Min or Max case length

TackDriver284

Handloader
Feb 13, 2016
2,308
1,553
I have fired 100 pieces of virgin Lapua brass for the 300 Win Mag. The cases measures at 2.620" plus or minus .001" and SAMMI specs shows minimum trim length as 2.610" and max at 2.620".
When I checked my rifles with a borescope recently for carbon rings to clean, I inserted a case and chambered it and used the borescope from the muzzle end and noticed that the case mouth is flush with the end of the carbon ring. There are more space in that carbon ring area to prevent the bullet from getting pinched when fired in case it should grow longer.
Just a theory, if you wish not to have carbon rings, leave your cases long, just enough not to get pinched. If you disagree, please elaborate.
Do I need to remove the carbon ring since it may pinch the bullet in the case mouth on the next firing, if I were to leave the trim length at max length?
Do you guys rather trim to 2.610" or clean the carbon ring and leave the trim length as 2.620" as max length?
 
If I know there is a carbon ring, I get rid of it.
Since every chamber is different, and if you know your rifle runs great at 2.610, run it at 2.610
Since every chamber is different, and if you know your rifle runs great at 2.615, run it at 2.615
Since every chamber is different, and if you know your rifle runs great at 2.620, run it at 2.620

You are meticulous when you reload (many are not). Knowing that, use what works for that rifle.
One you have determined what works best for that particular rifle, go that way and trust the gun.
If you are going to be close to a clean period, before a time which would involve more shooting or the need to know, everything will work right, then clean it, and make sure it is properly fouled (Many rifle take more fouling shots than one would imagine) before you go on that trip or to that match, etc...
 
My thoughts: (And this does not relate to what would work best for 1000 yd matches, how would I know?)

I've done what you've done. Inserted a case and checked the end case clearance with a borescope. Some chambers have a generous amount ahead of the neck with standard case length, others do not. For me if I see I have more room, I'd let it grow so I didn't have all that space out ahead for the carbon to build on. If I'd see a carbon ring, I'd get rid of it.
 
Thanks xphunter and Shade. Just what I needed to know. Time to get the cleaning kit out and get rid of that carbon ring.
 
If the Teslong reveals a carbon ring, I remove it. I use BoreTech C4. I'l soak the area with successive patches, leaving time in-between for the C4 to soften the carbon. For a really stubborn ring, I'll soak it overnight by leaving a soaked patch in the chamber neck. Then a bronze brush is used to finish removing the carbon.

I trim cases but I never trim to min spec. It's my understanding that all chambers are cut longer than the max case length spec. As long as the cases are below the max spec, I leave them alone. I might just check (using the Teslong from the muzzle) how much extra room there is when a max case is inserted, just for the heck of it.
 
If the Teslong reveals a carbon ring, I remove it. I use BoreTech C4. I'l soak the area with successive patches, leaving time in-between for the C4 to soften the carbon. For a really stubborn ring, I'll soak it overnight by leaving a soaked patch in the chamber neck. Then a bronze brush is used to finish removing the carbon.

I trim cases but I never trim to min spec. It's my understanding that all chambers are cut longer than the max case length spec. As long as the cases are below the max spec, I leave them alone. I might just check (using the Teslong from the muzzle) how much extra room there is when a max case is inserted, just for the heck of it.
Yup, its already cleaned out, I used Bore Tech Carbon remover, I paused at the carbon ring by feel, and give it a few twirls with the patches before pushing the patches out the muzzle end. Even used a nylon brush to twirl it in that area and several passes with it. It looks like there is about 2 mm of space ahead of the case mouth with the bolt closed, and I will do another firing without trimming, then recheck the length and trim to the shortest of the batch.
 
Lately on my stainless barrels I’ve been using CLR. It works wonder , BUT you can’t leave soak very long. I give it 5 min. and bronze brush it and patch Kroil to get it out.
CLR is not for the faint of heart. You have to pay attention how long it’s in there.
 
Lately on my stainless barrels I’ve been using CLR. It works wonder , BUT you can’t leave soak very long. I give it 5 min. and bronze brush it and patch Kroil to get it out.
CLR is not for the faint of heart. You have to pay attention how long it’s in there.

I had two SS brakes that I just couldn't get all the carbon out of. I poured a few inches of CLR into a disposable cup and dropped one in. I intended to pull it out in an hour to see how the CLR was working but totally forgot about it until the next day. When I pulled the brake out it looked the same, but when I put a Q-tip in the opening, all the carbon just floated off. The brake looked like it was new. There was no damage to the brake from the CLR.

I wouldn't try this with a brake that had any kind of finish on it. The CLR would likely alter the finish.
 
There are some reasons why I use Carb-Out rather than CLR. I don't have to worry about things as much with it.
You can click on the link I posted above, if you want to read up more on it or call him and have a chat with a chemist.
 
I've been using Seafoam for the last couple of years and it does a good job of removing carbon.
 
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