thinking I bought a AR-15 one, but mine is the JP AR-10 model.  I jsut used ar AR-15 rifle tube. 

Gotcha   Its  a bit cluttered with information out there on what is and isn't compatible..... Got to decide on a handguard now...... so many options

SVT_Tactical wrote: Putting together an aero precision M5 set (https://swfa.com/catalog/product/view/id/178864/).  Wanting to make sure I am on the right train of thought.  I purchased a LPK for the M5 from aero minus the fire control and pistol grip.   I have a barrel already from a buddy who bought a Ballistics Advantage 308 barrel then switched to creedmoor before firing the first shot. On the rest of the build...... my impression/knowledge is that the only 308 specific parts I'll need to finish will be - Buffer Buffer spring BCG Charging handle Ejection port cover The other parts can be from the AR15 platform/size pistol grip handguard fire control/trigger handguard buffer tube stock gas block gas tube Anything I got screwy here?

Handguard needs to be for AR-10, there are also different variants for height etc. so be careful there.

Better to go ahead and get an AR-10 trigger. If you get Timney be sure to get anti walk pins they are notorious for the standard pins falling out after use. 

Aero sells a Carbine Buffer Tube & Spring Kit for the M5.
https://aeroprecisionusa.com/m5-308-carbine-buffer-kit.html

You can build the whole thing virtually and look at available/compatible options on Gunstruction. They also have an app. It is very useful for this type of stuff. 

Chris Farris II wrote: If you get Timney be sure to get anti walk pins they are notorious for the standard pins falling out after use.

I think this is an issue of people not tightening down the tension screws in the trigger housing and using the set screws.  I ran two Timneys for years, still have one of them.  I took the one I still have through several carbine classes and lots and lots of rounds and I have never had a pin come loose.  They also come with a second set screw you tighten ontop of the tension screw so they cannot back out.  I dare bet most of the problems on the net are people not following the instructions.  I put a dab of blue locktite on my set screws and its never been an issue.

Timney instruction video
https://www.timneytriggers.com/videogallery/ar/how-to-install-a-timney-trigger-in-your-ar-rifle-28/

Think I'm going to try a UBR on this one.  Should just have to have a carbine buffer and spring for the 308AR

most of the parts are on order now.  hand guard and trigger are the only not decided yet.

Carbon fiber fore is a good way to shed some weight out front, especially if it will be suppressed.

It will be suppressed.  looking at gas blocks and options to help with gas as well.  Thinking the seekins adjustable will be ok. 

Only concern I have with the CF is the durability using a bipod

RC,  what CF one do you recommend?  Not seeing one designated for 308AR

Edited by SVT_Tactical - February/23/2018 at 12:37

The 12" Aero one is only 9.3 oz's.  Lancer carbon fibers weight more than that. 

supertool73 wrote: Chris Farris II wrote: If you get Timney be sure to get anti walk pins they are notorious for the standard pins falling out after use. I think this is an issue of people not tightening down the tension screws in the trigger housing and using the set screws.  I ran two Timneys for years, still have one of them.  I took the one I still have through several carbine classes and lots and lots of rounds and I have never had a pin come loose.  They also come with a second set screw you tighten ontop of the tension screw so they cannot back out.  I dare bet most of the problems on the net are people not following the instructions.  I put a dab of blue locktite on my set screws and its never been an issue. Timney instruction video https://www.timneytriggers.com/videogallery/ar/how-to-install-a-timney-trigger-in-your-ar-rifle-28/

I have tightened them down for customers myself and had them come back many of times with no pins. I have also had people that never have any issues with them. May very well be user error after it left the shop, but those pins are pretty cheap and worth the peace of mind to me.

I actually prefer the standard style aftermarket triggers like Geissele to the drop in but I have some CMCs and have had Timney before. 

CF2, you tried Elftmann yet?  I am really liking the one I bought. 

supertool73 wrote: CF2, you tried Elftmann yet?  I am really liking the one I bought.

I have played with and dry fired them, they feel nice. I have zero range time with them though. 

SVT_Tactical wrote: It will be suppressed.  looking at gas blocks and options to help with gas as well.  Thinking the seekins adjustable will be ok.  Only concern I have with the CF is the durability using a bipod RC,  what CF one do you recommend?  Not seeing one designated for 308AR

If you do not need too many rails, consider Brigand handguard.

supertool73 wrote: CF2, you tried Elftmann yet?  I am really liking the one I bought.

+1

I just recently got the Elftmann 3-Gun curved version for my new ultralight Grendel build, and it’s a really nice trigger! I set mine for 2.5 lbs.

koshkin wrote: If you do not need too many rails, consider Brigand handguard. ILya

There is no hand guard that is lighter, that’s for certain!

RC tried to fix the spacing on your post.... Thanks for the insight.

Dont' need much by way of rails other than a rail on the bottom and maybe the ability to add on at the 3 or 9 position for a light..... don't believe I'll need full length or anything.

koshkin wrote: If you do not need too many rails, consider Brigand handguard. ILya

Them things is spendy!

Looks like the ATLAS has a few rails right at the end.

https://brigandarms.com/product/atlas/

7 ounces, wow.  I might have some concerns on durability and stuff getting caught in all that carbon webbing.