Chamber length question

[Russ661]

I just bought a borescope off Amazon and in looking over the chamber of my 300 winmag it looks like there is quite a bit of distance from the actual end of the cartridge case to the final step of the chamber to the leade. Can anyone comment? Seems like a lot of wasted length to me. I am assuming the cartridge neck ends where the carbon line starts on the right of the photo and the eroded looking step is the end of the neck end of the chamber. What say you?

BTW, the borescope is from Teslong and runs around $50. https://www.amazon.com/dp/B07TTQF24F/?tag=lrhmag19-20

 

[AZShooter]

It is a strange view when you first look through a borescope. There is some room for the neck to lengthen and in many SAMMI spec factory barrels this can be over .050" and even up to .075" to the end of the chamber . Next is the area where the bullet sits past the end of the chamber. Then there is a portion of the leade and freebore then finally the ramp like area which is the beginning of the throat and lands. Yep quite a bit of distance.

Have you looked at several barrels yet? How about inspection of a crown? Don't forget about looking at the insides of a case.

 

[Mikecr]

Yes it is extreme chamber end clearance, and this is why the carbon ring is forming to begin with. Did you trim the mouths so short?

 

[Russ661]

Yes it is extreme chamber end clearance, and this is why the carbon ring is forming to begin with. Did you trim the mouths so short?

Negative. Cases have not been trimmed.

 

[elkaholic]

Negative. Cases have not been trimmed.

I usually only trim my cases .005" for that reason but thats a BIG gap there!

 

[Danny Butler]

I couldn't get the velocity out of the short throated match chambers I needed with the ELD 208. I pushed the throat out to .250 and it worked great. Some Remington and Bagara rifles are throated like that. They get good velocities.... 3000 FPS and above..

 

[elkaholic]

His problem is in the neck though! The throat is a separate issue.

 

[Mikecr]

Negative. Cases have not been trimmed.

Well you won't need to trim them for a while. But you do need to manage that carbon buildup. Don't let it grow to a point of interference fit with your necks.
And don't turn your necks, as the increased radial clearance will contribute to even more carbon blow-back. You're probably already seeing carbon film down fired case necks, possibly all the way onto shoulders (can see with a wipe test).

 

[Danny Butler]

His problem is in the neck though! The throat is a separate issue.

Me bad...

 

[Russ661]

Well you won't need to trim them for a while.

Silver lining, eh?

But you do need to manage that carbon buildup. Don't let it grow to a point of interference fit with your necks. And don't turn your necks, as the increased radial clearance will contribute to even more carbon blow-back. You're probably already seeing carbon film down fired case necks, possibly all the way onto shoulders (can see with a wipe test).

I've been seeing a lot of blow by, almost all the way down the necks. I don't turn necks, I'm not that advanced in my reloading capabilities, so that isn't a problem. I'll be sure to stay ahead of the carbon buildup now that I know it exists and I have a way to monitor it.
Thanks

 

[Mikecr]

The longer carbon sits the tougher it is to remove. I would spin a stiff brush in that chamber neck after every range session. Doing this, it should come right out very easily.

 

[jebel]

I used the Sinclair Chamber Length Gages to measure the length of my chambers. I found them all to be significantly longer than the suggested max case length - from 0.022" to 0.048" longer.

https://www.sinclairintl.com/reload...s/sinclair-chamber-length-gage-prod32925.aspx

 

[Russ661]

I used the Sinclair Chamber Length Gages to measure the length of my chambers. I found them all to be significantly longer than the suggested max case length - from 0.022" to 0.048" longer.

I forgot I had one of those gages in my reloading tool box. The measured length of the chamber (after numerous tries) is ~2.658 inches, .038 longer than the published cartridge length of 2.620 inches. I haven't had a chance to try cleaning the carbon out but I think the chamber length could increase. I'll post again if it does.

 

[elkaholic]

I forgot I had one of those gages in my reloading tool box. The measured length of the chamber (after numerous tries) is ~2.658 inches, .038 longer than the published cartridge length of 2.620 inches. I haven't had a chance to try cleaning the carbon out but I think the chamber length could increase. I'll post again if it does.

well, that explains that. RIDICULOUS to screw a chamber up that badly!
If it was mine, I'd have the barrel set back or just re barrel it if you can afford to.