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  #11  
Old 01-12-2013, 08:23 PM
Dean2 Dean2 is offline
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17FB is easier to resell as accurate and dies are less than half.
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  #12  
Old 01-12-2013, 08:30 PM
Oleman Oleman is offline
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Quote:
Originally Posted by Dean2 View Post
17FB is easier to resell as accurate and dies are less than half.
Really there are some pretty reasonable dies through Hornady. With out factory brass the 17 FB is no more resellable than a 17-222 or MACH IV.
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  #13  
Old 01-12-2013, 08:38 PM
sicero sicero is offline
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Anything but a factory chamber eliminates likely over 90*maybe 99*
of buyers at any price. I agree with Dean on this issue. Kenny
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  #14  
Old 02-11-2013, 12:10 AM
mackillan mackillan is offline
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Default Fireball

It looks like the fireball is being phased out.
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  #15  
Old 02-11-2013, 06:47 PM
20 EXTREME 20 EXTREME is offline
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Quote:
Originally Posted by sicero View Post
In real life they are the same thing. The only place you might get into trouble
is with a tight necked Mach IV. You either need to know enough to check the chamber out or have it done by someone who does know.
You can cite all kinds of differences by looking at reamer prints or saami specs
but that don't amount to a hill of beans. It don't matter if the chamber length
is 1.432" or 1.420" as the 221 FB or 17 FB brass is going to be 1.400" or less.
Yes you might find an oddball piece of brass longer than that but if you are a reloader you should know , all brass is to be trimmed to the same length or at least measured.
Same goes for the shoulder. Most common diameter at the shoulder for a Mach IV chamber is .6340". 17 FB chamber is a little larger in diameter but it don't matter as new brass comes small enough at the shoulder to fit in either chamber.
People in the know used 9 twist barrels for their Mach IV.
10 twist was common when the only bullet was a 25 gr HP.
I chamber for the 17 FB with a Mach IV reamer. It just makes the FB a little less sloppy.
You just need to know your chamber and how to fit brass to it.
I have my fire proof under wear on so have at it. Kenny
I am setting up a Cooper 21 in 17 Mach IV with New Rem 17 FB Brass. First I contated Cooper and got a copy of the print for the chamber reamer that they used.
[IMG][/IMG]

Next I measured the Rem 17 FB brass and found them to be 1.405" out of the bag. The chamber is cut to accept a Maximum Case Length of 1.400" so I trimmed them to 1.390" which is listed as 17 Mach IV Case Trim Length in a number of sources. Not trimming would have been a problem.

Then I measured the OAL to the lands with a Hornady 25 V-Max and found it to be 1.923". I then seated a bullet to 1.893" which is 0.030" off the lands with a seating depth of0.170". I measured the loaded round neck diameter at 0.200" which left me with 0.0015" clearance at the neck. I don't have to turn the necks but may clean them up slightly.
[IMG][/IMG]

While the new 17 FB cases were to Max Saami specs for shoulder lengths the shoulder and 0.200" datum diameter's were .0070" and 0.0039" under Max respectivly. This allowed them to fit in the Mach IV chamber with plenty of clearance after trimming. I them fired a round and found that there was 0.005" Headspace at the shoulder datum when comparing a new brass to the fired round and the length had increased to 1.395". The fired round holds about 0.5 grains more IMR 8208 than the new round.

I then FL sized the fired round with a Redding die and found that I could just size it with 0.0005" HS at the shoulder datum. The shoulder diameter was reduced back to the same as the new brass which increased the brass length to 1.400" for a total of 0.010" which is quite a lot and required trimming. Subsequent firing and FL sizing with the redding FL die stretched the case by another 0.003". I found that I could actually "bump" the shoulder by 0.0005" and reduce the shoulder and 0.200' datum diameter by 0.0005" with the redding Neck Sizer die.

It may be possible to do a minimum FL sizing, without moving the shoulder, with a 17 FB die which would be great. Perhaps someone could measure a FL sized 17 FB brass to help determine if that is possible.

I have loaded some test rounds with IMR 8208 XBR and RS X-Terminator using the Hornady 25 V-Max. Just waiting for the wind to die down and some warmer weather so I can run them over the Chrony.
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  #16  
Old 07-07-2021, 06:53 AM
obijohn obijohn is offline
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Trying to understand this...

From what I can garner, a .17 Mach IV will fit in a FB chamber, but not vice-versa. Not a good idea to fire the Mach IV in a FB chamber unless it's checked by a gunsmith and it is within spec for the Mach IV cartridge.

Can a Mach IV be rechambered for FB without having to set back the barrel?
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  #17  
Old 07-07-2021, 12:42 PM
Hog Patrol Hog Patrol is offline
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Quote:
Originally Posted by obijohn View Post
Trying to understand this...

From what I can garner, a .17 Mach IV will fit in a FB chamber, but not vice-versa. Not a good idea to fire the Mach IV in a FB chamber unless it's checked by a gunsmith and it is within spec for the Mach IV cartridge.

Can a Mach IV be rechambered for FB without having to set back the barrel?
It depends on the reamer used for the Mach IV.
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  #18  
Old 07-07-2021, 01:14 PM
Bill K Bill K is offline
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Quote:
Originally Posted by Hog Patrol View Post
It depends on the reamer used for the Mach IV.
True.

As for the Old, Old question from the OP, go with the 17FB, much easier to find dies, etc. and they shoot side by side, really overall.
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  #19  
Old 07-18-2021, 10:20 PM
Iowa Fox Iowa Fox is offline
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For me it would definitely be the Mach1V.

The 17 Fireball is a factory chamber and freebore in most cases so its a crap shoot.

If your thinking factory ammo with the Fireball you might find a box or two but if you need a few hundred for a trip good luck.

Plus I'm old enough that's all we had in the old days.
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  #20  
Old 01-07-2023, 04:13 PM
obijohn obijohn is offline
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Default Different variations of the Mach IV

I wonder how different the Kimber 84's factory Mach IV chambers are than the Coopers, given that Cooper Rifles was started by ex-Kimber employees.

It seems that the critical dimensions for interchangeability between the .17 FB and the .17 Mach IV are:
  • headspace
  • neck diameter of loaded factory FB ammo
  • throat/freebore

If the chamber allows these to fall within tolerances then the FB factory ammo is safe to fire in the Mach IV chamber, right? And this can be ascertained by cerro-casting the chamber and comparing the cast against a particular lot of factory ammo, right? Or, alternatively, could one use a .17 FB go/no-go gauge set to determine this for a particular Mach IV rifle?

Last edited by obijohn; 01-07-2023 at 04:15 PM.
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