Precisions ar upper? Build help….

[lycokayaker]

Hey gang

Help me out my initial plan was to buy an aero enhanced upper receiver pair it with a sgt of arms rail with the arca rail built in and run a bartlein or Douglas 24 inch 6 arc barrel. I’m wondering if I’m going to sacrifice some accuracy with an aero upper. Help educate me on what direction I should be going. I’m a bolt gun guy and the gas guns is uncharted territory. This will be a prs style gas gun.

 

[MontanaMan]

This thread will answer most of your questions with posts by many knowledgeable people here.

MM

Upper Selection

 

[cjs88]

Nothing wrong with Aero. I have the same upper that Craddock is putting together for me. I was going to go Seekins at first but the guys over at Craddock steered me away from them. Which was crazy given all the good things I hear about Seekins but I trust the people who work with uppers every day so went with the Aero.

 

[phantasm]

Nothing wrong with Aero. I have the same upper that Craddock is putting together for me. I was going to go Seekins at first but the guys over at Craddock steered me away from them. Which was crazy given all the good things I hear about Seekins but I trust the people who work with uppers every day so went with the Aero.

Any reason given to shy away from Seekins? That seems odd.

 

[cjs88]

Any reason given to shy away from Seekins? That seems odd.

They said a lot of the ones they've put together have measurements/tolerances, don't remember what exactly, that were off. They brought the concerns up to Seekins and they said they were brushed off.

 

[TonyTheTiger]

They said a lot of the ones they've put together have measurements/tolerances, don't remember what exactly, that were off. They brought the concerns up to Seekins and they said they were brushed off.

I've got a Seekins upper with a slightly bigger than normal bore. It shoots great but annoys me every time I notice it.

 

[canezach]

I did NOT have the best experience dealing with Seekins to the point I wish I had never dealt with them.

 

[loclass]

I'm using an Aero enhanced upper receiver with the Sgt of Arms handguard and a CLE chambered Criterion 6 arc. Factory ammo shot consistently 0.5-0.8 moa at 100 and my hand loads are a shade better than that. For a prs type gas gun the Aero upper works well.

 

[lycokayaker]

I'm using an Aero enhanced upper receiver with the Sgt of Arms handguard and a CLE chambered Criterion 6 arc. Factory ammo shot consistently 0.5-0.8 moa at 100 and my hand loads are a shade better than that. For a prs type gas gun the Aero upper works well.

did you bed the barrel or do anything fancy to it ?

 

[padom]

Get a BCM thermofit upper and be done... or go MEGA if you want a thick billet upper....


I've used and have many AERO uppers and lowers....but I'll never use one again. The last 3 were out of spec to the point they were unusable....bolt.wouldnt line up with barrel, wouldn't fit on lower....took months to get Aero to handle....lots of excuses...finally 4 months later they sent me new parts. I sold them and never bought any again.

The good part for you is Craddock is building it so what you get will be tested and vetted...

 

[padom]

I was told a while back these JSE Billet uppers are MEGA/ZEV. I've used a ton of them and they are very nice if you want billet...

JSE AR15 Billet Complete Upper Receiver

Please view details for more information.

www.jsesurplus.com

Otherwise, these are the best kept secret. Says scratched (NOT BLEM) AND everyone I've received look brand new can't find a scratch on them. Best thermofit upper out there for the money

BCM® Upper Receiver - M4 Flat Top (M4 Feedramps) Complete (Unassembled) - DEMO/Scratched

Fully Assembled, with round forward assist and ejection port cover, and T-Markings laser etched into receiver. This receiver has the M4 feedramps machined in.

bravocompanyusa.com

 

[bfoosh006]

FWIW, every SOLGW bare upper I have bought, has a thermo fit for the barrel extension, and has a snug to very tight fit on various brand lowers. ( BCM lower was VERY tight )
I am a fan of a tighter fit onto a lower with a precision oriented AR.
IMHO, it Makes for a far more consistent wielding AR.

I also prefer to lap the upper's receiver face , simple to do and I have never seen a AR shoot worse, but have seen them shoot better.
It also seems to help with fliers. I do it to all my uppers, large and small.

 

[loclass]

did you bed the barrel or do anything fancy to it ?

No bedding or anything special. I have also used BCM uppers in the past with great results as well. I used the Aero upper in this case because I wanted to used the Sgt of Arms handguard.

 

[cjs88]

Get a BCM thermofit upper and be done... or go MEGA if you want a thick billet upper....


I've used and have many AERO uppers and lowers....but I'll never use one again. The last 3 were out of spec to the point they were unusable....bolt.wouldnt line up with barrel, wouldn't fit on lower....took months to get Aero to handle....lots of excuses...finally 4 months later they sent me new parts. I sold them and never bought any again.

The good part for you is Craddock is building it so what you get will be tested and vetted...

It is what they recommended so I went with it. Kind of wanted to keep the cost down on everything else since the barrel was pricey. They recommended another brand too that is local to where they are. A bit more expensive and nothing I wanted in stock IIRC.

 

[Kinked_Chrome]

My current PRS gas gun is built on an M5 enhanced upper. It is good quality and the rifle is very accurate, but I would agree that lately Aero quality has gone down. Both me and a buddy recently had an issue there the face of the receiver was not flat. My buddies was an M5 enchanced and mine was an m4 enhanced. You could plainly see that the surface had not been completely machined or maybe it move while being machined. They took care of my buddy, but it took months for them to get to his ticket. I have not even tried with mine yet.

 

[padom]

My current PRS gas gun is built on an M5 enhanced upper. It is good quality and the rifle is very accurate, but I would agree that lately Aero quality has gone down. Both me and a buddy recently had an issue there the face of the receiver was not flat. My buddies was an M5 enchanced and mine was an m4 enhanced. You could plainly see that the surface had not been completely machined or maybe it move while being machined. They took care of my buddy, but it took months for them to get to his ticket. I have not even tried with mine yet.

My same experience. Nothing for months. Finally I called and demanded a manager said you've had my parts for 5 months ths but 4 months ago you told.me replacement shipped...

Was told that person I first dealt with was was fired, his records are complete chaos, they didn't know where my.shit was at. I forwarded her my emails back and forth and last one saying replacement shipped. Finally got new parts. I sold them instantly.and never bought another Aero part again.

Their customer service is complete shit and their QC is in the drain if it even exists. I've helped diagnose multiple non working M5 builds that ended up.being out of spec Aero uppers or lowers....

 

[B Man]

MEGA

This

 

[LRRPF52]

This will be a prs style gas gun.

In that case, I would look at billet receiver sets from known performer companies who actually care about their products. You can ask about the ID of your extension tunnel and correlate that with the OD of your extension to get an interference or thermo fit with your top-end barrel.

The barrel quality, chambering, and how it’s mated with the upper will all be some of the baseline essentials to a precision rifle. I wouldn’t waste your time and money on most forged uppers for this application. There are some companies making precision-machined forgings, but I think it makes sense to go known brand billet here.

JP, LaRue, Mega, Precision Firearms, and Seekins come to mind. I know there are others I’m forgetting. Doesn’t matter as much as the fitment of your barrel to the ID. I do like the uppers where the handguard doesn’t touch the barrel nut at all as well for a true free-float.

If we’re talking about run-of-the-mill mass-produced forged uppers, I think the conversation might be in the wrong place. I’ve seen a lot of uppers where the carrier raceway isn’t concentric or even centered on the forging, leaving obvious thin areas on one side, and thick on the other. BCM has a new beefed-up upper that addresses receiver wall thickness around the extension and raceway.

Next important components are muzzle device (if any), gas block, gas tube, barrel nut and torque, BCG, trigger, scope mount, and scope. All the things add up to a certain resonant system.

 

[Constructor]

Vltor Mur, BCM 2 if you can find one, Mega/Zev . First 2 have thicker walls and a tight fit. Mega /Zev has a tight fit.

 

[TonyTheTiger]

BCM has a new beefed-up upper that addresses receiver wall thickness around the extension and raceway.

Been looking for a stripped MK2 for like 3 years now. I stopped paying attention, are they actually available now?

 

[Kadams1563]

Been looking for a stripped MK2 for like 3 years now. I stopped paying attention, are they actually available now?

I only see them on complete uppers.

 

[TonyTheTiger]

I only see them on complete uppers.

Same.
Just googled availability, found some year old arfcom threads saying that BCM got so much negativity from people angry that the MK2 was incompatible with certain handguards that they took their ball and went home.

 

[simonp]

My last builds were BCM and Wilson both thermo. Couldn’t find Vltor on stock, picked up a GGP but it dies t have M4 feed ramps appetently so no idea what will become if it.

 

[B Man]

My last builds were BCM and Wilson both thermo. Couldn’t find Vltor on stock, picked up a GGP but it dies t have M4 feed ramps appetently so no idea what will become if it.

I have not found that to effect accuracy any at all with the GGP sets. For a lighter than Mega set build with accuracy in mind it’s became my second choice.

 

[LRRPF52]

I would also look at ADM and SilencerCo billet sets. Both have ambidextrous bolt hold open and release.

 

[kthomas]

Not cheap, but Noveske makes matched billet receiver sets: https://noveske.com/product-category/receivers/matched-sets/

 

[Jcaplinger199]

I have not found that to effect accuracy any at all with the GGP sets. For a lighter than Mega set build with accuracy in mind it’s became my second choice.
View attachment 8176649View attachment 8176650

What bipod is that?

 

[B Man]

What bipod is that?

Cheap UTG super duty with QD I bought years ago to throw in a hunting bag for my large frame for when I needed it hunting.

 

[Constructor]

Been looking for a stripped MK2 for like 3 years now. I stopped paying attention, are they actually available now?

If you look at both the BCM 2 and the Vltor you can see BCM beefed up their receiver similar to what Vltor has been doing for 15years.

 

[B Man]

If you look at both the BCM 2 and the Vltor you can see BCM beefed up their receiver similar to what Vltor has been doing for 15years.

Is Vltor still thermal fit? I have read a few times lately where they have not been.

 

[Constructor]

Is Vltor still thermal fit? I have read a few times lately where they have not been.

I don't know, They have always been tighter than the others until BCM started making theirs tight on purpose and Mega /Zev started teflon coating their receivers. Some of it also depends on the maker of the extension, some etensions come out on the large end of spec and some on the small end.

 

[srt-4_uk]

Is Vltor still thermal fit? I have read a few times lately where they have not been.

I bought one last year and it definitely wasn't. Shim fixed that.

 

[Rocketvapor]

No real dimensions? Just "tight fit" or NOT?
Measuring receiver bore might be a little difficult but extension O.D. is easy peasy.
Would be meaningful to report what extension OD you got a "tight fit" or had to shim.
Here's about 0.0008" taper that slips in for a ways then gets tight out in the thin threaded nose.
How do you shim a taper?

 

[B Man]

No real dimensions? Just "tight fit" or NOT?
Measuring receiver bore might be a little difficult but extension O.D. is easy peasy.
Would be meaningful to report what extension OD you got a "tight fit" or had to shim.
Here's about 0.0008" taper that slips in for a ways then gets tight out in the thin threaded nose.
How do you shim a taper?
View attachment 8179176

Loctite 620 and send it

 

[Rocketvapor]

@B Man
That's what many do to fix a loose fit. The point I was trying to make was what extension (O.D.) is a tight fit?

Not a single dimension has been posted (not just this thread).
Two people could assemble the SAME UPPER and have different results based on extension O.D.


I use a different shim method.

 

[B Man]

@B Man
That's what many do to fix a loose fit. The point I was trying to make was what extension (O.D.) is a tight fit?

Not a single dimension has been posted (not just this thread).
Two people could assemble the SAME UPPER and have different results based on extension O.D.


I use a different shim method.

I was being serious but not as I knew from your post and tools you have more to tell. I am curious what you mean by using a different method. I’m always eager to learn ways.

 

[Rocketvapor]

I'm just guessing here but those thermal fit uppers are made with a smaller bore than the run of the mill upper. DUH
I think the upper bore diameter is spec'd @ 1.000" +/-0.002".
The AR-15 extension is spec'd @ 0.998" -0.0008, + 0.

In addition to making the bore at, near, or less than spec (to fit most barrel extensions) tolerance would have to held to a lot better than +/- 0.002"

 

[srt-4_uk]

I think that's why most don't measure the extension. It's helt to much tighter tolerances than the upper for it to be in spec.

 

[Ernest 5.56]

What is everyone's method other than visual inspection for determining if the face of the receiver needs to be lapped???

I've thought about using a flashlight to see if there's visible light around the edges or possibly an automotive feeler gauge but I have no idea what the appropriate size feeler gauge would be.

 

[RickyRodney]

looks like you are getting some poor user experience feedback on the aero uppers. Which makes the ssgt. arms idea dead in the water. I went through the exact same thought process when buying parts.

I'd go seekins uppers and handguard for parts and then add an arca rail. Frank has a demo somewhere on the hide where he demonstrates forend pressure on the the rifle moving the zero and since then I'm personally dead set on integrated handguards. A little more expensive but its buy one cry once. I have a seekins large frame builder set and 2 uppers with integrated handguards and I'd say their quality is top notch. Better finish than the LMT lower I just bought. My 2 cents.

 

[Constructor]

Back in the 90s most AR15 parts were poor quality so if we wanted one to shoot well we had to make them work. Derrick Martin at Accuracy Speaks was probably the first guy I knew that lapped the receiver face and bedded the barrel extension with plain blue loctite. It worked then and still does.
Vltor and Mega were the first 2 I found that had an interference fit negating the real need to face the receiver but still doesn't hurt.
As someone above said different manufacturers grind the extensions to a different diameter which cause some to fit tight and some loose.

 

[Rocketvapor]

Looks like a couple X-Caliber extensions I got were actually a little OVER spec diameter.
Just not quite a thermal fit in my cheapo Bear Creek upper.

 

[Rocketvapor]

Here soon I will pull down my old X-Caliber 22N barrel and see how the spray on shim held up.
Over 5 years and about 3200 shots. New barrel about a month away.
Just received another BCA side charge upper. Here's what I get on this latest one.

To start I set the Chinese internal mic to a temperature corrected setting ring-
0.99988" @ 20C (68F), corrected to room temperature of 75F, (6uin/F X +7F= 42uin) = 0.99992 or about 0.0001" less than 1".

Measured upper bore @ 3 depths up to about an inch deep, @ 0 degrees vertical, 60 and 120 degrees.
Got these measurements: All about 0.0003" less than 1.0000". Corrected to 68F (13ppm/F) would be 0.9996" but 75F is probably more appropriate for assembling gun parts.

Was surprised with measurement repeatability of the Chinese mic. Will face off the receiver later.

 

[MontanaMan]

With all that attention to detail, did you bother to check the mic against a 1" Jo-Block or some other large size standard? If the mic has any problems, like lash, they would likely be magnified a those kind of length measurements. Just wondering...............................

MM

 

[Rocketvapor]

Came with a setting ring, labeled 0.99988" @ 20C.
Temperature correction for room temperature was insignificant at 42 microinches.
Maybe I'll ring together some blocks and check the mic.

Mic plus setting ring, 5 place value but no spec for $57.41.

So, I ordered a couple used rings, Class X.
Readings from .9985 X Master Carbide and .99988 Chinese ring

Why? Spending my COLA

 

[Distancerunr123]

Zev, mega, bcm, Solgw… you get a thermal fit quality forged upper. Zev/Mega are the same now and they oem for Solgw
Keep an eye out for blems too. I wouldn’t use anything else these days.
It also means if you want to pull the barrel you need a press because they definitely will not slide out.

 

[padom]

It also means if you want to pull the barrel you need a press because they definitely will not slide out.

You don't need a press at all...some of us have built hundreds of thermofit uppers...heat is all you need. Heat gun works great

 

[TonyTheTiger]

You don't need a press at all...some of us have built hundreds of thermofit uppers...heat is all you need. Heat gun works great

I've done it easily with just a 1" wooden dowel, a small hammer and some patience. Not rocket science.

 

[Ernest 5.56]

Zev, mega, bcm, Solgw… you get a thermal fit quality forged upper. Zev/Mega are the same now and they oem for Solgw
Keep an eye out for blems too. I wouldn’t use anything else these days.
It also means if you want to pull the barrel you need a press because they definitely will not slide out.

JP Enterprises has a video on their YouTube channel on how to remove a thermofit barrel five or six quick revolutions with a torch then whack the barrel extension with a hammer and a large wooden dowel

 

[Distancerunr123]

You don't need a press at all...some of us have built hundreds of thermofit uppers...heat is all you need. Heat gun works great

Everything I build the last 6 or so years has been thermal fit with a heat gun, I just haven’t messed with pulling a barrel yet. I did see someone mentioned a JP video so I’ll definitely check it out. I generally try to avoid a torch whenever possible..