Strange damage inside the barrel of my backpacker...

M

m_falafel

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I just went and tried my new 12ga Backpacker that I just bought new a few weeks ago.

after a few rounds of buckshot and one or two slugs I look at the choked end of the barrel and see that:

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From another angle:

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I'm pretty sure these imperfections weren't there when I got the gun... but I don't know, maybe they were and I just didn't see them while inspecting it? Also, the gun is clearly market as having a mod choke both on the receiver and on their website. I am not a shotgun professional, but shouldn't slugs fith through the choked end of the barrel? As you see on this picture, it won't go though at all.

44034073_10156912429774114_1761268862914920448_n.jpg
 
Modified choke diam. should be .710"
Slugs are usually. 690"
I am not an expert, but I share your concern that the slug pictured doesn't fit. And the led transfer is odd. Some slugs are bigger in diam. than standard .690". A certain amount of interference fit can be normal, but I have no idea what the acceptable spec would be.
 
bdft said:
That looks nasty. Are you sure that isn't plastic fouling from the wads? Slugs are a lot softer than the barrel and they squeeze a bit going out the end. I can't see the slug or lead buckshotmdoing the damage. Steel shot maybe.
Click to expand...

No it really is grooved inside the bore... I can feel it clearly when I run my fingers over it! And I didn't shoot any steel shot. Only federal premium slugs and Canada Ammo's Dominion Arms 9 pellet 00 Buckshot that they sold up until a few years ago. I still have about 200 left. That's their own brand so they can't say I shot some sketchy stuff!!

josh1976 said:
Modified choke diam. should be .710"
Slugs are usually. 690"
I am not an expert, but I share your concern that the slug pictured doesn't fit. And the led transfer is odd. Some slugs are bigger in diam. than standard .690". A certain amount of interference fit can be normal, but I have no idea what the acceptable spec would be.
Click to expand...

Just went back to the garage and measured the diameter with the calipers and it is .711, so the problem doesn't seem to be the diameter of the barrel...
 
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Looks like a bunch of plastic + lead fouling to me.... I would break out the bronze chamber brush, chuck it up in the cordless drill, and go to town.

Good, luck,

Brobee
 
m_falafel said:
No it really is grooved inside the bore... I can feel it clearly when I run my fingers over it! And I didn't shoot any steel shot. Only federal premium slugs and Canada Ammo's Dominion Arms 9 pellet 00 Buckshot that they sold up until a few years ago. I still have about 200 left. That's their own brand so they can't say I shot some sketchy stuff!!



Just went back to the garage and measured the diameter with the calipers and it is .711, so the problem doesn't seem to be the diameter of the barrel...
Click to expand...

So a cyl. bore choke is .730"
Ideally, rifled slugs should be shot thru CB or IC.
There are slug diam. variances from .690" up to CB (.730").
According to your picture and measurements, you have a .711" bore, and a .711" - .730" slug.
Your interference fit is between .000 - .019"
You are going to have increased led fouling given your combination.
Many people say this is fine. Many people go further and say you can safely shoot slugs thru full choke.
I stick with IC only for slugs. The interference tolerances are too variable between slug manufactures and based on use thru CB. And that is why you stick with cylinder bore or IC for slugs. I think your pictures simply show the result of interference fit on the slightly uncomfortable side, and is to be expected.
This is MY understanding, and I am ok to be stood corrected if need be...
 
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Lead fouling. Foster type slugs will deposit lead very quickly. I always wondered why lead are not lubed the same as cast bullets. Even a coating such lee lube would slow down lead build up. Lead doesn't deposit evenly,ridges will form. As others have said scrub that barrel.
 
josh1976 said:
So a cyl. bore choke is .730"
Ideally, rifled slugs should be shot thru CB.
There are slug diam. variances from .690" up to CB.
According to your picture and measurements, you have a .711" bore, and a .711" - .730" slug.
Your interference fit is between .000 - .030"
You are going to have increased led fouling given your combination.
Many people say this is fine. Many people go further and say you can safely shoot slugs thru full choke.
I stick with CB only for slugs. The interference tolerances are too variable between slug manufactures and based on use thru CB. And that is why you stick with cylinder bore for slugs. I think your pictures simply show the result of interference fit on the slightly uncomfortable side, and is to be expected.
This is MY understanding, and I am ok to be stood corrected if need be...
Click to expand...

I’ve never fired a slug through anything but a full choke because at the time that’s all I had and I never experienced any issues or any fouling even closely resembling that pic.
 
Snider shooter said:
Lead fouling. Foster type slugs will deposit lead very quickly. I always wondered why lead are not lubed the same as cast bullets. Even a coating such lee lube would slow down lead build up. Lead doesn't deposit evenly,ridges will form. As others have said scrub that barrel.
Click to expand...

What he said. You can clearly see an edge from the fouling buildup at the muzzle. The barrel is fire. Clean it.
 
Brobee said:
Looks like a bunch of plastic + lead fouling to me.... I would break out the bronze chamber brush, chuck it up in the cordless drill, and go to town.

Good, luck,

Brobee
Click to expand...

+ 2

I have two 870 barrels .... when I got them new I could feel the tool marks when I would stick my little finger in there. And those two barrels were leading heavily when shooting slugs. I polished those two barrels myself with a drill, cleaning rod, bronze brush and some fine steel wool .... Problem solved!
 
the spank said:
I’ve never fired a slug through anything but a full choke because at the time that’s all I had and I never experienced any issues or any fouling even closely resembling that pic.
Click to expand...

Ya. Same here. Never had fouling like that. But its important to realize there are considerable variations in slug diameters from brand to brand. With a cylinder bore or IC choke you are safe because slugs are made to suite a .730" bore. Some interference fit is good. It makes me cringe about the days when we sent unknown diameter slugs (possibly up to .730") thru a .695" full choke. That's a .035" interference. Not a great idea.
 
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josh1976 said:
So a cyl. bore choke is .730"
Ideally, rifled slugs should be shot thru CB or IC.
There are slug diam. variances from .690" up to CB (.730").
According to your picture and measurements, you have a .711" bore, and a .711" - .730" slug.
Your interference fit is between .000 - .019"
You are going to have increased led fouling given your combination.
Many people say this is fine. Many people go further and say you can safely shoot slugs thru full choke.
I stick with IC only for slugs. The interference tolerances are too variable between slug manufactures and based on use thru CB. And that is why you stick with cylinder bore or IC for slugs. I think your pictures simply show the result of interference fit on the slightly uncomfortable side, and is to be expected.
This is MY understanding, and I am ok to be stood corrected if need be...
Click to expand...

Cylinder or IC are recommended because they tend to be the most accurate options - although thatll be gun dependent. As for the interference fit, soft lead will swage through a choke no problem. If they're not safe for full choke you'd think they would say something on the box...
 
There may be residual machining marks in the barrel. Without before and after photos, hard to tell. Unlikely that shooting caused the marks. A good cleaning will get rid of the obvious fouling.
Ribbed lead Foster type slugs are designed to swage down when passing through a choke. They've been doing it for generations.
There are other types of slugs which should only be fired through cylinder or slug barrels. Sabotted slugs come to mind. Had a gun brought into the shop which had been fired with a sabotted solid copper slug. Said right on the box not to fire them through a barrel with a screw-in choke. Ripped the choke right out of the barrel.
 
Saw that happen to a little .410 when I was a kid, firing slugs through it left lead deposits that nothing could remove. But I do agree with the other posts that say you're looking at deposits and not grooving or gouging.
 
Easy fix- get some of that engine tuner in the can that you spray into the intake of thee engine while it is running .

Chuck up a 12 gauge brush in a drill and have at 'er- works amazingly!
Cat
 
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josh1976 said:
So a cyl. bore choke is .730"
Ideally, rifled slugs should be shot thru CB or IC.
There are slug diam. variances from .690" up to CB (.730").
According to your picture and measurements, you have a .711" bore, and a .711" - .730" slug.
Your interference fit is between .000 - .019"
You are going to have increased led fouling given your combination.
Many people say this is fine. Many people go further and say you can safely shoot slugs thru full choke.
I stick with IC only for slugs. The interference tolerances are too variable between slug manufactures and based on use thru CB. And that is why you stick with cylinder bore or IC for slugs. I think your pictures simply show the result of interference fit on the slightly uncomfortable side, and is to be expected.
This is MY understanding, and I am ok to be stood corrected if need be...
Click to expand...



Cylinder bore is only .730 if you have a barrel with an ID of .730 The trouble is that 12 gauge shotgun barrels can normally be anywhere from around .721 to .745 inches depending on age, make, etc, so your .730 inch cylinder choke will be a negative restriction on a .721 barrel and light mod on the .745 barrel. Points of constriction in relation to the bore id is a much more accurate gauge of choke than the generic use of IC, Mod, Full, etc.

I'm in agreement on the plastic and lead buildup in the muzzle of the op's shotgun. Give it a good cleaning and see what happens.
 
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