It is surprising it shoots as well as it's reported, sometimes?

[Nvreloader]

This discussion is pertaining to the 17WSM RF chamber spec's and ammunition Only.

I have just finished measuring 5000 rds of this caliber in 20/25gr bullet weights,
In Win/Hornady brands, and comparing the ammo dimensions against the SAAMI chamber spec's.

It appears that they (ammo makers and SAMMI) were not on the same page.
The measurements from the ammo run,
(from bolt face to the .236 shoulder datum diameter) runs from .895 to .995".
SAMMI calls for 1.017".

The measured throat lengths of the ammo runs from 1.205 to 1.220",
SAMMI shows 1.407" = quite a bit of slop?
Measured from bolt face to .168" bore diameter.

These generous dimension would lead one to believe,
that the spec's of the chamber spec's should be changed,
to BETTER fit the ammo and improved accuracy etc.

I would greatly interested in any info you have,
With your 17 WSM ammo etc.

Let's keep this discussion to ammo and chamber spec's please.

Tia,
Don

 

[rayjay]

In my experience all the 17s are like this. Both of my HM2s blow the shoulder forward .020" every shot. The HMRs I have measured are completely inconsistent. Out of the same rifle the shoulder gets blown forward anywhere from zero to .050". Explain that one. I made a couple of brass 'bushings' like come with Harrells dies.

 

[Nvreloader]

RJ
This is my first experience dealing with a bottle necked rim fire,
So I have a learning curve to handle.
I deal in CF cases only, until now,
my reason for getting this case,
As it should be cheaper than the 22-250,
In the ADC work I do in the hay fields,
300-600 rds per night, for over 6 months p/yr.

As soon as I get the reamer chamber spec's tighten up,
I build the rifle, and see the results etc.

Tia,
Don

 

[rayjay]

I just remembered something else. Iirc the case neck to chamber clearance is about minimal. Measuring the necks before and after shooting I kinda remember them growing only a couple of thou. My theory was that they give lots of room at the shoulder to cover tolerance stack of mass production ammo and then attempt to insure accuracy by a good fit at the case neck so the bullet is well aligned with the bore.

Do some measuring and see what you come up with. And remember that all I messed with was the HM2 and HMR.

 

[Nvreloader]

Jr.
After haveing measured the case necks,
Dimensions of loaded and fired cases run thus,
Loaded= .195"
Fired cases = .199"

The bullet jump is what has me scratching my head,
over .250+" before bore taper contact??

The bullet has left the case mouth, before contacting the bbl throat taper!
The bullet is slip sliding down the bore,
this cannot lead to the best accuracy, IMHO.

As there is only .240" of the bullet held in the case neck,
on OEM loaded ammo.

Tia,
Don

 

[rayjay]

All that jump lowers the pressure. Factory Weatherby magnums used the same ploy.