17 Hornady Hornet COAL
 

I need to tap into the vast knowledge here. I'm trying to find a load my CZ527 17 HH likes with a 20 grain V-max. I've tried IMR4198, Lil gun, and 2 others. They all stank. I just purchased some CFE BLK as I've read good things. My dilemma is what cartridge overall length to use with this powder. Hodgdon shows a 1.715" COAL. That's what the factory Hornady rounds measure. Shooters Reference shows a 1.715" length using a Federal 205M primer. If I use my Remington 7 1/2 primers they show a COAL of 1.800". The only thing they change is the primer, charges and bullet are the same. Is this simply a matter of the Remington primer having more oomph? I only have Remington 7 1/2's available. I don't want to damage my CZ. And... it shoots fabulous with the 25 grain Berger Varmint bullets and H335. It's these darn 20 grain bullets. I tried a search but nothing specific to my question. Thanks in advance for your time.

Magazine was the limiting factor on mine.
Don’t know what kind of groups your after with this rig. IMR4198(full, lightly compressed)and a 20 grain Vmax gave me what I was looking for out to 200.
I never tried 25’s as I was after splat factor.

I stayed at 1.715" with the IMR4198 and 11.1 grains. I figured that was probably a starting load when comparing data from other cartridges that use both H4198 and IMR4198. Stayed around 1 1/4 " group at 100 yards.

James Calhoon will swap out your magazine for a modified one that allows you to take better advantage of the generous throats on the CZ. Made a significant difference on our CZ 17 HH rifles.

Or get a single shot magazine follower from a couple sources. Works great in the CZ's, as long as you shoot single loading. :)

I have two CZ 527 Varmint model 17HH one of them likes 12gr 1680 w/20gr Vmax and the other prefers 12.2gr 1680 w/20gr Vmax. Same OAL in both which I think is around 1.720-1.730. I typically use Fed M or CCI BR primers but I have a small truck load of Rem 7 1/2's so that's what I've always used in my 17 Hornets.

The CZ freebore in the 17 Hornets is extremely generous so the bullet will nearly fall out of the case before it touches the rifling but these 20gr Vmax aren't really all that seating depth sensitive so jumping them a mile doesn't seem to really hurt a whole lot and it's not like these things are BR guns or something you're going to be shooting wayyyy out there so if you can get a load that'll consistently shoot no worse the 1 MOA, better on your good days or even a lot better on your really good days, I'd call it good and go have yourself some fun blazing away are ground squirrels and PD's.

As an experiment, when I bought my second CZ 17 Hornet, new right out of the box I sent it to Kevin Weaver to rechamber it with his 17 Hornet reamer because the factory CS reamers are pretty generous in the chamber as well as have more freebore. Kevin set the barrel back around 1/2 - 3/4 of an inch rechambered it with his tighter spec reamer, rethreaded it and spun it back on. The freebore is much shorter and the chamber is a fair bit tighter. I can't chamber a fire case in my other untouched CZ 17 Hornet. It does shoot noticeably better than the untouched one but does it shoot a lot better, not really.

Thanks for the input everyone. I don't have a 17 Hornet case for my overall length gauge. I don't want to set these things too long. With factory 20 grain Hornady ammunition it's a 1/2 inch rifle. I just don't know if I'll have pressure problems with 12.1 to 12.4 grains of CFE BLK, Rem. 7 1/2 primers, 20 grain Vmax at 1.715". That book listing of 1.800" is .085" longer with that combo. Scares me. I guess I could try it at that length.

Sit bullet at max length in a sized case, try to size the neck only about 1/4 of the way down so it just holds the bullet, with no primer. Run it gently into the chamber, measure length after you pull it out. When the bullet touches the lands it will push the bullet deeper into the case. It is the old time way of measuring distance to the lands. With my CZ, and a 20 grain Vmax set out as far as possible it still didn't touch the lands.

"I just don't know if I'll have pressure problems with 12.1 to 12.4 grains of CFE BLK, Rem. 7 1/2 primers, 20 grain Vmax at 1.715""

Hodgdon has 11.8 Grains published as the starting load & 12.8 as the maximum load. If I were to make a SWAG, I would not expect to see pressure problems start to manifest in your target weight of powder. That being said, I start with using the published starting load and will work up in .2 grain increments on small cases like hornets.

I have a friend with a CZ 527 Varmint model 17HH just like mine and his "go to" load with 20gr bullets is 12.4gr CFE BLK OAL 1.720 It's not a particularly speedy load, around 3400, so pressure should be a non issue for you but it shoots very well for him.

If you plan on stretching the OAL out to 1.800, unless you're seating into the lands, 12.4gr CFE BLK w/20's pressure won't be an issue