First Planned AR-15 Build

[AngryKoala]

Finally decided to bite the bullet and build my own AR-15. Please provide feedback. I already have some of the parts, others im waiting until black friday.
One of the things I'm not sure of is if the SA AGB will fit under the handguard. Based on the dimensions it should.
Also not sure if I need the JP VMOS or if I should just get the FMOS.
I may also switch the Geissele upper/lower/handguard with JP products and get a 13.5 criterion with 12.5" jp mlok.

12.5" AR-15 Pistol​	Part​
Upper Receiver​	Super Duty Upper Receiver​
Geissele Hand Guard 10.5"​
Criterion Core Barrel 12.5"​
JP VMOS BCG w/Enhanced Bolt​
JP SCS H2 Kit​
Geissele ACH​
JP SCS Buffer Retainer Pin and Spring​
JP Enhanced Carbine Buffer Tube​
Strike Industries Link Grip​
Superalitve Arms 0.625" AGB (melonite)​
Spikes Tactica Carbine Gas Tube (melonite)​
Surefire MB​
Lower Receiver​	Super Duty Lower Receiver (blem)​
Geissele Ultra Duty Lower Parts Kit​
Geissele SD-E​
Magpul MOE K2+​
SBA4 Tactical Brace​

Pasted weird for some reason.

 

[bigjake83]

Unless you're running a suppressor You don't need the H2 buffer and variable mass carrier. And You're making the same mistake most new people do, by buying all the cool gadget parts and putting in a mediocre at best barrel

 

[AngryKoala]

Unless you're running a suppressor You don't need the H2 buffer and variable mass carrier. And You're making the same mistake most new people do, by buying all the cool gadget parts and putting in a mediocre at best barrel

Yea I got those because I am going to be running a suppressor. I thought criterion was good? It seems to get good reviews.

I could get the jp barrel as they will do the work on it. I don't know a reliable gunsmith around me so getting a blank that needs cut, chambered etc wasn't in my initial thought process.

 

[RTV]

Unless you're running a suppressor You don't need the H2 buffer and variable mass carrier. And You're making the same mistake most new people do, by buying all the cool gadget parts and putting in a mediocre at best barrel

Criterion is one of if not the best chrome lined barrels you can get.

I think of them as a high quality chrome lined barrel that is made with match grade attention to detail and care and many people get very good accuracy results with them.

If I where to be building a RECCE type gun I would not hesitate to put a criterion barrel in anything but a dedicated precision competition rifle/ a rifle that's sole purpose is to punch small holes for the added barrel life/ corrosion resistance alone especially in my location where I am frequently shooting in cold/wet conditions.

OP:
No comments about the other parts just don't know very much about the JP stuff but the barrel is GTG depending on the rifles uses.

 

[UpSideDown]

This sounds like a pretty fantastic first AR.

- I strongly prefer BCM or LaRue grips over Magpul
- I would rather tune my gun with the action spring (buffer spring) and buffer weight, than with an adjustable mass BCG. I think that's an unneeded expense when you're already running the SA gas block. You might want to test a few Sprinco springs and buffer weights as you go. Maybe the Red or Orange spring.
- I'd try it without the Strike industries thing. Personal preference.
- If you put a muzzle brake on this gun, and don't run a suppressor on it 100% of the time, you will not have any friends.

 

[bigjake83]

Sorry OP... Belay my last

Thanks @RTV for pointing that out I honestly just glanced over it. My only experience with Criterion is with their SS offerings. I have no experience with their chrome lined stuff, All my chrome lined barrels are factory from LMT, KAC and BCM.

 

[AngryKoala]

Criterion is one of if not the best chrome lined barrels you can get.

I think of them as a high quality chrome lined barrel that is made with match grade attention to detail and care and many people get very good accuracy results with them.

If I where to be building a RECCE type gun I would not hesitate to put a criterion barrel in anything but a dedicated precision competition rifle/ a rifle that's sole purpose is to punch small holes for the added barrel life/ corrosion resistance alone especially in my location where I am frequently shooting in cold/wet conditions.

OP:
No comments about the other parts just don't know very much about the JP stuff but the barrel is GTG depending on the rifles uses.

Yea that is what I have read and because this gun is going to be a pistol I just didn't see the point in spending the cash on a SS barrel. Thank you for confirmation on the barrel.

This sounds like a pretty fantastic first AR.

- I strongly prefer BCM or LaRue grips over Magpul
- I would rather tune my gun with the action spring (buffer spring) and buffer weight, than with an adjustable mass BCG. I think that's an unneeded expense when you're already running the SA gas block. You might want to test a few Sprinco springs and buffer weights as you go. Maybe the Red or Orange spring.
- I'd try it without the Strike industries thing. Personal preference.
- If you put a muzzle brake on this gun, and don't run a suppressor on it 100% of the time, you will not have any friends.

I actually really like DD grips but I want to try a reduced angle grip. I am fairly ignorant (only run factory ARs) on what the best method for tuning is. I can definitely switch to the JP FMOS carrier but would like a little more explanation so I can learn. Why would you rather modify buffer/gas over BCG (assuming less reciprocating mass for light felt recoil?)? The SCS kit has 5 different springs so that sounds like what you mentioned. I'm going to try the strike grip, not sure if I'll like it.
Good point about the MB, ill have to wait for quite awhile to grab the suppressor so in the meantime I'll purchase a Warden as well to throw the blast forward. I am assuming by doing this I will negate the intention of the brake so maybe I should just get a FH or warcomp.

Sorry OP... Belay my last

Thanks @RTV for pointing that out I honestly just glanced over it. My only experience with Criterion is with their SS offerings. I have no experience with their chrome lined stuff, All my chrome lined barrels are factory from LMT, KAC and BCM.

Not your fault I should have stated my intentions for this pistol. It is still good to know when I do eventually go the precision route that I should look toward the other companies other than Criterion.

 

[UpSideDown]

I’d rather tune with springs and buffer weight because buffers are intended for that purpose. Tuning with the BCG isn’t bad, it’s just an expensive way to do it.

I also prefer the reduced angle grips. I just don’t like the feel of any of the magpul. BCM feels nicer, and LaRue is quite nice on a precision AR. it’s preference though.

I would throw a $5 A2 bird cage flash hider on it til you get your suppressor in. There’s no reason to buy a muzzle brake just to buy a Warden to defeat it. It’s still loud. The Warden really has no purpose once you own a can.

 

[AngryKoala]

I’d rather tune with springs and buffer weight because buffers are intended for that purpose. Tuning with the BCG isn’t bad, it’s just an expensive way to do it.

I also prefer the reduced angle grips. I just don’t like the feel of any of the magpul. BCM feels nicer, and LaRue is quite nice on a precision AR. it’s preference though.

I would throw a $5 A2 bird cage flash hider on it til you get your suppressor in. There’s no reason to buy a muzzle brake just to buy a Warden to defeat it. It’s still loud. The Warden really has no purpose once you own a can.

Could there be an advantage gained by having three points at which you can tune (Buffer, gas and BCG) vs two?
I agree on the grips as I have avoided magpul but I love overmolded grips. Unfortunately, all the other overmolded grips I've tried do not have the reduced angle (Hogue, DD).

Good point on the MB, will adjust the build accordingly. What are your thoughts on using a MB for a suppressor host? I have read it acts as a sacrificial baffle (makes sense) which helps extend suppressor life vs using a FH.

 

[UpSideDown]

You just don’t need that much adjustment in the system, it’s redundant.
Muzzle brakes are great inside suppressors. I’d toss on an A2 til your can is in and then use a brake once you have the can. Or if you’ll use the gun without a suppressor at times, use a different style attachment for your can if you want

 

[AngryKoala]

You just don’t need that much adjustment in the system, it’s redundant.
Muzzle brakes are great inside suppressors. I’d toss on an A2 til your can is in and then use a brake once you have the can. Or if you’ll use the gun without a suppressor at times, use a different style attachment for your can if you want

Good info and thank you for the help. Ill probably just grab a jp flashider since I am ordering from them anyway. I'll wait around on the PX and find a MB, ill have plenty of time before the can comes in haha.

 

[Precision Underground]

The parts look fine so I’ll make a vanity post. Do an 11.5” handguard. Pistols look better with more handguard and less barrel.

On the criterion, the bolt gun barrels ive had from them are stupid accurate. And if the borescope pics they posted on IG are not retouched the beauty alone is worth getting a core. Don’t expect 1/2 MOA with blaster ammo but my guess is that it will shoot with good ammo and a capable shooter.

 

[AngryKoala]

The parts look fine so I’ll make a vanity post. Do an 11.5” handguard. Pistols look better with more handguard and less barrel.

On the criterion, the bolt gun barrels ive had from them are stupid accurate. And if the borescope pics they posted on IG are not retouched the beauty alone is worth getting a core. Don’t expect 1/2 MOA with blaster ammo but my guess is that it will shoot with good ammo and a capable shooter.

I %100 agree but I wanted to keep the geissele handguard to match the receivers. However, I've been battling between a 12.5 and a 13.9 from criterion (wish I had money for both).
I may sell my geissele receivers and just grab the jp receivers and use their mlok handguard (12.5") on the 13.9 barrel.

Who else makes a sturdy mlok handguard? I'm not looking for lightweight, so durability and a very secure connection are my two points of emphasis.

Funny part is switching to JP 15 receivers and their lower/upper kit will actually be cheaper...who would of thought I would be able to utter those words.

 

[padom]

I just finished a 12.5" upper 2 months ago and love mine. Runs great. I'm gonna save you a bunch of money and tell you to skip the SA (they are great, I own 9 of them but unnecessary on this build). Use the Geissele super low profile gas block that comes with their handguard. Its great and will 100% fit and have plenty of clearance. Skip the JP VMOS and get a Rubber City adjustable gas key bcg. I've been running 3 of them now for 6 months and im not sure I'll go back to AGB...No worries of carbon lock/seizing set screws or getting to it under a handguard..

Other than that, looks good.

 

[JS8588]

I agree on the grips as I have avoided magpul but I love overmolded grips. Unfortunately, all the other overmolded grips I've tried do not have the reduced angle (Hogue, DD).

Home

DetailsThe Ergo Grips Tactical Deluxe Zero Angle pistol grip was originally designed for the Ruger Precision Rifle and now available for the AR family! The TDX-0 takes their popular grip design features such as their all-weather overmold texture and ergonomic finger grooves and combines them...

www.primaryarms.com

 

[AngryKoala]

I just finished a 12.5" upper 2 months ago and love mine. Runs great. I'm gonna save you a bunch of money and tell you to skip the SA (they are great, I own 9 of them but unnecessary on this build). Use the Geissele super low profile gas block that comes with their handguard. Its great and will 100% fit and have plenty of clearance. Skip the JP VMOS and get a Rubber City adjustable gas key bcg. I've been running 3 of them now for 6 months and im not sure I'll go back to AGB...No worries of carbon lock/seizing set screws or getting to it under a handguard..

Other than that, looks good.

Is the SA unnecessary due to the longer dwell in a 12.5? Is the AGB mainly meant for larger ports? Will the enhanced bolt fit in the RBC BCG?
I have more reading to do as I was unaware of an AGK.

What are the cons of an AGK. I guess I am trying to understand when you would use an AGK vs an AGB?
Sorry for all the questions but I love learning from those with more knowledge/experience.

Home

DetailsThe Ergo Grips Tactical Deluxe Zero Angle pistol grip was originally designed for the Ruger Precision Rifle and now available for the AR family! The TDX-0 takes their popular grip design features such as their all-weather overmold texture and ergonomic finger grooves and combines them...

www.primaryarms.com

Hey, good find ill have to try that out.

 

[padom]

Is the SA unnecessary due to the longer dwell in a 12.5? Is the AGB mainly meant for larger ports? Will the enhanced bolt fit in the RBC BCG?
I have more reading to do as I was unaware of an AGK.

What are the cons of an AGK. I guess I am trying to understand when you would use an AGK vs an AGB?
Sorry for all the questions but I love learning from those with more knowledge/experience.



Hey, good find ill have to try that out.

They both do the exact same thing. You choose either and agb or agk.... you adjust the gas with a set screw in the gas key just like with an agb. Probablem with AGB is dealing with carbon build up/seizing and clearance under handguards.

Rubber City is top of the line. I would use their bolt with their bcg. I've been running rubber city and JP bolts and BCG's for many years.

 

[AngryKoala]

They both do the exact same thing. You choose either and agb or agk.... you adjust the gas with a set screw in the gas key just like with an agb. Probablem with AGB is dealing with carbon build up/seizing and clearance under handguards.

Rubber City is top of the line. I would use their bolt with their bcg. I've been running rubber city and JP bolts and BCG's for many years.

I guess I find it interesting that when doing a fair amount of reading about parts and builds everyone mentions using an AGB so I am kind of curious as to why. The product you mentioned would solve the drawback of using an AGB.

I'll have to look at Rubber City as I was unaware of them and their product offerings.

 

[SandFam3]

I %100 agree but I wanted to keep the geissele handguard to match the receivers. However, I've been battling between a 12.5 and a 13.9 from criterion (wish I had money for both).
I may sell my geissele receivers and just grab the jp receivers and use their mlok handguard (12.5") on the 13.9 barrel.

Who else makes a sturdy mlok handguard? I'm not looking for lightweight, so durability and a very secure connection are my two points of emphasis.

Funny part is switching to JP 15 receivers and their lower/upper kit will actually be cheaper...who would of thought I would be able to utter those words.

Check out the Hodge/SOLGW wedgelock MLOK rail. Rock solid setup.

 

[JS8588]

I guess I find it interesting that when doing a fair amount of reading about parts and builds everyone mentions using an AGB so I am kind of curious as to why. The product you mentioned would solve the drawback of using an AGB.

I'll have to look at Rubber City as I was unaware of them and their product offerings.

Yeah, I'm an oddball when it comes to "adjustable" anything on my builds. To me adjustable means subject to failure. I don't mess with adjustable gas blocks or bolt carriers.

I have converted to using Battle Arms or V 7 ionbond coated titanium gas blocks on all builds. That extra weight saving up front just makes them handle a little nicer.

 

[RTV]

I guess I find it interesting that when doing a fair amount of reading about parts and builds everyone mentions using an AGB so I am kind of curious as to why. The product you mentioned would solve the drawback of using an AGB.

I'll have to look at Rubber City as I was unaware of them and their product offerings.

If this is a defend your life gun then I second skipping the adjustable gas block.

I would rather pick a barrel that is properly ported (criterion is good at that) and fine tune using buffer/spring and a VLTOR A5 kit.

It might be a little bit harsher than fine tuning the gas perfectly with an AGB but for a life and liberty gun you don't really want the gas to be on the razor edge of performance anyways. You want it to run like a scalded monkey hot, wet, dry and dirty without inducing unnecessary parts wear.

Its a balancing act for sure.

 

[AngryKoala]

So I changed some things based on the recommendations here. Going to go with a Rubber city bcg/bolt with adjustable gas key. Problem is now i have to find a low profile 0.625" non adjustable (dont want to pay the extra $$) gas block. Anyone have experience with one? I see aero and bcm have them. I'm looking for high quality. Thank you in advance.

 

[JS8588]

So I changed some things based on the recommendations here. Going to go with a Rubber city bcg/bolt with adjustable gas key. Problem is now i have to find a low profile 0.625" non adjustable (dont want to pay the extra $$) gas block. Anyone have experience with one? I see aero and bcm have them. I'm looking for high quality. Thank you in advance.

Welcome to Tactical Link - We've Got The Good Stuff

www.tacticallink.com

These fit TIGHT and weigh practically nothing. Highly recommend.

 

[Quiet6.8]

I run a 2aArmament adjustable BCG and their standard Ti GB and JPSCS in a few of my rifles , super easy to tune (6 torch in the ejection port), these rifles are run suppressed 100% of the time.

 

[AngryKoala]

Would there be an issue with titanium expanding at a different rate than the barrel (assuming no)?

 

[UpSideDown]

How much weight savings is there between a steel or titanium low pro gas block? Is that something that’s really worth the cost difference?

 

[JS8588]

Would there be an issue with titanium expanding at a different rate than the barrel (assuming no)?

None. Titanium expands less than steel, so as the barrel expands, you'll actually get a tighter gas seal.

It is ~1.4oz lighter than the bcm (0.48oz vs 1.93oz).

Just something I prefer (& am willing to pay for). Ymmv.

 

[357Max]

Might want to check out this grip. It has become my favorite hands down. Reduced angle. Actually it's a BCM gunfighter Mod 3, but with Wilson's Starburst texturing.

BCM | Starburst | Gunfighter | Grip | Black

Wilson Combat®/BCM Starburst Gunfighter Grip, Black

shopwilsoncombat.com

 

[357Max]

Here's a pick of the grip on a pistol. This shows the reduced angle better than link I posted.

 

[JS8588]

Here's a pick of the grip on a pistol. This shows the reduced angle better than link I posted.
View attachment 7473576

What lower is that? I'm an ambi lower aficionado & I don't recognize that one.

 

[AngryKoala]

None. Titanium expands less than steel, so as the barrel expands, you'll actually get a tighter gas seal.

It is ~1.4oz lighter than the bcm (0.48oz vs 1.93oz).

Just something I prefer (& am willing to pay for). Ymmv.

Yea, I am not overly concerned with the weight more so with durability. There doesn't seem to be as much 0.625" options. Unfortunately the titanium cost about the same as an AGB which isn't a huge deal but if I can save $40-50 then why not.

Might want to check out this grip. It has become my favorite hands down. Reduced angle. Actually it's a BCM gunfighter Mod 3, but with Wilson's Starburst texturing.

BCM | Starburst | Gunfighter | Grip | Black

Wilson Combat®/BCM Starburst Gunfighter Grip, Black

shopwilsoncombat.com

Looks amazing but it looks like it is polymer, I am not a huge fan of the feel of plastic. I prefer the elastomeric overmolding.

 

[357Max]

It's a JL Billet. I like them.

Hard to believe but their newest version is in stock. Prob not for long.

Skeletor AR15 Light Weight Matched Set, Ambidextrous, FFL Required

JL Billet manufactures the highest quality billet AR, AK parts and accessories that you'll find on the market. Billet uppers, lowers, hand guards, buttstocks, rails, Billet Ar15 Receiver.

www.jlbillet.com

 

[JS8588]

It's a JL Billet. I like them.

Hard to believe but their newest version is in stock. Prob not for long.

Skeletor AR15 Light Weight Matched Set, Ambidextrous, FFL Required

JL Billet manufactures the highest quality billet AR, AK parts and accessories that you'll find on the market. Billet uppers, lowers, hand guards, buttstocks, rails, Billet Ar15 Receiver.

www.jlbillet.com

I have zero use for the upper. Wonder if they'd sell me just the lower. Perfect for that 12 inch 6.5 Grendel barrel I've got in the parts drawer.

Time to write an email

 

[357Max]

I have zero use for the upper. Wonder if they'd sell me just the lower. Perfect for that 12 inch 6.5 Grendel barrel I've got in the parts drawer.

Time to write an email

Sorry OP don't mean to derail your thread. The Wilson grip is polymer, but it feels pretty good with the starburst pattern.

No email needed. Light weight lower is available and in stock separately.

 

[padom]

If youre dead set on that barrel, why not just get the Badger Ordance 0.625 fixed gas block that they offer with the barrel for the additional $69? If it was me, I wouldnt be using that barrel and id make sure i was using a .750 gas tenon so I could use the very very nice, free, super low profile gas block that comes free with the Geissele handguard you are going to use... Just my $0.02.... I have a pile of these Geissele gas blocks that guys give me because they come with their handguard and dont want them. I use them on all my AR's.

 

[AngryKoala]

If youre dead set on that barrel, why not just get the Badger Ordance 0.625 fixed gas block that they offer with the barrel for the additional $69? If it was me, I wouldnt be using that barrel and id make sure i was using a .750 gas tenon so I could use the very very nice, free, super low profile gas block that comes free with the Geissele handguard you are going to use... Just my $0.02.... I have a pile of these Geissele gas blocks that guys give me because they come with their handguard and dont want them. I use them on all my AR's.

Good question, I wasn't sure if that was a good gb or not as I am quite new at this so I'm still learning all of the names/associated quality. Also, before learning about the adjustable gas key i was set on the SA AGB.

The CORE series has a taper at the end that sounded good for balancing against the weight of the added accessories. They have a hybrid barrel that i believe is 0.750" which has a weird government/not really government profile.

 

[S197]

what is this build going to be used for? What ammo are you wanting to run? do you want it to be a work horse that eats everything?

criterion makes a good CL barrel, just buy a matched bolt with it.

lets us know your goals and we can get you on the right path.

 

[AngryKoala]

what is this build going to be used for? What ammo are you wanting to run? do you want it to be a work horse that eats everything?

criterion makes a good CL barrel, just buy a matched bolt with it.

lets us know your goals and we can get you on the right path.

Range, class and possibly home defense. Will be running mostly 193 through it but at this point whatever i can find for a "reasonable" price. I want it to run most ammo but I am okay with it not running everything as I think overgassing the system for reliability makes shooting less enjoyable (looking at you DD). My factory built 11.5 is my shtf gun so everything i build will be used mostly at the range/classes.

I plan on sending criterion my bolt to be headspaced. I am still trying to decide between the core series vs hybrid from criterion. I get some weight savings from core but assuming more accuracy shift if doing string firing vs the hybrid.

 

[S197]

Range, class and possibly home defense. Will be running mostly 193 through it but at this point whatever i can find for a "reasonable" price. I want it to run most ammo but I am okay with it not running everything as I think overgassing the system for reliability makes shooting less enjoyable (looking at you DD). My factory built 11.5 is my shtf gun so everything i build will be used mostly at the range/classes.

I plan on sending criterion my bolt to be headspaced. I am still trying to decide between the core series vs hybrid from criterion. I get some weight savings from core but assuming more accuracy shift if doing string firing vs the hybrid.

If you haven’t bought the jp bcg hold off on it. Save the cash for the barrel, or other parts. Buy the bolt from the barrel manufacturer, they would have the best matched set for their barrels. If you must have a jp carrier, wait until they offer a sale.

Get a buffer that can be adjusted. This way if you need to add weight (h2) you can. I think it’s 10.00 for tungsten weights. I do like the geissele set up, that spring design has worked well for multiple firearms and in other forms.

i do like the criterion core barrel, but I am not sure how well it will hold groups together once it gets hot. A while back criterion put a “how to” video on youtube about upper barrel assembly. Their top builder showed how he installed barrels to uppers and it was very disappointing. With that being said, centerion arms offers a really nice CL barrel.

 

[S197]

This is the video that bothered me. They are talking about accurizing the AR but when they trued the receiver face, he held the parts by hand and used a hand drill. You can not get an even amount of force when cutting this way, or have a consistent outcome . While this is such a small shortcut, it makes me wonder what else is cut short.

 

[AngryKoala]

If you haven’t bought the jp bcg hold off on it. Save the cash for the barrel, or other parts. Buy the bolt from the barrel manufacturer, they would have the best matched set for their barrels. If you must have a jp carrier, wait until they offer a sale.

Get a buffer that can be adjusted. This way if you need to add weight (h2) you can. I think it’s 10.00 for tungsten weights. I do like the geissele set up, that spring design has worked well for multiple firearms and in other forms.

i do like the criterion core barrel, but I am not sure how well it will hold groups together once it gets hot. A while back criterion put a “how to” video on youtube about upper barrel assembly. Their top builder showed how he installed barrels to uppers and it was very disappointing. With that being said, centerion arms offers a really nice CL barrel.

I am am buying the rubber city bcg/bolt (waiting on their bf sale) thanks to the recommendation in a previous post. Also buying the JP SCS kit (waiting for OP BF).
Most of their mass is in the rear on their core barrel so I would assume it would be okay. I am not beholden to their products they just seem to make the best (other peoples words) CL barrel, which is why I chose them. If their is a better or equal option with a 0.75" contour i would preferably pick that. I don't have the experience to know what is comparable.
Either way ill send the bolt in for headspacing with whatever companies barrel i buy.

I can't comment on the video but I can't imagine that is the correct method as you stated

 

[S197]

I would go with their hybrid barrel

 

[FishinGuns]

Check out Black River Tactical. I use their gas blocks with their inserts. I’m going to purchase two SLR Ti gas blocks and see about installing BRT’s HD kit in them.

FWIW, they have .625” and .750” gas blocks with HD ports installed. Easy button for the 12.5” Core. Since it’s not a pin & weld build, you can adjust your gas ports to your liking by just installing a different port, once you get your suppressor.

You can even install the HD ports in FSB’s, existing gas blocks, etc. It’s suppressor tunable while being hard use, bet your life reliable. The tuning is just more involved and it’s set it and forget it.

 

[JS8588]

The Core barrel will not require adjustable anything. It's conservatively ported.

 

[Strykervet]

For accuracy, a tack driver, I'd look at Krieger. I've used most of the high end makers and those are some of the best and they can deliver relatively fast. I used the Lilja Navy barrel and assembled a Recce rifle per USN specs and then built another one using the Krieger. The Krieger is more accurate and the mid gas makes it pretty soft too. I don't fuck with adjustable shit.

Noveske is my goto for SBR barrels and other short stuff. For 13" I'd get one of those. I don't expect to ever shoot them past 300 anyway.

JP FMOS is what I use to ensure reliability, the fucking things just work. If it gets enough gas, it'll do it's job. Many high end bbl. mfg.'s will use JP bolts to headspace their barrels and will include the bolt if you like. This isn't a bad option, especially if you need one.

Start with a standard buffer or go by the chart. I understand M4's currently use H2's and I probably need to change the ones in mine but those rifles are what a lot of you would call "overgassed" due to reliability concerns, ie, a little more is better than not enough.

A 3G trigger will make it a fast blaster but you won't be able to really set any shots or do much precision anything with it.

I'm a fan of the KAC URX4, it's one piece and if you bed the barrel it turns the upper into a singular and permanent upper/barrel unit.

IMO .300BLK makes a far better suppressed SBR option. That said, all my 5.56 shit is suppressed but it's also restricted to between 10.5 and 16". Shorter is anemic and longer is well, long for a high speed bb gun.

 

[padom]

Personally, I like the DD 1:7 Govt Profile chrome lined barrels with the .750 gas tenon... I have one right now on my go to AR and its a hammer with 55 vmax. Today, I would say buy what you can find, because its slim pickens out there for 10.5-12.5" AR barrels and may be for a while...

12.5" 5.56mm, Carbine, 1:7, GOV

Our 12.5” 5.56 barrel is the most accurate and longest lasting barrel attainable for your AR-15 build. We Cold Hammer Forge our barrels from 4150 Chrome Moly Vanadium steel, a process that sets us apart from other barrel manufacturers. It’s Mil-spec heavy phosphate coated and chrome lined with...

danieldefense.com

Here's some 5 shot group load development (seating depth test) with 55VMAX and H4895 out of my DD chrome lined 1:7
You can see the bottom row, 77CC/8208XBR didnt shoot bad either..