I'm shooting a 308 Cal. 168 Gr. SMK. Powder is IMR 4064 42.0 gr. Barrel 20" 1-12 Twist with alot of free bore.It's a Rem. LTR. At 200 yards I'm shoot 1/2-1'' groups. A friend let me use his cronograph to check Vel. It read 2489. for accuracy the books say 2600 fps. Can I expect tighter groups by making the bullet move faster,or am I looking for trouble. 200 Yards is the longest range in my neck of the HOODS.
Confused-Pressure & Velocity
- Thread starter cw308
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oneounceload
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You're getting 1/2 MOA and you're complaining? - on punching holes in paper? Velocity without accuracy is useless - I'd say you found a good load for your gun
My Sierra manual lists 41.4 gr of 4064 @2500 f/sec as their most accurate load..... they note they used a 26" barrel to get that velocity...... you have nearly duplicated it with a much shorter tube...... rejoice!
That said, because it was their most accurate load in their test rifle, does not mean it will be the most accurate in yours.
You might get tighter groups by pushing the bullet faster, or seating to a different depth, or using a different brand of brass, bullet or primer.....
.... the only way to know is to try it ..... test it...... a Chronograph can tell you much more than just the velocity: Standard Deviation is a measure of consitancy..... you might be able to do much better than 1" groups...... and you'll never know until you try!
That said, because it was their most accurate load in their test rifle, does not mean it will be the most accurate in yours.
You might get tighter groups by pushing the bullet faster, or seating to a different depth, or using a different brand of brass, bullet or primer.....
.... the only way to know is to try it ..... test it...... a Chronograph can tell you much more than just the velocity: Standard Deviation is a measure of consitancy..... you might be able to do much better than 1" groups...... and you'll never know until you try!
The 2600 fps is with a 24" barrel in most cases. You are probably losing 50-75 fps from the shorter 20" barrel
No 2 barrels shoot the same loads at the same velocity. I've seen different guns shoot 100 fps different with ammo from the same box even though they had equal barrel lengths. I have a 20" 308 that consistently shoots 5-10 fps faster than my 22" guns. Some barrels are just "fast", others are just "slow". You may have a "slow" barrel.
According to my loading manuals you are nowhere near a max load. It wouldn't hurt to experiment with slightly increasing powder charges and see what happens.
No 2 barrels shoot the same loads at the same velocity. I've seen different guns shoot 100 fps different with ammo from the same box even though they had equal barrel lengths. I have a 20" 308 that consistently shoots 5-10 fps faster than my 22" guns. Some barrels are just "fast", others are just "slow". You may have a "slow" barrel.
According to my loading manuals you are nowhere near a max load. It wouldn't hurt to experiment with slightly increasing powder charges and see what happens.
That equates to 1/4 to 1/2 moa. A light short barreled rifle is not an easy thing to shoot, so if that load works don't get caught up in the velocity race, it's generally counter productive. Anyway, at 2489fps you have a decent 800 yard load.
Congradulate yourself on some very very good shooting.
Congradulate yourself on some very very good shooting.
Art Eatman
Staff in Memoriam
A generality is that for many cartridges, best accuracy is obtained with loads which are a bit below maximum.
He's getting within 19 f/sec of what my book sez, for the charge listed, with a barrel that is 6" shorter than what Sierra used to test their load...... I'd say he has a pretty "fast barrel", all things considered.
On a side note, I ran some IMR-4064 7-08 loads from my Ruger Frontier over my Chrony last Saturday ...... even from that 16 1/2" barrel, I was not losing more than 200 f/sec from what Hornady said I would get from a 24" barrel ..... the more I use 4064, the more I like it. It seems to work really well for just about every use I put it to!
Thank You ALL
Enjoyed every post,You guys made my day. My groups are OK but always try to do better, must admit I also have a Jewell trigger set at 10 oz. for my shakey hands, 6x24 scope set mostly on 24 for my failing eyes & a muzzle brake for the lack of balls. THANKS AGAIN till the next time. Chris
Enjoyed every post,You guys made my day. My groups are OK but always try to do better, must admit I also have a Jewell trigger set at 10 oz. for my shakey hands, 6x24 scope set mostly on 24 for my failing eyes & a muzzle brake for the lack of balls. THANKS AGAIN till the next time. Chris
Art Eatman
Staff in Memoriam
Until next time...
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