Looking For "b.c" .222 & .270

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SKULLANDCROSSBONES65

New member
G'day. I'm looking for some ballistic coefficient information for 2 different projectiles.
1, .277 sierra 90 grain HP
2, .223 super roo 55 grain PSP BT
I have an idea that the 'super roo' might be a Winchester product Thanks for your help.
 
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rwilson452

New member
aw what the heck, I ain't that busy


Bullet Name Diameter inches Weight grains Sectional Density
.277 dia. 90 gr. HP .277 90 .168

Ballistic Coefficients
.195 @ 2800 fps and above
.203 between 2800 and 2200 fps
.219 between 2200 and 1800 fps
.240 @ 1800 fps and below
 
K

kraigwy

New member
Depends on the velocity:

Sierra list their 90 Gr 277 HP @
.195 @ 2800 and above
.203 @ 2200-2800
.219 @ 1800-2200
.240 @ 1800 and below

Sierra list their 55 Spitzer Boat tail 223

.250 @ 3000 and above
.245 @ 2000 - 3000
.235 below 2000

I didnt understand what 223 55 grn bullet you were talking about but this is the closest I could figure out.

Anyway you can get this information from the sierra reloading manuel or their web sight.
 
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SKULLANDCROSSBONES65

New member
G'day and thanks for pointing me in the right direction. I've reloaded some .270 and had speeds up to 3700 f/s. I'll be happy with a slower speed, I would prefer accuracy over speed.
 
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butta9999

New member
3700fps

That is a very hot load for your .270win. In all the data i have 3600fps is the quickest i can find. You must be working to a max load if not over, in doing that your barrel life will be greatly shortened.

Have you been keeping an eye on pressure signs. Seems to me they will be spiking pretty high.

In my opinion i never work with the lightest bullet for a large centerfire. You dont get good BC or SD and barrel life is reduced. The 130gr is an ideal bullet for the .270.

I have a friend who has a .300win mag like myself and he used to shoot 110gr out of it. I suggested for him to buy a .308win, but in the end he found a good 165gr bullet which performs so much more superior out of the .300.

A 90gr bullet works well out of my .243win but seems too light in the .270win

Like i said only my opinion....:)
 
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SKULLANDCROSSBONES65

New member
G'day. I was given 200 federal primers and around 100 x 90 grain sierra projectiles. I was using them partly for the learning process. The 3700 f/s was from AR2208 powder 53.5 grains. I was not trying to get max velocity. I think there was other gremlins at play.
 
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SKULLANDCROSSBONES65

New member
G'day, barrel length to rear of case is 22". Having a look into the affects of high temperature and muzzle velocity, as this could be an issue for my location.
 
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butta9999

New member
3700fps out of a 22 inch barrel seems way too high, especially since you are loading 1.5gr off max. You usually loose between 50fps-100fps for every inch of barrel that is shorter.

My manual states out of a 24 inch barrel with 55gr of 2208, 3600fps is the max. This is field testing data from Nick Harvey.

I'm not saying that its crap what your saying it just does not add up, i have looked over a lot of data and can not find any saying 3700fps out of a 22 inch barrel.

Maybe your chrony is out of whack. Ill look further...:confused:
 
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SKULLANDCROSSBONES65

New member
G'day butta. That length is to the back of the case, not the front of the projectile. I am going to open a post about the affects of temperature on muzzle velocity. The day of testing was probably around 40 c. From what I read this could add 200f/s. For now I am assuming Chrony data to be correct and looking for other possible causes.
 
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