Below is a list of Bullet Lengths of various .224 Caliber Bullets that either I have measured, the manufactures supplied the bullet lengths to me of friends have measured and provided the lengths to me.
.224" - 40gr. Speer Spire Point - .505"
.224" - 40gr. Sierra Hollow Point - .565"
.224" - 45gr. Hornady "Hornet" - .605"
.224" - 50gr. Speer TNT Hollow Point - .682"
.224" - 55gr. Winchester Pointed Soft Point - .693"
.224" - 52gr. Speer Flat Base Hollow Point - .698"
.224" - 40gr. Nosler Ballistic Tip - .703"
.224" - 55gr. Sierra Spitzer - .710"
.224" - 55gr. Sierra HPBT - .718"
.224" - 60gr. Nosler Partition - .775"
.224" - 50gr. Sierra BLITZKING - .780"
.224" - 50gr. Nosler Ballistic Tip - .788"
.224" - 64gr. Winchester Power Point - .798"
.224" - 50gr. Hornady V-MAX - .800"
.224" - 55gr. Nosler Ballistic Tip - .808"
.224" - 55gr. Hornady V-MAX - .813"
.224" - 65gr. Sierra Spitzer Boat Tail - .840"
.224" - 69gr. Sierra Matchking HPBT - .895"
.224" - 70gr. Berger VLD Match - .966"
.224" - 68gr. Hornady BTHP - .985"
.224" - 75gr. Hornady BTHP - 1.040"
.224" - 80gr. Nosler HPBT - 1.070"
.224" - 75gr. Swift Scirocco II - 1.085"
.224" - 75gr. Hornady A-MAX - 1.098"
While I do not have a NEF Handi Rifle in .223, I used to have one (I am quite sure it was a 1 in 12" Twist Barrel as it was prior to 2007) and it preferred the WinchesterUSA White Box 45gr. Hollow Points. Unfortunately I never did pull one of those rounds apart and measure the length of the bullet.
I currently have a 16" 1 in 9" Twist Bushmaster AR-15 .223. I have tried a few different bullets in it so far and it definately has a perference for 55gr. Nosler Ballistic Tips, generally putting 3 of them into a 1/2" to 5/8" group at 100 yards from the bench. I recently tried to work up a load with 40gr. Nosler Ballistic Tips in this 1 in 9" Twist Bushmaster and the absolute best group I was able to come up with was 1".
As has been stated bullet length has more to do with what twist rate will stabalize a given bullet, provided proper velocity is obtained.
If you run the bullet lengths on the Greenhill Twist Rate Calaculator (which can be found at
http://www.z-hat.com/twistrate.htm ) it uses below or above 2800 FPS for the cut off of velocity levels.
Larry