sierra told me this, is it true?

[gregpo]

when i talked to sierra today, they said that if you try to seat out to far you will loose neck tension, and that will cause large deviation in velocity's. He recommended to keep atleast .250 in case neck to keep proper neck tension. Is this all true?

Also
I'm having trouble measuring coal with 175 smk because variances in the bullet tips. I loaded a batch and they go from 2.800 to 2.815. Thats significant i think.

 

[deadly0311]

Re: sierra told me this, is it true?

measure from the Ogive, get a bullet comparator.

 

[marduk185]

Re: sierra told me this, is it true?

youll only get "deviation" if you do it differently from round to round. measure bullets base to ogive and if theyre all the same and you seat them with same die setting theyre gonna have same tension from round to round(assuming of course your brass is trimmed and prepped consistently.)

 

[EddieNFL]

Re: sierra told me this, is it true?

Ditto marduk's response.


<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">He recommended to keep atleast .250 in case neck to keep proper neck tension.</div></div>

I have a couple of 7TCU loads that seat .100" deep. The least accurate of the two is .75 MOA with an SD of nine...in a handgun.

 

[bohem]

Re: sierra told me this, is it true?

The general rule that I work off of is to keep at least 75% of the bullet caliber in the neck. Sometimes this isn't possible, but when it is, I work from that.

 

[Travelor]

Re: sierra told me this, is it true?

Actually the "old" rule was to keep one caliber of the bullet in the case, IIRC.

 

[bohem]

Re: sierra told me this, is it true?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Travelor</div><div class="ubbcode-body">Actually the "old" rule was to keep one caliber of the bullet in the case, IIRC. </div></div>

Yes, that's what I've heard and I used to work to that as well, it may be a little conservative, but it is a good thing to keep in mind.

 

[High Binder]

Re: sierra told me this, is it true?

I have one load that only seats .080" and it's a wicked good shooting load.

 

[wolfman]

Re: sierra told me this, is it true?

175 smks seem to tolerate jump to the lands really well. Assuming a saami/ factory chamber, I'd try seating at an oal that puts the boat tail/ shank junction of the bullet at the neck/ shoulde junction of the case (or just above) and see how that works.

 

[Armed Ferret]

Re: sierra told me this, is it true?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: marduk185</div><div class="ubbcode-body">measure bullets base to ogive and if theyre all the same</div></div>

sadly I've found Sierra has serious issues in this respect.

my final batch of SMK's I'll ever buy varied as much as .020" in base-ogive measurement, .030" or so base-tip measurement, and the two measurements were not related to each other at all.

Even my nosler ballistic tips have better QC than that. Sure, there's variance, but .003" is definitely a lot less than .020".

my AMAX that just came in from miwday's blem sale vary .002" base-ogive. Far more acceptable.

 

[TT]

Re: sierra told me this, is it true?

On neck tension - see Harod Vaughn's book, Rifle Accuracy Facts.

On base/ogive variation - Spoke with Oren Humphries (holder of a national F-Class record) he quit shooting Sierra and only shoots Berger. As Oren explained the box of bullets you purchase from Sierra are a mix from 3 different machines. And if you weigh them you will find 3 distinct Gaussian distributions. Furthermore, as you have experienced, there are deltas in the base/ogive measurements.

According to Oren Berger does not mix bullets from different machines in the same box.

The difference does show up on paper...