Cast bullet loading issues

[kombi1976]

I have a sporterised BSA Martini Cadet in 25-20 and it's turned out to be an accurate little rifle with jacketted loads, printing an average of 1" groups @100yds.
But I'm also loading some 75gn cast bullets & have had no end of trouble with them.
I'm using ADI AR2205, much the same as H110, & the factory recomended loads are a minimum of 6gn & a max of 7gn, both for 71gn & 86gn cast bullets.
I loaded some at 6gn to keep velocities down only to find they weren't producing enough pressure to seal the case neck against the chamber wall, had fouled down the outside of the case neck & left a lot of unburnt powder.
I then upped the charge to 6.5gn & the problem remains.
I sincerely doubt that going to 7gn will fix it.
Should I bump it up to 8gn as this is still 1.3gn below the min for jacketed 75gn bullets?
Or should I try pistol primers rather than rifle primers?

[JBMauser]

I would not be very concerned with unburned powder.  I would anneal the necks of the cases before I went to higher loads, Not that that is not a plan, I would just anneal to remove that variable.  what is the performance of the loads you have tested? JB

[JBMauser]

After thoughts.  Many of my best cast loads smoke the neck of the case.  these are low pressure loads.  You may not be able to build enough pressure to seal the neck as cast bullets will release from the neck at a lower pressure than a jacketed bullet and it offers less resistance in the bore which is a component of pressure.  make your powder decisions based on your target results and wipe your cases clean.  JB

[kombi1976]

To be honest I haven't paid much attention to accuracy simply because I've been concerned about the smoking and the possible danger.
I've made up some 8gn loads and will try these to see if it cures the problem.
If not I'm mystified and may give cast jobbies a miss. :|
Since it groups an inch or smaller with jacketed rounds I don't really need them.
It just would've given me something fun to play with. :wink:

[JBMauser]

I guess I need to clarify your situation.  Are you getting sooting past the neck and down the shoulder?  Sooting of the neck with a clean shoulder is normal and not a concern.  sooting down the shoulder is a problem.  Sooting the shoulder is an issure of pressure and headspace should be looked at as well.  to low a pressuer can actually move the shoulder back or so I have been told.  I have never encountered this problem.  JB

[Questor]

I see this kind of sooting in my low-pressure 45ACP loads. The sooting occurs because the pressure is too low for the brass to seal against the chamber. It's not a problem and is accepted as normal by target shooters who typically fire half a million rounds through their 45s before any serious maintenance is required.

I don't know if that's the case for your cartridge, though

[kombi1976]

I pretty sure the shoulder is staying clean and headspace is fine.
But what about that unburnt powder?
It's pretty gritty and annoying.

[Steve P]

I have several 7TCU cast bullet loads that are mild.  They always produce a sooty neck.  Always leave residue in the barrel, but it is burned powder and lube residue, not unburned powder.  I would surmise you too have a little lube residue left and smoke/lead on the neck.  If they are accurate, don't worry about it.  Just clean it up.  

Steve