I have a 1908 Mannlicher Schoenauer in 8X56MS that after firing a very mild load experiences extremely difficult bolt lift once the bolt handle has reached 1/2 way of its lift.
There was concern that some of these Mannlicher Schoenauer rifles had undersized bores and this might be causing a pressure situation. Although the case exhibited zero signs of pressure, I performed a cerrosafe cast of the barrel and measured a proper bore diameter.
So.........Last night I completely disassembled the bolt.
With no cartridge in the chamber the bolt will easily open. No resistance what so ever. These rifles exhibit a relatively hard bolt lift without anything in the chamber, so removing the firing pin and cocking piece removes all extra resistance to bolt lift.
Using the bolt without the firing pin or the cocking piece I inserted a piece of fired brass. I experienced extreme hard bolt lift once the bolt handle was raised to 1/2 its upward movement.
I full length sized this brass and although the resistance was lessened, it was still very difficult to move the bolt handle past the half way mark.
I measured this piece of brass and confirmed that all dimensions are under the spec I found on the internet for 8X56MS cartridge.
But to be sure I ground a few thou off the rim.....no improvement.
I then ground a few thou off the base of the cartridge....no improvement.
I them took the resized case and cut it 1/2" above the base and using this stub I inserted it into the bolt and pushed the bolt home. I wanted to be sure the resistance was not due to the extractor or the ejector......Bolt opened easily. So the issue is somewhere north of the first 1/2" of the brass.
I then took a piece of once fired brass and in the lathe removed one thou from the middle third of the case. Voila! The bolt handle moved easily!
I then smoked a piece of once fired brass to see if I could observe where it was hitting. The smoked case showed contact with the brass over it's whole length.
My conclusion is that I have a "banana" shaped chamber or an "oval" shaped chamber. Although I can't confirm either of these theories with the measuring equipment I have at my disposal.
I've had this happen with a few rifles in the past. Usually egg shaped chamber resulting from poor chambering jobs (not of my doing) with short cartridges (6BR and 6PPC).
My solution has always been a Cerrosafe cast of the chamber and using the casting attached to a long brass rod with grinding compound and an electric drill to polish the chamber round.
Unless anyone has something else they think I'm missing, I'm moving forward with this process.
Comments and suggestions welcome...........
Thanks
This photo shows the test brass. As you can see on the "smoked" piece, there is extra contact on the middle portion. The piece to the far right shows the turned down rim and the ground base. I also filed some brass off the shoulder to see if this might be the sticking point. And finally the turned center section.
The machining on this 1908 bolt is nothing short of amazing!
The bolt without the firing pin or cocking piece
There was concern that some of these Mannlicher Schoenauer rifles had undersized bores and this might be causing a pressure situation. Although the case exhibited zero signs of pressure, I performed a cerrosafe cast of the barrel and measured a proper bore diameter.
So.........Last night I completely disassembled the bolt.
With no cartridge in the chamber the bolt will easily open. No resistance what so ever. These rifles exhibit a relatively hard bolt lift without anything in the chamber, so removing the firing pin and cocking piece removes all extra resistance to bolt lift.
Using the bolt without the firing pin or the cocking piece I inserted a piece of fired brass. I experienced extreme hard bolt lift once the bolt handle was raised to 1/2 its upward movement.
I full length sized this brass and although the resistance was lessened, it was still very difficult to move the bolt handle past the half way mark.
I measured this piece of brass and confirmed that all dimensions are under the spec I found on the internet for 8X56MS cartridge.
But to be sure I ground a few thou off the rim.....no improvement.
I then ground a few thou off the base of the cartridge....no improvement.
I them took the resized case and cut it 1/2" above the base and using this stub I inserted it into the bolt and pushed the bolt home. I wanted to be sure the resistance was not due to the extractor or the ejector......Bolt opened easily. So the issue is somewhere north of the first 1/2" of the brass.
I then took a piece of once fired brass and in the lathe removed one thou from the middle third of the case. Voila! The bolt handle moved easily!
I then smoked a piece of once fired brass to see if I could observe where it was hitting. The smoked case showed contact with the brass over it's whole length.
My conclusion is that I have a "banana" shaped chamber or an "oval" shaped chamber. Although I can't confirm either of these theories with the measuring equipment I have at my disposal.
I've had this happen with a few rifles in the past. Usually egg shaped chamber resulting from poor chambering jobs (not of my doing) with short cartridges (6BR and 6PPC).
My solution has always been a Cerrosafe cast of the chamber and using the casting attached to a long brass rod with grinding compound and an electric drill to polish the chamber round.
Unless anyone has something else they think I'm missing, I'm moving forward with this process.
Comments and suggestions welcome...........
Thanks
This photo shows the test brass. As you can see on the "smoked" piece, there is extra contact on the middle portion. The piece to the far right shows the turned down rim and the ground base. I also filed some brass off the shoulder to see if this might be the sticking point. And finally the turned center section.
The machining on this 1908 bolt is nothing short of amazing!
The bolt without the firing pin or cocking piece
