Black soot on cases head scratcher for me???

[hweissert]

So I just picked up a new 284 Win from smith and started working on loads today. This is the 3rd I've gotten from same smith and off same reamer for all 3 rifles. I gave my son my first one, my buddy built the other, and I built another to replace the one I gave my son which is rifle I'm talking on. All 3 are Bartlein #4 barrels same twist length etc. First 2 built on Remington LA and mine on Stiller Predator LA. I got the load on my first one, which is now my sons and it shoots ragged holes with ogive of 2.485 on Hornady comparator over 56.7g of N165. My buddy got his and it shoots same exact load other then his touching is 1 thousands shorter at 2.484 but, same powder charge shoots same ragged holes. Flash forward today and I started break in on barrel and cleaning with some extras from sons rifle. After I had shot cleaned etc, I started load development and noticed mine has an ogive of 2.520" to touch and with same powder charges I'm getting black soot down the entire length of case and caking of soot all the way down around the case head and extractor groove. Now when I've seen this before, it's typically been under charged load. However, max shows 57.0 gr of N165 on quick load and that's the upper upper echelon. The same 56.7 load shoots like a house on fire but, have soot all over the case and very dirty chamber after firing. I proceeded with caution just to see if it were an under charge and I can in fact get it to clean up at around 2-3 grains to even 4-5 grains over of MAX powder charges. I tried 4 different powders of N160, N165, H4350, and H4831sc. All were the same. Book or QL max would have soot everywhere and rifle shoots lights out. Jump up to dangerous charges, cleans it up but only shoot 1/2-3/4" groups at best. ES and SD fantastic on dirty loads and not good on higher charges when it cleans up. Im not terrible interested at running it on the brink of disaster charges to get it to shoot clean. I'm puzzled. Anyone have any idea? Biggest thing that has me is the ogive difference when the other 2 are **** near identical then mine is 35 thousandths longer. Could it be a head space issue? Im
Savy on loading and shooting but, novice on gunsmithing.

 

[slikmrc]

I had the same thing happen last fall fire forming some new 300 wby brass. Didn't want to use H1000 so I loaded up some loads with H4895 and 165 grain bullets, was in the middle of the charge weights. Shot two of the loads, brass showed no to very little expansion anywhere on the cases. Pulled the bullets and charged the cases with H4831 and they fired and formed as normal with the pulled bullets. Thoughts were maybe poor case fill caused it . It darn sure spooked me, does your smith have any ideas?

 

[hweissert]

I had the same thing happen last fall fire forming some new 300 wby brass. Didn't want to use H1000 so I loaded up some loads with H4895 and 165 grain bullets, was in the middle of the charge weights. Shot two of the loads, brass showed no to very little expansion anywhere on the cases. Pulled the bullets and charged the cases with H4831 and they fired and formed as normal with the pulled bullets. Thoughts were maybe poor case fill caused it . It darn sure spooked me, does your smith have any ideas?

No he was a little puzzled too. Just has me scratching my head. I'm not even in the middle of the powder column. I'm on the upper end with that soot and having to go 5% plus over max charge to get it to seal. Case fill is not an issue I know and it's been the same over 4 different powders. N160, N165, H4350, and H4831sc. I'm gonna run it bk tomorrow and Ck head space but I wouldn't bet on it being not correct. Just has me puzzled with ogive measurements being so different on it than other 2 rifles when the barrels are same contour and cut with same reamer

 

[Hugnot]

Check out the inside neck diameter of the sooty cases - like try pushing a bullet into the necks. As expected, the fit will be tight enough so there will be no slip fit and bullets can't be pushed into the case neck or are really tight.

My guess is that the necks are work hardened to such a point that neck brass spring back occurs preventing a good neck seal and soot loaded gas escapes down the case and is deposited on the bolt. Try annealing the necks.

I have had that happen and checking out sooty fired brass showed tight necks and the clean cases had expanded necks - all with the same near maximum load. Annealing all cases fixed the problem - uniform neck tension.

 

[slikmrc]

That is a weird one. Even with a headspace issue would think the brass would seal. Would be interesting to know what kind of speed your getting. Hope your gunsmiths inspection gives you some answers.

 

[hweissert]

Check out the inside neck diameter of the sooty cases - like try pushing a bullet into the necks. As expected, the fit will be tight enough so there will be no slip fit and bullets can't be pushed into the case neck or are really tight.

My guess is that the necks are work hardened to such a point that neck brass spring back occurs preventing a good neck seal and soot loaded gas escapes down the case and is deposited on the bolt. Try annealing the necks.

I have had that happen and checking out sooty fired brass showed tight necks and the clean cases had expanded necks - all with the same near maximum load. Annealing all cases fixed the problem - uniform neck tension.

I thought on this one earlier. I checked all case necks and All seem to be same, concentric, and all the "lower charge" (near max) indeed has a tighter neck than the ones that I'm firing on the brink of disaster. However, this is all new Norma brass. I set up bushing sizer with 2 thousandths neck tension and resized a doz once fired and just for the hell of it, annealed them first. I rarely anneal mine until it's got a few firings. But just for sake here, I did. No change. Soot like crazy

 

[hweissert]

But the sooty cases shoot like crazy. The ones that seal open up on group size. lol. Guess I can carry a hanky to wipe my brass down afield

 

[DUSTY NOGGIN]

i think i would try a heavier bullet to fill that different length throat , did you ask smith to throat it longer , because that is usually a separate step ,

what bullet are you using ,

This is the 3rd I've gotten from same smith and off same reamer for all 3 rifles

what applies to you starts at about 7;00

 

[Tiny Tim]

If your smith doesn't find anything, try annealing your necks. Its a shot in the dark and not likely, but eliminates yet another variable. Its possible the final annealing was missed, especially in this time of mass demands on production.

 

[Hugnot]

I have had the same problem.

Upon going thru this stuff again I noticed that your cases were new and were then annealed.

My .223 cases were some .030 over spec trim length. Upon firing, the untrimmed, much sized, & un-annealed cases, were covered with soot. Having some 5 load cycles I thought it would be a good idea to anneal the cases, then upon measuring them, I found that they measured 1.780; .223 trim length should be 1.750 - I trimmed them to 1.750. The soot problem stopped, now I not sure the fix was the annealing or trimming.

I once had a chamber that was non-spec in regard to length and I had to trim brass an additional .010 less than spec.

Could chambering an over-length case cause crimping & prevent neck expansion making for soot deposits?

Upon trimming I noticed the sooty cases were .030 over spec trim length (1.750 spec trim, 1.780 sooty) .

 

[hweissert]

i think i would try a heavier bullet to fill that different length throat , did you ask smith to throat it longer , because that is usually a separate step ,

what bullet are you using ,



what applies to you starts at about 7;00

Shooting the Berger 168VLD hunting. Didn't request any deeper throat for longer bullet but, the 180's are not a lot longer than the 168. I still, even with the longer throat, have right at the diameter of the beating surface inside the case neck

 

[DUSTY NOGGIN]

i think larger bullet will be your answer, try not using the slowest powder of your options

once you fire out that norma to reach the full shoulder , you should see less , even if you stick with the 168s

 

[slikmrc]

Couple of other bandage is seat bullets deeper and crimp them. Could try a hotter primer to.

 

[longestrange]

Here are some things you mght try, but first please let me point out that 3,000 psi air from a scuba valve will penetrate your skin and cause serious damage. 3,000 psi hydraulic fluid from a pinhole leak will inject the fluid into your bloodstream and can kill you quite dead. You have 60,000 plus hot gas getting past the only real seal - your case mouth, and getting all the way back to the bolt face. Rifle manufacturers have various venting schemes to mitigate this but it might escape by another path, such as back through your firing pin hole. For reference, if you get your finger next to a revolver's front cylinder it will probably get amputated.
Thus I wouldn't even dream of troubleshooting the problem by firing the weapon until the cause has been definitively established and rectified, even with storm-trooper armor on.
A few things that can be checked without firing the weapon, in my humble opinion:
First, have a look at the reamer. If the reamer somehow was chipped near the case mouth, it could have left a smaller diameter bore in the chamber there. That would keep the front of the neck from expanding, greatly increasing the pressure required to make the rest of the case neck seal. That would be very similar to what Hugnot experienced in post 10. Wear in that area would also make the chamber conical with similar results. A micrometer might tell you something if so.

Another thing that might be going on is somehow a groove or crevice is running from the case mouth area to the shoulder in the chamber. Even a very shallow groove would prevent the neck from sealing into the chamber along that line.
One cause might be that the reamer was stopped in the process of cutting the chamber. Imagine a cheap blade type pencil sharpener - you turn the pencil and it shaves off wood. If you suddenly stop turning it it will leave part of the wood uncut. Your reamer could do the same thing, and subsequent polishing would only hide the issue from view.
There are a lot of other ways this type of groove could be produced, some quite technical in nature. If your bbl is made from 416R stainless then it has sulfur added to make it more machinable. The sulfur creates weak spots that help break the chips whilst turning, rather than one continuous chip. Carbides or other non-metallic inclusions, porosity, laps and seams in the rolled metal could result in the same type of phenomenon.
So how to test for this?
One way would be to solvent clean the cases you already fired and very carefully check for longitudinal bulges, possibly with a dial indicator on a lathe. Another would be to make a chamber cast and measure it carefully, possibly with a dial indicator. A borescope might see something as well, though you might need to use dye penetrant to see a microscopic crack.