AR feed ramps possibly scratching the bullet?


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ChCx2744
November 17, 2012, 09:41 PM
Hello. I have a question about my AR when I load a round. When I load a round into the chamber, something in the feed ramp or chamber area puts a scratch or two on the bullet. I'm not sure if it's the feed ramps doing the scratching or the chamber, but the bullet gets scratched and it happens each time I load a round, I think even when the gun cycles with every round. This doesn't affect the gun's performance in any way, but I'm curious if these scratches could cause any difference in accuracy, the bullet's trajectory or velocity? I don't know if the scratches are deep enough to cause any noticeable changes, but it's a rifle and accuracy is paramount to me. There should be pictures at the bottom. Also, be advised, that the scratches you see in the picture are only the length of the scratches, closer to the tip of the bullet under the left scratch is a large, serrated gash that you can't see. Any advice or information is appreciated.

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rcmodel
November 17, 2012, 11:06 PM
It's not the feed ramps.

It's the sharp edges on the barrel extension locking lugs.
I even think I see brass tracks in a place or two on them.

A different magazine that feeds right might be all you need to stop it.

rc

ApacheCoTodd
November 18, 2012, 01:29 AM
I'd be more concerned initially with the magazine as well.
Do you get scratches out of both left and right side feeds?
Show us the "gash" in a photo.

Can the scratches effect accuracy? Sure, but that's assuming every other variable as at it's peak first so on a practical level - not so much.

Walkalong
November 18, 2012, 10:32 AM
It's the sharp edges on the barrel extension locking lugs.Yep.
Can the scratches effect accuracy? Virtually none. You will never be able to prove a difference. Besides, 55 Gr FMJ isn't match quality anyway, not even close.

You can smooth off that front edge that the bullet is hitting, as it isn't the "working" edge of the barrel extension.

ChCx2744
November 18, 2012, 04:26 PM
I'm using Magpul Pmags. I'll see if it's only one side or the other ramp. I'll try to take a pic of the gash.

rcmodel
November 18, 2012, 04:38 PM
If you look at your barrel extension picture?

You can see brass tracks on the sharp edge of the lower left lug, right above the left feed ramp.

And matching brass tracks on the top right section of the barrel face where they are deflecting off the lug after scraping it and hitting the barrel face.

Thats not good, as it can drive bullets deeper in the cases and cause pressure problems.

rc

ChCx2744
November 18, 2012, 09:22 PM
Apparently this is not normal then...I would prefer not to do any removal of metal, even sanding or buffing something down...I'm no expert in either. What can I do to fix this? :confused:

rcmodel
November 19, 2012, 02:15 PM
First thing to do is buy a mil-spec aluminum 20 round magazine from Brownell's or Colt to rule out the P-Mags not feeding properly.

http://www.brownells.com/magazines/rifle-magazines/magazines/ar-15-m16-20-30-round-magazines-prod21225.aspx

If that doesn't work, then you have two options.

1. Send it back to whoever made it for warrenty repair.

2. Stone & Polish the sharp edge off the locking lug that is doing it.

Sometimes you just gotta do what you just gotta do.

rc

taliv
November 19, 2012, 02:59 PM
it is highly unlikely that the bullet is getting scratched on its way into the chamber

far more likely, it's getting scratched when you extract it, as the ejector spring pushes the bullet against the side of the lugs

test this by chambering a round as normal. now slowly pull the charging handle and as soon as you can see the case, stick your finger against it to counteract the force of the ejector. push on it to keep the case straight until fully extracted.

ChCx2744
November 19, 2012, 05:38 PM
rcmodel
2. Stone & Polish the sharp edge off the locking lug that is doing it.

Sorry if this is going to be an inconvenience to you, but could you perhaps save my picture and kinda like, label the areas I need to work on in Microsoft Paint or something real quick? lol I don't exactly know what areas I need to smooth out. :o

taliv
far more likely, it's getting scratched when you extract it, as the ejector spring pushes the bullet against the side of the lugs

test this by chambering a round as normal. now slowly pull the charging handle and as soon as you can see the case, stick your finger against it to counteract the force of the ejector. push on it to keep the case straight until fully extracted.

I tried this just now and it's definitely when I chamber it, not when it extracts. Something is scratching it when the round actually gets chambered.

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