Bullet Stability 220 Swift AI

[Coolhand]

Gentleman , yesterday I was fire forming Norma 220 Swift cases to AI. Firstly I loaded up some 40 grain Vmax's with 43 grains of RL17.
This fire forming load was very accurate producing a couple of groups that were in the vicinity of .75".
I then switched to a work up load using the 53 grain Vmax & started the powder charge at 40.5 grains. It seems that the 53 gr Vmax is yawing through the target in that the holes are slightly oval in shape.
Now the odd thing was that I also had 13 fire formed cases which were loaded from 44.8 - 46.4 of RL17 to check for pressure. I was not interested in group size but these 8 loads all printed to about an inch group. I then shot a 6 shot group with a load of 46.4 grains of RL17. This load was very produced very flat primers but the bolt lift was easy. Interestingly the group size was 3/4".
And the bullet holes were perfectly round as they should be, whereas with the low charge for fire forming the bullet holes were elongated.

Could the elongated shot holes be a consequence of fire forming the cases where the projectile is not perfectly centered within the leade ?
The barrel is a 1:14 Krieger 26".

regards
Mike.

 

[MrMajestic]

unless the extra velocity is just enough to do it.

Nah, it will just throw them sideways into the target faster. ;D

 

[CatShooter]

I have shot the 53 V-Max and 55gr SMK in 14" .220 Swifts and 22-250s... they "might" stabilize at top loads, but it is real iffy... slow them down, and they tumble.

Go to 50's of either flavor.

 

[40X Guy]

My 13 twist custom standard Swift will not shoot 53 V-Max's. That bullet should have a 12 twist as already mentioned to properly stabilize. They work great in my sons LRPV 22-250 with 12 twist. 55BT's will work in your 14 twist .220 AI. They are very accurate and do the job on woodchucks..

What kind of velocity were you getting with the 46.4 load of RL-17?

Frank

 

[Coolhand]

My 13 twist custom standard Swift will not shoot 53 V-Max's. That bullet should have a 12 twist as already mentioned to properly stabilize. They work great in my sons LRPV 22-250 with 12 twist. 55BT's will work in your 14 twist .220 AI. They are very accurate and do the job on woodchucks..

What kind of velocity were you getting with the 46.4 load of RL-17?

Frank

Frank , that load of 46.4 of RL-17 was very STIFF. I did not chrono any of the fire forming loads , I am going to replicate the test but back to 45.2 and chrono this load. My 'smith seems to think that it may not be stability problem and I may be a able prove it by repeating. He made the same point as Catshooter above, the 53 VMAX might prefer to be run hard.
I have loaded some 55 NBT's and will try them today.

regards
Mike.

 

[40X Guy]

Mike, lets us know results on the 55 BT's

Frank

 

[Coolhand]

A fruitful day at the BR Range , any perceived issues with the 53 Gr VMAX were dispelled , a load of 45.2 RL 17 & a 5 shot group measuring 0.476". I would suggest that this bullet will be finicky and appears to prefer being driven hard and perhaps seating depth can/will be critical.This string however was shot with the bullets seated to mag length.

Nosler 40 grain BT's + 49 grains RL17 range temp was 30c (86F) Quickload predicted a velocity of 4,230fps , Magnetospeed said the average was 4,423fps SD 27.2 ES 70. Group Size was outstanding at 0.464"

Hornady 40 grain VMAX + 49 grains RL17 , Quickload prediction 4,425fps, Magnetospeed Average 4,500fps , the high for this string was 4,538fps Low 4,478fps SD 24 ES 60. If you compare the two bullets side by side the most noticeable difference is the ogive shape & I wonder about the velocity difference between the two. In this case velocity meant nothing as the 40 gr VMAX shot a very open group that measured 1.077". The Nosler 40 was outstanding.

The old standby the 55 Sierra SPBT #1365 proved again what a great bullet it has been for many years producing a 5 shot grp of 0.523".
The Nosler 55 BT shows promise , 4 shots measured 0.318" but a flyer took it out to 0.890" don't know if it was me or the load.
I don't have any velocities for the 55's as the chrono battery died before I noticed and I had no spares , lesson learned.

Lastly and this was the surprise , 60 grain Nosler BT + 43 grains of RL17 , group was nothing to speak of, 3 in a clover leaf but one horizontally each side that measured 1.039" , the surprise being that a 1:14" twist is not supposed to stabilize a 60 grain projectile.
The group velocity average was 3,755fps, Min 3,739fps Max 3,71fps SD 13.5 ES 32. I am going to tweak this load and go buy as many as I can find!
Before I selected bullets for this rifle I measured the lengths and using published velocities & BC's plugged the data into the Miller Formula. According to this formula a 1:14" barrel shooting bullets from 40 gr to 60gr will not be stable and the 40 grain bullets will only be "marginally stable" My point being that the only way to know for sure is to buy a box and go see for ones self.
I will attempt to post some group pics but my scanner is of poor quality and the results may be pretty crappy.

regards
Mike.

 

[jaytee]

Nothing like resurrecting a 7 year old thread but I just loaded up and shot some 60 grain Sierra HP's, #1375 and had fantastic results. Had a 6 shot group of .591 and a 3 shot group of .291. This was out of a Ruger M77R with a 14 twist barrel. 33 grains of 4064 seated 10 thousandths off the lands. OAL at the ogive was 2.405.