Need Help....Heavy Powder Residue On Case...

[Lefty7mmstw]

I've had poor luck developing velocity with h1000 in the stw... I don't use the 250 unless I don't care how sooty the barrel is because the 250 is one of the dirtiest primers on the market.

You have a very deeply cut chamber then; I had that issue with a previous barrel on my 7stw also (my chamber was also cut in the 15 to 17 thou. deep range), but never had the sooting problem you are encountering. That barrel is not a very expensive crow bar and the rifle is wearing a Shilen Select match barrel. I never had the sooting issue with the deeply punched chamber; it simply tore the heck out of the brass.

 

[MagnumManiac]

OK, let's put some of your anxiety to rest.
Your chamber is NORMAL, the case headspaces off the belt, therefore, your shoulder position plays NO PART in the first firing.
As long as you only bump your shoulder .002"-.003", everything, including case life, will be fine.
I will guarantee that your problem will be from seating the bullet so far out of the case neck. Put it in further, say one calibre, and retest. It is NOT necessary for very good accuracy to be close to the rifling, this is a BR belief that has somehow become gospel. Even jumps of .150" or more can be tuned to be just as accurate as .010".
I believe the little amount of neck tension is causing your bullet to move with the primer ignition, causing poor chamber seal due to lack of normal start pressure. I saw this, and dented case bodies, when working up loads when the 7mmRUM first appeared, errattic ignition is the cause.

Cheers.
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[jjmp]

Hey leftySTW,that's the first time I've ever heard of a primer being dirty,powder heck yes , but never a primer? Please explain ... MM not all chambers are cut normal their all cut with different reamers some different with slight variations,some are just sloppy,some slip threw and become problems,with so many varying chambers the die manufacturers,(redding) says to headspace magnums off the front shoulder for best brass life ,and to stop the cases from forming cracks about 3/16s above the belt on magnums ,brass stretches every time it's shot,excessive fl resizing over works the brass and causes that cracking above the belt like stated above. This is a real problem and any reloader must understand this, regards jjmp

 

[MagnumManiac]

Hey leftySTW,that's the first time I've ever heard of a primer being dirty,powder heck yes , but never a primer? Please explain ... MM not all chambers are cut normal their all cut with different reamers some different with slight variations,some are just sloppy,some slip threw and become problems,with so many varying chambers the die manufacturers,(redding) says to headspace magnums off the front shoulder for best brass life ,and to stop the cases from forming cracks about 3/16s above the belt on magnums ,brass stretches every time it's shot,excessive fl resizing over works the brass and causes that cracking above the belt like stated above. This is a real problem and any reloader must understand this, regards jjmp

How many chambers have you cut, personally?
Do you understand that it is IMPOSSIBLE to change the headspace on a belted cartridge?
Do you understand that the case on a belted cartridge expands from the front rearwards?

ALL belted chambers have generous tolerances for the shoulder, it is NOT required for the first firing, the belt holds headspace correctly.
As the case fires and pressure builds, the case neck AND shoulder expand well before full pressure is reached. How do I know this? After fireforming numerous cartridges from one size to another with fast pistol powders, if there is sufficient pressure to open the top 2/3rds of the case, this occurrs perfectly with fully formed shoulders, but the pressure isn't quite adequate to blow out the thicker lower case walls. The result is a semi formed case. Pressure follows the least resistance , this also translates to the cartridge case, the thinner sections obturate easier.
Cases only stretch from ONE cause, excessive headspace, now, this is a general statement, but there are 2 deciding factors when discussing belted cases. Headspade of the belt CANNOT be changed by sizing the case, it is fixed. If it doesn't measure .220" from the front of the belt to the base of the case, and the rifle chamber is longer than this, we have a problem, not only with the excessive belt headspace, but the generous position of the shoulder.
Now, if you have generous belt headspace AND generous shoulder tolerance, what do you do? If you don't do anything, your cases will stretch and eventually split.
Simple, forget the belt is there, and headspace off the shoulder, if you get it right, your cases will last far longer than if you get it wrong.
Just for your information, chambers that have .026" clearance in the shoulder to base measurement on belted chambers have passed through my hands, unintensional, and intensional. The 375 Weatherby I have has more clearance than this when I fireform 300H+H brass in it, it NEVER splits after this, why? I control headspace with the shoulder once it's fireformed.
Just a bit of knowledge for you to digest.

Cheers.
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[IDelkhunter]

Thanks for the continued responses. I appreciate the help and have only been doing precision hand loading for about 2 years now, so I apologize in advance if I get some of the terminology wrong. Maybe some additional information will help clarify what I seeing:

1. I'm using Redding S Bushing FL Dies - in order to determine which bushing to use, I size a case a with a bushing I know to be .002-.003 small and seat a bullet and then measure the neck. I then subtract .002" and use that bushing. In this instance, with this lot of brass, I was using a .311 Bushing, which means my seated neck diameter was .313. Measurements after firing were showing .316-.317".

2. I always headspace fire formed brass off the shoulder .002", even with belted cartridges....so I'm doing what you suggest (ignore the belt). Taking measurements on the virgin cases after firing them, I'm seeing about 40% that grew .008-.010" and 60% that grew .015-.017". This would indicate to me that the case is not fully expanding to the chamber and completely sealing off. Am I understanding this correctly?

So, if I'm understanding this correctly, seating the bullet long could cause it to exit the case early before the brass has sealed off the chamber, allowing gases and soot to surround the entire case. Correct? So, seating the bullet deeper should assist in a more fully fire formed case?

 

[jjmp]

MM, q1 haven't chambered any I'm no GS,q2 I do now thanks for your help,q3 same answer as q2 thks. Well now ,guess I'm not the sharpest pencil in the pack ,but I'm learning ,sure didn't mean to spoil your breakfast , glad you came around to my way of thinking 3/4 through your post ,wouldn't you agree I get an A for effort? Regards and ungard/toushey till vee meet again,jjmp

 

[jjmp]

IDElkhunter,in my best Peter/Sellers accent I do believe you have solved the case,,but I defur,so Brighter minds can confer,so carry on you know!!! Really your doing great for only 2/yrs at it regards jjmp :

 

[Lefty7mmstw]

Hey leftySTW,that's the first time I've ever heard of a primer being dirty,powder heck yes , but never a primer? Please explain ... MM not all chambers are cut normal their all cut with different reamers some different with slight variations,some are just sloppy,some slip threw and become problems,with so many varying chambers the die manufacturers,(redding) says to headspace magnums off the front shoulder for best brass life ,and to stop the cases from forming cracks about 3/16s above the belt on magnums ,brass stretches every time it's shot,excessive fl resizing over works the brass and causes that cracking above the belt like stated above. This is a real problem and any reloader must understand this, regards jjmp

ever do any brisance testing for primers??? I have and the 250 was the only one to literally throw chunks of crap on the catch paper. The win lr and fed lr primers we tried failed to leave anything but a bit of smoke and the rem lr wasn't far behind. The reason we were looking at primers is we didn't want to fire the primer past the end of the barrel on out 30-30 contenders. The sad part was every primer we tried fired the flame out of an empty case beyond the end of the barrel.

As to headspace on a belted, it is controlled by the belt. I had my last chamber cut to sub 5 thou headspace for a bit of room as it is a hunting round. When I set my barrel back in 800 rounds I will opt for sub 3 thou headspace to lessen the growth a bit as she is still growing 5 to 7 thou a firing. I want 3 to 5 thou growth in my 7stw with full house loads.

 

[jjmp]

Thks leftySTW for your answer about the primers and no I've never heard of that kind of testing, but I do get the picture now good explanation. Thanks for touching on the headspace topic again it making perfect sense kinda like what a very good gunsmith would have learned years ago, aka tighter headspace then sammi specs,because that limits brass growth got it thanks ,jjmp