Reforming case mouth

[5th Armored]

Hi All-
I have seen some very good ideas on BOCN for removing dents and expanding case mouths but does anybody have any tips for decreasing the diameter of a case mouth? I have a German 20mm that is so belled out that it looks like somebody tried to use it as a mini flower vase! Also, the expander trick seems like it would work - as long as you can get it into the case - but what do you do for cases with badly deformed openings? I'm thinking that a tapered mandrel like a jeweller uses to size rings would be great - I wonder if anyone makes them in 88mm?:neutral: Any thoughts?
Cheers
Chris

 

[Falcon]

Are you able to post a photo? I have done alot of these cases. If I could see how bad it is, I could probably suggest some ways to sort it.

 

[raymeketa]

Both Falcon and I have made bushings that can be used to re-size a case mouth on large calibers. I have gone as big as 3". But - a big but - you almost need a lathe to make the bushing. Maybe Falcon has come up with a way to do it without a lathe?

Ray

 

[thekees]

Ray,

Can you put a picture on the net to get an idea?

Kees

 

[5th Armored]

I'd like to see a picture as well. I have access to a lathe in the workshop at work so I could probably get something made if I knew what to ask for. My camera is charging so I will post up a pic or 2 tomorrow. Thanks for the responses so far!
Cheers
Chris

 

[highlandotter]

If it is not too flared, you can use the proper caliber shell as a mandrel, with a plastic mallet. If it too deformed, you may have a longer case than it should be and then need to be trimmed back.I have never done this with cases larger than 40mm, so proceed with caution,

 

[raymeketa]

I'd have to dig out the tooling and camera to take photos, but I don't have the time right now. There's not really a whole lot to show. I have only this one photo of a bushing that I made several years ago. It is to resize the mouth of 1 Pdr cases. Made of a piece of brass water pipe. You simply push the case into it with an arbor, vise, drill press, or anything handy. I lubricate the case with powdered moly and I can knock the case out easily by holding the bushing in my hand, a short rod inside the case, and a couple of taps with a hammer.

The bushing is sized so that the projectile is a good firm fit without having to expand the neck after sizing. I machined a taper inside the bushing to re-form the shoulder (at top of bushing in photo).

Maybe Falcon has some photos handy?

Ray

 

[Slick]

A steel band clamp, the ones with the screw, have worked twice for me. Both times on 40MM cases. Gets it close. Then use a projectile for the mandrel. Light taps all around, with a small jewelers hammer, will get it closer. Even better is the actual device. A bench mounted contraption. Maybe Bougainville can show his example. Sorta difficult to explain, but quite obvious when you see it. A curved anvil(convex) "plate" , with a swingdown concave "hammer". Then you hit it with a hammer.

 

[spotter]

ive used the method rick describes on a 20mm succesfully......the steel band with a screw (called a jubilee clip here in the uk) also had succes using a good strong piece of wire wrapped round and tightened like a touriquette........

 

[Tmine35]

I'm using self made neck sizing dies and my small lathe for calibers 15...37mm. I haven't had a need for larger mouth sizing but my lathe also is too small for bigger cases.

The 20mm die has inner diameter of 20,7mm which gives ideal case inner diameter for projectile to be forced in by it's own inertia ( set the projectile on case mouth and hit the case base on a wood block - projectile goes in and stays there ).
Further the die has quite large conical mouth and 20,7mm diameter part is only 5 mm long to reduce friction and required force.

Important thing before pressing case in die is to get the expansion more or less symmetrical, you may try to knock it down on a steel rod but sometimes you have to expand it more on the opposite side. If it is not symmetrical the case neck does not remain straight. Also use oil in case neck and die.
Be careful not to press the case too deep in die - you do not feel it by hand.

The photos show a work I did just a few days ago, unfortunately I didn't know this post and can no longer send pictures "before". They however had quite well expanded "trumpet"-mouths.
The copper washed steel case even had a small crack which you see on photo.

 

[Gspragge]

sizing

I can send you this, I don't know what it is, but it's brass, has an opening diameter of 3/4" and is smooth inside and slowly tapers in.
it would resize the top area of the case which you could work down to what you want, a snug fit or once rounded resize out with a projectile.
This is what I do with 37mm where the top 1/8" or so is belled out using a Cow bell. I don't have a small case to try in it, as long as the neck contacts the inside of this before the shoulder it would work fine.

 

[imaokie2000]

Bushings work great, but if it is flared too much, you have to make several bushings to reduce the diameter back to normal. If you try and reduce it too much at one time, you'll crack or crush it. If you have access to a lathe with collet chuck large enough or know of a machine shop that has one, this works real well. Annel the case mouth first. This is very important to keep it from craking or crushing. Choose a collet that the case mouth will barely go into and tighten it down. Keep doing this with a smaller collet each time. I aneal the case mouth each time I squeeze it. Take it slow and easy and you will get real good results. Go too quick and........ OOOPS! You'll find out how hard it is to weld thin brass. I've done that too.:tinysmile_cry_t:

 

[BOUGAINVILLE]

Even better is the actual device. A bench mounted contraption. Maybe Bougainville can show his example. Sorta difficult to explain, but quite obvious when you see it. A curved anvil(convex) "plate" , with a swingdown concave "hammer". Then you hit it with a hammer.

Here is the link for my post. The first 3 photos are of the 40mm mandrel for reshaping Bofors 40mm casings for reloading.

http://www.bocn.co.uk/vbforum/threads/80988-Armourer-s-tools-recent-acquisitions

 

[Tmine35]

Got yesterday an Italian 20x138B brass case with mouth seriously bent due to inproper projectile pulling.
First I forced in the mouth a 19,6mm diameter round steel bar. See first picture
Then I knocked gently the mouth more or less symmetrical, also bending the neck to become straight. See second picture.
As described in my post on page 1 I pressed the mouth in a die and result is shown in third picture.