[Ballistic_Coefficiency]

I was checking out Sierra's web site to see if they had anything new... and i noticed they have a 90gr SMK in .224 caliber. I dont know how long they have had it... but that is not what this post is about. I noticed that the BC rating went up... 4 times consecutivly as the velocity went up... just like it "should". Then i looked at the highest velocity and its BC rating... it actually went down from the previous BC rating wich was at a lower velocity. Here is what im talking about: http://www.sierrabullets.com/index.cfm? ... llettype=0

BC Rating for .224" 90gr SMK

.504 @ 2200 fps and above
.511 between 2200 and 1900 fps
.500 between 1900 and 1750 fps
.467 between 1750 and 1575 fps
.400 @ 1575 fps and below

At first i thought it was a typo... then i realized there was not a picture of the bullet on the web site... so i could not tell how the tail was designed. Maybe its one of those 90 Degree tails like the 100gr .224" ammo and it might cause extra drag at higher velocities? I contacted Spade via yahoo messenger and we spoke for a minute or two... then he called Sierra and got the "stuff happens" answer. In other words... they really dont know why.

Any help would be much appreciated.

BC

 

[Cliffy]

Whats the min. twist you need for this bullet?
Cliffy

 

[APK]

Would my RRA be able to handle that? Would it have any advantages over a 77gr HPBT?

 

[spade]

alright guys.. you need a twist of about 1:7.7 " ... so dont even think about trying it...

 

[Ballistic_Coefficiency]

Whats the min. twist you need for this bullet?

1:7" to 1:8" at least. Prefferably 1:7"

Would my RRA be able to handle that? Would it have any advantages over a 77gr HPBT?

All depends on the barrel and twist rate. This type of ammo is used for long range (800 / 1,000 yards) rifles with heavy contour barrels and high quality fast twist rate rifling. The 90gr ammo has a much higher BC than that of the 77gr ammo... so it is more stable (when stabalized properly) and will sustain its velocity over a greater distance.

BC

 

[Cliffy]

Hey BC was thinking about bullet wieght for my new rifle, when it gets here, 22/303 with 1-8 twist. What wieght bullet and brand would you think work for shooting 300-800yds?
Cliffy

 

[spade]

jesus christ you people are incapable of staying on topic...

 

[Ballistic_Coefficiency]

Hey BC was thinking about bullet wieght for my new rifle, when it gets here, 22/303 with 1-8 twist. What wieght bullet and brand would you think work for shooting 300-800yds?
Cliffy

I would have to see the rifle specs before giving out suggestions on ammo... what caliber is this rifle going to be?

BC

 

[Cliffy]

BC it a 22cal and it should be between a 22-250 and the 220 swift for vel. was thinking 75gr A max or maybe 80gr sierra, will be spending alot of time working up loads, should just move reloading bench to the range so it handy I think.
Cliffy

 

[Ballistic_Coefficiency]

With a .220 Swift... you cant go wrong with the 80gr SMK!!! That would be a very nice 800 to 1,000 yard rifle. *(Dont forget though... you need around a 1:6 to 1:7 rate twist to use the heavy bullets in 224" caliber.)* Heck... you could do some varmint hunting out to 800 yards with it i bet! Ive been wanting a 220 Swift for quite a number of years now... i just keep finding myself buying another tactical rifle... bolt action or semi. :? Speaking of the 220 Swift... i had some guy at the range a week or so ago nearly make me go deaf. He seemed to forget that you have to clear the range and then declare range hot before even thinking about loading a rifle. :roll:

BC

 

[Ballistic_Coefficiency]

Question is still unanswered... and i keep getting this retarded answer from Sierra " that is just what we have found during testing ". And i have spoken with several different people there over the phone. I dont care if it is what they found during testing... i want to know ballistically WHY it is like that.

BC

 

[mele]

well, some things, as of yet, are still unable to be explained... like why a bumblebee can fly, or why an egg splits to create identical twins, etc.

given time, they will probably find out why their test results indicate what they do.

MEL

 

[Ballistic_Coefficiency]

Im still trying to find a picture of the 90gr .224" SMK... im thinking it might have a 90 degree tail angle causing extra drag at higher velocities. The 80gr .224" SMK does not have the same "problem" as the 90gr .224" SMK... its BC rating is higher at the top velocity to the previous BC rating. What im thinking they did to create the 90gr .224" SMK is they get the 80gr bullet... and changed the tail of it from a boat tail to a 90 degree angle tail to be able to squeeze the extra 10gr's in there. Im still trying to find into on it... its just one of those little things that bother me. "Pet Peeves" i beleive they are called.

BC

 

[caver101]

I just may have to (when I get a press) load some of those for the old colt 1:7 20" in the safe 8)