Bullet Stability

[Controller]

Hi guys looking for some insight on a problem that I have/have not. I am currently working up a load for a tikka T3 varmint in 300 wm. The rifle twist rate is 1-11. The load that I tested was H1000 with Nosler AB LR 210gr. The results at 100yards are very good 3 loads did sub half moa.

Now the problem. I know the twist rate is slow for the bullet weight. But would I see stability issues at 100yards or it just not far enough? When can I expect the problem if any?

Thanks for the input.

 

[mojoman]

I put in a 210gr bullet here https://bergerbullets.com/twist-rate-calculator/ it shows at sea level it is unstable, at 1800 ft it is stable, so kind of depends what altitude your at.
Also I used bergers 210 vld, in the calculator you can put in the BC and length of your bullet which may change the results.

 

[iron cat]

Hi guys looking for some insight on a problem that I have/have not. I am currently working up a load for a tikka T3 varmint in 300 wm. The rifle twist rate is 1-11. The load that I tested was H1000 with Nosler AB LR 210gr. The results at 100yards are very good 3 loads did sub half moa.

Now the problem. I know the twist rate is slow for the bullet weight. But would I see stability issues at 100yards or it just not far enough? When can I expect the problem if any?

Thanks for the input.

If it shoots well at 100, I would try it further out, and ultimately at the max distance you plan to hunt with it.
That will be the true test.

Cat

 

[Controller]

If it shoots well at 100, I would try it further out, and ultimately at the max distance you plan to hunt with it.
That will be the true test.

Cat

I did do the berger calculator. It does show unstable but it ain't extreme. 1.3 was the number. This will be for hunting so I not willing to take any chances. I might just get a faster twist gun since even at 190gr I wasn't hitting 1.5 stability with that darn 1-11 twist.

And yes I might just test it out at longer range unless, I get a new gun...

Thanks for the input guys

 

[jethunter]

would I see stability issues at 100yards or it just not far enough? When can I expect the problem if any?

It is possible that as the rate of spin reduces at longer ranges, there may a threshold crossed and stability degrades. You'd need to shoot to find out

 

[Hand Skills]

Typically velocity degrades at a greater rate than does 'spin'. This resulted in the idea of bullets 'going to sleep' or GAINING STABILITY as they travel. That was a popular idea back in the '90s

Here is an example of a bullet that has STOPPED (velocity = zero) and it is still gyroscopicly stable.

That being said, I spinning bullets faster generally improves BC to a point, and it also helps with terminal performance in a hunting context. A better stabilized bullet is less likely to turn or tumble on impact. Understabilized bullets can give erratic and inconsistent terminal performance.

The OP is clearly right on the edge of stability - in cold enough conditions (like winter) the air density might increase enough for the stability to be lost. Temperature can affect air density dramatically

 

[iron cat]

Hi guys looking for some insight on a problem that I have/have not. I am currently working up a load for a tikka T3 varmint in 300 wm. The rifle twist rate is 1-11. The load that I tested was H1000 with Nosler AB LR 210gr. The results at 100yards are very good 3 loads did sub half moa.

Now the problem. I know the twist rate is slow for the bullet weight. But would I see stability issues at 100yards or it just not far enough? When can I expect the problem if any?

Thanks for the input.

I.have to ask, is there a particular reason you chose those bullets for that twist?
Cat

 

[bearhunter]

OP, I seriously doubt you will have stability issues with that load until you're way beyond the distances you feel capable of shooting.

If you were going to have stability issues, it would show up at 100 yds. with uncalled "flyers"

You're in Ottawa? from your location, it's under 1800ft elevation, I believe around 250 feet (75m) or less.

I know folks shooting those bullets with the 300Win Mag, using 1-12 twist rates. at targets 400 yds and further out. They're happy.

Half moa rifles don't grow on trees, no matter if they're off shelf or custom jobs with high end barrels and optics.

I would hang onto that rifle.

I don't know how much you shoot, but 300WM can be hard on leades, depending on pressures.

I don't shoot those rounds, but some of the folks I know do and they are usually looking for new barrels around 1500-2000 rounds.

 

[I Dont Care About You]

would I see stability issues at 100yards or it just not far enough? When can I expect the problem if any?

Bullets become more stable with distance because forward velocity drops much faster than rotational speed.

IF you are concerned about stability you can try to push the bullet a little faster. Forward speed increases rotational rate and increases stability.

It is possible that as the rate of spin reduces at longer ranges, there may a threshold crossed and stability degrades. You'd need to shoot to find out

The rate of spin degrades much more slowly than forward velocity. Bullets become more stable with distance.

 

[jamesharrison]

Inputting your data with a full case of H1000 & the Nosler 210 gr. AB LR bullet in a 24" barrel, QL shows 2,607 fps MV. Plug those #'s in to Berger's Stability Calculator & this is what it spits out:
"Your bullet is MARGINALLY STABLE. Your bullet stability is marginal. You may shoot good groups under these conditions, but the BC of the bullet will not be optimized. BC is lowered by 8%."

What distance are you planning to hunt at? As noted above, what altitude? What temperature? And if you want to really get into esoterics, what is the relative humidity, barometric pressure, direction of firing, the Coriolis effect, &c., &c., &c.

 

[I Dont Care About You]

What temperature?

This is a good point. You could have a bullet stable during summer testing that will not be stable in November.

 

[jamesharrison]

Using the same numbers, if you were after mountain goat at 5,000' ASL & it was +15 C, your bullet would be stable.

BUT, say you're after Muskox on the Arctic coast [Sea level] & it's a brisk -40 out, then your load is unstable!

 

[Controller]

I.have to ask, is there a particular reason you chose those bullets for that twist?
Cat

To be honest I didn't think about that when I made that choice. Which brought me to where I am now... Yes changing the bullet is an option for sure. And if it's the only solution then I might just do that. I am mainly seeking to understand the ballistics at play here and then I will decide what route to take. Changing the gun is another option...

 

[Controller]

Inputting your data with a full case of H1000 & the Nosler 210 gr. AB LR bullet in a 24" barrel, QL shows 2,607 fps MV. Plug those #'s in to Berger's Stability Calculator & this is what it spits out:
"Your bullet is MARGINALLY STABLE. Your bullet stability is marginal. You may shoot good groups under these conditions, but the BC of the bullet will not be optimized. BC is lowered by 8%."

What distance are you planning to hunt at? As noted above, what altitude? What temperature? And if you want to really get into esoterics, what is the relative humidity, barometric pressure, direction of firing, the Coriolis effect, &c., &c., &c.

The distance is 500m. Altitude is low 250m ASL. I am assuming the temperature will be or should be in the single digits. but last year we had a couple days in 20c...

 

[Controller]

OP, I seriously doubt you will have stability issues with that load until you're way beyond the distances you feel capable of shooting.

If you were going to have stability issues, it would show up at 100 yds. with uncalled "flyers"

You're in Ottawa? from your location, it's under 1800ft elevation, I believe around 250 feet (75m) or less.

I know folks shooting those bullets with the 300Win Mag, using 1-12 twist rates. at targets 400 yds and further out. They're happy.

Half moa rifles don't grow on trees, no matter if they're off shelf or custom jobs with high end barrels and optics.

I would hang onto that rifle.

I don't know how much you shoot, but 300WM can be hard on leades, depending on pressures.

I don't shoot those rounds, but some of the folks I know do and they are usually looking for new barrels around 1500-2000 rounds.

I am going to try again this week at greater range and see what happens. I appreciate the feedback. Thanks

 

[jamesharrison]

The distance is 500m. Altitude is low 250m ASL. I am assuming the temperature will be or should be in the single digits. but last year we had a couple days in 20c...

Then we're back to the original, ie: "Your bullet is MARGINALLY STABLE. Your bullet stability is marginal. You may shoot good groups under these conditions, but the BC of the bullet will not be optimized. BC is lowered by 8%."

That will result in a G7 BC of .304 vs. .333.

BUT, you will probably have "fun" with wind drift at that distance, as even with a 15 klick wind, you'll have over a foot of windage to deal with.

 

[guntech]

Shoot the present load at long range in cold weather is an option or I would simply use a slightly shorter bullet and not worry about it. It isn't like you need a specialty long range bullet for hunting.