New AR build, stuck charging handle

[doboy001]

Hey guys,
I'm new to AR building as this is my first AR and I've been browsing this website to get ideas. Right now, my build is complete but I'm having issues with the charging handle not pulling back when the lower and upper is lock together. When I don't lock the upper receiver, I'm able to pull the charging handle and everything seems to work fine.

After spending a couple hours and reassembling the BCG I think I know that the charging handle is stuck on the top of the upper rail. The pivot pin is really tight trying to push the pin to lock the upper and lower in the rear. I have no problem locking the pin in the front. I think by locking the rear pin to lock the upper and lower, it is somehow pushing the BCG upwards and therefore pushing the charging handle to the very top.

I was thinking of buying another charging handle but before I do that I wanted to get some advise on what to do. I even shaved a little of the lower so it doesn't rub against the charging handle

Build:
Aero M4E1 upper and lower
PSA Nickle BCG
Strike Industries Latchless Charging handle

I've attached some pictures, just click on the OneDrive link


https://1drv.ms/f/s!AlDztIecskS3gpkq-dCBWtz5jK24lA

[crosseyedshooter]

I want to say that charging handle could be out of spec and too thick, but it's hard to tell just from photos. Do you have a mil-spec charging handle you can borrow to try out?

[doboy001]

No, I don't have one at home. Will pick one up at Turners or Riflegear today to try out

[tonyxcom]

Try it without the BCG.

Are you sure the CH isn't hitting your stock? In one of the images it looks like your stock and upper receiver aren't parallel.

[KaLiFORNIA]

Coating binding?

[protohyp]

it looks like the charging handle is hitting either buffer tube tower or the butt plate or castle nut. that will prevent the charging handle from moving freely.

take out your BCG and install just the charging handle and see if you still get binding.

pay attention to when you hear metal on metal and then inspect where its happening. you can also take a sharpie and mark up the bottom of the charging handle and see if it transfers marker to the buffer tower.

[doboy001]

I don't think the CH is hitting the stock. I have no issue clearing the stock. I'm going to take out the BCG and try it. Will get back to you guys.

[ZombieLivesMatter]

You have anyone else with a AR you can try to swap CH and BCG before going out and buying new ones. If you're by LA I can help.

[1snowridr]

OP, what safety is that?

[doboy001]

Originally Posted by 1snowridr

OP, what safety is that?

It's an Odin Works Ambi Saftey. I use it as a thumb rest also in the fire mode

I'm in OC and all my friends are in IE or LA area so I don't really have anybody to switch CH and BCG

So I took out the BCG and the CH seems to move fine without it. The rear pin is still really hard when trying to lock the lower and upper. I'm wondering if the stock/grip is tightening the lower receiver but I don't really want to take it all apart

See pictures

[Sparrow Dynamics]

When troubleshooting, try to eliminate variables and try changing one thing at a time. Eventually the issue will smack you in the face.

[Blade Gunner]

The Aero lower has a tensioning screw. It might need adjustment.

[protohyp]

Originally Posted by Blade Gunner

The Aero lower has a tensioning screw. It might need adjustment.

agreed on this. I absolutely hate those things. worthless in my opinion.

but then again cerakote/paint always screws with things that are already tight fitting anyway.

[boopiejones]

Could it be an out of spec buffer tube retainer pin? I suppose the bolt could be hitting it when you attempt to pull back on the charging handle.

Try leaving in the bolt and charging handle, but removing the buffer/spring and the buffer retainer and spring. Can you pull back the handle now?

[doboy001]

so I think I figure it out. I took out my Hera Stock/Grip and adjusted the tension screw. I'm really having a tough time locking the rear upper. No matter how I adjust the tension screw I can't pin the rear upper and lower together. What is happening is that when I push down really hard on the upper I'm able to use the rear Pin and lock the upper and lower together. What happens is that since the Pin pushes the upper receiver downwards, it also pushes the CH upwards and making it stuck.

So my question, is how do I fix this?? I could try to shave off the rear upper receiver hole so it aligns with the lower receiver so I the pin doesn't pull the upper receiver downwards.

Any suggestions?

[protohyp]

Originally Posted by doboy001

so I think I figure it out. I took out my Hera Stock/Grip and adjusted the tension screw. I'm really having a tough time locking the rear upper. No matter how I adjust the tension screw I can't pin the rear upper and lower together. What is happening is that when I push down really hard on the upper I'm able to use the rear Pin and lock the upper and lower together. What happens is that since the Pin pushes the upper receiver downwards, it also pushes the CH upwards and making it stuck.

So my question, is how do I fix this?? I could try to shave off the rear upper receiver hole so it aligns with the lower receiver so I the pin doesn't pull the upper receiver downwards.

Any suggestions?

Is the front takedown pin easy to take out?

I have a spikes honey badger where the front takedown pin hole is not centered effectively making the rear pin bind.

You can try removing the front takedown pin and the testing how hard it is to remove the rear takedown pin. If it’s easy to do and you try to insert the front takedown pin and there is resistance...well one of those two holes is out of spec.


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[doboy001]

I took everything out, the CH, the buffer/spring and the rear take down locks easily. I put the buffer/spring back in and I can't lock the rear take down pin. I took the buffer/spring out and put the CH back and I can't lock the rear take down pin.

The front take down pin has resistance when I try to push it out when the rear take down pin goes in easily

[ARDude]

This going to sound crazy, but it's true. Had a friend build an AR for the first time on his own.
He actually installed 2 carbine buffer springs. I don't know how he did it, but he called me saying he couldn't pull the charging handle back.

I asked him why he put 2 springs in, and he said the kit came with 2, so he thought they both were supposed to go in it.

[doboy001]

Originally Posted by ARDude

This going to sound crazy, but it's true. Had a friend build an AR for the first time on his own.
He actually installed 2 carbine buffer springs. I don't know how he did it, but he called me saying he couldn't pull the charging handle back.

I asked him why he put 2 springs in, and he said the kit came with 2, so he thought they both were supposed to go in it.

it's only one buffer spring..the KAK industries buffer kit only came with one long spring

[ARDude]

Originally Posted by doboy001

it's only one buffer spring..the KAK industries buffer kit only came with one long spring

Roger that, just thought it was a funny story. I bring it up every time I see the guy.

He has since built 5 AR's in 4 different calibers, without any mistakes.

[FlyingShooter]

Try calling Aero, and let them know whats going on too. They are usually pretty helpful, and they may have some info on any recent out of spec uppers/lowers that went out based on other reports-especially with cerakote.

[protohyp]

Originally Posted by doboy001

I took everything out, the CH, the buffer/spring and the rear take down locks easily. I put the buffer/spring back in and I can't lock the rear take down pin. I took the buffer/spring out and put the CH back and I can't lock the rear take down pin.

The front take down pin has resistance when I try to push it out when the rear take down pin goes in easily

So to me it sounds like that rear pin hole on the lower receiver (or the receiver lug on the upper) are in the wrong position

Do you have another upper receiver you can throw on there?


There should be a little bit of slop (for lack of a better term) between the receiver to allow parts to fit together without binding. When that is all good and people complain that their receivers fit loosely people offer wedges and sets screws to take away that slop.

Barring all that you have deduced with the set screw as I said if you’re getting resistance from either pin going in when one is engaged either the cerakote is at fault or the pin locations are.

Search around your house for a dowel or something with a smaller diameter than .249 and insert it in the rear takedown pin hole to retain the receivers. And then try charging the handle with everything installed.

It’s going to drive you nuts doing all these things as mentioned before but try the cheap fixes first before you start buying things to attempt to fix something such as buying another charging handle


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[doboy001]

I'm going to call Aero. I tried everything to get the upper and lower to lock down properly.

[Daze]

I have also had a fitment issue with a painted upper / lower combo (also Aluma-Hyde from Brownells.) It had not been properly cured after installation in my opinion, nor had the surfaces it had been applied to properly prepped and degreased. Pins felt very tight, rear one more so than front. I had to use a tool to push them out.

I would not shave down any areas around the takedown pins. Try a little sand paper on the areas where the upper and lower make contact and see if that improves your fit.

Originally Posted by Ishootforblood

I painted a lower receiver with Brownell's Aluma-Hyde, and later experienced a problem where the upper and lower would not pin together. I determined that I had applied the paint a bit thick on top of the lower (where the lower and upper make contact. I sanded the paint (Aluma-Hyde) down a bit, and now the two halves now fit nicely. I'm guessing by your description (and by your photos) that this might be part of your problem? Good luck.

[boopiejones]

Sorry if I missed them, but did you post any pics of the inside of the lower? Might be helpful to post pics of the lower with the buffer installed. Reason I ask is because you mentioned the upper won’t close properly with the buffer installed but the bolt and charging handle out. There shouldn’t be any interference between the buffer and the upper when the bolt is out.

Also, where are you located? You’ll probably find someone local that’s willing to help diagnose the problem.

[doboy001]

Here are pictures of the lower receiver with the buffer/spring installed

I'm in Orange County area/ Irvine ...this is my first AR and my first build so everything is new to me

[protohyp]

Originally Posted by doboy001

Here are pictures of the lower receiver with the buffer/spring installed

I'm in Orange County area/ Irvine ...this is my first AR and my first build so everything is new to me

to me all that cerakote removed from the top of the buffer tower tells me that that the charging handle is hitting it making it hard to charge.

That area should have just a few marks from the charging handle hitting it but that looks like something is chattering across it.

[doboy001]

Originally Posted by protohyp

So to me it sounds like that rear pin hole on the lower receiver (or the receiver lug on the upper) are in the wrong position

Do you have another upper receiver you can throw on there?


There should be a little bit of slop (for lack of a better term) between the receiver to allow parts to fit together without binding. When that is all good and people complain that their receivers fit loosely people offer wedges and sets screws to take away that slop.

Barring all that you have deduced with the set screw as I said if you’re getting resistance from either pin going in when one is engaged either the cerakote is at fault or the pin locations are.

Search around your house for a dowel or something with a smaller diameter than .249 and insert it in the rear takedown pin hole to retain the receivers. And then try charging the handle with everything installed.

It’s going to drive you nuts doing all these things as mentioned before but try the cheap fixes first before you start buying things to attempt to fix something such as buying another charging handle


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so I stuck in a 5.5mm hex wrench in the rear take down pin hole to hold the upper and lower receiver together. The CH and BCG has no problem with movement...very smooth. I put in 2 dummy rounds in the magazine and pulled the CH handle and it loaded the round and ejected the round fine after I pulled the CH again.

Does that lead to a misalign rear take down hole on the upper?

[doboy001]

Originally Posted by protohyp

to me all that cerakote removed from the top of the buffer tower tells me that that the charging handle is hitting it making it hard to charge.

That area should have just a few marks from the charging handle hitting it but that looks like something is chattering across it.

That's me. I filed it down yesterday thinking it's hitting the top of the lower receiver but after doing that it didn't fix it so I came on this message board to find help

[protohyp]

Originally Posted by doboy001

so I stuck in a 5.5mm hex wrench in the rear take down pin hole to hold the upper and lower receiver together. The CH and BCG has no problem with movement...very smooth. I put in 2 dummy rounds in the magazine and pulled the CH handle and it loaded the round and ejected the round fine after I pulled the CH again.



Does that lead to a misalign rear take down hole on the upper?

It could but it could also be the build up of cerakote between the receivers. Obviously there is no spec on how thick cerakote should be but as someone had mentioned previously it did hinder them mating receivers easily.

If it is separating the receivers enough it could also be pushing the BCG upwards on the inside of the buffer tube but that really shouldn’t hinder its movement bust obviously stranger things have happened




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[strakill]

Originally Posted by doboy001

so I stuck in a 5.5mm hex wrench in the rear take down pin hole to hold the upper and lower receiver together. The CH and BCG has no problem with movement...very smooth. I put in 2 dummy rounds in the magazine and pulled the CH handle and it loaded the round and ejected the round fine after I pulled the CH again.

Does that lead to a misalign rear take down hole on the upper?

Upper or lower might be out of spec. Do you have access to a known good upper or lower?

[protohyp]

This is the offending hole one one of my lowers. In California rotating the receiver for mag changes this hinders it’s movement because the rail hits the thick part.



Plus since it is in the wrong place the pins are not easy to take out.

But it shoots great!


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[Mr. Meeseeks]

I'm with the guys that say try both halves on different uppers and lowers first. If they don't fit you'll know something is off.

Hard to tell but it's probably the paint/coating. This is a common problem when ever an assembly of some sort is coated. Custom builders of all types of things usually have a prep stage before final assembly of freshly coated parts.

Before resorting to anything drastic, I'd run a dowel with medium to fine grit sandpaper through the holes and maybe lightly hand twist the corresponding size drill bits through them as well if necessary.

If that's not enough to get them to fit together, I'd also use some fine sandpaper wrapped around a small block/blocks to knock down the coating where ever the two receivers meet.

I'd try my best not to take it down to bare metal or even remove all the paint; just enough off here and there for the assembly to come together.

Be careful at the edges, the coating will sand off quickly and show bare metal fast at leading edges. Test fit as you go. Then if possible touch up blemishes with the same paint when you're done fitting.

I'd use automotive wet sand paper probably 300 - 600 grit.

[ar15barrels]

Originally Posted by doboy001

I took everything out, the CH, the buffer/spring and the rear take down locks easily.

This tells us that the pin holes in the upper and lower are fine.

Originally Posted by doboy001

I put the buffer/spring back in and I can't lock the rear take down pin.

You have a problem with the buffer striking the upper receiver if ONLY the buffer and spring cause the problem without the charging handle and bolt carrier in place.
If the upper and lower will close freely with the bolt carrier, buffer and spring in place but NOT the charging handle in place, then the carrier/buffer parts and their bores are all inline and OK and the charging handle is likely the problem.

Originally Posted by doboy001

I took the buffer/spring out and put the CH back and I can't lock the rear take down pin.

If just the charging handle without the buffer/spring/carrier causes a problem, that absolutely points to the charging handle being the problem.
If it's not the charging handle itself (most suslect due to being a non-milspec unit), then it's the track in the reciever that the charging handle slides in.

[ar15barrels]

Originally Posted by doboy001

so I stuck in a 5.5mm hex wrench in the rear take down pin hole to hold the upper and lower receiver together. The CH and BCG has no problem with movement...very smooth. I put in 2 dummy rounds in the magazine and pulled the CH handle and it loaded the round and ejected the round fine after I pulled the CH again.

Does that lead to a misalign rear take down hole on the upper?

No.
The 5.5mm is simply creating extra room for the mis-fitting charging handle to move.
You already eliminated a problem with the holes in the two receivers when you said that the receivers fit together properly and pins slide into place without the charging handle.

[ar15barrels]

Originally Posted by protohyp

It could but it could also be the build up of cerakote between the receivers.

This statement pretty much eliminates that theory:

Originally Posted by doboy001

I took everything out, the CH, the buffer/spring and the rear take down locks easily.

If there was too much paint, the upper and lower would NEVER go together easily.

[ar15barrels]

Originally Posted by loosewreck

Hard to tell but it's probably the paint/coating. This is a common problem when ever an assembly of some sort is coated. Custom builders of all types of things usually have a prep stage before final assembly of freshly coated parts.

Before resorting to anything drastic, I'd run a dowel with medium to fine grit sandpaper through the holes and maybe lightly hand twist the corresponding size drill bits through them as well if necessary.

If that's not enough to get them to fit together, I'd also use some fine sandpaper wrapped around a small block/blocks to knock down the coating where ever the two receivers meet.

Originally Posted by doboy001

I took everything out, the CH, the buffer/spring and the rear take down locks easily.

The upper and lower already fit together so it's not a pin hole problem or a paint problem.
No need to mess up the holes.

[doboy001]

Originally Posted by ar15barrels

This tells us that the pin holes in the upper and lower are fine.



You have a problem with the buffer striking the upper receiver if ONLY the buffer and spring cause the problem without the charging handle and bolt carrier in place.
If the upper and lower will close freely with the bolt carrier, buffer and spring in place but NOT the charging handle in place, then the carrier/buffer parts and their bores are all inline and OK and the charging handle is likely the problem.



If just the charging handle without the buffer/spring/carrier causes a problem, that absolutely points to the charging handle being the problem.
If it's not the charging handle itself (most suslect due to being a non-milspec unit), then it's the track in the reciever that the charging handle slides in.

I don't know how the buffer is hitting the upper. I looked so many times and I don't feel any resistance when I put the upper down to the lower. I'm getting an upper receiver from a friend today and I'm going to try it tonight after work. Even with the charging handle inserted with no BCG and buffer it's still having problem clamping down on the rear take down pin.

I took a picture.

[ar15barrels]

Originally Posted by doboy001

I don't know how the buffer is hitting the upper. I looked so many times and I don't feel any resistance when I put the upper down to the lower. I'm getting an upper receiver from a friend today and I'm going to try it tonight after work. Even with the charging handle inserted with no BCG and buffer it's still having problem clamping down on the rear take down pin.

Perhaps I misunderstood your statement above that when you installed ONLY the buffer and spring that the upper would not close down properly?

Or perhaps you reinstalled the buffer, spring, bolt carrier or the buffer, spring, bolt carrier and charging handle?

If installing the charging handle without the bolt carrier, buffer or spring causes a problem, then the FIRST thing to look at is the charging handle.

Hopefully your friend's charging handle confirms this.


A test you can try with what you have now is to leave JUST the charging handle out and push the bolt carrier rearward through the ejection port with your thumb in the cutout where the ejection port cover fits.
If you can get the bolt carrier group to move freely for 3/4", then get a screwdriver in front of it and pull it back to the back edge of the ejection port.

If that is successful, you know that the bore in the upper reciever matches up with the bore in the lower reciever.

[SVT-40]

Originally Posted by ar15barrels

If just the charging handle without the buffer/spring/carrier causes a problem, that absolutely points to the charging handle being the problem.
If it's not the charging handle itself (most suslect due to being a non-milspec unit), then it's the track in the reciever that the charging handle slides in.

Probably a bit of both of the above. A non standard charging handle, as well as a thick coat of paint inside the charging handle track.

A good reminder to not paint the inside of upper receivers.

Additionally some uppers have a dry film of lubricant already inside.. So adding paint could just cause issues.