# bullet stability calculator

#### Bigeclipse

##### Well-Known Member
All

I'm just trying to understand how Bergers bullet stability calculator should be analysed. What I mean by this is I've been putting in different bullet combos and I've seen some results come in at say 1.6 while others are over 2.0. According to berger, below 1.5 and you now are hitting "marginal" stability but above 1.5 you are "stable". So does this literally mean anything above 1.5 and you should be good or does it mean you really want to be as far above 1.5 as possible? I know this is theoretical and doesn't mean a bullet will shoot well in your rifle...but prior to trying to work a load up I want to eliminate bullet lengths/weight that will likely not work in my rifles.

I know this question may seem dumb to some of you but I'm just trying to grasp that if above 1.5...you should be good to go or do you try to go as high above it as possible?

1.5 is good enough...little to no benefit to getting any higher at the muzzle, because the SG factor goes UP, not down, as the bullet flies downrange.

My friend used HSM 180gr Berger VLD in his 7MM Rem Mag (1:9.5"). According to Berger's twist rate calculator, he's SG is only marginal and recommends a 1:9" However, he harvested a bull elk in 2013 just shy of 400 yards.

^^^

I take Berger's calculators as a best practice guide, not hard fast rules. In other words, of course you can do what you want with twist rates, but they are giving you the most ideal twist rate for optimum bullet bc's and stability factors given specific parameters such as altitude, velocity, etc.

Thanks for the info everyone!!!

I take Berger's calculators as a best practice guide, not hard fast rules. In other words, of course you can do what you want with twist rates, but they are giving you the most ideal twist rate for optimum bullet bc's and stability factors given specific parameters such as altitude, velocity, etc.

Yup
Most bullets will be stable enough for the majority of shooting around 1-1.2. Optimum stability comes around 1.5.

I shoot the 215 hybrid in 1-11 twist ( Marginally stabililized ) doing load development. Got great accuracy results out to 260 yds. ( farthest tested so far). Brian litz (of berger) told me may be possible to get great accuracy but to expect a reduced BC. Due to marginally stabilized bullet approximately 10℅. I will when finalizing development do some long range shooting to validate drops (BC.) And accuracy is still there due to loss of stability. I'm no expert just passing on what I have been told by one.

One of my most accurate 1000 yard combos is a 1-12 Kreiger chambered in 300 WSM shooting 200 grain hybrids. The "calculator" tells me that the stabillity factor is 1.12.

My plans when I baught the BBL was to shoot the 187 BIB. That didn't work out so well, but the 200's were awesome. It wasn't till the end of the season that I ran the twist calculations on Bergers website.

Good luck, Tod

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