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Big bore ar 15 round cycling


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So, I got my replacement 458 upper, slapped it on a lower and went to the range. Well, it shoots, but it doesnt chamber the next round. Do I need a heavier buffer weight and stronger spring? Anyone ran into this type of issue before?

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Are you using factory ammo? Carbine length gas? I use a standard spring and buffer in mine. Never a problem cycling.

 

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Really need more info. Ejecting and bolt closes on empty chamber? Round halfway in the chamber? Bolts closed 95% . Did you half moon your steel mag? 

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Im running a carbine length gas tube. The bolt will eject the spend casing but only push the new round half way. I been using black butterfly 350 grain ammo to try out the rifle. As far as the half moon thing? No idea. The mags I got are made specifically for 458 socom. 

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Screenshot-20210606-072823-Chrome.jpgI had no idea they were making them now. We did it ourselves. It sounds under gassed. Are the spent cases thrown far from the gun? 

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If you only load one round in the mag will it lock the bolt back? Easiest way to tell if it's under gassed.

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The 458 specific mags are new to me too.

I have mags in an ammo can that run fine but don't remember what they are. More than likely surplus GI mags.

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I just use Lancer mags in mine. My upper is an RRA. Never had a feed problem, even with 500 grain subs. 

Does your feed ramp look like this?

IMG_5969.jpg

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Here is one of my stock Lancer mags with a couple of hand loads. My Lancer mags have fed a large variety of loads, both factory and hand loads.

IMG_5971.jpg

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This is what keeps happening. Sometimes, it will cycle the next round fine, but most of the time, I hangs half way.

 

And yes, the feed ramp looks like the picture mike posted.

20210606_151917.jpg

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1 hour ago, RC3 said:

This is what keeps happening. Sometimes, it will cycle the next round fine, but most of the time, I hangs half way.

 

And yes, the feed ramp looks like the picture mike posted.

20210606_151917.jpg

Are there scratches on the case where the ramp hits, if so you need to polish the ramp a bit.

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5 hours ago, RC3 said:

This is what keeps happening. Sometimes, it will cycle the next round fine, but most of the time, I hangs half way.

 

And yes, the feed ramp looks like the picture mike posted.

20210606_151917.jpg

Who made the upper? You may have an issue in the barrel assembly. I can't imagine the case not being scratched up when that happens. Red's right. It will give clues.

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5 hours ago, RED333 said:

Are there scratches on the case where the ramp hits, if so you need to polish the ramp a bit.

 

scratches and dents on the casing

 

55 minutes ago, mikegideon said:

Who made the upper? You may have an issue in the barrel assembly. I can't imagine the case not being scratched up when that happens. Red's right. It will give clues.

bear creek arsenal. This is a replacement upper

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Have you tried different mags/brand of mags?

Something differently not right with that. Looks like the round not getting to the bolt face properly.

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3 minutes ago, DWARREN123 said:

Have you tried different mags/brand of mags?

Something differently not right with that. Looks like the round not getting to the bolt face properly.

The only mags I have are the ones bear creek offered on their website. They are D&H mags. I never had a single issue out of the 5.56 mags from d&h before, but I will look into a replacement mag and see if that fixes the issue.

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25 minutes ago, RC3 said:

 

scratches and dents on the casing

 

bear creek arsenal. This is a replacement upper

I was really hoping you would say Tromix 🙂 

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4 minutes ago, mikegideon said:

I was really hoping you would say Tromix 🙂 

I been wanting to build a 458 for YEARS. When  I finally decided to build the damn thing, nothing but issues. I may just asked them to swap it out for a 5.56 upper. THOSE never gave me issues. Im just going to go and get an AR 10 instead. Got a bunch of left over 308 from the prt 91's and fal.

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1 minute ago, RC3 said:

I been wanting to build a 458 for YEARS. When  I finally decided to build the damn thing, nothing but issues. I may just asked them to swap it out for a 5.56 upper. THOSE never gave me issues. Im just going to go and get an AR 10 instead. Got a bunch of left over 308 from the prt 91's and fal.

I love the caliber.  But, there are some pitfalls to the build. My RRA upper was flawless. And Tony Rumore (Tromix) in Tulsa built the prototype.

I don't know Bear Creek. I do know that you can't go wrong with Tromix. I bought my RRA probably 10 years ago. They still make the uppers too.

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The barrel extension and feed ramps is your problem. It is pretty much a given with Bear Creek, Radical, and a few others.  Very few work without some significant modification/rework. 

You can a) try to return/replace it with a caliber they do not have issues with. b) send it to someone to rework like https://www.warrdogz.com/ who has a ton of experience getting 458 uppers feeding and cycling correctly. c) remove the bear creek barrel and bolt and buy a Tromix barrel and bolt to replace it. d) take your chances with your own handwork and hope you have a good touch with a dermel. 

I have a working Bear Creek side charging 458 upper. It did not work out of the box. It took some deburring, polishing, and break in to get it cycling somewhat reliably. My Tromix barreled upper I put together had no such issues and will eat anything I feed it straight out of the box. The Tromix barrel replaced my first Radical 458 barrel that was absolute junk. 

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Posted (edited)
4 hours ago, OldIronFan said:

The barrel extension and feed ramps is your problem. It is pretty much a given with Bear Creek, Radical, and a few others.  Very few work without some significant modification/rework. 

You can a) try to return/replace it with a caliber they do not have issues with. b) send it to someone to rework like https://www.warrdogz.com/ who has a ton of experience getting 458 uppers feeding and cycling correctly. c) remove the bear creek barrel and bolt and buy a Tromix barrel and bolt to replace it. d) take your chances with your own handwork and hope you have a good touch with a dermel. 

I have a working Bear Creek side charging 458 upper. It did not work out of the box. It took some deburring, polishing, and break in to get it cycling somewhat reliably. My Tromix barreled upper I put together had no such issues and will eat anything I feed it straight out of the box. The Tromix barrel replaced my first Radical 458 barrel that was absolute junk. 

Thanks for the heads up So, for an extra 355 bucks, I can get a working 458 upper? https://tromix.com/product/458-barrel-bolt-combo/

If I swap out the barrel and bolt, everything should work again right?

Edited by RC3
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I have two 458 barrels. One I got from Marty Tee Weeme. It's a 6.5". That upper is perfect. I later got an 11.5" from someone else. They never removed the lug at 6 o'clock. After I fixed that, it shot great for a while. The guy had a custom reamer made for the first gen starline brass. After starline increased the neck thickness on the 458, the gun would cycle subs. That chamber was a fitted chamber at that point. I had to have the chamber re-cut. The 458 is a hammer, but can be a pita.

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2 hours ago, RC3 said:

Thanks for the heads up So, for an extra 355 bucks, I can get a working 458 upper? https://tromix.com/product/458-barrel-bolt-combo/

If I swap out the barrel and bolt, everything should work again right?

That is certainly a good option. Tromix is the gold standard for the .458 SOCOM caliber. 
It is not a cheap or easy pill to swallow though. 

The rework from someone like WarDogz or another qualified smith is less expensive (in the $200 range last time I checked) and will likely yield positive results. There is the risk they come back to you and say there is a need to spend additional dollars on parts though if the bolt or extension is not viable to rework (this is not as likely but certainly possible) 

You can always try to do the rework yourself (deburr or smooth lugs/ramps and polish chamber) knowing that if you gack something up you may have to replace the barrel anyway. 

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52 minutes ago, alleycat72 said:

I have two 458 barrels. One I got from Marty Tee Weeme. It's a 6.5". That upper is perfect. I later got an 11.5" from someone else. They never removed the lug at 6 o'clock. After I fixed that, it shot great for a while. The guy had a custom reamer made for the first gen starline brass. After starline increased the neck thickness on the 458, the gun would cycle subs. That chamber was a fitted chamber at that point. I had to have the chamber re-cut. The 458 is a hammer, but can be a pita.

Marty was a good source. He's the daddy of the caliber. Rock River always did a good job too. They can just make you wait for months.

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Back in the day, Marty wouldn’t sell a barrel  without a corresponding bolt that was matched to headspace correctly.

I think both my .458 SOCOM and .338 Spectre barrels were sold as a pair with a bolt.

 

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Posted (edited)
43 minutes ago, OldIronFan said:

That is certainly a good option. Tromix is the gold standard for the .458 SOCOM caliber. 
It is not a cheap or easy pill to swallow though. 

The rework from someone like WarDogz or another qualified smith is less expensive (in the $200 range last time I checked) and will likely yield positive results. There is the risk they come back to you and say there is a need to spend additional dollars on parts though if the bolt or extension is not viable to rework (this is not as likely but certainly possible) 

You can always try to do the rework yourself (deburr or smooth lugs/ramps and polish chamber) knowing that if you gack something up you may have to replace the barrel anyway. 

Yeah, thats a negative on doing the work myself with a dremel. Might as well replace the barrel and bolt then. I just dont want to spend another $355 plus on something again and have it not work reliably.

Edited by RC3
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