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ao3
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Used CPA rifle 38-55
Mar 2nd, 2022 at 11:08am
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Just got a used CPA rifle, took the forarm off to see the info,,    Badger barrel, 15TW,  it looks like .374 ,i take that as bore size??    What size bullets should i use, and weight.    Will just be shooting at 100yds,fixed ammo,smokeless powder.  Just a fun gun,by myself on a farm, nice and relaxing    Thanks  AO3
« Last Edit: Mar 2nd, 2022 at 6:11pm by ao3 »  
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RJ-35-40
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Re: Used CPA rifle 38-55
Reply #1 - Mar 2nd, 2022 at 11:57am
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ao3 wrote on Mar 2nd, 2022 at 11:08am:
Just got a used CPA rifle, took the forarm off to see the info,,    Badger barrel, 15TW,  it looks like .374 ,i take that as bore size??    What size bullets should i use, and weight.    Thanks   AO3


I'm sorry but I don't have the time right now to do the search.Others may know the max bullet length off the top of their head.

However you should look up the Greenhill formula and do the quick math.

Of course that is just a starting point because while the constant factor of 150 used in the formula is good for velocities starting around 1700 fps, many use 125 as a constant for black powder velocities.

CPA, great rifle. best of luck with it.

Later today or tomorrow I'll hopefully have the time to dig up and post my notes on the formula.

PS, I have 38-55 CPA with a 14 twist and my bullet is a 330 grain.
YMMV

Bob
  
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1isenough
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Re: Used CPA rifle 38-55
Reply #2 - Mar 2nd, 2022 at 2:05pm
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See the calculator at the bottom.  You know your groove diameter and twist, so you need to answer two more questions: 1. at what velocity do you plan to shoot - hunting, plinking or rams.  In the process you need to decide what propellant you will use.; 2. If you answer #1 then you can solve the bullet length question using the attached calculator.  Notice that weight is not a factor.  Once you solve bullet length, the weight answer will generally fall into place.   

If you decide to explore a bullet first, put the length in and the calculator will solve the velocity for you.  Then go to re-loading pages like Load Data and see what propellant will meet that need. 

I have a lined barrel (TJ's) with a .375 groove and 14 twist.  It likes the 245g RN/FP coated bullet from Penn, with either 31.0 grains of IMR3031 or 33.3 grains of IMR4895.  Load Data info suggests these loads are around 1550-1650 fps. Both loads shoot 1 1/2" groups pretty much all the time (100 yds).

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gunlaker
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Re: Used CPA rifle 38-55
Reply #3 - Mar 2nd, 2022 at 2:14pm
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Are you planning on breech seating or using fixed ammo?  If you are breech seating, this bullet works extremely well in my CPA .38-55 with the same Badger barrel.

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You might need a breech seater with a bit of leverage like the Russ Weber one.   My rifle does not have the shallow leade like they describe on their site, but they chambered it with a 6 degree angle from the case mouth right to the rifling.  With a shallower leade you can probably get by with a plugged case as I use the same bullets in a couple of rifles with 1.5 and 2.5 degree leades and they seat easily with a push tool.

For fixed ammo I can't say as I've never tried any in this rifle.

The 0.374" should be the groove diameter.  I'm surprised at the small diameter, and surprised that it's only 3 decimal places.  Paul marked all of my barrels to 4 decimal places.  My Badger .38-55 is marked .3758". 

Chris.


  
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boats
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Re: Used CPA rifle 38-55
Reply #4 - Mar 2nd, 2022 at 8:39pm
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Make it simple, most of the guys in our club use Meister Bullets 245 Gr .377 in 38/55. We shoot offhand matches with iron sights.

I have a two good molds for my 18 twist .375 barreled CPA, 310 & 330 gr . However volume shooting at 200 yards fixed ammo only use the store bought Meisters with 17 grs of 4227. It chronographs at 1200 FPS. Sweet spot for offhand shooting.

This week shot about 40 practice Tuesday  & Saturday match will warm up, shoot 40 shot match, then shoot off round likely the match probably 60 total. 100 cartridges week you need a lot of bullets..

If I was shooting bench would only use bullets hand cast & for our club 500 yard offhand matches go to the longer and heavier hand castbullet. Offhand 200 lack of shooter errors more important than the last bit of accuracy a longer bullet would provide.

Get the gun shooting work out kinks with the Meisters then experiment with custom molds, bench rest, scopes etc. if you desire  my advise 

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