georgetwalkerjr
To what extent have ya'll found the 17HMR to be ammo sensitive in terms of accuracy? I've got a CZ heavy barrel, which seems to like the Hornady product, and does poorly with CCI in particular. Thanks. George
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George,
We've had a long-term 17 Mach 2 research project. This round shares the same 17gr bullet with most of the 17HMR ammo. Yes, these 17 rimfires can be very ammo sensitive.
What we've noted in particular:
1) Crimp is inconsistent. These bullets are seated so the bullet ogive is right on the case mouth, at least with the 17gr V-max bullet. Because of that, slight variations in seating depth mean sometimes the crimp is on the full bullet diameter, sometimes it is not. If you look at your ammo, some of the rounds have a tight crimp, actually rolled over, while others look like a mild taper crimp.
2) Run-out. This is a major issue with the 17 rimfires. Using a Nielson Bros. concentricity gauge, we found that a few rounds per box had run-out of up to .009". By contrast, with Eley Tenex 22LR ammo, 90+ % will have run-out of .002 or less. At least half the 17-cal rimfire rounds in the samples we checked had run-out of .003+.
3) Velocity spread. For a variety of reasons,crimp being one), the ammo has a very wide velocity spread: 70-90 fps on average. Some lots of ammo were quite a bit better than others.
We haven't tested it, but there are many reports that the Hornady 17 HMR with the 20gr hollowpoint XTP bullet is more accurate in many rifles. We think this is due to the longer bearing surface which allows for more consistent crimps and probably results in less run-out, on average, but that's just a supposition. Suggest you try the 17 HMR with the 20gr Flat-base bullet and see how it works for you.
CCI also makes a 17 HMR with a 20gr "GamePoint" bullet:
Photos from Cabelas.com
We've had a long-term 17 Mach 2 research project. This round shares the same 17gr bullet with most of the 17HMR ammo. Yes, these 17 rimfires can be very ammo sensitive.
What we've noted in particular:
1) Crimp is inconsistent. These bullets are seated so the bullet ogive is right on the case mouth, at least with the 17gr V-max bullet. Because of that, slight variations in seating depth mean sometimes the crimp is on the full bullet diameter, sometimes it is not. If you look at your ammo, some of the rounds have a tight crimp, actually rolled over, while others look like a mild taper crimp.
2) Run-out. This is a major issue with the 17 rimfires. Using a Nielson Bros. concentricity gauge, we found that a few rounds per box had run-out of up to .009". By contrast, with Eley Tenex 22LR ammo, 90+ % will have run-out of .002 or less. At least half the 17-cal rimfire rounds in the samples we checked had run-out of .003+.
3) Velocity spread. For a variety of reasons,crimp being one), the ammo has a very wide velocity spread: 70-90 fps on average. Some lots of ammo were quite a bit better than others.
We haven't tested it, but there are many reports that the Hornady 17 HMR with the 20gr hollowpoint XTP bullet is more accurate in many rifles. We think this is due to the longer bearing surface which allows for more consistent crimps and probably results in less run-out, on average, but that's just a supposition. Suggest you try the 17 HMR with the 20gr Flat-base bullet and see how it works for you.
CCI also makes a 17 HMR with a 20gr "GamePoint" bullet:
Photos from Cabelas.com
except for a super precision made gun, all my 17's have been very ammo sensitive, the worst being my rossi. However my annie 6417 pistol, with a 12 in bbl, shoots everything moa, and I do mean everything. Thats why Annie's kick butt!
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