17 Mach IV vs. 17 Rem Fireball

[Doc T]

     Are these EXACTLY the same cartridges or is there some minor difference?  What I am getting at is if Remington's factory 17 Fireball ammo will shoot in a Contender barrel chambered for 17 Mach IV.  Thanks.

Doc T

[Paladin]

I'll vote yes, same diameter, same length and same shoulder angle. have fun

[Steve P]

I believe the shoulder height is different.  Don't quote me on this.  That is not saying one wont shoot in the other, but one set of dies may not properly load the other.  I have packed all of my manuals for a move, so I cannot check. 

Steve

[Doc T]

I'm going to check with Remington and T/C next week.  If I get a definitive answer, I'll post it.  In the meantime, if anyone else has any info, please speak up.

Doc T

[Ladobe]

They are NOT exactly the same.  In a word, the 17 Remington Fireball "mimics" the 17 Mach IV is how I would label it.   Big Green gloats that their new offering improves on the 17 Mach IV, but then don't say why.  I guess they think offering factory ammo (one load only so far I think) being shot in a SAMMI chamber is an improvement.   BS - the full potential of the 17RF case can't be achieved nor approach the 17M4 without tuned reloads for your particular firearm.   IOW, unless you don't reload and are stuck with shooting only factory ammo it's just sales hype to sell their rifles.

Some of the specs I have so far to compare them (the ones that might be important)...

Case length
17RF 1.420
17M4 1.400

Neck diameter
17RF .206
17M4 .199

Neck length
17RF ?
17M4 .203

Shoulder diameter
17RF .3673
17M4 .360

Length to shoulder
17RF ?
17M4 1.058

Head diameter
17RF .3769
17M4 .376

Both have 30 degree shoulders.  The specs for the 17M4 are the standardized specs supposedly.

Interchangeable?   Guess it depends on how close the neck length and length to shoulder is between these two cartridges (still haven't found these for the 17RF yet) AND the specs of the chamber in a particular firearm.    After Vern O'Brien put the 17M4 on the map and especially before it became a more or less standardized wildcat I'd bet there is some variation in the 17M4's out there.   Neck diameters and neck length for sure even after standardized with lots of wildcatters who neck turn their brass and/or want longer necks.   

With three 17M4's already in the safe, I won't be looking for a 17RF myself.   

Anyway, might be some new info for you Doc T.