90-grain .224 bullets

[Donna]

Hello all,

A friend of mine made herself a custom single shot bolt action AR-15 .223 AI with a 7.7-inch twist Krieger barrel. Last week I made her some 90-grain open tip rebated boattails for testing and on the 100-yard range in the area the groups started getting down to less than 1/4 MOA when they were pushed out above 2500 fps with no signs of excessive pressures. We were pleased with that. :grin:

Donna :wink:

[Paul McC]

G’day Donna,
      I am most interested in this 90 grain .224 projectile you produced, do you have any details for this projectile. In particular, the projectile length, any calculated or measured ballistics co-efficient, and the jacket length, and type that you used. I would also like to know the overall length of the loaded round.

   I know that ignorant Antipodeans can be a pain in the posterior, but what the heck, if I don’t ask, I’ll never learn.

Thanks, Paul.

[Donna]

Hello Paul McC,

I would imagine that since Sierra Bullets are making the 80 grainers, the largest 22 caliber that are commercially made, there are a lot of people interested in 90 grainers. :eek:

I am using the famous “J4” jackets by Burger and mine come out to be a wamping 1.092 inches long. By the numbers, below 3000 fps they would require a 6.89-inch twist while above 3000 fps they only require an 8.27-inch twist. These have only been tested out to 100-yards and they start to be stabilized above 2500 fps in a 7.7-inch twist, oh by the way she is using a 26-inch barrel. :wink:  If you’re interested in using them in a .223 Remington caliber forget it you won’t get the velocity needed for stability. My friend is using a .223 AI, and that creates an entirely different burning characteristics then the .223 Remington. The .223 AI allows for a 25% more powder capacity and with the Sierra 69-grain bullets is developing about 36% more velocity then the .223 Remington. But if you want to try them out have fun. :roll:

I have not measured the BC but if the Form Factor were constant it would be about a 30% increase in the BC. But I should have a reliable measurement within the month; there are several tests that I have to perform first. :?

Donna :wink:

[TomF]

Hi Donna.

Does the rebated boat tail give you an advantage on a .22 cal bullet?  I thought I read in one of Corbin's articles that id didn't make much of a difference on smaller calibers, but maybe I'm not remembering correctly.

Have you made any flat base bullets and compared the accuracy and ballistics?  Just wondering what the "real world" test shows.

Thanks.

[Donna]

Hello TomF,

Glad to have you on the swaging forum. A boattail or rebated boattail will enhance the performance or increase the BC of any bullet relative to its flat base counterpart. But remember that performance enhancement is greatest in the transition, the zone between subsonic and supersonic, and subsonic boundary zones. And the increase in BC from a boattail or rebated boattail for a small caliber is less than the increase in a larger caliber to the point of a fletching or thin wire were the increase would decrease to zero. But to some people the difference in a 22 caliber or smaller is not worth the bother. But to others is means the difference between winning a match or not.

My die set is not capable of making a flat base bullet as of this time but that will soon change. Comparing the BC of a flat base to a rebated boattail is in the works along with calculating the BC of any bullet in flight among others.

I’ll keep you all informed as to my progress in this 90 grain bullet.

Donna :wink: