Why Some Mag Wells Have No Rear Grooves And...

Some Do? Riesch explains that some makers put the two rear grooves in the mag well and some didn't do that in the manufacturing process.. What are they for?

Grooves for the magazine locking lugs. Don't really need to go full length, so machining step is eliminated. That's my guess!

Ken, That would be true if the mag locking lugs went into the mag well but they rest against the mag catch outside of the mag well.. The way I read it Riesch was saying the grooves were part of the way the T.H. was made and some manufactures didn't need to make them, thus some T.H. have the smooth mag well. I would think that eliminating those two slots would have really sped up production and it would have been across the board.

The grooves are for the locking lugs on the rear of the magazine. Why some trigger housings have full length grooves and some have partial length grooves is due to the tooling and milling process the particular manufacturer used. It's the same reason why some receivers have a square mill cut on the right side of the receiver and others have a round mill cut. There are a plethora of differences in like carbine parts that are directly attributed to the tooling the various manufacturers had on hand or could obtain.

Probably easier/quicker to just cut the magazine lug reliefs all the way through instead of having the mills stop at a certain point, requiring another clean-up/checking/measuring operation. If some manufacturers decided to do it 'right', that was their option. At least this way they were sure the cuts were deep enough to not impede magazine locking.

If they cut the mag well with a broach, they would have had to cut the grooves full length. If they cut the well some other way, or used a different broach, they would have had to cut the grooves in a later step using a rotary mill. Just a difference in how the tooling was set up. The U.S. allowed manufacturers a fairly wide latitude in setting up their tooling as long as the product was IAW specifications.

Jim