Barrel heat & accuracy

[todbartell]

Hit the range this mornig with a couple 223's to see how barrel heat effects accuracy



Test subjects :

• Remington Model 700 SPS Varmint, 26" 1:12 twist, Vortex PST 6-24x50, Talley LW

Muzzle diameter .820"
~ Ammunition : 55gr Hornady SP over 24.6grs H335 & 24.4grs IMR 8208xbr

• Mossberg MVP Varmint, 24" 1:9 twist, Vortex Crossfire II 3-9x40, Leupold Rifleman rings/Weaver base

Muzzle diameter .751", fluted barrel
~ Ammunition : 55gr Hornady SP over 25.9grs H335 & 25.6grs IMR 8208xbr

--

Target distance 100 yards. All groups shot off the bench with Caldwell ROCK front rest & rear bunny ear bag. Started in top left corner and worked left to right, down a row, left to right, bottom row left to right. Started with cold bore, shot nine 10 round groups with only pausing to reload. Barrel was allowed to cool to cold between different powders

Rem 700 / H335

Avg group 1.44"
Groups 1-3 avg size 1.75"
Groups 4-6 avg size 1.31"
Groups 7-9 avg size 1.27"
Best group 1.13" (8th group, shots #71-80)
Worst group 2.51" (3rd group, shots #21-30)
Cold bore group : 1.39"
9th group : 1.35"


Rem 700 / IMR 8208xbr

Avg group 1.79"
Groups 1-3 avg size 1.72"
Groups 4-6 avg size 1.73"
Groups 7-9 avg size 1.91"
Best group 1.36" (2nd group, shots #11-20)
Worst group 2.14" (9th group, shots #81-90)
Cold bore group : 1.79"
9th group : 2.14"
---

Mossberg MVP / H335

Avg group 2.31"
Groups 1-3 avg size 2.69"
Groups 4-6 avg size 1.91"
Groups 7-9 avg size 2.34"
Best group 1.70" (5th group, shots #41-50)
Worst group 2.88" (1st group, shots #1-10)
Cold bore group : 2.88"
9th group : 2.31"

Mossberg MVP / IMR 8208xbr

Avg group 1.99"
Groups 1-3 avg size 2.04"
Groups 4-6 avg size 2.13"
Groups 7-9 avg size 1.82"
Best group 1.60" (7th group, shots #61-70)
Worst group 2.47" (5th group, shots #41-50)
Cold bore group : 2.2"
9th group : 1.84"

• Average group between both powders for each rifle :

Rem 700, groups
#1-3 average size : 1.74"
#4-6 average size : 1.52"
#7-9 average size : 1.59"

Mossberg MVP, groups
#1-3 average size : 2.37"
#4-6 average size : 2.02"
#7-9 average size : 2.08"

• Velocity notes :

Rem 700 / H335
First ten shots : 3090 fps
Shots #81-90 : 3099 fps

Rem 700 / IMR 8208xbr
First ten shots : 3095 fps
Shots #81-90 : 3136 fps

MVP / H335
First ten shots : 3155 fps
Shots #81-90 : 3157 fps

MVP / IMR 8208xbr
First ten shots : 3163 fps
Shots #81-90 : 3201 fps

On average, the 9th and final ten shot group resulted in a 0.25moa tighter group than the cold bore group

 

[Superbrad]

I often wondered about this...... Nice post..... I wonder if you had used a pencil barrel like a rem 799 if the results would change?....

 

[todbartell]

I often wondered about this...... Nice post..... I wonder if you had used a pencil barrel like a rem 799 if the results would change?....

Yeah maybe. I have a sporter barrel 270 Win that I could try, probably just do nine 3 shot groups though instead of 90 lol

this was more of a 'gopher test'