The lack of fouling buildup in the breech is one reason I shoot Swiss.
Patch lube can effect this as well.
There are a lot of strange things with fouling that may be related to bore size.
In testing a 58 caliber barrel with I found that it fouled heavily, throughout the bore with over 100 grains of ff or fff Swiss. Yet my 50 caliber shoots 90 gr of fff with no problems.
I had questioned people having fouling problems with the 58, thinking it was some fluke, or patch lube etc. But my experience with this barrel makes me think its something to do with bore size, ball weight and charge weight? I am told that once the burn temp reaches a certain point the fouling cakes and it could be that the 58 is prone to this? Swiss is somewhat hotter than Goex. Which I did not test. But I had no current production Goex and shooting older made in Moosic stuff would not be useful in my context. In 20-20 hindsight I should have shot some just as a control.
This rifle has this breeching
The only other 58 I ever had any experience with was one I made back in the 1960s and used 120 gr of Dupont (virtually the same as Moosic GOI/Goex) FFF in it with no fouling problems it was a "plain" flat breech
My 16 bore rifle will shoot to 170 gr of FF Swiss will not cause heavy fouling. But it makes a lot of recoil over 140 which gives as flat a trajectory as I need.
But it has a Nock breech.
This will change the way the powder burns or so we are told. Its supposed to make it more efficient based on early 19th century testing I have read.
Switching a 45 (or any caliber) from FFF to FF would reduce the burn temp and also reduce the velocity with the same vol or weight of charge. The reduced burn temp will reduce efficiency but this may be offset by other considerations and accuracy might be one. Caked fouling might be another.
This is why its important to shoot FF and FFF in rifles to compare accuracy and fouling.
I shoot a lot of FFF in bores under
Dan