Upper receiver? 😳YIKES BARREL EXTENTION 😳

[supercorndogs]

I have a 6 arc upper that seems to be throwing lots of fliers. It seems to want to shoot, it will stack 3 or 4 usually then dump one 1 moa low or high. I was looking it over and noticed the feed ramps don't line up well between the reciver and barrel. I noticed one feed ramp in the barrel extention picking up some copper and deburred it.

Would I be crazy to think this upper reciver might be the problem? Sorry tried but couldn't get my bare feet in the pictures.

 

[whatsupdoc]

Take the barrel off and shim the barrel extension pin so that it does not rotate in the upper.

There is too much slop between the locating pin and the upper receiver notch that the pin engages
so the barrel has rotated too far and the feed ramps are misaligned.

 

[supercorndogs]

The feed ramps in the upper receiver also don't line up in the other dimension. There is a bump at the transition from receiver to barrel extention with the barrel extention being lower than or closer to muzzle than the ramps in the upper receiver where they are supposed to mate up.

 

[hlee]

Align them in the rotational dimension, then use a chainsaw file to blend the receiver to the barrel extension…

 

[msgriff]

In addition to bedding, I would also lap the upper receiver face. It will also help make the barrel extension flush on the inside. Make sure that you have enough clearance between the barrel nut and the upper and don't take too much material off.

In addition to positioning the barrel extension correctly in relation to the upper when torqueing the barrel nut, the Midwest Ind. URR also acts as a gauge to check clocking. It's more reliable than just feed ramp alignment.

 

[supercorndogs]

In addition to bedding, I would also lap the upper receiver face. It will also help make the barrel extension flush on the inside. Make sure that you have enough clearance between the barrel nut and the upper and don't take too much material off.

In addition to positioning the barrel extension correctly in relation to the upper when torqueing the barrel nut, the Midwest Ind. URR also acts as a gauge to check clocking. It's more reliable than just feed ramp alignment.

To move the barrel back enough I am pretty sure the alignment groove would need to be cut deeper also. I know the picture is kind of crummy but you can see it has a long way to go. I don't know if the alignment groove is loose or just not aligned with the feed ramps but it is rotated a long way. One feed ramp is farther off than the other too. I am looking at all these peice and wondering where else is it not quite right.

I already tried bedding it to reduce the fliers.

 

[redneckbmxer24]

That’s definitely not ideal to have them misaligned but I don’t seem any copper deposits or anywhere that the bullet is dragging.

Was the fit sloppy when you put it together? What receiver and barrel?

 

[DHDeal]

Is it consistently throwing a particular shot during a string? I'm sure you've already checked clearances to include gas tube alignment.

I like my upper and lower to be tight and use a Accushim in all of them. I shim not "bed" all barrels and use either a Young Manufacturing NM or JP carrier and a heavy walled upper. I clean my rifles after shooting so the extra tightness does not matter as far as fouling is concerned (they are all shot suppressed). I also treat ammo loaded for my AR's the same as the ammo I load for benchrest rifles. Is this factory or your own reloaded ammo you are seeing flyers with?

I also tend to only use Proof, Bartlein, or when I'm slumming a Criterion barrels.

I won't say I never get a flyer but when I do I usually know why (me). I suspect you are doing some, if not all, of the tricks mentioned.

 

[supercorndogs]

That’s definitely not ideal to have them misaligned but I don’t seem any copper deposits or anywhere that the bullet is dragging.

Was the fit sloppy when you put it together? What receiver and barrel?

There was some copper but it was on the barrel extention feed ramp mainly on one side. You can see where it bit the nose of one bullet worse than the other. The extention to receiver bore was not tight. I am not sure about alignment groove to pin clearance.

AR stoner billet upper, Rainer ultramatch barrel.

I thought for a moment the line near the neck was from the feed ramp but I think it's on the side of the bullet based on the feed ramp marks. I think it's where the bullet rubbed the end of the chamber on the way out. OAL did not change from chamebering.

 

[redneckbmxer24]

I’d start by trying a different receiver and bedding it, my money would be on it causing the alignment issues. AR stone parts are not known for high quality.

 

[supercorndogs]

I’d start by trying a different receiver and bedding it, my money would be on it causing the alignment issues. AR stone parts are not known for high quality.

That was kind of the conclusion I had come to last night when I was looking it over. I was thinking of ditching the AR stoner handguard and its aluminum barrel nut as well.

I probably would have tried it sooner had I not already glued the barrel in.

I have already checked most everything else I can think of. I almost contacted Rainer but I just kept seeing several shots stacking close together like it wants to shoot.

The groups remind me a lot of a bolt action with a bedding problem. It might put two through the same hole way out of the group. Then return to stacking at POA. Then throw one out in a diffrent direction.

Even if it's not the "problem" this receiver with its problems and lack of forward assist seems like it's not worth messing with to me.

 

[DHDeal]

Depends on what your plans are for the rifle but since you have an above average barrel (IMHO since it's a Criterion chambered by Craddock per the rumor mill) I'd try another upper and still shim it (or bed it if you don't have shim stock).

I have 3 Ultramatch barrels and they all shoot very well. Regardless of how you feel about Rainier, the Ultramatch starts with a good blank chambered by a very good smith. I'd say your barrel is not the issue. The upper could be a better one. Not that you asked but CMC/Forward Contols Design uppers are heavier walled and so is the Iron City Hatchet. They have versions without a FA if that's your flavor. If you don't want to go that route, get a BCM upper which is a known thermal fit. I suspect that will help with the flyers.

The other stuff I mentioned is just what I do. I also lightly smooth the 2 lugs on the extension at 2 and 4 o'clock so my brass doesn't get the fang marks.

 

[redneckbmxer24]

That was kind of the conclusion I had come to last night when I was looking it over. I was thinking of ditching the AR stoner handguard and its aluminum barrel nut as well.

I probably would have tried it sooner had I not already glued the barrel in.

I have already checked most everything else I can think of. I almost contacted Rainer but I just kept seeing several shots stacking close together like it wants to shoot.

The groups remind me a lot of a bolt action with a bedding problem. It might put two through the same hole way out of the group. Then return to stacking at POA. Then throw one out in a diffrent direction.

Even if it's not the "problem" this receiver with its problems and lack of forward assist seems like it's not worth messing with to me.

Yeah you’re not doing yourself any favors with those parts. There have certainly been some bad Rainier barrels (I’ve gotten them) but generally you get a good barrel and if you get a bad one it just sprays with no consistency. I’m not saying it’s entirely impossible it could be the barrel but if I was going to start throwing parts at it I’d start with the receiver because it’s much more likely to be the problem and is the least expensive component. Worst case scenario it still doesn’t shoot you’ve eliminated that possibility and Rainier can replace the barrel.

There was a guy on here recently selling a Seekins receiver and handguard set for a decent deal. I forget if it was the IRMT version or not. If you’re going to replace both I’d go for something that the HG bolts directly to the receiver and not the barrel nut. The Mega is also very good.

 

[supercorndogs]

Yeah you’re not doing yourself any favors with those parts. There have certainly been some bad Rainier barrels (I’ve gotten them) but generally you get a good barrel and if you get a bad one it just sprays with no consistency. I’m not saying it’s entirely impossible it could be the barrel but if I was going to start throwing parts at it I’d start with the receiver because it’s much more likely to be the problem and is the least expensive component. Worst case scenario it still doesn’t shoot you’ve eliminated that possibility and Rainier can replace the barrel.

There was a guy on here recently selling a Seekins receiver and handguard set for a decent deal. I forget if it was the IRMT version or not. If you’re going to replace both I’d go for something that the HG bolts directly to the receiver and not the barrel nut. The Mega is also very good.

I have some BCM and RRA upper recivers laying around. I will probably put it in an RRA upper receiver and if it calms it down I will move it to a BCM thermal fit and add loctite.

 

[supercorndogs]

Anyone ever notice burned green loctite smells like blackcats.

 

[hlee]

Anyone ever notice burned green loctite smells like blackcats.

That’s just the vaporized carcinogens…

 

[redneckbmxer24]

You should wear a respirator any time you're heating up loctite. The toxins it puts off is some nasty shit.

 

[supercorndogs]

I found a bump on the inside of the left feed ramp. Looking at it closer I see one on the right feed ramp on the outside also.

 

[whatsupdoc]

The feed ramps in the upper receiver also don't line up in the other dimension. There is a bump at the transition from receiver to barrel extention with the barrel extention being lower than or closer to muzzle than the ramps in the upper receiver where they are supposed to mate up.

As long as the barrel extension feed ramps are not protruding past the upper ramps you are good.

Another issue I have encountered when the barrel extension is out of time is the bolt lug edges will
get shaved by the barrel extension lugs.

 

[supercorndogs]

Yikes. I think I got it figured out. It's no wonder I didn't notice those bumps when I assembled. I dont think they were there. I think the barrel extention is de-forming. I can feel where the lugs deformed the extention when I insert the bolt and turn it. I can feel the diffrence between the two barrels. And obviously the backside of the extention should be flat.

I had it all the way back together to.
Then decided to take apart again to get a better look at the feed ramps. I was thinking about just reshaping them but noticed on the first one material from behind is gone. Stuff that would be there is the high spots were left by a cut somehow.

Then I kind of remembered there might have been another thread on here with a Rainer UM with soft barrel extention doing the same thing. Now I guess I gotta contact Rainer. At least I can quit wasting ammo trying to figure it out.

 

[whatsupdoc]

Likely due to the extension being out of time and the bolt lugs were striking the extension lugs on extraction.
Check the bolt lugs for damage.

 

[supercorndogs]

I am not sure I think that's what is happening. The deformations seem to me to be where the bolt is in battery. And are also on the same side the reciver is canted to. Or am I looking at this all wrong?

 

[supercorndogs]

There are a few more pictures above I didn't add to post that can be clicked on as well as a few more below of stuff.

 

[supercorndogs]

I don't see damage to the bolt lugs.

Am I way off in the weeds thinking this is caused by a soft barrel extention? Is this purely a mistimed barrel extention problem? And the deformation is located there because the bolt is clocked to far, then starts moving back before it fully unlocks.

I haven't had any feeding or ejection problems. It's probably has 250-300 rounds.

I would appreciate getting en education here. I just wanted to put as much info up as I could, as well as give what I though about what I was looking at. I have never seen something like this before.

 

[whatsupdoc]

Bolt does look fine, at this point I would just send that barrel back and see what the MFG will do for you.

 

[supercorndogs]

I contacted Rainer and they want the entire upper. They said kind of the same thing about the barrel extention timing. And the lugs beating it up. I thought they meant denting them hitting them on the way in. I will have to go reread the emails.

I offered to send them the barrel, and bolt and/or upper reciver or everything. I told them I don't want reuse the AR stoner upper receiver so I didn't see the point in sending it all. I will see what they say. I had several emails back and forth with them today. The last one probably went out after closing time. They offered to send me a shipping label. Also.

In later news I haven't shot my Grendel in A while.

 

[whatsupdoc]

Regardless of what upper I use shimming the extension locating pin is standard operating procedure.
I simply cut and wrap a piece of shim stock around the pin.

A few years ago I got a hold of an AR stoner complete upper, I cut off the A front sight post, bonded the barrel to the upper and
put a free floating hand guard on it. That POS upper would put 10 rounds into 5 inches at 380 yards and
never ever had a single malfunction of any kind in over 5K rounds. I gave it away only because it was an AR stoner.

 

[natdscott]

Align them in the rotational dimension, then use a chainsaw file to blend the receiver to the barrel extension…

GaSP!!! A FILE?!! on my RIFLE?!

hehehe. Yeah, they also happen to be about the right diameter.

Hey, I know! We could start a flame thread about whether Stihl, Husky, or Oregon files are best!

In addition to bedding, I would also lap the upper receiver face. It will also help make the barrel extension flush on the inside. Make sure that you have enough clearance between the barrel nut and the upper and don't take too much material off.

I was gonna troll you about lapping, but for that specific purpose, it makes some sense.

OP: basically, don't lap the face of an AR beyond the point where there's still a little anodizing left in spots. If it "needed" more than that, it needed a jig and lathe. And they never need that much.

 

[redneckbmxer24]

I’d cut my losses and buy that Seekins 6 ARC in the classifieds and not worry about anything.

 

[supercorndogs]

I would hate to cut my losses on a 400 dollar barrel with 300 rounds through it. Again.


Code silence after I sent them.what they asked for. No shipping label or response yet.

I am not 100% where I should stand here. If the damage is from barrel clocking, It's my fault for building and shooting it like that.

If it's the barrel extention then it's Rainers baby. The barrel extention being the actual problem seems like a long shot the more I think about it. Like bad batches of steel. There are pretty low odds there would be just 1 and I would be the first to find it.

If it's the upper receiver. I should probably get midway in the mix. I have another of their thick walled billet upper recivers on a good shooting WOA barrel. I would bet they will replace this reciver.

 

[supercorndogs]

Ok I have been messing with it again. The locating pin slot is not loose. The location is not off. I think the feed ramps were just cut funky.

 

[whatsupdoc]

With the pin centered how do the feed ramps align.

Rotate the barrel clockwise from the front and check the alignment again.

 

[supercorndogs]

With the pin centered how do the feed ramps align.

Rotate the barrel clockwise from the front and check the alignment again.

You can't rotate the barrel in the receiver. It fits tight in the groove. The alignment is still the same as the first picture. The reciver seems GTG besides the crummy feed ramp cuts.

Rainer is sending me an RMA to send it in and they are going to replace the barrel. They want the complete upper so they can test fire it before sending it back.

 

[LRRPF52]

There was some copper but it was on the barrel extention feed ramp mainly on one side. You can see where it bit the nose of one bullet worse than the other. The extention to receiver bore was not tight. I am not sure about alignment groove to pin clearance.

AR stoner billet upper, Rainer ultramatch barrel.

I thought for a moment the line near the neck was from the feed ramp but I think it's on the side of the bullet based on the feed ramp marks. I think it's where the bullet rubbed the end of the chamber on the way out. OAL did not change from chamebering.

From Midway’s site:

• Machined From Solid 6061-T6 Aluminum

If it says “AR-Stoner”, I avoid the parts as a rule based on past experience and the experience of many others. AR-Stoner is often re-branded low price point excrement marketing by Midway as their house brand. I love Midway and have ordered from them for decades, but I must dispassionately call out trash parts when I see them.

You basically installed custom headers onto a refurbished junkyard engine block off a Yugo.

One thing I do to barrel extensions, if they haven’t been tumble-polished by the barrel-maker, is de-edge, blend, and polish the feed ramps. Only do this if you are moderately mechanically-inclined. Especially if you reload and want lots of life out of valuable brass, you’ll want the sharp edges removed from the barrel extension, bolt, and magazines if present. You want smooth transition for your brass out of the fee lips, up the ramp, and into the chamber.

I also bed the barrel into the upper before torquing the barrel nut, letting the sealant set and dry before applying torque, with the nut holding the flange securely to the upper receiver face. This ensures the extension and barrel are properly clocked and can’t be turned out of TDC when torque is applied.

I do this after trouble-shooting the bolt articulation into the extension in positions of function. The way I assemble an upper today feels entirely different than when I just bashed parts together 20-30 years ago for M4orgeries.

 

[mettee]

Hey, I know! We could start a flame thread about whether Stihl, Husky, or Oregon files are best!

Vallorbe

 

[supercorndogs]

From Midway’s site:

• Machined From Solid 6061-T6 Aluminum

If it says “AR-Stoner”, I avoid the parts as a rule based on past experience and the experience of many others. AR-Stoner is often re-branded low price point excrement marketing by Midway as their house brand. I love Midway and have ordered from them for decades, but I must dispassionately call out trash parts when I see them.

You basically installed a custom headers onto a refurbished junkyard engine block off a Yugo.

One thing I do to barrel extensions, if they haven’t been tumble-polished by the barrel-maker, is de-edge, blend, and polish the feed ramps. Only do this if you are moderately mechanically-inclined. Especially if you reload and want lots of life out of valuable brass, you’ll want the sharp edges removed from the barrel extension, bolt, and magazines if present. You want smooth transition for your brass out of the fee lips, up the ramp, and into the chamber.

I also bed the barrel into the upper before torquing the barrel nut, letting the sealant set and dry before applying torque, with the nut holding the flange securely to the upper receiver face. This ensures the extension and barrel are properly clocked and can’t be turned out of TDC when torque is applied.

I do this after trouble-shooting the bolt articulation into the extension in positions of function. The way I assemble an upper today feels entirely different than when I just bashed parts together 20-30 years ago for M4orgeries.

The barrel appears to be the problem though. I wouldn't have reservations reusing the receiver now that I have looked it over. I want forward assist on this rifle though.

 

[supercorndogs]

Rainer is sending me a new barrel. Sounds like I should have it this week to the middle of next week.

 

[natdscott]

Rainer is sending me a new barrel. Sounds like I should have it this week to the middle of next week.

Well, since that's settled, I'll relate this:

https://forum.accurateshooter.com/threads/rainier-arms-customer-service.3927816/

 

[357Max]

Rainer is sending me a new barrel. Sounds like I should have it this week to the middle of next week.

They replaced mine for the same reason. Soft extension. Head space opened up .013" & that was checking with a new JP bolt. 22" ultra match.
FYI - My maxim bolt looked perfect, but it wasn't. I would strongly suggest a new bolt for the replacement barrel.

 

[supercorndogs]

They replaced mine for the same reason. Soft extension. Head space opened up .013" & that was checking with a new JP bolt. 22" ultra match.
FYI - My maxim bolt looked perfect, but it wasn't. I would strongly suggest a new bolt for the replacement barrel.

How many rounds? You can see a definite wear pattern on my bolt. I havent measured any brass yet to see how far back I am pushing the shoulders now.

I thought I saw another soft barrel extention thread on a Rainer UM. It's too bad too because the barrel seemed like it wanted to shoot pretty well and cleaned up like a dream. Oh well, hope my old brass still fits.

 

[mtrmn]

Hey, I know! We could start a flame thread about whether Stihl, Husky, or Oregon files are best!

Pferd

 

[357Max]

How many rounds? You can see a definite wear pattern on my bolt. I havent measured any brass yet to see how far back I am pushing the shoulders now.

I thought I saw another soft barrel extention thread on a Rainer UM. It's too bad too because the barrel seemed like it wanted to shoot pretty well and cleaned up like a dream. Oh well, hope my old brass still fits.

Update to my previous posts about the lug set back on the Rainier UM barrel. Rainier agreed the extension was soft.
Under 500 rounds. Below shows the contrast between the unused extractor lug vs. what all the others looked like @ +.013 head space.

Had closer to 400 rounds on it. Bolt was trash. Had to push shoulders back .016 to chamber in new barrel.

I just recently put the replacement barrel on. Only 40 rounds so far. Will be keeping an eye on head space.

Also have a new Centurion 18" +1" gas 6 ARC that I'll build soon.

 

[supercorndogs]

I received my barrel yesterday. Headspace is shorter than when I set my die on the last one. So I have been decapping and sizing my primed brass. I tried pulling the decapping rod out of a 6.5 grendel die to size my loaded ammo but it wont bump the shoulders enough. I could modify my extra die, but it's probably not worth it to avoid pulling down 15rds. Lol

There was a miscommunication somewhere and they put it all back together in the AR stoner set. I pulled it back apart and used a diffrent receiver and handguard. I was going to replace the bolt but they already test fired it with the old bolt.

I still might replace it before I go shoot it.

 

[supercorndogs]

I put 20rds through it and the barrel extention on the new barrel is already deforming like the old one.

 

[LRRPF52]

I put 20rds through it and the barrel extention on the new barrel is already deforming like the old one.

Can you point to where you’re seeing the deformation because I’m not seeing it.

 

[Rocketvapor]

The Heavy walled Stoner upper is a probably a BCA.
They make rear charge, right charge and left charge.
I got a dual right/rear charge upper I haven't used yet.
Many don't like BCA stuff but I have SEVERAL of their upper receivers.
I haven't run into one with a clocking error.
I do face them off a little.
The Right Side Charging upper is $99, with a BCG.
I like the extra support the heavy walled upper gives to a 28" bull barrel.

Not as tight as some, so I use my spray on shim.
Working on load (still, forever ) but I'm pretty close to an MOA @ 600.
I'm sure I would do better with a high end upper.

 

[supercorndogs]

Can you point to where you’re seeing the deformation because I’m not seeing it.

Same places as the first barrel. They just aren't as pronounced yet. Top right sides of the feed ramps where the lugs lock into battery.

 

[supercorndogs]

Here is what it should look like on one side vs the other.

 

[Ernest 5.56]

What is that? Shavings from the lugs

 

[supercorndogs]

Probably paper towel from wiping the feed ramps clean.