32-20

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  • Last Post 01 September 2012
wch posted this 26 August 2012

I am considering ordering a new barrel for my CPA Rifles bench gun and want to know of any experiences with a cast bullet barrel chambered in 32-20, but having a 308 caliber bore. Any advice on twist rate (I plan on shooting heavy bullets in this rifle) and powder types and load data is appreciated. Thanks.

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Ed Harris posted this 26 August 2012

There are better cases than .32-20 for a modern single-shot bench gun.  Unless you are content with subsonic loads, it doesn't have enough capacity to drive 200-grain bullets, and   because .32-20 brass is thin, fragile it won't last long. It also tends to be expensive and hard to locate in sufficient quality and quantity..

The 7.62x39 has just the right capacity for cast bullets, works great in a .308 bore with any common match quality barrels, and has sufficient case capacity to drive bullets as heavy as 200 grains to 1800-2000 fps in a strong-actioned rifle.  Case capacity is also small enoug thhat you are not fighting excessive airspace if you wannt to go subsonic with heavy bullets.  Brass is plentiful, cheap and Lapua Norma and IMI cases are of match quality and don't need to be prepped.

I built my 7.62x39 using a Sako action, McMillan stock and 14” twist Hart barrel with Lapua-style chamber using a reamer from JGS.  Using #311299 seated out so the GC does not protrude into the powder space, I use a “nominal caseful without compression” of RL-7 and Federal 210M. The Lapua chamber already has what is essentially an Ardito throat in it.  For high velocity loads for 200 yard shooting the 14” twist is the way to go.  For heavy bullet subsonic stuff you want an 8” or 10” twist.  A 12” twist is an OK compromise.

Use good bullets that fit, use a powder which fills the case and gives the desired velocity with the chosen bullet. RL-7, 8208, 4198, H322 are all good powders for the 7.62x39.

 

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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John Grantham posted this 26 August 2012

Talk to Paul or Gail at CPA.  They've  done quite a bit of work with the 32/20. From what I've seen they are sucessful with it.

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hunterspistol posted this 26 August 2012

:coffee     What you describe is the TC Contender chambering.  It works better than some but, only if you put in the attention it takes.   The brass is thin, we use Starline for it.   It's a standard silhouette chambering for a 10” barrel.   It does well in a handgun but, as they've said, there are better rifle cartridges. 

     Even in the TC, it's more a pea shooter when the powder charge is adjusted for best accuracy.  I had to back the powder down from 8.0 grains because the group pattern goes wide (as in 2&1/2 feet wide!). 

    This is not a rifle, a longer barrel would be entirely different.

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wch posted this 26 August 2012

I have talked with Paul Shuttleworth; his 32-20 CPA uses a .321 bore; I have dies for the standard 32-20 cartridge, and molds for any number of 30 caliber bullets. Jan Peterson of California has shot a new bench best group of .577 inches using a 211 gr bullet and the 32-20 CPA chamber. My aim is accuracy at 200 yards, so I don't need horsepower as much as consistency.

I thank all of you who have answered. Walt

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John Grantham posted this 26 August 2012

I have 3 different barrels for my CPA in 32/20.  I have a 308 bore in a 10 twist, a 320 in a 12 twist, and a 324 in a 12 twist. I cast in 20/1 alloy, breech seat, and load for about 1300 fps in all three tubes. Can't live on the difference. All three bullets weigh in that 200 to 210 range. If my wind reading skills were better all three would shoot in the 550 to 625 group size. 

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frnkeore posted this 29 August 2012

Ed, In this “case” we are breech seating and that gives us a greater capacity. My Win case has 21 gr water weight plus we load the bullet about 1/16th out of the case, giving us even more capacity.

I use the .308 groove on mine, too. QL gives me 20K with a 190 gr PB and 1300 fps velocity with powders in the #9/4227 range. I use 8.9 gr H108 in a 26” barrel.

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Ed Harris posted this 29 August 2012

Ah Ha! Wasn't familiar with the CPA action and didn't realize what you were doing. In that case the .32 H&R Magnum is probably just the ticket if you will be staying within the velocity range of plainbased bullets, breech-seated. My ten-inch twist, four-groove gov't form .308 barrel in .32 S&W Long shoots well, but I am throat-limited to bore-riding nose bullets no heavier than about 140 grains. In a longer throated barrel the H&R Magnum should have enough case capacity to drive a 200-gr. bullet with nominal caseful of RL-7 or 4198.

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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John Grantham posted this 31 August 2012

Ed Harris wrote: .32 H&R Magnum is probably just the ticket if you will be staying within the velocity range of plainbased bullets, breech-seated.

 

I have to disagree.  There is only one cartridge better than the 32/20 for 32 calibre  plain base bullets and that is the 32 Miller,  hands down.  I've never seen a 32H&R mag keep up with either the 32/20 or the Miller.

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Ed Harris posted this 31 August 2012

Can you post cartridge drawing for 32 Miller, how is this different from a necked up .30 Herrett or .30 Johnson Special?

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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32ideal posted this 31 August 2012

Ed it is a necked down 357 Mag or 357 Max case, some folks cut and neck up the RWS 5.6x50R case.

Mike

 

 

Ed Harris wrote:

Can you post cartridge drawing for 32 Miller, how is this different from a necked up .30 Herrett or .30 Johnson Special?

 

 

 

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JSH posted this 01 September 2012

Well gents I am sure going to watch this thread as I am a 30-20/32-20 nut. I have shot the 150-220's with fair to excellent results. AA#9 or WC 820 is my go to powder in the TC pistol format. FYI the RCBS Sil. bore rider has given me excelllent results when sized properly. As to primers, my results have been better with a small standard pistol than a magnum or standard rifle primer. jeff

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