• This Forum is for adults 18 years of age or over. By continuing to use this Forum you are confirming that you are 18 or older. No content shall be viewed by any person under 18 in California.

Erosion from blowback on necks

Pigdog

This is kinda a follow a follow on from the "is this case stuffed thread"

Can any of the experienced shooters here confirm that when you are getting soot on case necks due to neck not sealing properly before bullet release does those hot gases cause erosion of the chamber in the area where the neck is not sealing properly??

My 6.5x47l has a .286 neck. Necks have been turned by previous owner to 8.5 thou thick. This gives a loaded round diameter of .281 after sizing through a .281 bushing. Load used is 40g H4350 with 139 scenars at 2.840coal 10 thou off lands. All cases have just been annealed and had 5-6 firings estimated pressure from quickload 58k psi.

A clever gentleman from the other thread worked out why I'm getting soot on necks (zero neck tension and 5 thou of neck to chamber clearance. He suggested maybe trying a .279 bushing to give some more neck tension. I don't want to have to buy new lapua cases and neck turning gear as that is gunna set me back several hundred and my wife is already pissed I'm getting another gun Saturday. My main concern is if this soot and gas escaping is damaging the gun causing more erosion?? I have contacted Sinclair to see what attachment I need to clean my chamber as i already have their recoil lug cleaning tool. If the soot is not doing any damage I'm very happy with how the gun shoots and would be ok with simply cleaning the chamber to keep on top of the soot.

Can any experts help a mug out

Thanks
 
Last edited:
I never heard of erosion from it, but you'll need to watch for and manage carbon buildup at the chamber neck.
You might expect higher velocity SD/ES also, as sealing may be inconsistent.
 
Pigdog said:
If the soot is not doing any damage I'm very happy with how the gun shoots and would be ok with simply cleaning the chamber to keep on top of the soot.
Click to expand...

I am the only shooter that does not want anything between the chamber and case but air, I do not want a lot of air but the air that I do have between the chamber and case must be clean air. I understand that makes no sense to a reloader, there are a few reloaders that pack their chambers with grease, I call them 'slide and glide shooters'.

Back to the carbon build-up on the neck, the carbon build up matters because it is matter, it has weight and it takes up space. A reloader can not be convinced carbon between the neck and chamber is caused by time, for the neck to seal the chamber from gas blosiong back between the case and chamber the neck must expand first. A reloader should not have trouble getting the case to expand with fast powder, slow powder can allow gas to escape back between the neck and chamber before the pressure is high enough to seal.

I tested an old Japanese 6.5mm50 rifle, after chambering a round I covered the receiver with a white towel, after firing I examined the white towel, it had two black smoke spots on the towel, what does that mean? The barrel was shot out, when the bullet went through the barrel there was not enough pressure behind the bullet to seal the case from the chamber.

And then there is 'time' to get a grop on that a reloader must be able to think pluralistically as in two or more things at once.

F. Guffey
 
fguffey said:
I am the only shooter that does not want anything between the chamber and case but air, I do not want a lot of air but the air that I do have between the chamber and case must be clean air. I understand that makes no sense to a reloader, there are a few reloaders that pack their chambers with grease, I call them 'slide and glide shooters'.

Back to the carbon build-up on the neck, the carbon build up matters because it is matter, it has weight and it takes up space. A reloader can not be convinced carbon between the neck and chamber is caused by time, for the neck to seal the chamber from gas blosiong back between the case and chamber the neck must expand first. A reloader should not have trouble getting the case to expand with fast powder, slow powder can allow gas to escape back between the neck and chamber before the pressure is high enough to seal.

I tested an old Japanese 6.5mm50 rifle, after chambering a round I covered the receiver with a white towel, after firing I examined the white towel, it had two black smoke spots on the towel, what does that mean? The barrel was shot out, when the bullet went through the barrel there was not enough pressure behind the bullet to seal the case from the chamber.

And then there is 'time' to get a grop on that a reloader must be able to think pluralistically as in two or more things at once.
F. Guffey
Click to expand...

I want everything that you want. So you can no longer say that you are the only one that wants something.
 
I am the only shooter that understands the things that I say, though I say them over and over expecting understanding to dawn. I understand that this makes no sense to a reloader, because most reloader's are sensible people capable of understanding what most people are talking about. I call them "normal shooters" - those who say and practice things that can be understood by everyone except me. I'm somewhere where I don't know where I am.
 
mikecr said:
I never heard of erosion from it, but you'll need to watch for and manage carbon buildup at the chamber neck.
You might expect higher velocity SD/ES also, as sealing may be inconsistent.
Click to expand...

thanks mike this is the sort of knowledge I'm looking for.

Guys can we keep the topic on hand if possible I'm not sure what is going on between fguffey and the others but I'm more interested in if anyone can offer practical advice on where I go to from here I'm thinking of the possible following scenarios.

1.) increase loads so that I'm running at absolute max pressure of 63kpsi (not real keen on this)
2.)Size necks with a bushing down to .279 thoughts on this?
3.)don't worry about it continue shooting and get a chamber cleaning kit and clean regularly
4.)put the gun in the safe until I can afford new lapua brass, neck turning gear and a new full length sizing die as recommended in the article on this site about neck turning before getting started he said you need to full length size with a non bushing die which I don't have.
5.) other?

thanks for keeping on topic
 
fguffey said:
A reloader can not be convinced carbon between the neck and chamber is caused by time,
Click to expand...

A faster burning powder, moving the bullet closer to the lands, avoid full length sizing, and then there is neck tension, I do not use neck tension, I use bullet hold, I want all the bullet hold I can get. What effect does bullet hold have on time?

Reloaders are infatuated with neck tension with no way to measure it. I have tension gages, all of my tension gages are calibrated in pounds.

F. Guffye
 
I bought a gun that I had a hell of a time sizing to the headspace in that every round had an outside appearance of head separation. Go and no-go gauges shown a proper headspacing. I finally did a chamber cast and the chamber had erosion from head separations from the previous owner.
 
Pigdog said:
thanks mike this is the sort of knowledge I'm looking for.

Guys can we keep the topic on hand if possible I'm not sure what is going on between fguffey and the others but I'm more interested in if anyone can offer practical advice on where I go to from here I'm thinking of the possible following scenarios.

1.) increase loads so that I'm running at absolute max pressure of 63kpsi (not real keen on this)
2.)Size necks with a bushing down to .279 thoughts on this?
3.)don't worry about it continue shooting and get a chamber cleaning kit and clean regularly
4.)put the gun in the safe until I can afford new lapua brass, neck turning gear and a new full length sizing die as recommended in the article on this site about neck turning before getting started he said you need to full length size with a non bushing die which I don't have.
5.) other?

thanks for keeping on topic
Click to expand...
Pig dog
If you are not seeing negative results on target and you like the load then I wouldn't worry at all if the carbon is limited to the necks only. Moving down the shoulder and body, on the other hand, is a sign of a light load. One the neck only is also a sign of a good load if not excessive. In the search bar on this forum type in "carbon pattern on neck" this thread should give you piece of mind if your cases look similar to the OPs pictures from that thread. To Mike's point make sure a carbon ring doesn't start to form in the chamber neck area (different problem) and you should be good to go. Chamber erosion is a none issue. The barrel throat will be toast way before any small amount of blowback would have any impact to the chamber. 005 is not excessive at all in clearance. I shoot a 308 with .0065 clearance with neck turned brass to .0125 in a .339 neck with no problems. I have a borescope and absolutely NO sign of any chamber effects. My experience is .003 to .007 is the sweet spot and really depends on the shooters preference. Many brands of commercial 308 ammo have loaded round measurements of .336 and most over the counter rifles are spec'd at .342 and .343 as examples for you.

Anneal your necks to keep them from work hardening is the key. As they work harden the carbon will increase. Hope this helps and gives you a different perspective from the other thread referenced above
 
Last edited:
Toejoe12 said:
Pig dog
If you are not seeing negative results on target and you like the load then I wouldn't worry at all if the carbon is limited to the necks only. Moving down the shoulder and body, on the other hand, is a sign of a light load. One the neck only is also a sign of a good load if not excessive. In the search bar on this forum type in "carbon pattern on neck" this thread should give you piece of mind if your cases look similar to the OPs pictures from that thread. To Mike's point make sure a carbon ring doesn't start to form in the chamber neck area (different problem) and you should be good to go. Chamber erosion is a none issue. The barrel throat will be toast way before any small amount of blowback would have any impact to the chamber. 005 is not excessive at all in clearance. I shoot a 308 with .0065 clearance with neck turned brass to .0125 in a .339 neck with no problems. I have a borescope and absolutely NO sign of any chamber effects. My experience is .003 to .007 is the sweet spot and really depends on the shooters preference. Many brands of commercial 308 ammo have loaded round measurements of .336 and most over the counter rifles are spec'd at .342 and .343 as examples for you.

Anneal your necks to keep them from work hardening is the key. As they work harden the carbon will increase. Hope this helps and gives you a different perspective from the other thread referenced above
Click to expand...

Thanks mate some great info there, I get soot on the necks and shoulder but none on the body at all, seems the headspace is tight (only neck sizing) so it is sealing it off there.
 
Pigdog said:
4.)put the gun in the safe until I can afford new lapua brass, neck turning gear and a new full length sizing die as recommended in the article on this site about neck turning before getting started he said you need to full length size with a non bushing die which I don't have.
Click to expand...
I sure didn't want to push you in that direction. There are already too many safe queens out there, keep shooting. Sounds like you got some good advice, except for that little distraction in the middle!
 
You must log in or register to reply here.

Upgrades & Donations

This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.


Click Upgrade Membership Button ABOVE to get Gold or Silver Status.

You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.


To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.

Classified Ads

Forum statistics

Threads
165,890
Messages
2,205,572
Members
79,189
Latest member
Kydama1337

Share This Page

Back
Top