I've had my M&P 10 for a year and a half or so, I have no feed or injection issues, if functions very well. It has a Magpul PRS stock and once I got the buffer spring and buffer worked out it's
extremely smooth.
I am getting, on every round, these marks. It's hard to get a good photo of them but maybe these will show it. They seem to be superficial and once they go through the ultrasonic cleaner and press they are gone. Just wonder what causes them. My ejector spring seems really strong, rounds go 8 to 10 feet in a fairly
predictable pattern. Happens no matter what magazine I use, and all brass equally. I'm sure I'm not the only one seeing this, if it's been answered before please point me to the right post.
Thanks in advance for any ideas.
Bruce

Yes, assuming you're asking about the neck marks. I don't have the "straight line marks" your pictures show but I do have the dings. Guessing they're from hitting the deflector on ejection but not entirely sure.

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Webfarmer

Mag lips or bbl extension.
When being fed.

Thanks for both comments, seems to happen with both the factory steel mag and the magpul mag, have to check that again. If it's the feed ramps have to assume there is a bur somewhere. Will look there next. That extractor spring seems
really strong, anyone modified it or changed the factory one? 10+ feet seems farther than necessary, though not as bad as the PTR 91....

Yep, feed ramp(s). On my AR, the left feed ramp needed extra work but I did both. The biggest problem is at the rear of the ramps where it meets the channels for the bolt. (Whatever they're called.) Also the chamber is probably rough and putting more down force on the round as the bolt slams it home. Mine was bending the bullet and jamming on short Remington brand .223 FMJ rounds on the left ramp but had no problem with longer Rem. Fusion rounds. They still had the scratches though.

The scratches on your shell don't look too bad but they shouldn't be there. Mine was even bending the cases. The photo below was taken to show the bending but there were deep scratches on it also.

Attached Images

Bullet-1.jpg (19.5 KB, 56 views)

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Si vis pacem para bellum.

Thanks Tinhack. I have some good magnification lenses (comes with being a Dentist who, at over 65, needs the extra magnification!) and should be able to get in there and see what's happening. Also some good photo lenses from work that can show it. If I find anything worth posting will do so. Appreciate the comments. I've been ignoring the nicks in the cases but it's not right and should be addressed. Took the rifle out Friday, had a good session with new LC brass, 168gn Sierras and BLC-2 powder, 42 gns. Other than the case marks things went well.

Here's a picture extracted from a video that shows where the scratches are occurring. The two edges where the ramp meets the channel need to be relieved. The hook-pic points to one edge. Be careful sticking your pinky in there to check. The edges can be razor sharp.

Forgot to mention: About the only way to get to this area and do a good job is to remove the barrel. If you don't think you have the steady hand or can do this, turn the job over to a gun smith.

Attached Images

Bullet-5 Extra.jpg (100.6 KB, 102 views)

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Si vis pacem para bellum.

Thanks again, good photo. I need to have a good look in there and be sure of what I'm polishing before removing the barrel. It would be worth it if I was sure of what and where I was polishing.
Will work on that and post results. I'm sure that's what is causing these marks. Machining roughness or poor or cleaning techniques?

This got me thinking about the shapes of these feed ramps. Looks like the M&P 10 has 5 squared off ramps and 3 angled ramps.
I went over to my office and got my small camera (think teeth...)
and tried to get some images of the barrel and feed ramps.
Not that easy. Here's one that shows them fairly well. These are the flat or squared off ones, not as likely to ding up a case it seems...


Then these bottom three are far sharper and seem likely to be the problem...

Each of these sharper ramps are sharp, perhaps some careful smoothing of the edges would make the difference...

Did you ever resolve this issue? And if so, what (if any) difference did this make to the riffle's accuracy?

I am having the same issue. I noticed it on the range last week (before seeing this post). Some of my brass is actually slightly bent at the neck, corresponding to these gouges. On my prior visit to the range, my 100 meter groups were sub 1" and on this last range day, My groups were, in some cases, as wide as 3.5". While attempting to rule out the potential cause of the drastic difference, I noticed these gouges and indentations in my spent brass. I'm not sure if the gouges have always been on the spent brass from this riffle, or if it is a new development, thus accounting for my lousy day at the range

Any ideas or observations welcome...