Help decide 17-222 or 17 Mach IV

[B23]

I have a CZ 527 Varmint in 17 Rem. that I bought awhile back and I'm considering having it re-chambered to either 17-222 or 17 Mach IV. The available brass for the 17 Rem is pretty crappy stuff and to add insult to injury, considering what you get, it's expensive. With either of these other two I can use necked down Lapua brass that cost the same or less and has considerably better quality.

This is a near new gun with only 30 rounds down the pipe which is the only reason I'm considering doing a set back and re-chamber. I've considered having a new custom put on this but I'd rather not if I can get away with it.

I briefly considered the 17 Fireball but getting brass for those seems to be rather difficult and would likely be low quality also and the 17 Mach IV is just a straight neck down from 221 FB.

I welcome thoughts and ideas on this, particularly with regard to 17-222 and 17 mach IV.

 

[STS]

The Mach IV seems to be the perfect case capacity for the 25 grain bullets. VV N-133 and the better 25's will yield superb groups if the rifle is a quality piece. If you lean toward the larger bullets then the .222 case would probably be better. I've worn out a couple of 10 twist Shilen barrels chambered in Mach IV.

 

[Sniper338]

mach

 

[B23]

The Mach IV seems to be the perfect case capacity for the 25 grain bullets. VV N-133 and the better 25's will yield superb groups if the rifle is a quality piece. If you lean toward the larger bullets then the .222 case would probably be better. I've worn out a couple of 10 twist Shilen barrels chambered in Mach IV.

The 25's, either HP's or Vmax, are the bullets I'm looking at using most. I've leaning a little more toward the 17 Mach IV because I like that is seems to do a lot with a pretty small amount of powder and my thinking is it will powder foul considerably less than the larger cased .17's.

What's your process for necking down 221 FB brass? Did you use a no neck turn reamer or do you have to turn necks?

 

[Tim s]

The Mach IV is a marvel. 25's can reasonably get to 4000 fps.
I never did moe than clean up necks because 221 brass is generally lousey.
You must be careful loading on the warm side, 2 tenths in powder can make a difference and max loads at 50 deg. Are going to be a problem at 85.
Try and find some of the old Remington hppl slugs.....devestating performance,

 

[Tommie]

1 vote for 17-222

Better brass options.
Will feed easy from your magazine.

 

[varmintshooter]

I'm not clear on why you want a mach IV over a fireball. I have a FB and make brass from 223 or 221, not really a problem. Why not go 17-223 almost a 17 rem and brass is everywhere. I was shooting my FB today hitting golf balls @ 200 yds pretty consistently with both 20 vmax and 25 hornady hp's. Its a fun little cartridge.

 

[B23]

I'm not clear on why you want a mach IV over a fireball. I have a FB and make brass from 223 or 221, not really a problem. Why not go 17-223 almost a 17 rem and brass is everywhere. I was shooting my FB today hitting golf balls @ 200 yds pretty consistently with both 20 vmax and 25 hornady hp's. Its a fun little cartridge.

Because I don't want, yet another, rifle I have to fire form for and I want to use Lapua brass and both the 17 Mach IV or 17-222 is just a straight neck down from 221 FB or 222 brass.

Does anyone know if there is much performance difference between the 17-222 and the 17 Mach IV. I like the idea of the 17-222 because I can use the same magazine the gun came with but that's kind of a minor detail.

 

[aer21]

You can get .221 fireball Lapua brass and neck it down in a few stages for the .17 fireball. That’s what I did and it’s been working fine. The necked down brass I had fits tight in my chamber so it ends up being just like forming an ackley. Difference being the changes are very slight from .221 to .17 fireball, I believe it forms to a 30 degree shoulder and a slight amount less taper. When I extract a fired case, visually, you pretty much can’t tell the difference from it and and unformed one.

 

[STS]

The 25's, either HP's or Vmax, are the bullets I'm looking at using most. I've leaning a little more toward the 17 Mach IV because I like that is seems to do a lot with a pretty small amount of powder and my thinking is it will powder foul considerably less than the larger cased .17's.

What's your process for necking down 221 FB brass? Did you use a no neck turn reamer or do you have to turn necks?

I use a set of RCBS Mach IV case forming dies. I have 2 .17 Mach IV reamers both of which are tight neck dimensions that require turning.