Carbon buildup during a match....

[Emmett Dibble]

Big lurker, did some poking around couldn't find the answer...

I shoot silhouette. Shoot a lot of lever action silhouette. Pistol cartridge, as the name implies is straight wall cartridges in rifles. 357 is very common.

The problem I am having is carbon fouling, not carbon ring, starting about 3-5" after the leade and ending about 8-10".

The way it presents itself is somewhere around 30 - 40 rounds, about the middle of the match, the carbon build up in the barrel will harden up between relays. You shoot 5 shots in 2 minutes, there is a 30 second break, you shoot 5 more shots in 2 minutes, another 30 second break, then another 5 shots in 2 minutes, then the rifle may sit in the rack for 10-20 minutes and you repeat. About half way through the match the carbon will harden and make the first shot slow/low then the resulting warm/hot shots will come back up to established POA/POI.

I had one rifle that did this before. I have other rifles that don't.It took a while on the current rifle to deduce exactly what was happening. (second one, sold the first one that displayed this phenomenon thinking it was the rifle)

I clean and use a bore scope to inspect. I started a routine of inspecting before I clean and that is how I realized that the problem isn't a rifle/barrel problem but a carbon build up problem.

The particular rifle is a Uberti 1866 in 38 special, 24" barrel and the load is 6.6g Longshot under a Speer 125gr Gold Dot with a very light taper crimp. I have bullet, powder, crimp tested the hell out of this gun and that set up gets me +/- 2 MOA all day long till the carbon build up then the first shot (after the barrel cools off 10 - 15 minutes) prints low (like 6-10"@100 yards) and the report is off... subsequent shots will follow up to where they are supposed to be.

Any ideas? FWIW, the other rifle that did this and I assumed it was just CBF was 357, different powder and bullet.

Picture for clarification...

 

[jelenko]

You're convinced that the barrel isn't bending as it heats up?

 

[Emmett Dibble]

You're convinced that the barrel isn't bending as it heats up?

Yes, cold clean, shoots lights out. I have sat there on the bench with targets at 100 yards and verified it's around the 30-40 round mark it starts appearing and by 60 - 80 rounds it's very pronounced. Basicly shot 100 rounds through it at the pace of practice and then a 60 round match with a 5 shot shoot off at the end, using a timer and following the normal shot/relay time pace. Can clean the carbon out and it's back to POA/POI clean and cold. I really like shooting the rifle and have been using only for club matches because of this problem.

 

[acloco]

Could be unburnt powder.

What primer are you using?

 

[bozo699]

How long does it take to clean the carbon out? If it’s sitting in the rack for 20-30 minutes do you have time to clean it?.. or if you did clean it would the first couple rounds be off just as far? Is the barrel really rough those first few inches and lastly have you tried different primers and or powder to see if this problem changes?
Wayne

 

[Emmett Dibble]

Could be unburnt powder.

What primer are you using?

Fiocchi Small pistol primers, the other rifle I was having the same problem with how do use in Winchester small pistol primers.

 

[Emmett Dibble]

How long does it take to clean the carbon out? If it’s sitting in the rack for 20-30 minutes do you have time to clean it?.. or if you did clean it would the first couple rounds be off just as far? Is the barrel really rough those first few inches and lastly have you tried different primers and or powder to see if this problem changes?
Wayne

The barrels aren’t match grade by any means, but it has been fire lapped and they’re fairly smooth. The powder/primer combination. This powder gives the best accuracy out of everything I’ve tried in this rifle. I could develop a cleaning regiment during the match but it’s kind of a pain in the butt. During my off relays I’m usually spotting for somebody else.

 

[Emmett Dibble]

It’s definitely baked on carbon. It takes a bit of saturation and scrubbing to get it out, it’s not simply a wet patch, brush, dry patch routine…

 

[CaptainMal]

I have a variation of your problem with one of my 6mm BRA's. Shoot about 30-40 rounds and the pressure, because of a carbon build-up, starts crating and blowing primers. Sure I go home and literally dissolve and scrub the carbon out but that does not help if I need to shoot more at a match.

Solution ... harder primers. Found out the formula for Federal 205M's is the same in their 205MAR primers. The MAR's are a thicker cup used to stop slam fires in AR autoloaders. Now, if I notice the start of an issue, I switch to the other primers and see no changes.

Damnable carbon in 6mm BR variants is a systemic problem.

 

[acloco]

I would follow CaptainMal's lead.....time to switch to a different primer.

Might only require switching to a small pistol magnum.

How many grains of powder are you loading?

 

[Emmett Dibble]

It’s 6.6 of a longshot under 125 grain Speer gold dot. I didn’t consider changing to magnum primers but it can’t hurt. There is absolutely no pressure signs and it’s not top of the load recipe. It’s running about 1400 FPS out of the 24 inch barrel.

 

[PigButtons]

Just brainstorming here but you said "light taper crimp". You might try putting a strong taper crimp or Lee "Factory Crimp". The thought being if it is unburnt powder that is then deposited and the successive shots cook and cake it into the barrel, the more aggressive crimp may help build pressure and increase the burn efficiency thereby eliminating some of the deposit behavior.

 

[Emmett Dibble]

The set up item using right now is the most accurate load in the rifle. Pistol cartridge lever action rifle‘s or a PITA to get to shoot sub 3MOA. I’ve gone through four or five bullet selections and five or six powder flavors also playing with COL and Crimp to get it to shoot where it’s at. I single load so theoretically I don’t need any crimp at all but this actually shoots best with a very light crimp. Basically just enough to take the flare out and lightly put the brass into the Canalure. Even though I searched the forum and couldn’t find any threads about a similar problem I am hoping for a easy fix that doesn’t involve change in my set up for this rifle.

it may just be a confluence of things that stack up to this issue in this rifle. I think there’s probably more of it in this game but people just don’t notice or blame themselves for errant shots.

 

[DGP4]

I've switched to Winchester Super Target and Clean Shot powders for my 38 target loads. MUCH cleaner burning than other powders. I load Hornady 125 gr. XTP over 4.6 grains of Clean Shot and it is very accurate and clean burning. I use WST under 148 gr, double end wadcutters and 158 gr. SWC. Also super clean burn.

 

[acloco]

It’s 6.6 of a longshot under 125 grain Speer gold dot. I didn’t consider changing to magnum primers but it can’t hurt. There is absolutely no pressure signs and it’s not top of the load recipe. It’s running about 1400 FPS out of the 24 inch barrel.

Hmmm....where did you get the recipe?

You might be experiencing, or close to, a flame over. Spark from the primer is igniting the top of the powder stack, because of the low volume.

Have pictures of fired cases (prior to cleaning)? External and internal please.

 

[Emmett Dibble]

Hmmm....where did you get the recipe?

You might be experiencing, or close to, a flame over. Spark from the primer is igniting the top of the powder stack, because of the low volume.

Have pictures of fired cases (prior to cleaning)? External and internal please.

IMR lists max at 7gr. 6.6 is where it shoots best. No smoking cases if that is what your asking and besides for accuracy that is one of the things I try to avoid with powder selection in pistol cartridges. If I get great accuracy but have smoked cases I "may" live with it but honestly if a loading smokes cases it usually isn't the most accurate.

You have to remember this is a lever gun... the chambers are "generous" to start off with...

Also this is originaly a black powder cartridge so any smokeless powder except for maybe Trailboss is going to have a low fill volume. Actually Longshot does a better job then some of the others being a flake as opposed to ball powder.

With this discussion it does make me look back and CFE Pistol is what I was using previously and was getting good accuracy from as well. I switched to Longshot because I fell into a bunch of it and it was as good or better accuracy with a little more velocity (not chroni measured but by sight settings).

This thread has giving me some food for thought. I like the Mag primer idea and is something I hadn't thought of trying. It will be quick and easy to try on the next load batch and to test at the next match I shoot.

 

[DocBII]

cedestech,

I've found WSP and Fed small pistol, either match or regular, to be the cleanest primers. You may also wish to try one of the VV powders as a clean burning powder.

HTH,
DocBII

 

[acloco]

Which caliber is this? 38 ?

 

[Emmett Dibble]

38special

 

[piie]

Get a boresnake and then go test at the range (simulate match and rack time) if it helps to pull the snake through a couple of times during that 20minute break- if it helps, you might try it during shorter breaks too - doesnt take long… ive been doing this with my rifles - pull the snake with brush area soaked in some ballistol through twice while barrel is still warm before packing up for home.