New AR Build Question -- Uppers & BCGs

[Kruel J]

And I would be more worried about severe failures at that point. The OP was asking about the need to buy a specific BCG. If the rest of the upper is assembled right, he should be good to go. Manufactures sell complete uppers MINUS BCG's every minute of the day (like the one in the OP) and buyers drop in off-the-shelf BCG's with no issues.

@the OP, you did fine with your choices. Enjoy that rifle!

 

[Boboclown]

Noted. But unless a bolt is severely lacking in quality or plain worn out it should be just fine.

For functionality pretty much. For squeezing every ounce of precision you want it as tight as you can safely do so. But we're talking about a small difference that won't matter at that point.

 

[Kruel J]

For functionality pretty much. For squeezing every ounce of precision you want it as tight as you can safely do so. But we're talking about a small difference that won't matter at that point.

Agreed. I was more stating that all things being equal a drop in BCG should do quite nicely for the OP. But I appreciate your comments!

 

[Mr Smith]

He'll be fine with what he picked.

One of the many reasons I like AR-15's in 5.56: almost any AR part from any manufacture will work with them because they run standardized specs. really not many proprietary parts other than maybe free float hand guards using special barrel nuts that usually come with the hand guard. My DD-LR-12.0 came with special barrel nut and tool, but other than that almost any ol AR part will go on there.

I built my own rifle and very few parts on it are made by the same manufacturer.

 

[HB of CJ]

Any Washington State Laws prohibiting specific machine gun parts? Does your BC have the M16 lower bottom profile or is it a "cut back" profile making it a non M16 part? Or do your state laws, if any, not apply?

If yes and yes, then no big deal. Easy to take a hobby power tool and cut back what you have.

If it were me, I would go with the USGI spec tube, buffer and spring. Also, and this is a difference of opinion, consider establishing the exact head space before firing. Low probability, but a possibility never the less.

Also proper barrel torquing may be a concern. Old school, new school. PEM me if you have any questions.

Respectfully. Hundreds of AR15 builds. If it can go wrong ... it did! Yikes!

 

[Flopsweat]

Any Washington State Laws prohibiting specific machine gun parts? Does your BC have the M16 lower bottom profile or is it a "cut back" profile making it a non M16 part? Or do your state laws, if any, not apply?

If yes and yes, then no big deal. Easy to take a hobby power tool and cut back what you have.

If it were me, I would go with the USGI spec tube, buffer and spring. Also, and this is a difference of opinion, consider establishing the exact head space before firing. Low probability, but a possibility never the less.

Also proper barrel torquing may be a concern. Old school, new school. PEM me if you have any questions.

Respectfully. Hundreds of AR15 builds. If it can go wrong ... it did! Yikes!

I'm not aware of any WA State law that would prohibit a full auto bolt. There better not be...

I've built a lot of ARs too and this my preferred headspace gauge:

 

[DirectDrive]

Any Washington State Laws prohibiting specific machine gun parts? Does your BC have the M16 lower bottom profile or is it a "cut back" profile making it a non M16 part? Or do your state laws, if any, not apply?

M16 carrier is legal.
Semi-auto carriers are actually not that common anymore.

If it were me, I would go with the USGI spec tube, buffer and spring. Also, and this is a difference of opinion, consider establishing the exact head space before firing. Low probability, but a possibility never the less.

Yes, the milspec buffertube is best. They are built to a set of standards.
Commercial O.D.'s can vary....I've had trouble with these.
I use headspace gauges, but many don't with the AR platform.

Also proper barrel torquing may be a concern. Old school, new school. PEM me if you have any questions.

I use the 3x torque procedure from the M16/M4 Tech Manual and the prescribed AeroShell 33MS grease for barrel nut lube. I try to stay between 30-40 ft lbs on the final pass.

The AR platform is very forgiving and all sorts of things have been done to it.
Some smart, some not so smart.

 

[gryghin]

I'm surprised that you bought a PTAC Complete upper from PSA and didn't see that they had their BCGs also on sale, unless you picked it up from somewhere else, which I hear is also likely.

My oldest boy has that upper, no issues with it. I have a few of the PSA and PTAC BCGs and haven't had any issues with them.

 

[Osarion]

I'm surprised that you bought a PTAC Complete upper from PSA and didn't see that they had their BCGs also on sale, unless you picked it up from somewhere else, which I hear is also likely.

My oldest boy has that upper, no issues with it. I have a few of the PSA and PTAC BCGs and haven't had any issues with them.

I picked up the BCM on the advice of some friends. Save for the BCM and charging handle the rifle is all ready to go! Will post my 1st AR pic tomorrow after the Fed Ex driver gets here Thanks for the advice & tips all.

 

[gryghin]

I picked up the BCM on the advice of some friends. Save for the BCM and charging handle the rifle is all ready to go! Will post my 1st AR pic tomorrow after the Fed Ex driver gets here Thanks for the advice & tips all.

I grew up in South Carolina and still have a lot of friends and family there. They turned me on to this local company and haven't had any issues.

I agree, rely on friends & family advice. I have a good buddy at work that swears by Bravo Company.

 

[HB of CJ]

Thank you all. We have found in the past that most of the major players got their carriers from just a few sources and usually, (not always) the carriers WERE cut back M16 versions. This apparently came from their legal department. Thank you for the updated current information.

Great to hear Washington State has no specifics prohibiting M16 bolt carriers. Good news.

In my opinion, establishing exact head space during the build is still an excellent idea. Low probability of a problem nowadays but still a proper build procedure. Low probability defined as usually not a concern for the home assembler. But a potential for the professional precision builder.

Barrel torquing. Old method. New method. The old method clamped the barrel and the upper floated and hand supported. Upper receiver front flat dressing/polishing needed. Dry. No lube. Go to 40-42 pounds corrected on the final squeeze. Carrier Free Bounce test. Very time consuming indeed.

Then it gets worserer. If one wants OEM irons front and rear, (taper pins) getting the build to print exactly correct at 100-300 yards is another time consumer. Up and down easy. Right to left with the rear aperture exactly centered within 2-4 clicks is very difficult. Perhaps today much easier?

Respectfully. Hundreds of AR15 builds. It is all your fault! Now I want to build a Left Hand 20" HB A2 Rifle!! Oh no! Looks like Stag has what I need. I can borrow beg or hock the required tools and stuff. The nice work bench and that 6 inch smooth jaw bench vise is in the works!

 

[DirectDrive]

Barrel torquing. Old method. New method. The old method clamped the barrel and the upper floated and hand supported. Upper receiver front flat dressing needed. Dry. No lube. Go to 40-42 pounds corrected on the final squeeze. Carrier Bounce test. Very time consuming indeed.

Clamping the barrel in proper barrel blocks is called the "USGI Method" and details on this can be found in the M16/M4 Tech Manual.
Lubing the "front flat" is a friction point and often over-looked.
Not using the approved grease on the threads is not recommended.
With a steel barrel nut and an alloy receiver thread galling would be a concern.
And the recommended torque values were reached using the approved grease , the offset in the USGI wrench and the torque wrench inline with the USGI.

As previously stated, AR is a resilient platform and all manner of things have been done to it that would not be approved by Eugene Stoner, chief designer.
How do I know ?
IRTFM

 

[Brutus57]

Ended up spending a bit more than I wanted to (shocking lol) and went with these:
BCM Bolt Carrier Group MPI Auto M16

<broken link removed>

Can't go wrong with BCM. My Franken AR is an Aero Precision lower with a BCM HBAR upper. First BCG was a PSA, upgraded to an NIB on sale and use the PSA BCG in another freedom toy....works just fine on both firearms.

Brutus Out

 

[titsonritz]

Also, and this is a difference of opinion, consider establishing the exact head space before firing.

I've built a lot of ARs too and this my preferred headspace gauge:
View attachment 340767

I use headspace gauges, but many don't with the AR platform.

Head spacing is not needed for ARs. The only one needed is...Gauge, Headspace, Field, M16 PN 7799734, unfortunately they are nearly impossible to find anymore. Civvy ones are made but without ejector relief cut so the ejector must be removed, here is Brownells

 

[DirectDrive]

Head spacing is not needed for ARs. The only one needed is...Gauge, Headspace, Field, M16 PN 7799734, unfortunately they are nearly impossible to find anymore. Civvy ones are made but without ejector relief cut so the ejector must be removed, here is Brownells

I use that Field Gauge.
If you are going to have one, that is it.

 

[HB of CJ]

Perhaps a short post outlining the old fashioned way of correctly using a head space gage might be in order. But ... then again would it do any good?

But ... the AR15 family is head space tolerant. Fortunately.

Ejector group need not be removed. Extractor group maybe, maybe not. Depends upon proper technique. Ninety nine AR15 builds will be OK. One will not.

It is the one that will cause major problems.

Having said that, does anybody recommend a "good" video on how to use a AR15 head space gage? I will bet anybody here a nice smile that they are wrong.

Respectfully.

 

[DirectDrive]

Having said that, does anybody recommend a "good" video on how to use a AR15 head space gage? I will bet anybody here a nice smile that they are wrong.

Respectfully.

Depends on whether you are checking a NEW rifle or a USED rifle.
A new rifle should headspace into a specific range considered acceptable by industry standards for a new AR.
You would check a used rifle (esp, a heavily used rifle) to make sure it isn't worn to an unsafe condition.

These are the consensus values :

New Rifle Headspace: 1.4646" to 1.4706"
SAAMI headspace gauges to use: 1.465" and 1.470"

Unsafe Rifle Headspace: 1.4736"
Use the Colt M16/AR15 Field Gauge: 1.4736" (Colt II) or,
The US military gauge: 1.4730" (Colt I)