Carbon Ring/Case Length

[Dfin]

I’m looking to minimize carbon ring buildup by closing up the exposed area past the end of the trimmed case but before the step from the neck to the throat. How much clearance do I actually need between the end of the trimmed case and the step?

I know the recommended trim lengths but at that length I’m seeing excessive carbon buildup, so would like to hear from folks who have spent some time on this.

 

[AlNyhus]

I'm going to preface this by saying that you need to know what your chamber length is. Don't assume, go by the reamer print or a reloading manual. The best and easiest way to do this is with a Sinclair Chamber Length gauge.

After determining the chamber length, I use .020 as my 'trim to' length. That gives a good cushion and doesn't give a big space for carbon to build up.

For what it's worth. -Al

 

[JEFFPPC]

Drill the primer pocket out. Insert a borescope and you can see the space. Trim so you have minimal space and measure/trim each time loading.

 

[AlNyhus]

Drill the primer pocket out. Insert a borescope and you can see the space. Trim so you have minimal space and measure/trim each time loading.

Yes...another good way to do it. -Al

 

[SteveUrban]

A chamber cast will tell you what you want to know. Careful measuring will show you where the taper in the throat begins. This will be the stop point.

 

[DShortt]

Drill the primer pocket out. Insert a borescope and you can see the space. Trim so you have minimal space and measure/trim each time loading.

I've gone in through the muzzle end with a flexible borescope, too. No need to alter anything that way.

 

[243winxb]

Dummy round.
Place a flat base bullet, nose first, into a sized piece of brass.
Measure at OAL maximum length. Chamber dummy round. Measure again. This should give an idea of the chamber length.

If to much force is need to close bolt, use a fired case & pinch neck so its oval. Take many measurement, till you get enough that are the same. Thats maximum.

A trim length that is to long, very dangerous.

 

[Dfin]

I have a Sinclair chamber length gauge, so all good on measuring. Once I have a good dimension, how much clearance is necessary? I’ve heard anything from .005”-.020”.

 

[DLT]

Drill the primer pocket out. Insert a borescope and you can see the space. Trim so you have minimal space and measure/trim each time loading.

Or go in from muzzle end. What I usually do

 

[SteveUrban]

I have a Sinclair chamber length gauge, so all good on measuring. Once I have a good dimension, how much clearance is necessary? I’ve heard anything from .005”-.020”.

I go .005” for the milsurp and BP cartridges, if the necks are long enough!

 

[Straightshooter1]

I’m looking to minimize carbon ring buildup by closing up the exposed area past the end of the trimmed case but before the step from the neck to the throat. How much clearance do I actually need between the end of the trimmed case and the step?

I know the recommended trim lengths but at that length I’m seeing excessive carbon buildup, so would like to hear from folks who have spent some time on this.

You don't need much clearance as long as you're trimming your cases after each sizing to keep them as uniform as possible. You're going to need a little clearance to allow for any variations you get in the case lengths.

I like to have ~.005 clearance, not so much about reducing the size of the carbon ring, but because I usually load long, I like to have sufficient neck to bearing surface contact for my cartridges.

 

[DShortt]

Keep an eye out for the carbon ring still. Just because the area is shorter doesn't mean it won't/can't still develop.

 

[JEFFPPC]

Keep an eye out for the carbon ring still. Just because the area is shorter doesn't mean it won't/can't still develop.

Proper cleaning required of course, should be normal practice. After all there are several bazillion posts on this forum and others about what to use and how. LOL.

 

[Bronsin]

I have a Sinclair chamber length gauge, so all good on measuring. Once I have a good dimension, how much clearance is necessary? I’ve heard anything from .005”-.020”.

I recommend .020. There's nothing to be gained by running it up closer than that.

 

[Dfin]

I recommend .020. There's nothing to be gained by running it up closer than that.

You don’t think it will limit the carbon ring?

 

[Bronsin]

I

You don’t think it will limit the carbon ring?

I don't spend much time worrying about the carbon ring honestly. One of my most accurate PPC's had a 1.525 case length and all my brass was 1.490. Even with .035 it didn't matter. The carbon ring is soft like the majority of the fouling in a barrel. Hard carbon is the problem. I clean after every relay, and all I do for the carbon ring is to soak a patch in BoreTech C4 and push it into the throat and let it sit for 15 minutes. It eats the carbon right out of there.

 

[Dfin]

I

I don't spend much time worrying about the carbon ring honestly. One of my most accurate PPC's had a 1.525 case length and all my brass was 1.490. Even with .035 it didn't matter. The carbon ring is soft like the majority of the fouling in a barrel. Hard carbon is the problem. I clean after every relay, and all I do for the carbon ring is to soak a patch in BoreTech C4 and push it into the throat and let it sit for 15 minutes. It eats the carbon right out of there.

That was my experience as well..before Varget. I generally have to do an overnight soak with C4, clean, and do a 2nd overnight soak to get rid of the ring. I never had this problem with N140/150.