Removing deposit from chamber shoulder

[DoneNOut]

I have a Remington Auto 8 35 Remington. It is gouging the brass right where the shoulder meets the neck. So, logic dictates it's a deposit of something. I'm going to buy a bore scope, but after I find said deposit, what's the best way to remove it from the chamber?

 

[tobnpr]

History?
"New to you"- or is this a recent development where there had been no issues previously?
Sure looks like a foreign object in the chamber. You don't necessarily need a borescope (though it'll certainly give you more info)- just shine a light into the chamber and take a look.

 

[ShtrRdy]

If the cartridge was fed from a magazine there might be a sharp edge in the path.

 

[MagnumManiac]

If it is a foreign object that has been subject to cases firing against it, it is likely stuck in there good.
I don't know how, but I ended up with some (3) bits of corncob in one of my 300WM chambers right in the middle of the shoulder. It was being crushed each shot and I had to use a dowel and some scotch brute pad between the split ends to get it out. I didn't notice it til after I got home testing a new batch
If it is rust, the only way is with a dowel wrapped in emery cloth spun up in a lathe.

Cheers.

 

[shortgrass]

Ya' need to varify what it is before deciding upon removal method.

 

[DoneNOut]

If the cartridge was fed from a magazine there might be a sharp edge in the path.

Well, this has a lot of merit. Here a pic of the magazine. I suspect the two circled indentions might be the culprit. They were sharp, so I polished with 400, 800 grit sand paper. I can't get the gouge to replicated by chambering a round, although I am not moving the bolt anywhere near the velocity it goes when fired. We shall see if this did it next range trip. I'll be sure to mark the top of the cases with a black marker for reference.

 

[OmegaRed]

If you need a borescope, check out Teslong. They are ridiculously cheap for the quality. Useful in all kinds of non gun maintenance work too (cars, looking in wall cavities, etc.)

 

[MNbogboy]

If the magazine was indeed chipped and the broken piece/pieces found their way into the chamber and somehow got lodged in there, then removal may be a simple as cleaning up the chamber with the original reamer ( if available).
My guess is there is no way to find that original reamer. Being it is an autoloader the violent action of the firing mechanism may have caused the breakage of the mag lips and helped carry them inside.

 

[DoneNOut]

Update:

The sandpaper on the magazine did the trick. Thanks all for opining on the matter. I am currently in a conundrum with finding a load for the gun. AA2520, Varget, Lever, H4198, and IMR 3031. I am getting pierced primers, flattened primers, and then primers that back out. I read where backed out primers are a sign of low pressure and pierced and flattened a sign of high pressure. When you load 5 round and three show high and two show low, that will drive a guy nuts. Just recently 36.5gr 3031 didn't show any high pressure and only 2 back out primers. 2030fps. 37gr next to try.

 

[MNbogboy]

The backed out primers in old guns are usually an indicator of excessive headspace. A go gauge with tape or plastic gauge could help you verify this.

 

[tobnpr]

With old autoloaders like this, it could also be improper bolt timing.
If the bolt unlocks before the drop in pressure releasing the case from the chamber walls, the remaining pressure will cause the primer to back out.

I would check headspace first as suggested.
If that checks out within tolerances, I'd look for a smith that has experience with timing issues for this system- which is Browning's long-recoil operation (I've no direct experience working on this). As with any centenarian firearm- it's logical to look at headspace/wear of components. The camming mechanism that locks/unlocks the bolt may have wear in one or more components that's allowing the bolt to unlock from the barrel prematurely.

Here's a couple of good videos showing the operation of the long-recoil mechanism in detail and actual disassembly of the Model 7 mechanism.