Confused by bullet manufacturer response

[tooter]

I called a premier bullet manufacturer last week trying to get a fix on optimal rotation for a given bullet/barrel twist. I got a lot of 'mumble-jumble' about barrel harmonics,rifle signatures etc. I changed the question to ask at what velocity range would be ideal; got the same load of 'I have no idea!' I was searching to understand frangibility of lighter bullets in faster twist barrels. I do understand at a 'high level', the issue of variables and constraints, but I don't understand the 'secrecy' around data that I know, they know, that is backed up by gaubs of data collection and statistical analysis.

I must be a total 'numb-think' on this issue, but please, someone help me understand why a business selling bullets in high volume keeps information so close to their vest?

 

[spclark]

Sierra puts recommended speed data right on their products' description pages on the web. Nothing about twists though.

Berger does just the reverse - no speeds, but recommended twists are provided.

I can't imagine why a customer rep would give you double-talk unless you somehow got hold of someone who didn't want to let on they were filing in for somebody else.

Within ranges of bullet weights for a given diameter, there are 'rules of thumb' that can get you close enough for most purposes.

What particular bullet + twist combo are you looking to understand better?

 

[Cheechako]

tooter

I can't imagine a major bullet manufacturer giving you a big run-a-round about simple things such as twists. It may be that you phrased the questions wrong or possibly you were trying to pin them down on some exact numbers. Bullet stability and structural integrity depends on several factors and any answer would have to contain a few 'it depends'. I'd guess that the manufacturer was reluctant to give you precise numbers only to have you come back later when things didn't work out exactly.

JMHO

Ray

 

[GerryM]

Tooter'
You must have been in touch with a ballistition.
Recommended twist rates are in most reloading books . Tests are done in the tunnels for the best accuracy, They usually give the rifle twist rate, type of rifle, primer powder and case company. The facts are driven by those particular combinations from lab reports .
The twist rates burger puts are are for their own bullet s due to a different design . IE point boat tail. Ojive .
Low drag bullets are different then the standard shape bullets made by the major bullet makers.
Weight comes into play also. If your looking for information on heavy bullets a faster twist is needed for best stability. Now here's where some things come into play
Light bullets spinning very fast say in a 8 twist may be over stabilized. I have seen some bullets burn right up before reaching the targest, due to being to light for the Fast twist.
They will stabilize but at a lower velocity.
It has to be worked out at the range by your own testing at times. Also not all custom barrels are really at the twist rates they say they are. Some may be off up to I/2 a turn.
Usually they are close though.
There's a lot of load data right here to look at.
Trial and error is the best way. Just be careful and watch for pressure signs.
I'm surprized that the tech was unable to put it into laymens terms for you.

 

[tooter]

Gents, Thanks for responding. Ok, so I posted this in the wrong interest group though I felt this query reasonably generic and this group has more extensive reader overage.

My inquiry was specific to shooting 52 to 55 gr. bullets in a new .223AI with a 1-9 twist Kreiger. I ultimately did get an 'oh well, I guess these puppy's will hold together pretty well' but with no further qualification. The rep I spoke with seemed knowledgeable but was also well programed to an 'I have no idea' response. I queered him from a pure exterior ballistics angle but without engagement or shift in what he would reveal to me.

I'm returning to shooting after an extended period of family and career focus priority. So, I'm on a steep catch-up curve. My professional experience though tells me 'it's all in how you approach people'. Perhaps I need to try another time. I just want to avoid buying boxes of bullets plus the follow-on trial only to learn they are not capable of reaching the target at peak RPM/velocity.

Your indulgence is sincerely much appreciated.

 

[CPorter]

An easy way to figure if the bullets will work without blowing up is look at the reloading books, find their recommended velocity & twist and convert for your use. Hornady recommends that the spsx varmint bullet not be launched faster than 3500 fps in the standard 14 twist barrel. With a 9 twist that would probably be reduced to 9/14*3500 = 2250fps.

The 55 grain Nosler ballistic tips have a max velocity in the books of 3690 fps but this is pressure limited not due to the construction of the bullet. Varmint Al has a real good article on it here:
http://www.varmintal.com/ashot.htm

 

[tooter]

I did go to Varmint Al's web page. This is a great site with much information; especially that on twist and stability.

Thanks for the help.

Tooter

 

[alf]

No matter how much reading and research you do, you'll never get a definitive answer. Too many other vaiables at play. There are certain parameters you can stay within that MAY work, but until you shoot the bullets in question, you are only guessing.

Case in point with the 6.5 140 Bergers blowing up. Some barrels would, some wouldn't. They never could come to a conclusion on why. Only speculation.

 

[1000yardstare]

Another possibility is that lawyers are controlling customer relations. Manufacturers are scared skinny of law suites and don`t want to volunteer any more information than they absolutely have to. I know you would wonder how an honest discussion of twist rates would place a company`s legal status in jeopardy but after 9/11 the insurance underwriters are silent partners in the decisions of a company`s board of directors.

 

[Ackman]

You're wondering how a bullet will work. Forget the tables and don't go by what anyone says. Just shoot it in your gun and then you'll know.