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Thread: Case Stretching.

  1. #1
    Boolit Buddy
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    Case Stretching.

    I was just reading about case stretching. Itís the first time Iíve heard of it. Do many people do it? What is the advantage? Does it keep the case thicker at the mouth so it lasts longer ? I assume it pulls brass from the Center or lower of the case. In a video it said the brass needs to be annealed. Is there a risk of the base getting too soft when you start annealing that far down ? When and how often should you do it?

    Thanks

  2. #2
    Boolit Master

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    Case stretching is really only a problem with full blown high pressure speads. Reloading for the pressures and speeds i do most my brass doesnt stretche. My .270 Win is the only one that stretches cases every now and then. I still check it though in all my calibers.

    I do neck turn to get a uniform case neck tension. Annealing is a double edged sword. I anneal alot during brass caliber conversion and fireforming to relieve all the stress and work hardening. After that maybe about every 5 ish reloads sometimes more depending if i dont see any case neck problems. I keep the brass in batches so if one cracks a case neck they all get annealed. Down side is it opens groups a little bit the first time reshooting, but then the groups settle back in the 2nd or 3rd reload. Its not enough of opening a group for me to worry about. Maybe if i was shooting a competition and .25 inches was the difference between a win or loose. Its not enough for me to miss a deer. It does make my brass last longer. I will wear out primer pockets before i crack a case neck. Annealing in my opinion is more to prolong brass life and not so much to create accurate ammo.

    There is a risk to annealing the case web area. Thats why I use my fingers and a candle. When it gets to hot to hold it goes into a damp towel. Templac is the best way to go to ensure you hit the correct temp. Some stand the cases up in a basin of water and nock them over to protect the web. Which is how i started. Using a blow torch. To each their own and all methods work. Just hold the case into the blue part of the flame.

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  3. #3
    Boolit Grand Master

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    Case stretching like you describe can be done to make a short case longer to match the chamber better. Or for an obsolete case that can then be formed from some other. Brass is swaged from the case head and lower side walls up to lengthen the cases. It takes a lot of force to get any real amount. A lot use a heavy hydrolic press similar to a bullet swaging press for this. Under pressure materials become fluid and flow since the ram stops it from flowing down and the die limits it from going out it has to flow up and lengthen the case. This is the same as making a new case it starts as a flat coil and is formed into a cup then thru several draws it lengthens and becomes the straight walled case then a necking shoulder step and the bottle necked case. What these dies are doing is making the new shorter 48-55 brass long enough to fit original chambers and possibly even fit some of the other longer cases in 38 cal. I believe they used to stretch some 45-70 to 45-90 also. In this process the heavier thicker cases are preferred to have as much material to work with as possible. Im not sure how far you could go before thickness and distortion ( in primer pockets rims and body) became an issue.

  4. #4
    Boolit Master Reverend Al's Avatar
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    "Red River Rick" out in Winnipeg, Manitoba sells the Kal-Max case stretcher which is used in conjunction with a standard "Porto Power" hydraulic unit of at least 4 tons (although I had him set mine up with a 10 ton unit). He offers dies to stretch straight cases in 38, 40, 45, and 50 calibre. Those lengthened cases can then be re-formed to obsolete or hard to find cartridges, or trimmed to be an exact fit to your individual chamber length.

    http://kal.castpics.net/CaseStretcher.html
    I may have passed my "Best Before" date, but I haven't reached my "Expiry" date!

  5. #5
    Boolit Master

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    Well now, I learned something new today.

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    "Speak softly and carry a big stick; you will go far."
    ~Theodore Roosevelt~

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check