Partial case sizing of bullet

[adam_mac84]

I have found a load that runs well as cast in 9mm 356-124-2r. Seated to 1.050 chambers in my m&p. Shoots well no leading. PC boolits come out ~.359

I can also size and shoot in same gun .356 seated 1.120 (if I need longer OAL)

Anyhow. Got a glock. So starting over. Slugged right at .355. I tested my 1.050 OAL that I had been using. Passes plunk. But I pulled the dummy round. Behind the lube groove is swaged down to .355, in front of band remains .357+.

I am being more cautious with the glock now. So was thinking. Will this .355 obturate and plug sufficiently if ahead of it there is a good seal? Obviously I intend to take the OAL that works and back it off and work back up to minor PF.

I am using Lyman m die to try to prevent bullet sizing in case


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[Ed_Shot]

Which expander plug are you using in your M1 die?

[adam_mac84]

I don't know if I know the answer to that? Came with. It's for 9mm. Are u asking diameter of the steps?


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[Ed_Shot]

I don't know if I know the answer to that? Came with. It's for 9mm. Are u asking diameter of the steps?


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Is your expander plug marked "38AP" either on the top or on the nose of the plug?

You are asking the right question: What is the diameter of the nose (first step) of your expanding plug?

[adam_mac84]

I will throw calipers on tonight after work! Thanks


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[44MAG#1]

If your Glock barrel slugs "right at" .355" and the base band is swaged down to .355" I fail to see the problem.
Are you sure you are not over thinking this? Now if the cases were swaging down the base band 2 or 3 thousands under groove diameter I could see where IT MAY CAUSE A PROBLEM but not necessarily that it will.
My method for anything is KISS. More times than not the KISS principle works well. When it doesn't then look at problem solving. Not before.

[Ed_Shot]

Here is an excellent discussion about Lyman M dies and 9MM neck expansion.

https://www.google.com/url?q=http://castboolits.gunloads.com/archive/index.php/t-158806.html&sa=U&ved=0ahUKEwjIl_LhyqnUAhVMQSYKHe7sDvsQFggKMAM&client=internal-uds-cse&usg=AFQjCNGa3oOraXHPsnxqmSRNiUrzLrGQ8g

I use Lyman dies for 9MM and 38/357. My 38AP expansion plug that came with the 9MM dies measures .353 on the nose (first step) of the expansion plug. The second step expands just the case mouth. My 38P expansion plug that came with my 38/357 dies measures .356 on the nose (first step) of the expansion plug and the second step expands just the case mouth.

The nose (first step) of the 38P expansion plug is longer and less tapered than the nose on the 38AP plug, so much so that you can't get the 38P plug into a 9MM case (without destroying it) far enough to bell the case mouth with the second step of the plug. The first draw back of the 38AP plug is that if you want to use a 9MM boolit sized larger than .356 you are only expanding the case body .353 and asking to have your boolit downsized. The second draw back of the 38AP expander is that (given the tapered 9MM case) it doesn't expand the 9MM case deep enough to seat boolits to the OAL you are using without having the case squeezing them down. You indicate you are getting the diameter of your boolit bases reduced.

Good solutions are brought up here on the forum. One is to have a 38P plug machined to work correctly in a 9MM case (WISH I HAD ONE !!!). NOE sells excellent expansion plugs for the LEE expansion die. Another is to get a Lee expansion 9MM die with a 38 SW expansion plug, I tried this and did not care for it.

Pardon the long winded explanation but here's how I expand my 9MM cases. I load for several different 9MM's and size all 9MM boolits to .358. and to a standard OAL for each different boolit that will function perfectly in all my weapons. I will grant you that 9MM OAL is best determined by the chamber to the individual weapon. That said, if you are only loading for one 9MM use the weapon's chamber as the chamber gauge. I use a Lyman 9MM chamber gauge.

An empty resized and de-capped 9MM case should easily plunk into your weapons chamber or chamber gauge. I "first" use a Lyman M die with a 38P expansion plug to expand the cases "as deep as possible" and still allow the case it plunk into the chamber/chamber gauge as if it were not expanded. There will be a slight bulge in the middle of the case and the case mouth will not be flared. At this point the the interior of the case is expanded to .356 as deep as possible. Then using another Lyman M die with a 38AP expander plug I do another expansion to flare the case mouths. Yes, it takes more time but it gets the job done.