I purchased a Browning X-Bolt for Christmas. Hurray! But bullets are a bit harder to find. I did find a 175grain Nosler ABLR bullet that I liked and purchased it but later calculated the bullets stability to be 1.37, just below the 1.5 military stability criteria in my 1 in 9.5 twist rate barrel. Bullet length included the polymer tip in overall length. Without the polymer tip as part of the bullet length, the formula now says the bullet is very stable. 

Experts argue about including polymer tips or not.  I will load some in a week or so.  

Lets take a look at this imperfect science…

It is known that barrel twist rate and a given bullets size, length, BC and velocity effects bullet stability. As a general rule bullets that are exiting the barrel have some yaw or as some say “yaw spiral” or gyroscopic effect.

It is the bullets “yaw” that can affect the grouping of a bullet, but yaw diminishes as it travels down range making groups tighter..

Calculators

You will need the length of the bullet below to enter this in the stability formula. Some folks subtract the polymer tip from bullet length. The JBM formula below takes the polymer tip into account. Measure the bullets overall length and measure the polymer tip length. 

https://www.jbmballistics.com/ballistics/lengths/lengths.shtml

https://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

At typical 100 yard ranges your bullet may exhibit some yaw thus grouping may be somewhat larger than expected. I ran into this with the .243 Winchester and my former 338 Win Mag where yaw was pronounced with heavy, longer bullets. 

The good news is, this minor yaw will disappear at longer distances and stability and grouping improves, 

The only way to know how stable your bullet is, is to shoot some at temperatures and distances your going to hunt in.

Accordingly, I would fire them at 100 and 150 yards and then shoot out to my max hunting distance of say 500 to 600 yards for group. 

UPDATE

I had some Nosler 140g E-Tips and 7mm brass in my cupboard and eagerly loaded and shot them at 100 yards with 62g IMR 4831 powder clocking an estimated 2900 ± fps at the muzzle. Yes, that is a bit slow, but Nosler recommends working up loads with gilding copper E-Tips.

Below is the very first 100 yard 3 shot bench rest group. It measured 3/4 inch. Sub-MOA! Luckily there was no measurable wind and I used a COL of 3.24 inches where my bullets had at least 0.05 inches off the lands.

Can’t wait for my heavier bullets to arrive. 

Good Shooting!