Wednesday, September 15, 2010

Barrel installation and extractor relief cut

Progress report on the .45-70 Mosin build.

Objectives of the this build session were
1) Properly torque the barrel and verify head space.
2) Cut the extractor relief.
3) Install barrel.
4) Test fire.

Barrel installation

Tools:  For the barrel install we used the previously described action wrench to hold the receiver, and a very simple set of aluminum blocks to clamp the barrel. The final setup looked like this.
The action was screwed on hand tight to the barrel, and a hash mark was made using a marker. The action was then turned until the hash marks were 1:30 to 2 o'clock apart. A new hash mark was drawn. The barrel was then removed and reinstalled, to ensure proper hash mark alignments. Once the alignment was verified, a hash mark was engraved onto the barrel to match the factory hash mark on the bottom of the receiver.

Extractor relief cut

Tools: The proper way to cut the extractor relief is with a rotary table. We do not have this rather costly device. Instead a 1-2-3 block was clamped perpendicular to the mill vice, to serve as a working zero. A mill was used to take small sequential cuts along the diameter of the barrel.

(This subject will be revisited in a separate post at a later date. Do to time constraints at our day jobs a more thorough explanation of this critical step is not possible at this time.)

The barrel was removed from the action. The hash mark engraved in the earlier step, matches the hash mark on the pulled barrel. This gives us a reliable refernce point for the extractor relife layout. The extractor relief cut was copied from the pulled Mosin barrel. Here is the rough cut.

A dremel tool with a small round diamond bit was used to clean up the machining marks. 

Barrel install

This is a straight forward repeat of the earlier step. Make sure that the hash marks align properly. If everything was done right the extractor relief cut will align with the extractor relief on the internal locking collar of the receiver. Now is the time to do extensive safety testing. First check the head space using the masking tape method. In Volands case (Mid 1930ties Tula action), the action will lock on a spent shell and two layers of masking tape. Next check that the extractor clears the barrel. Use a dummy round or a spent cartridge for these tests. Make sure that the action will lock with an empty shell, and the extractor installed.
In our case the rifle passed with flying colors.

Test fire

We were very excited to test fire this creation, after so many hours of work. In order to do a safe test fire, a stock was needed. Voland will be using a modified Finnish M39 stock for the project. The Sarco/Navy arms .45-70 barrel, round receiver combo fits perfectly into the M39 stock. The stock was shortened in the front to clear the muzzle. Here is the assembled rifle (The magazine is not functional a this time).
Here is the video of the initial test fire, using winchester factory ammo. We were so excited about the test that a crucial piece of safety gear was not worn, ear muffs, were left off. Be careful hearing aids are expensive.

Brass looked healthy following the test fire. More testing will follow.

Next time we will update on

1) Extractor modification
2) Stock
3) Sights