AR 308 build in 6.5 Creedmoor - need advice

[mark_y]

I have been waiting to order a M308 build kit from aero, when back in stock, but I have a question about the gas block. I have a 22" Criterion barrel in 6.5 Creedmoor and I also bought a headspaced JP enhanced bolt from Criterion. I want to use an adjustable gas block, but the size required is  .875. Does anyone make one that will fit under a 15" Aero keymod handguard?

Also trying to decide between a jp lmos carrier or a jp full mass carrier. I think if I use a low mass carrier it might be good to be able to adj. the gas. Opinions?

[sketch]

Welcome abord mark tell us about your experiences and interests in the intro section! 

As for the gas block .875 i just installed a slr but had to file down the inside of my ff hand guard (other than areo) to make room.. I would look at the id of the hand guard and if not posted in the info give the manufacturer a call?

carrier weight can go in either direction also inconjunction with other components of the ar ie: buffer/ springs...  Again if this is a first let us know and this band of bros/knowledge with your help can make it happen? 

Leave your credit card number here:

[mark_y]

Yes, this is my 1st build. I own a couple Ar-15s and 1 Adams arms 308 but have never built one. Gathering parts now and was looking at the pri adj. Gas block, but description says it doesn't fit under most hand guards. Don't know about the Aero hand guard fit. Hence the request for sugestions.

Credit card info? Thats a good one!7

[jtallen83]

Check out SLR blocks, call or email them about fitment issues;

http://slrrifleworks.com/index.php?route=product/category&path=57_103_82

[shepp]

Welcome to the forum 

[EngrBob]

Howdy from the Texas side of the borders.  I put a non-adjustable .875 diameter low profile block on my 6.5 Creedmore build from Ground Zero Precision.  It functions perfectly in my setup, your results may vary.

[mark_y]

Sorry, it took awhile to get back to the forum. The Aero inside dimension of the handguard is 1.8 in,  according to their website. This build will probably take a while due to Christmas coming up, lots of kids to buy for! I would like to be able to adj. gas if possible, but the handguard coming is 15". I currently have a standard ar10 rifle size buffer tube and spring. The 2 things than I really need to decide on is a low mass carrier vs full mass carrier  and whether or not i can make a SLR adj. .875 gas block work with this setup. If i have to mill out the hand guard slightly, how much clearance is needed between the barrel and hand guard?

[jtallen83]

With a heavy bench gun like you describe I don't know how much advantage you would gain from a low mass BC, maybe faster follow up shots but unless you are going to shoot competition I doubt you would notice much. I did a low reciprocating mass AR15 build, lots of adjustments on gas, buffer weight, and buffer spring to make it all play well. If you do go that route it would probably pay to stick with JP stuff.

Have you called SLR about gas block clearance? They have great CS, bet they will figure it out if they don't already know.

[mark_y]

 Left a message with SLR and will wait for a callback about the clearance. I was thinking that an adj gas block would be better for the rifle to not have more blowback than necessary. The bolt carriers that I am looking at are JP carriers., low mass vs full mass. I am not a competition shooter, just want the most accurate that i can build in an AR308 platform. I am also considering the JP silent buffer spring assy, but I will probably have to wait to upgrade the buffer spring. 

If the consensus is to go with a full mass carrier, then that is probably what I will do. I am looking for advise from those most likely a lot more knowledgeble than myself. Thanks for the help.

[98Z5V]

Depends on what you intend for the rifle, really. If it's on a bench it's whole life, punching paper and steel at long ranges, that's one thing.  If it's your hunting rifle, and you have to lug it around the mountains, that's another ballgame.

Weight tames recoil.  Well.  And it's simple to set up,with common components. 

Lightweight schit has it's own issues, and it's mostly tuning.  You have to tune all that stuff to the load you're shooting, and alot of times, it won't work with other loads, as effectively.

Your call, honestly, based on intent for the rifle.

[mark_y]

I do enjoy punching paper, but I also hunt. I do not want to tune for every different load I shoot. I want a general setting that will not change much, or at all, once set. I am looking for an accurate rifle. I am not recoil sensitive, this will be one of my lightest recoil rifles,  just looking for performance. I will be the 1st to admit that I only know what I have read about building an AR style rifle and that is limited. Most of my guns are bolt and lever action other than the ar-15s and 1 AR-308 that i own. When I look at a gun, i am not looking for a single purpose weapon, but one that i can grab for a hunt or target shooting. 

Thanks again for the help

[98Z5V]

That barrel you have has to be the Hybrid barrel from Criterion.  If you built with standard parts, you'll still come in somewhere from 12~14 pounds, loaded and with glass.  Using lighter parts, you might get it down to 10~11 pounds (loaded, glass). 

Decision time, and judgment call on your part.  Either way, we'll be here for you. 

[survivalshop]

 There is one thing that most don't think about when using lightened action components , its not just the Buffer & its spring that help feed the next round into the chamber , the BCG has a lot to do with it . As said , there is a balancing act when using lightened components in the action of a semi auto feeding action , which are designed with action components to be able to handle a wide verity of loadings with out issues .

 From the very beginning of my building of AR's I have always used M16 Bolt Carriers for my builds , no matter what they are built to do of for . The reason is reliability of the feeding cycle. When they first went to the lighter AR 15 BC's in the Colt rifles, because of the BATF new reg's. , I got a lot of them in for feeding issues , the lighten'ed AR 15 BC was replaced with an M16 & the issues were resolved ( the BATF came out with a list of M 16 parts that could not be used in Commercial AR 15 's , which turned out to be BS anyway ) . That was a long time ago & Colt changed their Buffer systems to fix it & keep with in the BATF reg's . Then came the Enhanced AR 15 BC , which was a little heavier then the std AR 15 & that also helped the feeding issues . 

  As 98 posted , it all depends on what you want to use the rifle for , all around , use a std weight BCG for the 6.5 & use a adj. Gas Block .If a Match rifle , you can fine tune it to your best loading .

 The Barrel is where most of the weight is going to be any way . 

Edited November 1, 2016 by survivalshop

[D.R.D.]

Here ya go:

http://www.precisionreflex.com/Detail.aspx?PROD=186813

http://www.dwilsonmfg.com/store/p27/AR10_Carrier_Assembly_w%2F_small_parts_.html

 

[survivalshop]

[mark_y]

Sounds like the full mass bolt carrier it will be. I still haven't heard back from slr rifles about the adj gas block clearance, i left 2 messages. The upper and handguard should arrive in a few days, so maybe I can figure it out before ordering the gas block.

Thanks for the replies,

Mark

[shepp]

1 hour ago, mark_y said:

Sounds like the full mass bolt carrier it will be. I still haven't heard back from slr rifles about the adj gas block clearance, i left 2 messages. The upper and handguard should arrive in a few days, so maybe I can figure it out before ordering the gas block.

Thanks for the replies,

Mark

I'm sure they're busy right now with it being election season give them a few days

[SKY_Soldier]

Have been following this group of comments & suggestions posed by Mark_y.  I’m in the process of having a mostly Aero Precision 6.5 Creedmore built on a AR10 platform. My design requirements started with as many “lightweight” high quality components as possible, minimizing front end barrel weight, and bold carrier group. The current in-process gas block is a non-adjustable AP .875. However, due to /researched/reported issues with cartridge ejection from “smoke stacking” and a varied cartridge grain load and shortened barrel life (?) and possible add on of a suppressor at some point, I asked the gun shop builder if the non adjustable .875 AP gas blockbuster may be a concern. He said that he didn’t know of any issues. So, I’m left with some doubt. Any update from Mark or anyone about their experiences and what has block you ended up using? 

[Armed Eye Doc]

Welcome to the forum @SKY_Soldier.  You would have better luck by starting your own thread with a full list of parts and questions. 

In general, a standard gas block will work fine with a properly balanced gas vs. recoil system.  You mentioned a possibility of a suppressor.  That is the one condition that usually will require an adjustable gas block.

[98Z5V]

12 hours ago, SKY_Soldier said:

Have been following this group of comments & suggestions posed by Mark_y.  I’m in the process of having a mostly Aero Precision 6.5 Creedmore built on a AR10 platform. My design requirements started with as many “lightweight” high quality components as possible, minimizing front end barrel weight, and bold carrier group. The current in-process gas block is a non-adjustable AP .875. However, due to /researched/reported issues with cartridge ejection from “smoke stacking” and a varied cartridge grain load and shortened barrel life (?) and possible add on of a suppressor at some point, I asked the gun shop builder if the non adjustable .875 AP gas blockbuster may be a concern. He said that he didn’t know of any issues. So, I’m left with some doubt. Any update from Mark or anyone about their experiences and what has block you ended up using? 

That's a whole bunch of fucked up words that you combined into things that don't exist. What country do you live in?  ESL, by chance? (English as a Second Language)...

PLEASE start your own topic about what you're trying to do here.  The thread you jumped into was already 4 years-ish old.

I look forward to your new topic. I hope you're not a troll, or a fake-bot, working your way in here.  We'll find out shortly. 

I'm going out on a limb here, and predicting...

 

Edited July 30, 2020 by 98Z5V

[DNP]

I’m sensing a lot of auto-correct from posting by phone actually. I agree thought. Start a build thread specific to your build and it will be of better use. Start off with a lost of currently owned parts and parts on your wishlist. These guys will have some better input with a full picture. If you’re running an 875 gas block, you’re not headed in a “lightweight” direction.  If you’re after “high end” parts and a suppressor, yet worried about barrel life....your budget or expectations need a reality check.  Not trying to be harsh, just stating a fact. Welcome aboard. Get that new thread going.