Lyman M die and neck sizing

[SilverBow]

Hi everyone,

I just received my first Lyman M die, which I'm using to reload some 35 Rem cases. Before the M die, I'd FL size/expand with a set of Lee dies and then flare the case mouth with a Lee Universal Expander.

I know that the M die should just replace the Univ. Exp., in which case the necks are expanded by both the FL die and the M die. However, in hopes of avoiding overworking the brass, I decided to experiment by removing the decapper/expander button before FL sizing. Here's what I got for neck dimensions:

Neck OD - before: 0.383" after 0.372"
Neck ID - before: 0.358" after 0.346"

The first step on the M die mandrel is 0.356" and the second step is 0.360". Each time I tried to use the M die on the sized, but unexpanded necks, I ended up crumpling the neck onto itself. So for my dies, the FL die must be used to expand the necks.

What surprised me was how much the neck was sized down by the FL die before being re-expanded by the expander button. Ignoring the M die, it seems like the Lee FL sizer is taking the neck ID from 0.358" to 0.346" and then back to 0.356" --- that seems like a lot of overworking of the brass.

I'm wondering if all manufacturers' FL dies behave like this and if the neck compression/expansion is significant enough to fatigue the brass? For those who are using M dies, do you use any methods in which the M die is the sole neck expander?

[GabbyM]

Now you know why some of us spend extra money on high price dies.
Looks like your brass neck wall thickness is .013” which isn't over thick so yes your die is working the neck much more than necessary. This is about typical though with standard die sets. For my really high volume rifle rounds I shoot in 223 and 243 I have neck dies with changeable bushings. I qualify all the necks with a neck turn tool. Then you chose a bushing sized to bring the neck down to dimension. All the expander button does is slightly bump it's way out. Checks for thick neck as you'll feel the harder pull on the upstroke. Now, in the last couple of years, they've come up with these bushing bump dies that in addition to neck sizing will bump the shoulder to guarantee head space and an easy feed in your high power competition rifle. $75 die with three bushings. There is no end to spending money on toys once you get into precision shooting.

I think you can send that die into Lee and they will hone the neck size portion to your specified size.
That may just be RCBS that does that?

You might try loading a .358” or .359” bullet right in that .358” fired case neck without even resizing it. If you don't have case stretch from the over working it's really not hurting much. You may need to anneal the necks after five or so firings to counter work hardening but most rifle brass wears out in the primer pocket or from case head separation first. Comes down to how you can spend a lot of time fixing something that may not be broke.

Is this for a lever gun or single shot?

[woody1]

WOW! I've had dies that I thought overresized the necks but not by that much. What are you loading for? Do you really have to FL resize? To specifically answer your question...re: For those who are using M dies, do you use any methods in which the M die is the sole neck expander?[/ If I can get away with it, I always neck size only and use the biggest sizer that doesn't leave the neck too large for the boolit I'm using. Especially with cast, which are often (usually) larger than the nominal jacketed bullet the dies are made for, dies usually over resize the neck. Now specifically to the 35 Remington, I have a set of Truline dies that neck size only followed by the M die. If you have or can get a carbide 38/357 size die, try it or several as each will prob'ly size slightly different dimensions also. It may or may not be larger than what you're getting now but worth a try. When I'm not FL sizing and loading using standard dies, I use a universal decapper and the 38/357 carbide size die followed by the M die. HTH Regards, Woody

[SilverBow]

Is this for a lever gun or single shot?

The 35 Rem is for a Marlin 336. I'm resizing some 1F brass that was given to me, so I figured it would be a safer bet to FL size. Once I've fired this brass in my rifle, I'm hoping to just neck size or lightly bump the shoulder back by unscrewing my FL die.

I can definitely now understand why bushing dies are popular vis-a-vis the control that they offer. I wouldn't have known how much my brass was being downsized had I not removed the expander plug. I always figured that it was just going down a couple thousandth's.

I just found this article in which the author does a similar test:
http://findarticles.com/p/articles/mi_m0BQY/is_5_47/ai_72407705/

From his/her results, the neck was being downsized even more than mine: 0.020"

You're absolutely right about being able to spend $$$ on tool after tool. I'm a bit of obsessive, or so my wife says, so I like to measure and try to minimize variation. It seems a bit silly on a levergun, but I enjoy the process. I'm a scientist by profession :)

[Maven]

"For those who are using M dies, do you use any methods in which the M die is the sole neck expander? If I can get away with it, I always neck size only...."

Thumbs up to the above. I prefer to neck size whenever possible via Lee Collet Dies and even a Lee Loader (8 x 57mm). However, after using high pressure jacketed bullet loads in my .243Win., I decap and FL size without the expander ball, then use the M-die to complete the process. In this instance as well as those where I partially FL size and then use the appropriate M-die, I haven't seen much evidence of overworked case necks.