M die vs case flaring?

[Archey]

Has anyone ever done any accuracy comparisons between the Lyman M die for expanding vs case mouth flaring? Should I expect any accuracy improvements if I switch to an M die from my Lee expander?

[deerspy]

I have not done any testing and have not used the M die I just bought the RCBS .309 expander die for my 30-30 the it enlarged the neck and belled mouth I think it works good for my .3105 diameter cast bullet.

[Doc Highwall]

The only way to control neck tension is if you use something like a Lyman M-Die or one of the RCBS expanders. They not only expand the neck to a known size but put a small flair on the case mouth and prevent the bullet from being sized down from having too much neck tension.

Neck tension affects bullet pull which is part of your start pressure which does affect powder burn/accuracy.

[Archey]

Yes, I understand how neck tension is affects bullet pull. I guess that I should change my question. Will I notice increased accuracy if I switch from my lee flaring die to a M die? Is it worth the money to buy one?

[gpalma]

Assuming for a handgun cartridge? Not sure there is any empirical data that exists. But, from a technical standpoint, the M die gives you a nice flat seating surface and should be more consistent.

For my rifle, I have been using the expanders from Buffalo Arms. They can more readily control the tension and precisely align the bullet for seating.

[GOPHER SLAYER]

Neck flaring dies should be outlawed by Royal decree or by the Pope or O'bozzo or somebody. When I started reloading many decades ago, I thought there has got to be a better way. After the case is primed and has powder in it and you place the bullet in the case and it leans sideways so you hold it as long as you can with two fingers as it enters the seating die, you raise the press handle and then you hope it lines up as it is seated. Bugger. When I tried an "M" die the first time, my prayers were answered. You just push the bullet into the case, down to the step made by the " M" die and it goes into the seating die straight. Happy days are here at last.

[enfieldphile]

Hasn't O'bozzo admitted to having been "expanded" some time in the past?

Honestly, I have a .30 cal rifle M die and a the Lee flare die. I use both. Both work well. I have not noticed a increase or decrease of accuracy. Neither causes shaved alloy.
On this one, I think it's more a case of operator skill vs the tools.

Neck flaring dies should be outlawed by Royal decree or by the Pope or O'bozzo or somebody...Happy days are here at last.

[oldfart1956]

Two completely different tools for two different jobs. The M die expands the entire neck and provides an over-expanded area for easy seating of the boolit. A flaring die expands the neck only at the end. If the neck is too small in dia. the flaring tool won't prevent swaging the cast boolit down upon entry. It will prevent shaving lead from said boolit. The M die will prevent swaging down, and will expand it enough to also prevent shaving. Shove the case far enough in the M die and it will flare it out! If you're considering an M die get the Multi-Expand Powder Charge Die. It gives you 7 different sized expanders plus an attachment to funnel powder thru if using a powder drop system. The expanders are easily modified to work for non-standard sizes and lengths. Expanders can also be made by using 3/8 X 24 threaded bolts/cap screws. (at least up to .500+ dia.) Sometimes having an expander long enough is as important as getting the dia. right. No special tools/skills needed to do the modifications. A drill/drill press and a file, finish up with sandpaper and polish with Flitz or whatever. Audie...the Oldfart..

[Char-Gar]

There are two parts to an expander plug...

1. The plug itself that opens up the neck to .001 -.002 under cast bullet diamteter.
2. The top of the plug that flair or opens up the case mouth a few thousands larger to keep from shaving lead from the bullet upon seating.

The RCBS and other makes put a flair or bell on the case mouth for No. 2 above.
The Lyman M die puts a second step with parallel sides on the case mouth to accomplish No. 2 above.

I prefer the M die simply because I can set the bullet into the case mouth and it does not rock around like it does on a flair/bell. But any difference in accuracy between the two types of cast mouth openings? Not a bit, it matters not.

Note: I shun Lee stuff, so I can't make any comment about anything they make or sell.

[Doc Highwall]

I say it does increase accuracy, first the bullet is started straight into the case and second the start pressures are more uniformed because the neck tension in more even. Even bench rest shooters with jacketed bullets are using them and are sold by Sinclair.

[Outpost75]

The mouth of the case needs to be flared enough to positively eliminate any possibility of shaving lead when the buklet is seated. The remainder of the caseneck must also be expanded sufficiently to avoid damaging a softer, cast bullet, but still provide sdequate neck tension. This ia obtained by using a stepped expander plug with has a short portion 0.002 over bullet diameter, to permit hand starting of the cast bulet to the top of the GC, with the remainder of ghe neck being expanded to 0.002" under bullet diameyer, to provide adequate neck tension.

EITHER the LymanM die or RCBS cast bullet neck expander will do this correctly.

[Char-Gar]

I say it does increase accuracy, first the bullet is started straight into the case and second the start pressures are more uniformed because the neck tension in more even. Even bench rest shooters with jacketed bullets are using them and are sold by Sinclair.

A straight seated bullet is important, but that is the job of the seating die. A straight line seater like the Vickerman or Wilson will get the job done regardless of the case mouth being belled with an RCBS die or opened with an M die.

I use straight line seaters of several makes on all of my cast bullet rifle loads and I have never seen any difference accuracy wise between RCBS or Lyman M expanding dies.

[Archey]

Thank you everyone for the insight. I am on the fence about buying a M die or similar for 30 cal rifle. I think that I will get one next time I make an online order.

[L Ross]

Archey, you might also consider the sized diameter of your cast 30 caliber bullet. I use the 31R Lyman M-die for all my .310" thru .314" bullets.

Duke

[725]

I like my Lee. I like my M-die. As the ram moves up I have the habit of turning the case about to be loaded in it's shell holder. The bullet wiggles that last little distance as it enters the case, and as a result I get pretty straight seating.

[UNIQUEDOT]

The first time you use an (M) die you will wonder how you ever got by without it! I admit that I don't always use them, but I also wouldn't be without them.

[Char-Gar]

Thank you everyone for the insight. I am on the fence about buying a M die or similar for 30 cal rifle. I think that I will get one next time I make an online order.

As you deliberate which way to go, here are a couple of items for you to consider;

1. The standard 30 cal Lyman M die is too small for most 30 cal cast bullets. You need the 31 cal for best results.

2. RCBS makes a 30 cal cast bullet expanding die and it uses spuds which can be changed. RCBS sells these spuds in .308 - .311. A full set give you good neck tension on bullet from .309 through about .313.

Over the years I have put together a mish-mash of Lyman 310 expanders that go from .308 through .315 by thousands. They work well, but if I was starting over I would just by the RCBS set and be done with it. I have a set and they work well. They only time I use the odd Lyman 310s is when I need to go over .313.

Either way you go, you will be pleased with the results. There are only three considerations 1) expand the case neck enough not to damage alloy bullet by seating them. 2) have enough neck tension to keep the bullet in place until sent on their way by the expanding gas and 3) open the case mouths enough so lead is not shave from the bullet while seating. Cover these bases and you are good to go.

[UNIQUEDOT]

1. The standard 30 cal Lyman M die is too small for most 30 cal cast bullets. You need the 31 cal for best results.

2. RCBS makes a 30 cal cast bullet expanding die and it uses spuds which can be changed. RCBS sells these spuds in .308 - .311. A full set give you good neck tension on bullet from .309 through about .313.

Over the years I have put together a mish-mash of Lyman 310 expanders that go from .308 through .315 by thousands. They work well, but if I was starting over I would just by the RCBS set and be done with it. I have a set and they work well. They only time I use the odd Lyman 310s is when I need to go over .313.

Keep in mind that he has never used or owned an (M) die before and your post may be unclear to him as he wouldn't be looking for 310 (M) expanders, but rather a standard thread die and the tried and true (M) die has interchangeable plugs as well.

[Doc Highwall]

I agree with Char-Gar about the RCBS expanders, but one thing not mentioned is the cylindrical portion of the neck expander has to be at least .025"- .050" longer then the seating depth of the bullet into the case neck. I had one from RCBS that was at least .100" too short that I had to turn down in the lathe and they are hard.

I would buy at least three 30 caliber expanders and polish them down to the sizes I wanted in .0005" increments such as .3090" .3095" and .3100" and then go see what works best of that gun/load combination.

You can polish them using a hand drill and the best advise I can give is go slow you only have to make them once, so measure twice and cut once.

[Char-Gar]

Keep in mind that he has never used or owned an (M) die before and your post may be unclear to him as he wouldn't be looking for 310 (M) expanders, but rather a standard thread die and the tried and true (M) die has interchangeable plugs as well.

That is a good point. I mentioned the 310 expanders not to send him on the trail to hunt them down, but just as an after thought mainly for others who read this stuff. It was not my intention to confuse him, but it he does a little research to find out what 310 expanders are all about, he will be somewhat more knowledgably about the topic.