Author Topic: Relief cut on Expander Plugs  (Read 4107 times)

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2150

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Relief cut on Expander Plugs
« on: January 05, 2011, 01:32:49 pm »
Recently I acquired an older Star Universal Progressive reloader circa 1951. It had tooling for both .38 Special and .45 ACP. The machine was little used and apparently all original. Each of the case Expander Plugs had a small "relief cut" at the junction of the full diameter bullet shaft and the angular incline which initiates the belling process. On the .45 ACP plug the bullet shaft was about 2/3s of the length of the the traditional expander plug. I have seen many sets of Star tooling since the late 1960's but this was a first encounter for me. Any information to share? Thanks/BFJ

MikeA

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Re: Relief cut on Expander Plugs
« Reply #1 on: January 05, 2011, 08:38:39 pm »
As a guess I would say that the cut was to relieve pressure in the case and
prevent the primer from backing out.  Just a guess mind you as none of mine
have such.
Mike A.

NYKenn

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Re: Relief cut on Expander Plugs
« Reply #2 on: January 05, 2011, 09:11:01 pm »
Brad;

MikeA may have the answer, it seems reasonable.
Maybe you cannot tell,  but do the cuts look like they may be original or an after thought by a previous owner?

Kenn
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fc60

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Re: Relief cut on Expander Plugs
« Reply #3 on: January 06, 2011, 01:00:19 pm »
It would be nice to have a close up photo of the parts in question.

Cheers,

Dave

2150

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Re: Relief cut on Expander Plugs
« Reply #4 on: January 07, 2011, 07:40:58 pm »
The cuts appear to have been factory turned and "probably" served to make a smooth transition from the straight diameter of the plug shaft onto the tapered cone portion of the belling process. I imagine that any "crud" that had formed on the inside of the case mouth could be mechanically peeled just before the trip up the expander/belling slope. I will try and get some good quality photos to share. Apparently the relief groove was not necessary, did not work or was of insufficient value to warrant the extra machining operation and was discontinued.