What Does this Mean?

jackstrawIII · September 14, 2020, 08:05 PM

Hey guys.

Took my Model 70 (308 Win) to the range to fire some of my hand loads and the cases are coming out looking unusually scuffed/marred around where the case would expand to fill the chamber. Not sure if you can tell in the attached photo, but it looks like a million little scratches all around the case. I’ve never seen cases do this before.

Any thoughts? Is that a pressure sign? The loads aren’t crazy hot though. Could there be something in the chamber causing that?

Thanks.

nhyrum · September 14, 2020, 08:14 PM

By the way the line has the abrupt edge just at the end of the web, it leads me to believe it has something to do with how the case expands under pressure. Almost like there's a lot of surface contamination in the chamber that gets impressioned on the case where it expands. I'd check the chamber with one of those small flexible cameras.

Sent from my SM-G975U using Tapatalk

**44 AMP** · September 14, 2020, 10:04 PM

Clean the chamber (and the ammo) and try again. See if you get the same, or different results.

My GUESS is dust/dirt in the chamber, or on the brass when fired.

noylj · September 14, 2020, 11:21 PM

Gee, looks pretty normal to me. Clean 'em and load 'em.
Maybe a bit too OCD? Maybe some residue in chamber from low pressure loads?
If concern is the cutoff from the dull "fired" surface to the shiny web surface, you could for gits and shiggles cut the case axially and see what the inside looks compared to the outside.

nhyrum · September 14, 2020, 11:34 PM

I dunno, the more I look at the piece of brass, the more it looks like it's about to separate at the case head. Could be too much headspace, which could be from pushing the shoulder back too far.

Sent from my SM-G975U using Tapatalk

**Aguila Blanca** · September 14, 2020, 11:45 PM

Quote:

Originally Posted by nhyrum

I dunno, the more I look at the piece of brass, the more it looks like it's about to separate at the case head. Could be too much headspace, which could be from pushing the shoulder back too far.

That ring at the base looks to me like the result of full-length resizing, and that's the extent of the sizing die running down on the case. So, in addition to scrubbing the chamber, I would suggest taking a close look at the die to see if there's anything in it that might be scuffing the surface of the cases.

jetinteriorguy · September 15, 2020, 06:54 AM

Quote:

Originally Posted by Aguila Blanca

That ring at the base looks to me like the result of full-length resizing, and that's the extent of the sizing die running down on the case. So, in addition to scrubbing the chamber, I would suggest taking a close look at the die to see if there's anything in it that might be scuffing the surface of the cases.

This.

jackstrawIII · September 15, 2020, 07:59 AM

Several of you guys have recommended cleaning the chamber. What’s the best way to do this?

I clean the bore of my rifles with patches with o-ring jags, but these don’t do anything for the chamber.

What do you guys recommend?

Thanks.

**Unclenick** · September 15, 2020, 08:17 AM

There are chamber brushes with fat locking lug cleaning sections and chamber mops designed for this. You use them with regular cleaning solvents. You will find them hard to use with a cleaning rod that has a spinning handle. You want a solid handle or a T-handle rod so you can turn them in the chamber.

Marco Califo · September 15, 2020, 03:24 PM

I think you full length sizing die may need cleaning. When was the last time you cleaned it? You do not need to clean it often, but when it is dirty you need to clean it. And only size very clean brass. Take the expander ball assembly out so you can see through the die. Roll up a paper towel and insert and pull through while twisting it. If it does not come out clean, and is dark and oily, repeat. The lubricant can build up and catches dirt. Also tumble your brass in corncob so I it will shine and not look so fuzzy.

**Unclenick** · September 15, 2020, 03:40 PM

As a second thought, I notice the lower portion only has the markings, and if the breech end of the chamber were too wide, as can happen if cut with an off-center or dull reamer being fed too fast. You would get some extra-hard resizing effort in that area.

JackstrawIII, can you get some diameter measurments of the head below the line and just above the line and report how far above the bottom of the head those two measurements are. Also get the case body right at the shoulder.

Scorch · September 15, 2020, 05:28 PM

Looks normal to me (gunsmith for 35 years). If you want them to be shiny when they come out you will need to polish the chamber. I say just shoot it.

jackstrawIII · September 15, 2020, 09:06 PM

Unclenick, here are the case dimensions per your request:

Just above the extractor groove (below the ring of scuffing): .4670"
At the widest point (where the scuffing starts): .4715"
At the shoulder: .4570"
Distance from the bottom of the case to the start of the scuffing ring: .2520"

And everyone else, thanks for all the tips on chamber and die cleaning. Going to give those a shot and see if it helps for now.

**Aguila Blanca** · September 15, 2020, 09:29 PM

What is it just below the scuffing? (Say .200" from the extractor groove bevel.)

jackstrawIII · September 16, 2020, 08:21 AM

Aguila,

It measures .4700" just below the scuff line.

September 14, 2020, 10:04 PM	#3
44 AMP Staff Join Date: March 11, 2006 Location: Upper US Posts: 28,846	Clean the chamber (and the ammo) and try again. See if you get the same, or different results. My GUESS is dust/dirt in the chamber, or on the brass when fired. __________________ All else being equal (and it almost never is) bigger bullets tend to work better.

September 15, 2020, 07:59 AM	#8
jackstrawIII Senior Member Join Date: July 20, 2016 Location: Upstate NY. Posts: 901	Several of you guys have recommended cleaning the chamber. What’s the best way to do this? I clean the bore of my rifles with patches with o-ring jags, but these don’t do anything for the chamber. What do you guys recommend? Thanks. __________________ In God we trust.

September 15, 2020, 08:17 AM	#9
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	There are chamber brushes with fat locking lug cleaning sections and chamber mops designed for this. You use them with regular cleaning solvents. You will find them hard to use with a cleaning rod that has a spinning handle. You want a solid handle or a T-handle rod so you can turn them in the chamber. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

September 15, 2020, 03:24 PM	#10
Marco Califo Senior Member Join Date: April 4, 2011 Location: LA (Greater Los Angeles Area) Posts: 2,598	I think you full length sizing die may need cleaning. When was the last time you cleaned it? You do not need to clean it often, but when it is dirty you need to clean it. And only size very clean brass. Take the expander ball assembly out so you can see through the die. Roll up a paper towel and insert and pull through while twisting it. If it does not come out clean, and is dark and oily, repeat. The lubricant can build up and catches dirt. Also tumble your brass in corncob so I it will shine and not look so fuzzy. __________________ ............

September 15, 2020, 03:40 PM	#11
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	As a second thought, I notice the lower portion only has the markings, and if the breech end of the chamber were too wide, as can happen if cut with an off-center or dull reamer being fed too fast. You would get some extra-hard resizing effort in that area. JackstrawIII, can you get some diameter measurments of the head below the line and just above the line and report how far above the bottom of the head those two measurements are. Also get the case body right at the shoulder. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

September 14, 2020, 08:14 PM	#2
nhyrum Senior Member Join Date: March 9, 2016 Posts: 588	By the way the line has the abrupt edge just at the end of the web, it leads me to believe it has something to do with how the case expands under pressure. Almost like there's a lot of surface contamination in the chamber that gets impressioned on the case where it expands. I'd check the chamber with one of those small flexible cameras. Sent from my SM-G975U using Tapatalk

September 14, 2020, 11:21 PM	#4
noylj Senior Member Join Date: October 21, 2007 Location: Between CA and NM Posts: 858	Gee, looks pretty normal to me. Clean 'em and load 'em. Maybe a bit too OCD? Maybe some residue in chamber from low pressure loads? If concern is the cutoff from the dull "fired" surface to the shiny web surface, you could for gits and shiggles cut the case axially and see what the inside looks compared to the outside.

September 14, 2020, 11:34 PM	#5
nhyrum Senior Member Join Date: March 9, 2016 Posts: 588	I dunno, the more I look at the piece of brass, the more it looks like it's about to separate at the case head. Could be too much headspace, which could be from pushing the shoulder back too far. Sent from my SM-G975U using Tapatalk

September 15, 2020, 05:28 PM	#12
Scorch Senior Member Join Date: February 13, 2006 Location: Washington state Posts: 15,248	Looks normal to me (gunsmith for 35 years). If you want them to be shiny when they come out you will need to polish the chamber. I say just shoot it. __________________ Never try to educate someone who resists knowledge at all costs. But what do I know? Summit Arms Services

September 15, 2020, 09:06 PM	#13
jackstrawIII Senior Member Join Date: July 20, 2016 Location: Upstate NY. Posts: 901	Unclenick, here are the case dimensions per your request: Just above the extractor groove (below the ring of scuffing): .4670" At the widest point (where the scuffing starts): .4715" At the shoulder: .4570" Distance from the bottom of the case to the start of the scuffing ring: .2520" And everyone else, thanks for all the tips on chamber and die cleaning. Going to give those a shot and see if it helps for now. __________________ In God we trust.

September 15, 2020, 09:29 PM	#14
Aguila Blanca Staff Join Date: September 25, 2008 Location: CONUS Posts: 18,468	What is it just below the scuffing? (Say .200" from the extractor groove bevel.) __________________ NRA Life Member / Certified Instructor NRA Chief RSO / CMP RSO 1911 Certified Armorer Jeepaholic

September 16, 2020, 08:21 AM	#15
jackstrawIII Senior Member Join Date: July 20, 2016 Location: Upstate NY. Posts: 901	Aguila, It measures .4700" just below the scuff line. __________________ In God we trust.