.510 expander advice

Hello all,
I am working on getting some dummy rounds made for a wildcat project and I was wondering if anyone could give me some advice.

My project is a 7mm blaser magnum (chosen because I could get quite a bit of norma brass in this chambering, other brass would work as well for this case) cut off at the shoulder (1.8 inch) and then stuffed with a .510 projectile. It looks like it will be close to a .540 cylinder chamber.

Before I can get anywhere, I need to open the neck up for the 510 bullets. The inner diameter of the neck is right at .480 right now. I figured if I could get the neck up to the correct inner diameter, I can just fire the rest and the I will just do my resizing for neck tension with a bushing die of some kind.

Any advice on how to open it up to .510 diameter?

Thanks
Nate

if you are not doing too many get a large center punch or a .50 BMG projectile and tap it into the cases after you cut them off.
I use a Lyman .50/70 M die and it is a bit too large for your application but you could polish the expander down if needed.

EDG, does that Lyman 50/70 expander open up the case to .510?

I had honestly thought about just expanding them by seating a pulled bmg bullet for the first load. But it is .03 of an inch worth of expansion and I just don't know if that's gonna screw up my brass.

If I can do them that way, that would be awesome. I need to find a seating die I guess so I can try to "expand by seating" and see what happens.

There are two ways to go about it in my opinion, depending on what you are looking to achieve. If you just need to expand the mouth to allow for a bullet to be seated, then yes the .50-70 or .50-90 expander will work. You can also buy a custom one like this
https://www.buffaloarms.com/508-511-...s-van508511rcb

The other way is to buy a proper expander ball that you would use in a normal FL die. All the die companies make them and you can get them in normal or carbide from most. You will also need a die set at some point, and CH4D is where I would point you. Ch4D dies are built on the same pattern as RCBS so the parts are interchangeable and if you are just starting out doing the basic case work and you are not ready for the die set, go with the RCBS stuff so later they will interchange.

Here are the measurements for a new Lyman 50-70 M die plug.

This plug is marked on the end 50 R

This plug is a little different than most rifle plugs. It has 3 diameters close to the bullet diameter.

.510 diameter - this is the first diameter into the case but its effective length is only .250 long. It looks like a large auto pistol expander it is so short.

.5145 - this is the step that we are used to and it is .080 long. This step could be polished out to make the first step longer then you can polish down the top step to just over your bullet diameter.

.5175 - This is not a functional diameter on most M dies but it might help some rifles with oversize bores or you can do some polishing to make the effective lengths and diameters longer or larger. This diameter is .215 long and is the top end of the plug.

For my use I should have made my own M die expander.

Quote:

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Originally Posted by TOWS220

EDG, does that Lyman 50/70 expander open up the case to .510?

I had honestly thought about just expanding them by seating a pulled bmg bullet for the first load. But it is .03 of an inch worth of expansion and I just don't know if that's gonna screw up my brass.

If I can do them that way, that would be awesome. I need to find a seating die I guess so I can try to "expand by seating" and see what happens.

---

So, a quick update.
I ordered a lee .50 ae 3 die set just to get things going, along with a shellholder (magnum size case head).

First thing I did was use the lee powder thru expander to start opening up the case mouth. Once I got to the limit of what the lee expander can do, I went ahead and seated a FMJ 50 bmg projo to length. This did the rest of the expanding job.

Everything looks good, the middle should fireform (right?).

One more question, as I am completely new to this whole wildcat business. What kind of expansion can be achieved with fireforming right at the base of the cartridge, ie just above the extractor cut? I know this is the thickest part so I wasn't sure if brass will expand well down there.

Next step is I am going to see about getting this expander plug modded so that I dont have to do so much "expanding by seating".

You have an adequate expanding process since you only have to do it one time per case. Any thing more is for your convenience if you are expanding large numbers of cases.

Fire forming at the base of the cartridge depends on 3 things that would be difficult to explain to a rookie that has not seen the results from several different fireforming episodes.
The 3 things are
1. Clearance between the case and the chamber. If the case head diameter is .007 or so smaller than the chamber you are likely to get a bulge or step when fired with loads having mid 40KSI pressures.
2. Thickness of the case walls at the junction of the case head and case walls. Thick heavy cases are more difficult to bulge. Thin cases bulge more easily and can form a step with high pressure and a lot of clearance.
3. The pressure of your loads. Pressures above about 45,000 PSI will form a step if there is significant clearance and the case walls are thin.
This is a good reason to keep pressures low if your chamber is sloppy fit with your brass.



You can examine the brass that you fire in other rounds to see the expansion at the junction of the case head and the thinner case walls.
You can have different expansion results with the same chamber by varying your load pressures and your brass.

I make .50 Alaskan out of .348 Winchester brass and do use a neck expander to a point after annealing the neck and shoulder.
I then fire for the brass using Unique and corn meal. The cases are slightly out of round at the mouth but fit the chamber perfectly.
The case trimmer takes care of the mouth with no issues as long as the cutter is at speed.
I use .50 BMG 750 grain bullets and get very good accuracy out to 500 meters.

Rapid rob and anyone else who has experience with cartridges like this, I am going to be starting a general thread for this project in the projects section.

I would love to hear from anyone with first hand knowledge loading for something like this and I would appreciate if someone knowledgeable on wildcat design can look at the drawings I have of my cartridge and chamber dimensions.