17 HMR Chrony Data...

[rcmark]

CZ 455 in 17 HMR
Hornady 17 HMR V-Max.

I was surprised it shoots MOA with a extreme spread of 145!

 

[Phil]

Am I reading this wrong????

Shot #1.................. 2528 fps.

Shot #21................ 2728 fps.

ES....200 fps.?


Phil.

 

[105gr]

And the chrony looks way too close.

 

[kram]

You only got an ES of 145 Iwas doing 10 shot strings with the same ammo about 3 weeks ago and my ES was over 300 in every instance, wih one that reached 4470 fps!. Thats right,4470! There were more than a few well into the 3000-3500 bracket as well. There were also a lot of slower rounds too. I would have to exclude the wildcat rounds to get any sort of average.I use a magnetospeed chronograph and shoot out of an Anshutz 1727 f. I also sent an email to Hornady to ask what the story was and they replied with some hoop-la about my barrel not being clean etc etc and basically brushed me off I think.I sent another back stating my meticulous care of the rifle and that this was not the first time I have conducted this test but have since had no reply.

 

[HuskerP7M8]

kram,

You have either a problem with your chronograph or a problem setting it up.
If you actually got a velocity of 4,470 fps, your rifle would be in pieces and I would hope you were wearing safety glasses.

Landy

 

[Doc Highwall]

Your chronograph is so close to the muzzle that you are picking up pieces of un-burnt powder at the 4470 fps reading. Try it with the chronograph out farther from the muzzle to get more realistic readings.

 

[kram]

Your chronograph is so close to the muzzle that you are picking up pieces of un-burnt powder at the 4470 fps reading. Try it with the chronograph out farther from the muzzle to get more realistic readings.

Thanks doc thats a good idea ,i'll try that. We were following the instructions on the mounting length and there is room for a couple of inches more. We had no problems with the 223 or the 308 prior to the 17 and I didnt even think of that as we have to go to hi sensitivity to get a reading off the little rounds.

 

[HuskerP7M8]

The problem lies elsewhere. The MagnetoSpeed doesn't employ optical sensors and is immune to muzzle blast.
The earlier post in this thread showing the chronograph with optical sensors is probably too close though.

Landy

 

[kram]

O.k, so we just went out and tested 30 rounds. 10x 20grn XTP hornady, 10 x 17 grn vmax Hornady,10 x 17grn vmax Ohlin made Wincester. The result was the same with the Hornady rounds. E.S of 297 fps with a high of 3724 from the 17 grn Vmax., ES of 210 for the 20grn XTP Hornady witha high of 2733. The most consistent were the Winchesters with an ES of 76fps and a high of 2660. The mystery however , is the hornady rounds still group under moa , inside 100 metres anyway. Maybe the the difference would be more pronounced abit further out but I didnt have time to set it up to try. So, rcmark your 145 es aint lookin so bad from where I'm at.

 

[vmaxpro]

Somethings def going on there. I ran a full box out of curiosity with a prochrono at 15 FEET away and ES was 37.

 

[CTK]

sounds like the Magnetospeed is a bit wonky sometimes.

 

[kram]

sounds like the Magnetospeed is a bit wonky sometimes.

I was starting to think that myself, but it reads very well with any other round we use it on and the high and low fliers on the targets are suggesting that it is telling the truth. We will try more tomorrow and post the results with pics tomorrow night.

 

[CTK]

Hope it is wonky. Otherwise very scary.

 

[TheOtherZilla]

Personally while 17 hummer velocity is interestin, I just shoot mine.. The velocity is what it is.. Nothing I can do about it. So I shoot pdawgs and enjoy..

 

[kram]

Personally while 17 hummer velocity is interestin, I just shoot mine.. The velocity is what it is.. Nothing I can do about it. So I shoot pdawgs and enjoy..

Zilla, I like your attitude. In the end I'm gonna still cull pests anyway...

 

[kram]

Sorry I aint got to another test yet, work has a way of getting in the road. I am however, planning on doing a video starting this weekend an will find a way of posting a link to it. Hey rc have you tried another test yet?

 

[rifleman700]

I was at the range awhile back and another shooter was having this same problem shooting a 17 HMR through a Magneto Speed with Winchester ammo. I could tell he was getting frustrated so I went over to see if I could help and he was livid that his 17 HMR would have ES of 400 fps. We took his rifle over and shot it through my Oehler and there was no ES problem and the ES was down to 25 fps. He then got on the phone and called MS and they spent some time with him changing settings and before long it was working fine. Not sure what they changed but he gave me the thumbs up that it was measuring exactly what my Oehler was.

As far as the Chrony it looks too close to the muzzle. Try moving it 10-12' away from the muzzle. Not sure how a Chrony works but you may try putting black poster board on the inside of your screens to manage the light better. There may not be enough bullet material to pick up in the sensors and the board will help.

 

[hogpatrol]

The early versions of the magnetospeed were sketchy with .22 and .17 rimfires. I had one and with proper settings, they work fine. The latest versions don't have the same issues.

 

[rcmark]

Your chronograph is so close to the muzzle that you are picking up pieces of un-burnt powder at the 4470 fps reading. Try it with the chronograph out farther from the muzzle to get more realistic readings.

Tried it makes not difference.