Machining (Exam 3) Flashcards
The process used to create a specific mark will affect the…
Uniqueness
How does lapping affect the uniqueness of marks?
It polishes out rough spots such that there are less individual marks overall
Define deep-drilling.
Creating a hole for the barrel’s bore
Define lapping.
Polishing prior to rifling in high-end barrels only
Define crowning.
Way to protect muzzle edges of the rifling from damage
Define chambering and throating.
Process used to create the chamber and taper the intersection of the chamber and the rifling
Define rifling.
Spiral grooves cut into the firearm’s bore
How do drilling & reaming affect the bore & chamber?
They leave spinning marks perpendicular to bullet trajectory or cartridge leaving the case
Is there a subclass to drilling & reaming?
No
What is cut rifling?
Cutting away material from the grooves
What is single-point cut rifling?
Rifling that cuts one groove at a time
What is broach cut rifling?
Rifling that cuts all grooves at the same time
Broaching between consecutive barrels creates…
Subclass
Are the marks created by broaching parallel or perpendicular to the rifling?
Parallel
How does button rifling work (HINT: think like it’s a button)?
Pushes the grooves down (no metal removed)
How does electrochemical rifling work?
Wet-etching the interior of the barrel under an electric current
How does hammer-forged rifling work?
Hammering the barrel around a mandrel
Does hammer-forged rifling leave individual marks?
No, not really
Does button rifling leave individual marks?
No, not really
Does electrochemical rifling leave individual marks?
No, minimal marks
How does electron discharge machine rifling work?
Electrical sparks melt away drilling & reaming marks from grooves but not lands
Nominal caliber measures…
Bore size (land to land)
Define twist rate.
Length of barrel required to complete a full rotation
What is the difference between conventional and polygonal rifling?
Conventional rifling is more rectangular while polygonal rifling has more hill & valley shapes
How do you determine twist direction?
Seeing which direction the spiral is coming from and going toward
Will a Glock have polygonal or conventional rifling?
Polygonal
Individual characteristics are unique to a specific firearm and are created by imperfections that do not… (HINT: rifling direction)
Run in the same direction as the rifling
Considering that shotgun barrels are smooth, do they leave markings on projectiles?
No
