Need some help, do I have a problem here?

[Tpb10505]

I posted this on AR15.com but didn't get much of a response so maybe you guys can help

Okay so I put a Rainier Arms 18" SPR barrel on my Mega upper and took it to the range for the first time yesterday. I didn't have any malfunctions after tuning the JP gas block but noticed this on ejected rounds I didn't fire. Here's a few I cycled through after I got home.... I realize I could probably easily fix this myself with some smoothing, but I'd rather have Rainier fix it if its something that came from them. Here are some pics...

On rounds cycled by firing, the bullet has two bilateral gouges which I think originate from the difference in the base of the barrel feed ramps and that of the upper.

What do ya'll think? I appreciate any help

(Side note: the barrel has M4 feed ramps, and the upper is supposed to work with any barrel. Two of the bullets have been pushed back into the case by getting caught on the ramps from manually cycling to provide examples of the damage to the bullet.)

 

[Spiff]

No problem, that's normal. They're not getting scratched on the way in, they're getting scratched on the extension lugs when you extract them. Every AR should do this.

 

[Eellis]

Man I had something similar with mine. I replaced the gas tube ,extractor spring and the gas rings . I don't know which one fixed it but shoots great now. Do you have an extra bcg to try and narrow down the problems?

 

[Chambers]

Spiff said it.

 

[Tpb10505]

I have a JP bolt, captured spring and adjustable gas tube... none of which I care to replace lol. I did talk to someone at Rainier that said he had the same barrel and his did that but went away with use. Other than that it runs. I think its doing just over 1 MOA at 100. I plan to load for it when I can get new dies. I'm pretty new to the AR so I apologize if it was a silly question lol. Thanks all for being so helpful

 

[jtischauser]

No problem, that's normal. They're not getting scratched on the way in, they're getting scratched on the extension lugs when you extract them. Every AR should do this.

Do they tilt in the bolt face on the way out or what? I had a barrel that did this but not all barrels do it. What's up with that?

 

[Spiff]

Do they tilt in the bolt face on the way out or what? I had a barrel that did this but not all barrels do it. What's up with that?

Yeah, as soon as the chamber has enough room it starts pivoting around the extractor because the ejector is pushing on the other side.

 

[jtischauser]

So are they hitting the lugs on the ejection port side then?

 

[Eellis]

No problem, that's normal. They're not getting scratched on the way in, they're getting scratched on the extension lugs when you extract them. Every AR should do this.

. If they are not hittin on the way in then what is jamming the bullet back into the casing. I'm just curious I really have know idea. Warning I'm by no means a gunsmith. That's my disclosure statement.

 

[Spiff]

So are they hitting the lugs on the ejection port side then?

Yep!

 

[Spiff]

. If they are not hittin on the way in then what is jamming the bullet back into the casing. I'm just curious I really have know idea. Warning I'm by no means a gunsmith. That's my disclosure statement.

Sorry, I was rocking some speed reading and completely skipped that part. Those rounds do appear to be pushed in more than I would consider normal (I think any pushing in is abnormal on an AR, but I don't know that for a fact.) At a glance of your picture, it appears that you have rifle feed ramps on the barrel extension and m4 feed ramps on the upper which is kind of a no-no. Check out this image for me and verify if that's what's going on. It could probably be fixed rather handily with a dremel, but that's probably not what you want to do.

http://imageshack.us/photo/my-images/440/feedramps2.jpg/sr=1

 

[Chambers]

Factory ammo?

 

[Eellis]

my m4 ramps look like this. I don't know if it makes a difference but yours don't look like they are lined up properly? Alright everybody check your rifles!

 

[Wall]

At a glance of your picture, it appears that you have rifle feed ramps on the barrel extension and m4 feed ramps on the upper which is kind of a no-no. Check out this image for me and verify if that's what's going on. It could probably be fixed rather handily with a dremel, but that's probably not what you want to do.

http://imageshack.us...ramps2.jpg/sr=1

It looks like an M4 Extension to me.

 

[Eellis]

Sorry spiff I'm to slow. But I agree.

 

[Spiff]

You can't out-post a Semi-Pro!

 

[Tpb10505]

The website says the extensions are M4, but they clearly don't line up... I think the ones that are pushed back were from me manually cycling the bolt and it not having enough force to chamber the first "try". From the rounds cycled by firing, I don't think the feed ramps are an issue now knowing those gouges are from the lugs on exit. But I still wish the extensions lined up, dont really know what to do since everything seems to be working fine otherwise.

 

[Tpb10505]

Also, i manually chambered a round by using my finger and the bullet doesnt even come close to contacting the bottom of the extension where there is a difference in contour, so I don't think its something I should worry about

 

[Eellis]

If it shoots fine then I don't see a problem.

 

[Matt1911]

You say it runs fine so if it ain't broke, don't fix it.
I had rifle feed ramps in an M4 cut upper in my first AR and ran a couple thousand rounds through it without issue.