Bullet Seating & Pressure Rings

[PMA3]

What would be the pros and cons of the following two examples as it relates to custom dies and 1000 yard BR: Sizing 60% of the neck and seating the bullet so the pressure ring is IN THE UNSIZED portion of the neck versus sizing 80% of the neck and seating the bullet so the pressure ring is IN THE SIZED portion of the neck.

 

[BoydAllen]

The pressure ring will expand the sized portion of the neck slightly as it passes through, lessening neck tension (not the diameter difference, but the force that it takes to move the bullet). That may or may not be a problem, depending on the components of the load. Some combinations may not require much neck tension for best accuracy. If they do, it would be better for the pressure ring to fall within the sized portion of the neck.

 

[PMA3]

Boyd,

By seating the bullet with the pressure ring in the sized portion of the neck, it seems that the bullet grip would be more uniform and produce a more consistent bullet release which should equate to a lower ES in velocity. I usually try to run about .001" neck tension, which , I believe, is on the low end of the spectrum for 100-200 BR. The load components are:
1. 6.5 x 47 brass necked down to 6mm.
2. BR-4 primer
3. 39.6 gr. H-4350
4. Berger 105 Hybrid

Any other comments would be greatly appreciated......thanks Boyd.

 

[BoydAllen]

I am a big fan of the " if it works better you are on the right track" method of operation. I also have experienced situations where what I thought would work better did not, and what I doubted would work did. In short, I am a big fan of testing, and along with that trying things that may not make sense.

In short range one of the popular powders, 133, requires significant neck tension to give its best accuracy, but there are other good powders that do not have the same requirement. Also the sectional densities of the bullets are not high. In long range, the powders are different, and the bullets have higher sectional density, so that building starting pressure is less a matter of neck tension. If you do something and it lowers ESs, (I think that small sample SDs are junk.) then whatever you did was by definition correct. As always, results validate procedures.

 

[PMA3]

Thanks Boyd....testing is my next step to compare both alternatives.

 

[dmoran]

Paul -
About 50% with 1/2 to 1-thou is typical of where I'm at in my 6Dasher's, completed in 2 steps:
First I size the entire neck with f/l bushing die to 1-thou total clearance of my chamber.
Then with a neck bushing die, I size about half the neck to my desired neck tension.
Donovan

 

[PMA3]

Donovan,

Why do you size the neck in two steps.....what's the advantage? If you're shooting Berger 105 Hybrids, isn't the pressure ring BELOW the neck sizing die line at 50% and into the NON-SIZED portion of the neck? In Boyer's book for short range BR, he states that flat base bullets seated with the pressure ring in the non-sized portion of the neck will severely handicap your search for an accurate load. I'm trying to equate his findings to the long range game using boat tail bullets....it seems there should be some sort of correlation. My custom die was cut with the same chamber reamer and without any shims added to control the amount of neck sizing, it will only size about 78-80% of the neck....I was using .030" of shims and sizing approx. 66% of the neck but the pressure ring was in the non-sized portion of the neck. It got me to thinking that this MAY be a problem for 1000 yd BR as well. Too much thinking sometimes can drive you crazy regardless of which discipline you shoot.

 

[lpreddick]

I am under the impression that pressure rings exist on flat based bullets and not on boat tail ones. I'v found this to be true. Long range bullets are invariably boat tail so they will not expand a sized neck as flat base ones. I have some old berger 110 mef 25 cal bullets that have a pressure ring .001 greater than bearing surface and if I seated below sized neck, I could push them into case. Therefore, if you seat a boat tail thru the sized neck there should be consistent neck tension regardless of where the bearing surface/boat tail junction stops. I feel steady uniform resitence when seating bts but can definitely feel a little snap when the fb pressure ring goes thru sized neck. Correct me if I am misinterpreting my observations.

 

[PMA3]

On the Berger 105 Hybrid, I always thought the pressure ring was the point where the bearing surface ends and the boat tail begins. This point is also the "fattest" diameter on the bullet. If I say that a particular lot of bullets measures .2433", this is the point where I take the measurement.

 

[dmoran]

Paul -

It's all about bullet release for me... In my testing, this is what I find works best for me. I call it my 2-staged necks.
First I size the entire neck to have clearance, so that I am not experiencing any false-shouldered effects (which can result in pressure variances), but will retain no grip on the bullet (slip) . Then I neck size about .125" that will grip the bullet. This has proved out in my own testing to yield very consistent pressure spreads (less then 600-psi traces), hence the words "bullet release". Part of my final tuning is; how much of the neck I size, along with neck tensions.

With boat-tails, I don't like dominate pressure rings, and have never had good luck with them.
Others have and make them work, but I sell them and buy others when I get them. I also do not like thick bullets and my chambers are spec'd for bullets under .2435 and prefer them .2433 or smaller with little to no bands (.0005 or less).

On a note: back in the early 2000's I shot 100/200-BR then moved on to 600/1000-BR in 2005.
Very little of what I did for short range processes transferred over to long range. They are 2 completely different animals in my opinion and experience, that take totally separate scenario's to most all the effecting aspects.

My 2-Cents
Donovan

 

[BoydAllen]

Because of my experience with Sierras I too had thought that BTs do not have pressure rings, but after an exchange of posts on the subject, I got out several different brands of bullets and found that I had been wrong. I found that some BTs do in fact have pressure rings, and I corrected myself in that thread.

 

[PMA3]

Boyd,

I didn't have very good luck with the older Sierra's (too many bearing surface sub-lots) and knew that they didn't have pressure rings but the Berger 105 hybrids and 108 Bt's have what I refer to as pressure rings...were these Berger's some of the ones you sampled with pressure rings?

Donovan,

The Berger's mentioned above shot pretty well in my rifles but, as you found, neither rifle liked the fatter bullets. I found a lot that measured .2433"-.2434" and bought 3000. Most of the guys I shoot with use the 105 hybrids and do very well AND they prefer the bullets under .2435" also. I arrive at my neck tension using a different procedure than you but we both end up at the same point.... .001". The pressure ring issue for you is moot based upon the bullets you are using.

 

[BoydAllen]

I don't have a fast twist 6mm. I just got out every box of BTs that I had of various brands and calibers, and got to work with my micrometer. In short range, some of the top shooters are running up around .003 total neck clearance, because it gives them better accuracy. One record holder told me that he though that it was because it gave a more consistent bullet release.

 

[savagedasher]

Paul -
About 50% with 1/2 to 1-thou is typical of where I'm at in my 6Dasher's, completed in 2 steps:
First I size the entire neck with f/l bushing die to 1-thou total clearance of my chamber.
Then with a neck bushing die, I size about half the neck to my desired neck tension.
Donovan

For what it means I do the same. When I size the neck I can just twist the bullet in the neck . I then resize part of the neck to desired size for tension. Depending on the bullets pressure ring.
That is part of the reason I get very low ES & SD ;D ;D + 1 Larry