17 HM2 Runout

[jb77]

Moderator, I looked for the article that you did on runout in 17 HM2 ammo but couldn't find it. I was wondering if runouts had been compared between 17 HMR and 17 HM2.

I trust your data on the 17 HM2 and have seen shots that were outside the group for no other reason than that induced by runout.

I do not typically see this with HMR ammo, as I do not have the instruments to test runout I was wondering if the HMR had been checked and what the results were if any.

This leads to the question that if the runout is significantly less on the HMR then why is it so, and could'nt the HM2 be held to these same standards?

Anyone have anything to add?

 

[Forum Boss]

I haven't personally measured run-out on HMR ammo but I would suspect it is less for the following reasons.

1. The HMR has a longer, straighter neck. The HM2 neck flares downward so it doesn't support much of the shank of the bullet

2. The Mach 2 designers made a serious mistake when they spec'd the round as short as possible,to enhance feeding in a Ruger 10/22). This means that the max diameter of the bullet is right at the case mouth, and in some instances BELOW the case mouth.

By contrast, bullets in the HMR are seated longer. The 20-grainers in particular have much more shank forward of the case mouth. I think this makes it easier for the seating dies to set the bullet straight. More bullet shank and a longer case neck should also improve the centering of the bullets in the neck.

3. With the longer-seated bullets of the HMR it may be possible to get the bullet into the rifling with a "tight chamber". This should straighten our crooked bullets somewhat. However with the Mach 2 it is virtually impossible to get the bullet to touch the rifling as the bullet starts curving right at the case mouth.

Here is a video showing Eley 17 Mach 2 ammo with .009" run-out. I've personally seen rounds as bad as .014". Typical runout, measured on the bullet slightly forward of the case mouth, is .003-.004. About 2-4 rounds per box will have run-out of .000-.0015.

VIDEO: http://youtube.com/watch?v=OF4uH8FkSsI

Joe Friedrich recently did a run-out test on the $20/box Lapua X-ACT 22LR ammo. Out of a box of fifty, he said nothing was over .001" and in the majority of the rounds "The needle didn't even move."

This tells me we really don't know how accurate 17 Mach 2 and 17 HMR can be. The ammo manufacturers, right now, don't care -- they've even refused to supply components so we could handload some rounds for testing purposes.

I tell you I think we could get a big gain in 17 Mach 2 accuracy if Eley could just seat the 17gr bullets .015" longer, and do so consistently. We've seen rounds vary in overall length from .978" to 1.002".

 

[jb77]

Paul, outstanding reply. I actually got a couple of rounds out and started looking at the differences between the 2 and when you know what you are looking at it becomes obvious.

No wonder there is runout when the crimp is that high on the ogive of the bullet.

All in all still a great little plinking cartridge.

 

[robbor]

Ive heard about the runout also but that was a long time ago.
I wonder how good the Eley is that is currently being produced?

 

[ScottElliott]

Nothing new produced...there still selling stuff produced a few years back....

 

[Forum Boss]

I sorted 300 pieces of Eley 17 Mach 2 this afternoon. Out of 300 rounds, there were 36 with .002" or less run-out.

Among these 36 "good" rounds, the cartridge Overall Length,COAL) varied from 0.984" to 0.999".

Run-out # Percent
0.0005 1 0%
0.001 9 3%
0.002 26 9%
0.003 44 15%
0.004 52 17%
0.005 51 17%
0.006 45 15%
0.007 36 12%
0.008 18 6%
0.009 7 2%
0.010 9 3%
0.011 2 1%
--------------------------
Total 300 100%

NB: I put everything over .006" run-out in one pile for "really bad". That is 117 rounds, 39% of the total. I will not shoot anything over .003" run-out in a match.

Problem is, even if you sort for run-out, then you are left with a few low run-out rounds that can vary in COAL by as much as .020".

You also need to inspect for bullet flaws and mangled crimps.

I think it is not unrealistic that, to get 25 rounds with less than .0025" run-out, all COAL within .003", and no mangled crimps or defective bullets/tips, you would have to sort through 1500+ rounds.

 

[Marksman]

What setup are you guys using to measure runout on rimfire ammo?

 

[Forum Boss]

What setup are you guys using to measure runout on rimfire ammo?

Link: http://nielsonbrothersarms.com/Club.HTML

Nielson Brothers Concentricity Checker, club model: