Ordered in March, and picked up today, a beautiful Mod 21 Varminter in 17 Mach IV. Has the heavy varmint (0.76") barrel, and nice wood. Now the loading begins!
Have 20 Bergers and Vmax, and 25 gr Calhoun and Hornadys. Plan on using H335, Varget, and Benchmark. Any other suggestions?

Mulerider, I have the same rifle. Mine doesn't care for the V Max,(3/4 to 7/8's inch, sure pops a gopher though) I've shot 20 and 25 Berger both match and mef, and I just got Berger's 22 grainer's both in match and mef that I haven't tried yet. I've used H322, H335, H4198, VV N133, and Benchmark. Keep in mind I've only been seriously working up loads for this rifle for about 2 month's, with that in mind my observations are as follows. Most accurate combo is H335 and 25 grain Berger match, 2'nd is H335 and 20 grain Berger match. The problem I've had is that the batch of H335 I'm using shows a huge sensitivity to temprature. Example, with the 20's at 65degrees I'm chronoing 4,025ish, at 80degrees same load 4'150ish, hunting prarie dogs at a 100+ it blew primers. VV N133 has the best velocity, and now that varmint season is over I intend on taking another good look at it, as well as Benchmark. H4198 has the best standard deviations but that might be cause it's a pain to meter accurately and I have to weigh every charge, something I don't like doing on varmint loads. I'm thinking the 22 grainers might have the best combo of velocity and accuracy. My rifle didn't shoot well at first, but hats off to Cooper, cause it sure does now. Sighting in for this last prarie dog hunt I shot 2-20grain match, 2-20grain mef's and 2-25 grain match into a 6 shot group that meassured in the .2's, the 25grain mef's shoot to a slightly differant point of impact, but still group well. I'd be curious as to how the Calhoun's shoot, haven't tried em yet, great rifle, lotta fun.---Shoot Safe---montdoug

since today was "break-in the barrel" day, grouping was suspect. Everything I shot used Benchmark; the Berger 20's were best, with 5@ .62" (4 of those measuring .32). Vmax's kinda crummy at 1.0", and the 25 Calhoons way out at 1.6". 20 grainers were running right 4000fps, the 25's at 3850. After cleaning, I shot a fouler prior to trying for a group.
The bolt was difficult to close on various rounds; I know the case length and OAL is okay, so I ran my neck reamer thru the fired cases, definitely was necessary on some, less on other. Wasn't expecting that, and groups may certainly improve with more even neck tension.
Plenty of combo's to try; I'm still optimistic.

Sidenote: tried some 30gr Bergers in my 221 Fireball, using 17.5gr LilGun. This powder has given me 3500+ fps with 40's.....and the avg on the 30's was 3975fps! One reading was over 4000, which is not a number associated with a 221 Fireball. The load was likely too hot, and I will back off a few tenths on the next try.