sooty brass

pete evans

Well-Known Member
havnt done much reloading but have 2 loads for .243 (70 balistic tip over 39gr h4895 and 100gr spbt over 33gr h4895) both accurate and brass comes out ok no pressure signs etc. been given some h4350 and loaded up some rounds of 100gr spbt used the same preping sizing trimming and seating as the other two rounds and loaded up from 38gr.
Velocities were as one would expect accuracy so so for 1st group 2nd and 3rd opened up alarmingly 4" at 150yds. The brass was sooty? no signs of excess pressure on primer. what the main cause of this? doesnt happen with other loads with identical brass, heads and prep?

Pete
 
Soot on the outside of the case? Could be low pressure, the case is not expanding to seal against the inside of the chamber?...
 
What cases are you using?
I used Accurate Arms 4350 (very similar burn rate to H4350) with RP cases for quite some time with no sooting then I switched to Lapua cases using the same powder charge etc I had sooting all the way down the case.
Lower charges made it worse.
Upped the powder charge by 0.5 grains and the sooting stopped half way down the case.
Upped again by another 0.5 grains and the sooting stopped half way down the shoulder.
In the end I had to load the lapua cases with 1.5 grains more powder to get them to seal in the chamber.
Obviously only increase powder charges with care keeping an eye out for signs of pressure
 
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I had the same problem with my 6.5x55, it stopped when I increased the charge or decreased the OAL.
 
I suspect as others have said that this is almost certainly low pressure rather than high pressure.

Starting with book minimum loads from one reloading manual I found that I was getting soot on my cases and I'd worked up to max before the problem cleared up. I then found another load, in another manual, that started at the max load as printed in the first manual, when I worked up this load I got to the book max with no pressure signs. So, I guess it is true that rifles are all different and you need to keep your wits about you.

It is said that very low powder loads can lead to something called secondary detonation which can cause a big pressure spike and blow up the rifle. Now, I've no idea if this is true or not but I think the bottom line is that low pressure loads can be as risky as excessive pressure loads and it is worth keeping it between the hedges.
 
Compare the case capacities by filling with water and weighing the water. Odds on the new cases have a greater internal capacity . Bigger volume means lower pressure with the same powder charge so upping the powder will bring the pressures back to where the smaller cases are with the lower charge. check the case capacity first though.
 
I had a guest 'rifle' at one time who used a Mannlicher stutzen in .243. His stags were always killed with exactitude, but his extracted, (reloaded), cases were always sooty on the neck and shoulder.

His fired primers were plump and not filling the primer cup. Not enough pressure to seal the chamber, but his rifle was accurate with that load, and it killed.

Sometimes a rifle will tolerate a lighter load and deliver accuracy - and in this case - killing; which is after all what the business is about.

Some rifles will, however, deliver the goods after a 'dead' spot, just like an old fashioned carburettor, and after moving up a grain of powder or two in the cartridge, (as long as the primer does not show signs of stress by being unduly flattened or punctured), the rifle will settle down to excellent grouping again without backblow pressure in the chamber.

The neck of the case has to seal the wall of the chamber before the gasses blow back. It's as simple as that.

One little thought. Case cleaning can become a bit of a fixation. Make sure that the cleaned case is left with as close to a factory textured surface as possible and not shining like a regimental cap-badge. The case needs to grip the chamber wall in order to create a sure seal and assist in helping the bolt to contain the rearwards pressure.
 
Absent minded as usual, I forgot to reinforce caorach's comments on how to blow up your rifle.

It's been a point of sometimes heated discussion and opinion for years, but the advice is :- do not reduce the quantity of magnum or slow burning powder in cartridges which use such powders, below a certain point, or you are liable to incur detonation rather than the controlled burning which is desired.
Detonation can have detrimental effects in nose-picking capabilities for the future - or the ability to scrutinise page three !
This subject lies within the shadowy realms - at least it used to in my earlier years of reloading when I used a mallet to drive the bullets home, but I have not heard since if the matter has been resolved.

One argument was that a greatly reduced measure of slow burning powder created too great an oxygen-to-nitro mix in the case which enabled instant detonation instead of a controlled burn.
I simply do not know, but I do know that it is wiser to be sure than to take unwise and needless risks.
 
I have read a little on the US NRA's studies on detonation, as well as those from the Aberdeen Proving Ground for the US Army and it is a gray zone. In any event, while they have yet to figure out exactly the physics inside the case at ignition, the results (tho rare) are pretty well documented. It is generally believed that light charges of slow power lay horizontally in the case and on ignition, provide an enlarged burning area of powder to ignite. As Eco says, excessive pressure ensues and the bullet becomes an obstruction causing a rifle to burst.

With all that said, it makes me a little nuts to hear shooters say "Stay away from the lower end of the reloading data: you could blow your rifle up!" It is simply not the truth and unless otherwise noted**, most reloading manuals advise starting at 5-10% below minimum charges and work up; and that includes slow burning powders. You must be well below that level to even worry about detonation. Starting loads can leave sooty cases when a slower powder is used. It does no harm.

I shoot more reduced (slower than even starting loads listed in manuals) than full power loads in my rifles. It is easy on the brass, easy on the gun, and easy on my sissy shoulder! I reserve full power loads for the field. Reduced loads are accurate and inexpensive when assembled with proper components. JMHO~Muir

(** Some pistol powders, for example, are never to be reduced from starting listed loads)
 
unlikely to have det probs as i start from min load. problem is I got soot approaching max plus crap accuracy. Is it possible that by shooting 3x 5 shot groups in quick time, 5 mins or so, that the gun would heat up enough to open the groups up? the 1st group was okish bout 1" last group was rubbish 2-3".
Might just forget about it as I have decent load with 4895. Just a bit frustrating as 4350 considered good powder for .243.
The case volume thing may be possible but I have always used the same cases to date with no issues, federal.
 
Hi Pete,

Can I ask what OAL you are using and how much of the bullet is seated in the neck?

I had the same problem with bad accuracy and dirty cases, but by seeting the bullets deeper the accuracy improved and the cases came out clean!
 
I've been seating to the same depth as the federal powershock ready rolled. I should imagine that is deeper than most homeloads but certainly worth a try.

Pete
 
Just a thought, but you might want to crimp the loads with a Lee Factory Crimp Die. Additionally, you might try starting over with 4350 and a different primer; perhaps a magnum primer. Remember though, when switching to a different primer you need to start over at the bottom.~Muir
 
Hi Pete

I had the same problem with my 6.5, well not a problem really as I realised right away what was wrong. The book said starting load of 46 grains -51 grains ...but anything under 46.5 grains made the neck and far down the shoulder really sooty. It stopped when I increased the load.

Pete
 
I've been seating to the same depth as the federal powershock ready rolled. I should imagine that is deeper than most homeloads but certainly worth a try.

Pete

I've ended up doing the same thing in my .243. I started out trying to be clever and seated my bullets just off the lands, trying to work up a load based on OAL. Accuracy was so-so but acceptable at about an inch and a half to two inches, which I just put down to the 100grn bullets being maybe a bit on the heavy side for my barrel. I stalked with the loads, killed deer and was content. Then one day I planned a trip to the range and just threw some shells together with the bullet seated on the crimping canelure. The first group I fired went into an inch. I've not messed with the seating depth since.
 
A question for Muir, I am getting soot marks on the necks of my cases but not the shoulders, in fact the necks are very dirty, this is happening with all loads and even factory ammo, I am not worried about it as the rifle still shoots to P.OA.


Now the question, would I be correct in assuming that this is due to wear in the throat, this from the rifle that has been mentioned on other posts having fired approx 26000 rounds [ which some people find hard to believe]
As I said I am not really worried about it just interested, in fact now just interested in how many rounds it will take to
wear out this barrel,

Can you give any reason why this barrel should have lasted so long when you hear of others shot out with a few thousand rounds. its a Sako A11 IN .243
The other thing I find strange, is I believe all Sako barrels in .243 were a 1in10 twist I have tried to measure the twist in this barrel and unless I am doing something wrong, which is quite possible its a 1 in 12

Any ideas please on the longevity of this barrel?
 
Bog: No saying why the barrel lasted so long. Good steel and sensible loadings will usually add to the longevity of a barrel. Look at the 204 Ruger caliber. Barrels are toasted after 1100 rounds of factory ammo and less with hot handloads.

You don't mention how long the soot on the necks has been showing up but I'm assuming it is a fairly recent or progressing event. As it causes no problems other than an additional case cleaning shore you should be all right. Don't give it too much thought as I have seen the same in new factory rifles with factory ammo. In this country, it is an easy thing to take the rifle to a gunsmith and have the barrel set back a turn of the threads and rechambered. I used to do it all the time...~Muir
 
Hi Pete,

Can I ask what OAL you are using and how much of the bullet is seated in the neck?

I had the same problem with bad accuracy and dirty cases, but by seeting the bullets deeper the accuracy improved and the cases came out clean!

The simple answer is that by seating the bullets deeper you reduced the capacity and there fore upped the pressure.
 
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