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General Discussion To Gateway To Airguns => The Shop => : Jaymo June 15, 2008, 03:10:54 PM

: .25 cal bore and groove dias?
: Jaymo June 15, 2008, 03:10:54 PM

Anybody know what they are? I have a .257 Roberts barrel that I was thinking about making a .25 cal air rifle barrel out of. Unless I can find a round ball mold or the right sized round balls or bullets/bullet molds for a .280 Remington  barrel. I really hate to cut the breech off and turn down the .257 barrel as it's an old Remington barrel in beautiful shape. The .280 is a Ruger barrel, much newer, less valuable. Then there's the old .303 British barrel, or the .30-06 barrel.  I think a hotrodded B50 would be sweet in .25, .27, .30, or .31 cal.

: 5 groove .303 likely easiest to cast for, have lower friction.
: 3n00n June 15, 2008, 04:06:22 PM

Standard Lee and Lyman .311 molds. The 30-06 would probably work alright, but morefriction would shave a good bit ofenergy.

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My RCBS and Lyman .257 molds are tougher to cast with, and take alot of time to get up to temperature as well as throwing alot of 'half fills' even at temperature. Most 25cal are .25" bore with .257" grooves.

: RE: 5 groove .303 likely easiest to cast for, have lower friction.
: June 18, 2008, 02:31:34 PM

The groove dia. for a .257  Roberts is .257, twist is 1-12". The .25-20 and 250 Savage (250-3000) are both  1-14" twist and has a .256 and .257  groove dia. respectively. I cast bullets in four different moulds for these. in six different guns. Casting good bullets in small cals. is more difficult as mentioned, but good technique, equipment, metal, and attention to details, can overcome difficulties. The .25-20 I cast for do best with bullets down to 65 grains but perform best with 86 grain bullets. iIalso cast bullets in twenty -two cals. ,like for the Hornet and Bee. Now that gets much harder, the bullet base is everything , even if gas -checked. I would think that the 1-14" twist would be best for the lighter bullets, but the .25 cal. airgun shot is quite a leap from 65grain .25 cal cast bullets. The .250 Savage was always handicaped by the slower twist as Savage was trying to get the 3000fps velocity and used a 86 grain bullet to get it. The 100 grain bullets don't stabilize well in that twist even though they are better for hunting big game in that caliber. Some rifles in that cal. had 1-10" twist and seldom will give good accuracy with bullets lighter than 75 grains.