GregLaROCHE
11-04-2018, 10:21 AM
I am shooting a Marlin .45-70 from the mid eighties. It has a micro groove barrel. That means the bore diameter takes up most of the space in the barrel because the grooves are very thin. In what is considered a normal barrel, the grooves are much larger.
Therefore, a lead boolit has more space to obturate. Some of the lead can move into the grooves. Does lead move in other directions also? The boolit probably elongates too, if there is not enough space for the excess lead to go into the grooves.
If a higher BHN alloy is being used, it seems like it would take a higher chamber pressure for the boolit to obturate enough to pass through the barrel. Is one to three thousands over bore still advised with a hard alloy?
I am particularly concerned, because my micro groove barrel has even less space that what is considered a normal barrel, so it can only change in length.
What do others think about this?
Therefore, a lead boolit has more space to obturate. Some of the lead can move into the grooves. Does lead move in other directions also? The boolit probably elongates too, if there is not enough space for the excess lead to go into the grooves.
If a higher BHN alloy is being used, it seems like it would take a higher chamber pressure for the boolit to obturate enough to pass through the barrel. Is one to three thousands over bore still advised with a hard alloy?
I am particularly concerned, because my micro groove barrel has even less space that what is considered a normal barrel, so it can only change in length.
What do others think about this?