BCM Receiver Extension Question

[captdreifus]

So I was doing my monthly AR checkup today, being a holiday and all. I noticed on one of my factory BCM lowers that the RE has several "cracks" or machining marks all around it. I wiped down the RE with CLP and the lines did not go away, as I thought it was plastic shavings from the stock. Will this cause problems down the line? I'll try to affix a picture. The lines do no look very deep but has the markings on the entire circumference of the RE.

57481


Thanks for your input. Enjoy your Memorial Day.

Updated with clearer picture.

57482


****UPDATE****

After several e-mails back and forth of me asking questions, BCM sent me a shipping label (2 day UPS) to have the lower inspected. The lower was at BCM for approximately one day, and they had fixed the issue.

I sent an e-mail and inquired what had been done. BCM stated that the original RE was in spec but they had switched it out for another. I also had a Troy sling mount attached to the RE which the allen bolt was rounded. They removed it. They also installed their QD endplate for me.

Basically BCM went above and beyond to put my mind at ease. I can't thank them enough.

[wigbones]

It's a little hard to tell from the pictures but it doesn't look like anything that would cause problems.

[captdreifus]

The speckles in the red circle are small "cracks" /lines.

[lsllc]

If they were cracks it would be a major concern. But I can’t identify any cracks. What it looks like is anodizing. I think it would be prudent to upload better photos perhaps. Drag your fingernail across, can you catch your nail on them?


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[captdreifus]

Updated OP with new picture.

[RHINOWSO]

Call BCM and cutout the middle man.

[captdreifus]

I was going to contact BCM if it was indeed a problem. Wanted to verify on here first that it was a problem. Could be normal for all I know.

[GH41]

Call BCM and cutout the middle man.

Per the rules he should have done that before naming names.

[AKDoug]

Piss poor extrusion. I doubt they are very deep and probably won't effect performance, but still not good.

[MSW]

Piss poor extrusion. I doubt they are very deep and probably won't effect performance, but still not good.

I thought mil-spec are machined, not extruded?

[AKDoug]

I thought mil-spec are machined, not extruded?

From what I've read, I believe that mil-spec is hammer extruded.. kinda like a hammer forged barrel. I could be wrong, though.

[AKDoug]

I thought mil-spec are machined, not extruded?

Did a little more research. One source says Colts' are forged then machined. That might explain why this one looks like it the victim of galling from the machining process.

[captdreifus]

Obviously I’m a long time lurker and did not follow the rules. I contacted BCM and we shall see what they have to say.

[MSW]

Did a little more research. One source says Colts' are forged then machined. That might explain why this one looks like it the victim of galling from the machining process.

Thank you. The forging, then machining would explain the cracks. Good to know.

[sgtrock82]

I have a vltor RE that has the same tiny cracks. I got it many years ago during one of the great "panics". It didnt see much use being on a back up gun but now resides in the spares bin. I always wondered if this was a serious defect, finding a replacement at the time was problematic so I went with it till I could replace it.

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[hk_shootr]

I don't see cracks. I see voids from the forging process, would suspect the extension was too cool. When the billet or dies are not hot enough, the alloy is not as mailable, it starts to tear. It’s quite possible these are the marks you are seeing.

[bamashooter]

Obviously I’m a long time lurker and did not follow the rules. I contacted BCM and we shall see what they have to say.

Looks minor to nothing to me. I'm sure you did the right thing contacting BCM. BTW, I can't find any rule violation. I find the rules but not one that would have been violated short of of a very, very, loose interpretation.* I see you posting an observation, asking for other to take a look. Would like to see the specific rule please. Thanks.

* "4) Contact The Manufacturer or Dealer First – Internet forums have a large global audience and unsubstantiated or ill-informed comments will affect the livelihoods of a lot of hard working people in the industry. If you have an issue with a manufacturer or dealer that you would like to resolve, we ask that your first contact them to resolve it."

[556Cliff]

Milspec receiver extensions are hammer extruded, I'm not sure if that's a type of forging or not.

There was a video of the process somewhere on YouTube showing Colt carbine REs being hammer extruded.

[tehpwnag3]

I have to agree. Those marks are in the tube, not the anodizing. Seen it before .


Piss poor extrusion. I doubt they are very deep and probably won't effect performance, but still not good.

[tehpwnag3]

I can't find the video but it was a surprisingly quick process, and worth posting in this thread for all to see.


Milspec receiver extensions are hammer extruded, I'm not sure if that's a type of forging or not.

There was a video of the process somewhere on YouTube showing Colt carbine REs being hammer extruded.

[Sry0fcr]

I don't see cracks. I see voids from the forging process, would suspect the extension was too cool. When the billet or dies are not hot enough, the alloy is not as mailable, it starts to tear. It’s quite possible these are the marks you are seeing.

I'm seeing voids as well. Would not pass muster in any of my shops.

[CPM]

Nope.

[556Cliff]

I can't find the video but it was a surprisingly quick process, and worth posting in this thread for all to see.

I think I found the video. > https://www.youtube.com/watch?v=QG_RswsPCjo

[lsllc]

Second photo is much more clear. Looks like that’s a bad forging. Contact customer service.


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[tehpwnag3]

The one I recall was a horizontal fixture, but the end result was the same. Thanks for posting that!


I think I found the video. > https://www.youtube.com/watch?v=QG_RswsPCjo

[sgtrock82]

I don't see cracks. I see voids from the forging process, would suspect the extension was too cool. When the billet or dies are not hot enough, the alloy is not as mailable, it starts to tear. It’s quite possible these are the marks you are seeing.Thank you, "voids" is a much better word choice
I think I found the video. > https://www.youtube.com/watch?v=QG_RswsPCjoFascinating! Thanks for posting this video, not at all how I thought it might work.

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[Iraqgunz]

Closed until the OP reports back from BCM.

[captdreifus]

See OP for update. BCM is awesome!!!