17 HM2 Concentricity

[Forum Boss]

With the help of Stan Ware, www.SGRCustomRifles.com, we've been working on a 17 HM2 accuracy project for quite some time.

It appears that the caliber may be a LOT more accurate than some people think.

However, there is an issue with run-out. We think this may be the explanation for some of the "mystery fliers" people have observed.

I just checked a couple boxes of Eley today with the Nielson Bros. Concentricity Gauge,fantastic tool). Here are the results.

Run-out measured on bullet:
Box 1, Lot 4105-40079
.001 = 4 plus 2 @ .0015
.002 = 15,many of these were closer to .0025)
.003 = 8
.004 = 13
.005 = 5
.006 = 2
.007 = 0
.008 = 1

Box 2, Lot 4105-40079
.001 = 5 plus 3 @ .0015
.002 = 12
.003 = 14
.004 = 3
.005 = 10
.006 = 2
.007 = 0
.008 = 1

Those .008s really wobbled! The Worst ones are quite obvious.

Total .002 or better = 41%,in both cases about 20 per box)

And YES, run-out does make a difference. Check out these ONE HUNDRED Yard groups:

 

[Forum Boss]

Here are concentricity test results, using the Nielson Bros. tool, for CCI 17 Mach 2, Lot J16K07

CCI Box 1
.001 = 6 plus 3 at .0015
.002 = 19,one bad nose tilt)
.003 = 19,three bad nose tilt, one short-seated)
.004 = 1
.005 = 2
.006 = 0

CCI Box 2
.001 = 7 plus 2 at .0015
.002 = 19,two bad nose tilt)
.003 = 19,one bad nose tilt)
.004 = 3
.005 = 0
.006 = 0

On first review, this looks better than the Eley. There were only 3 cases with .004 or greater run-out. However, one thing I noticed with the CCI was disturbing.

Nose Tilt--With the CCI ammo, even when the run-out,measured right in front of the ogive) wasn't too bad,i.e. .002), you could visibly see the nose of the bullet moving up and down as you rotated the case. Clearly the bullets were not seated straight in the case. On some of the .003s, my guess is the bullet tip might be as much as .005 off-axis--it was quite noticeable to the naked eye.

Bullet tips--also, when measuring the CCI, it was quite apparent that many of the polymer bullet tips were not uniform. The base wasn't a straight line at the top of the jacket, but rather formed a kind of wavy line.

I could also tell there were variances in seating depth, because the initial reading on the dial indicator varied by as much as .005 from round to round.

This is something we'd noted with all the 17 Mach 2 ammo. The distance from base to ogive varied by up to .008. In a few extreme cases, even more.

This tells me, that to do a proper sort, one should start with concentricity--but that's not enough. Then you should do a visual inspection of the tips, and then measure the "good ones" base to ogive once you have completed a concentricity sort.

 

[Flybuster]

This is very interesting, do you have to have a special gauge to measure your concentricy?

 

[Clarence]

Mod:
I would only question bad TIR if the rifle is that of production and with less than tight chamber,custom)if we have a good chamber, and something resembling reasonable neck tension the TIR goes away out of the box due to alignmentin that custom chamber, whay say ye?
That work is excellent and is appreciated by all

Clarence

 

[Forum Boss]

Mod:
I would only question bad TIR if the rifle is that of production and with less than tight chamber,custom)if we have a good chamber, and something resembling reasonable neck tension the TIR goes away out of the box due to alignmentin that custom chamber, whay say ye?
That work is excellent and is appreciated by all

Clarence

In the case of the 17 HM2, unfortunately you are wrong. Where the run-out comes from crooked case necks yes, maybe, you can get a little straightening, but not much. We have about .0015 clearance per side on the necks and that's not enough to straighten much.

In terms of throat, our rifle had an absolutely minimum spec chamber. We tried to get the rounds into the rifling if possible. We found this was impossible because the bullet's ogive is right on the case mouth,and sometimes inside the case mouth).

We really, really wish the round was spec'd just .020 longer--then we could get the ogive to contact the rifling.

Most of the run-out is actually the bullet seated crooked in the case. In recent batches of ammo we've also see bullets that aren't very round.

Sad to say, the last batch of ammo I checked was worse--with many rounds +.009" run-out and 4 or 5 defective bullets per box. Sure enough.

The best five rounds in the box gave a .13" 4-shot group with 1 low right about 3/8" away, at 50 yards.,We'll never really know about the flyers.) The worst five rounds went about 1.2" at 50 yards.

 

[Clarence]

Mod:
Y mean to tell me that Hornady is actually crimping over the Ogive??? what a mess and I had thought that I may buy one but if the ammo is not up to par then I will not. The chamber,custom) fix is out of the question as one could NOT seat the bullet into the lands, to provide for the jam one would have to reduce the barrel internals and that would create havoc with the pressures.
I dod not know on the H2!

Clarence

 

[Forum Boss]

Clarence,

The SAAMI OAL spec on the Round is 1.000" plus/minus .005". The longest round I've measured was .999", the shortest was .978". When the bullets are seated very short, yes, the ogive can actually be below the case mouth, and more often than not then the case mouth gets mangled by the seating die--I saw this in a lot of Remington 17HM2 I bought recently. There were enough mangled case mouths,and scratched or dented bullets) that I sent the whole lot back.

I discussed with Stan Ware how we could get the bullets into the rifling, and the best we could come up with is some kind of venturi-like throat, but you still have the problem of how to get the lands to touch the jacket and still leave room for the neckwall.

As noted, if Hornady/CCI/Eley et al had just spec'd the round at 1.050" max, then the ammo-makers could experiment with longer bullets and get to the lands. But with the SAAMI case length set so short,to improve feeding in a 10/22), there's not much you can do.

If we could obtain primed cases, we've thought about hand-loading some ammo just to see if the results could be made more uniform. But Eley, CCI and Hornady won't sell us the primed cases.

 

[Link]

Hi
I see you checked Eley and CCI how about the other manufacturers are they the same?
Doesn't someone make a quality round?

Thanks Link