Projectile Lengths
 

Purpose of this thread is for the membership here to use for calculating twist rate requirements without having to go buy a box of whatever bullet just to find out it wont work.

Feel free to measure any bullets you use, handgun and rifle alike and post the measurements here. Make sure you list the bullet diameter along with the length measurement.

Here is a handy link to a twist calculator I use quite often and it will fit in with the use of this thread quite nicely.
http://kwk.us/twist.html

Re: Projectile Lengths
 

Here are the ones I have in stock.

200 LSWC Dardas, .452" dia., .652" length
200 Berrys TCFP, .452" dia., .531" length
185 Hornady XTP, .451" dia., .530" length

240 Hornady XTP, .430" dia., .703" length

125 Hornady XTP, .357" dia., .547" length

125 LRN Dardas, .356" dia., .602" length

100 Berrys HBRN (.380 ACP), .356" dia., .485" length
102 Golden Saber (.380 ACP), .355" dia., .473" length


174 Sierra MatchKing, .311", 1.206"

180 gr Winchester FailSafe, .308" dia., 1.303" length
175 Sierra MatchKing, .308" dia., 1.232" length
168 Hornady Amax, .308" dia., 1.278" length
165 Hornady InterBond, .308" dia., 1.312" length
155 Hornady Amax, .308" dia., 1.214" length
110 Sierra Varminter, .308" dia., .803" length

140 Hornady Amax, .264" dia., 1.380" length

105 Hornady Amax, .243" dia., 1.234" length
85 Sierra GameKing, .243" dia., .938" length

69 Sierra MatchKing, .224" dia., .895" length
62 Barnes TSX BT, .224" dia., .939" length
53 Sierra MatchKing, .224" dia., .700" length


I will make it a point to update as I get new projectiles.

Re: Projectile Lengths
 

Question.

Isn't the bearing surface of the bullet what dictates how it relates to twist rate and not total length? Basically from base to Ogive instead of base to tip?

Re: Projectile Lengths
 

Not at all. its the total length of the bullet that makes it require a specific RPM, and Bullet RPM is a fuction of velocity and rifling pitch.

Take the 165 Hdy IB I listed above VS the 180 gr Failsafe also listed above. The failsafe requires 13.2 twist (180 gr bullet measuring 1.303" at 2700 fps, which is .30-06 velocity for that weight) and the IB requires 13.4 twist (165 gr bullet measuring 1.312 at 2800 fps, which is also .30-06 velocity for that weight) and the Failsafe has almost twice the bearing surface because it doesnt have a Boat tail. Now slow them both down in reduced loads to 2500 fps and the FS requires 12.7 and the IB requires 12.7, so internal ballistcally speaking they are equals in thier requirements as far as barrel twist is concerned.

Re: Projectile Lengths
 

A SLOWER BULLET OF THE SAME LENGTH NEEDS A HIGHER TWIST RATE.. ?

Re: Projectile Lengths
 

yes, because the velocity multiplied by the rifling pitch is what gives you the required RPM. Its why .300AAC blackout barrels are generally 7 or 8 twist.

Re: Projectile Lengths
 

150 Hornady spire point .277 1.220

130 Hornady SST .277 1.232 boat tail

85 Sierra Game King HP .243 .950

100 Sierra Game King spitzer .243 1.075

105 Speer round nose .243 .960

Re: Projectile Lengths
 

how do we determine the specific gravity of said projectile? Sierra's website does not list that data

Re: Projectile Lengths
 

copper clad lead core jacketed bullets are 10.9

Re: Projectile Lengths
 

Anyone by chance have measurements for 0.223 bullets?

Re: Projectile Lengths
 

Just the ones I have listed above.

Re: Projectile Lengths
 

Thanks, somehow I glossed right over them

Re: Projectile Lengths
 

.223 Rem: (.224 diameter)
50 Vmax/Zmax = .770"
55 Vmax = .811
53 Vmax = .828
52 Sierra MK = .714

6,5mm:
123 Lapua Scenar = 1.302"
120 Amax = 1.205
140 Amax = 1.372