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Discussion Starter · #1 ·
Hi all hope someone can help. I purchased a c96 swedish mauser supposedly in 303/25. However it wasnt it was 303/25 rimless. The old procedure for making these cartridges was to grind off the rim of a 303 and then grind in a groove to make it rimless. Then also neck down to 250. That is too hard so i scoured the the case data and noted that 220 swift is virtually identical to 303/25 rimless just needs to be necked up. So after annealing and necking up in two steps it worked well. My problem lies in the fire forming. I started with a 100 grain projectile in front off 36 grains of 2208 and the result was case head seperation as the case wants to bulge (about 12 thousands) to fit the chamber. I think my load was too hot and that fireforming to meet the chamber was too violent. I note that the necks and shoulders were still perfect and 220 swift being a solid case should be able to take the fireforming. So can anyone suggest a procedure or gentle load to fire form the brass.
 

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What are you using for headspace? THEY evidently formed a shoulder to HS on. You don't have a shoulder unless you neck UP and then back DOWN. 220Swift brass, being 22 caliber is too thin to do that but maybe once. You need rimless .303 British or maybe somebody can recommend a substitute.

BTW--You don't 'grind' brass. It turns just fine. You need a lathe, a shell holder and a form tool. I can show you a picture of a form tool and describe how to make a case holder but it does no good unless you have a lathe.

You know you are poking a dragon don't you? DON'T assume anything in a used gun. Cast the chamber, measure and safety check. A Mauser might have just saved your eyes.
 

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Discussion Starter · #3 ·
Hi
No i dont have a lathe. I should have said i did cast the chamber and hence how i found out it was 303/25 rimless. I also went back to the gun shop where i bought it and found some fired brass as it was a deceased estate lot. I thought 220 swift brass was quite stout, the fired brass from the gun shop weighs 175gn and 220 swift weighs 168 grains. With regard to the head space are you saying that the case head seperation is due to too much head space and not load power. The reason i was thinking of fire forming with a weaker load and also that my load in general is too hot anyway is that two cases survived firing albeit it with flattened primers. I would like to send a photo of a fired 220 swift and a fired 303 modified to 303/25 rimless but cant see a photo upload. BTW was using safety glasses and face shield, i am novice but not stupid.
 

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Weight of the brass has nothnig whatsoever to do with it and quite frankly, if you aren't aware of "headspace, How it's determined, How to set it, How its DANGEROUS to have too much of it, we need to start back at pure basics....and I'm willing.

FIRST OFF--QUIT SHOOTING!! ;)

Headspace is defined as the face of the bolt or breech to whatever in the chamber stops forward motion of the cartridge case. In Rimmed cartridges, the thickness of the rim is the headspace dimension. In rimless it is to a datum in the shoulder that in VERY precisely located. Plus .010 is DANGEROUS to your face sheild AND the guy wearing it. Mauser blow DOWN. Have you got a hubcap in your lap?

I'm going to be off line for about two hours but email your photos to j belk 09 at gm ail dot com. I'll answer at length but first consult your loading manuals for the lessons on HEADSPACE. It is VERY important.
 
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Discussion Starter · #5 ·
Yep will email the photos. Yes know how head space is dangerous but no i dont know how to assess it in this rifle so your input would be appreciated.
 

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I can see by the pictures you're lucky guy!

The first pictures is a fired 25-303, then two fired 25-Swifts and a chamber cast.

It sure looks to me like the shoulder on the 303 is much further forward. It seems like you could get a measurement from what was the front of the rim to the point of the shoulder. That should match the same measurement on the cast. Compare that with the measurement of the Swift case. I think you're going to find a BIG difference.
A more accurate method of measurement is to use a .38 Special case turned upside down over the neck so it rest on the shoulder. Measure the total length and compare them between cartridges. By the SAAMI specs below you're firing a two lug center fire rifle with .026!!! excess headspace. Lucky indeed!

The first thing I'd do is cut the neck off the .303 Brit case and see if it'll feed, chamber and extract. If so, it means there IS a rim recess and the only reason to cut the rim off is to make them feed better.

You are beyond critical in safety issues and really need to figure this out before more experiments.

The sectioned Swift case is just to show the base configuration. It's a little different than some.
 

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Discussion Starter · #7 ·
Yes your calc of 0.026 seems spot on, i measured the difference at 0.024. So the case body is stretching back to the bolt face by this distance. So my question is, is there a safe way to do that stretch and then move on with chamber fire formed cartridges. I used 36 grains of 2208, can you do a mild stretch with half that amount or less or do the stretch over a couple of firings of very weak loads. I do want to avoid buying and using a lathe if i can. There is definately no rim recess as the bolt face and extractors are original and will not accept a 303 rimmed (can only accept a .48 rim). FYI while rare these guns i did find some info on them and they are referred to as Boer Mausers named after the modification of these mausers after the Boer war. Idea was to use the rimless 303-25 so the bolt didnt have to be modified apparently.
 

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Discussion Starter · #8 ·
Ok just read an article by Nick Harvey here in Australia and it then made me understand what you said earlier about sizing up and coming back down. Ie i could size these up to 270 and then only a portion of the neck back down to 257. Resize down only enough that the bolt will close. Hence the cartridge will be sitting on the ridge between the 257 and 270 forcing the case head to sit on the bolt face. This should then result in the shoulder being fire formed forward rather than the case head being slammed back into the bolt. I have a 270 reamer and i have an annealing machine so this could be done. Any thoughts and suggestions for powder/projectile load. Thanks
 

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You're going to lose a few cases to neck splits even with annealing, but that process of up then down will work. ONLY re-size back to 25 cal until the bolt closes with feeling. Lock the die in that position.

Load with (to start) 15 grains of Unique or Aussie equivalent. Load just ONE. Stuff a bit of toilet paper to keep the powder located then fill the remainder with corn meal or other organic filler of about the same density. I use grits because I'm a Southerner. ;) To cap the case full of stuff, just gouge out a piece of common candle wax to keep it all in place.
Shoot it OUTSIDE in a safe direction. Inspect the case very carefully. You want the shoulder to be as SHARP as that fired case you have.
The base will (SHOULD) have a bulge because the chamber is about .009 bigger than the brass. You want to be able to see that on the FIRST shot. Get all the expanding done its going to do ONE time.
If the case is still rounded and ill-defined, raise the charge by a full grain until you have a good case.
Be sure to trim if needed before fire-forming.

I would anneal the Swift brass at the .25 step going UP to .270 and then again after fire-forming. Then neck size and fire your load of choice. THAT brass fits THAT rifle with ZERO head-space.

Total process--22 to .24 to .25, anneal, to .270, back to 25, fire-form, anneal, load and shoot. Adjust and experiment and find out what works for you best.

Other powders work just as well and there's a BUNCH of them that fit the bill, but I started with Unique and can pretty well guess what load to use for what volume.

I have a .240 Cobra which is a 6mm-Swift Improved. The powder capacity is one grain less than a 6mm Rem. Your capacity will be a couple grains short of that so an load listed as maximum for a 250 Sav. should be very close to your starter load.

Don't push the rifle to maximum and use the 6.5x55 as your guide to pressures acceptable to the gun.
 
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If you weren't in South Australia, I could really help you out.

A couple of years ago, thanks to very strange cartridge restrictions for deer hunting in the state of Indiana, I had cause (?) to commission a local machine shop to create a carbide cutter that turns 303 British brass into a rimless case head. Suffice to say that you could probably find a local shop to do the same for you...the question is whether or not it's worth it to you, of if you'd rather just rebarrel your rifle.

https://www.shootersforum.com/wildcat-cartridges/125097-35-remington-p.html
 

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The rimless cutter takes about ten minutes to make and I have several on hand. Here's a picture of one and a drawing of another that uses an insert.
No need for carbide for brass, just a 3 deg. negative rake in HSS is all.

I see no reason I can't send you a cutter by mail but you'll still need access to a lathe. All you need is an old full length die to lap the neck out a little so the case fits tight in the die for turning off the rim. It takes much more time to stop the machine and change cases as it does to turn them. Two seconds of work at the maximum and a very small lathe can do the job.

The 'finger' is only a locator that rubs but doesn't cut the bottom of the case. The only cutting surfaces are between the lines.
 

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Pendous--
The 25-303, which is a 25-Swift is about three grains less capacity than a 257 Roberts which is a 25-7x57 or 25-6mm Rem. Great fun!!
 

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The rimless cutter takes about ten minutes to make and I have several on hand. Here's a picture of one and a drawing of another that uses an insert.
No need for carbide for brass, just a 3 deg. negative rake in HSS is all.

I see no reason I can't send you a cutter by mail but you'll still need access to a lathe. All you need is an old full length die to lap the neck out a little so the case fits tight in the die for turning off the rim. It takes much more time to stop the machine and change cases as it does to turn them. Two seconds of work at the maximum and a very small lathe can do the job.

The 'finger' is only a locator that rubs but doesn't cut the bottom of the case. The only cutting surfaces are between the lines.
Does this remove the rim, or just cut in the extraction groove? Is the rim turned off in a separate operation?

I know nothing at all about machining, but it seems to me that turn off the rim or thinning it, from either side, would be relatively easy operations, whereas cutting in the extraction groove to specific depth is a somewhat greater challenge?
 

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Great question. I sure wish we had a VIDEO site. ;)

Look at the diagram above. The right hand red arrow points to a cutting surface. So the tool is held and ninety degrees to the case with the rim facing to the right. The 'finger' is brought to the base of the case and then the tool advances straight in. That flat cutting surface at the right arrow is the first to make contact with the .303 rim. As the tool advances, a curl of brass comes off and the rim is gone. The next surface is the middle and left red arrows which cuts the extractor groove with its angled chamfer to the front. When the dull portion of the tool on the left side of the tool rubs the case, you know its the right depth. It's done in one go in less time than it takes to tell about it.

It is called 'plunge cutting' on a lathe. It is not a 'turning' process but it's done while the case and spindle ARE turning. Don't you just love English!
 

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Great question. I sure wish we had a VIDEO site. ;)

Look at the diagram above. The right hand red arrow points to a cutting surface. So the tool is held and ninety degrees to the case with the rim facing to the right. The 'finger' is brought to the base of the case and then the tool advances straight in. That flat cutting surface at the right arrow is the first to make contact with the .303 rim. As the tool advances, a curl of brass comes off and the rim is gone. The next surface is the middle and left red arrows which cuts the extractor groove with its angled chamfer to the front. When the dull portion of the tool on the left side of the tool rubs the case, you know its the right depth. It's done in one go in less time than it takes to tell about it.

It is called 'plunge cutting' on a lathe. It is not a 'turning' process but it's done while the case and spindle ARE turning. Don't you just love English!
OK, that is exactly like the cutter I had made by a local tool and die shop, with two minor exceptions: The tool I had made also thins the rim slightly (from the case body side) and the part of the tool that touches the case body (acting as a positive depth stop) is radiused to match the case. That is probably of little consequence and likely cost me another $150 in having the tool made! :D
 

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likely cost me another $150
I'd like to get paid like THAT! I suspect they had a CAD/CAM guy program a wire edm to cut a profile. I do it the old fashioned way with precision grinder and diamond wheels for a simple shape like that. OR, a fine abrasive wheel is dressed to profile and plunge ground. For a hundred cases or so, I'd file the cutter out of cold rolled steel and case harden it. Filed out of O-1 and hardened it could last a thousand.
 
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I think I'd try 7x64 Brenneke brass as a parent. Size in stages down to the solid case head, then trim to length, anneal and try-fit in the chamber. My Brenneke brass mikes @.458" at case head, so if you need to take a bit off you can spin it in a hand drill and use a file with a safe edge toward the rim. YMMV.

I've made .43 Spanish brass from .348 Win using this method, but I lathed off the excess, annealed, then fire formed using the aforementioned "grits" method....

Good luck!
 

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ALSO - I use the "size-up, size-down" method to make .280AI brass from .270Win brass, with excellent results. I leave the case lube on, so when fired, the brass can move back against the bolt face instead of sticking to the chamber and stretching during the "grits firing"...

You may not need to cut an extractor groove on your .220 Swift brass, as long as that great big Mauser extractor is biting all the way around....

Another trick to use when fire forming brass with a reduced head diameter is to put a single wrap of 1/8" wide masking tape just forward of the extractor groove. This allows even expansion of the parent case when fire forming - then you peel it off and reload as usual....

Good luck and BE SAFE!
 
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