Which bullet ?

G

Gina1

Guest
OK, guys got a question.
First the reason for this question. I shoot full bore at the Historic Camp White. (est 1942) in White City, Oregon. We have a 600 yard range.
I'm shooting a .223 Savage action with a Pac-Nor barrel 1/9 twist. I've been using Sierra MK 69G and Berger 70G VLD bullets. The problem is the winds on this range are weird. The wind flags at the 100, 300, 500, and 600 yards marks can be blowing in different directions at the same time (in light and variable winds ). Plus if there is a tail wind, you get an upsweep at the target berm.
My question is this.... The 69 sierra with 22 grains of 8208 XBR powder gives me 2,900'/sec. Would switching to a lighter bullet (Sierra 52 MK) allow the bullet to get to the target faster so that the winds will have less effect, or being a lighter bullet, will the same winds have more effect in that shorter time. ???
Figure you guys have centuries of experience. Any thoughts ??

Thanks

Gina
 
Gina

The light bullets will get there faster and be moved more by the wind. Have you tried 80 or 82 grain bullets? They will be effected less by the wind.

Many ranges have the same wind conditions, try waiting for the flags to agree.

Best Wishes

Terry
 
dont think 80 or 82 is reccommended witha 9 twist.....you should be able to go up to the 75, maybe 77..non plastic tipped bullets and do a little better in the wind.

mike in co
 
My shooting partner was shooting Sierra 69 grainers out to 500 meters this week end, with a 1:9 twist.

We spot for each other and I was suprised how well it 69 did in the wind.
 
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Read very carefully what Terry Balding said for 'tis the TRUTH!

Faster as you described WILL NOT drift less in the wind, in fact generally the reverse is true.

al
 
Gina,
You should be watching mirage in those conditions, Gina.
 
Bullet Stability and Accuracy

The bullet weight and BC rating are important. But when wind is considered the third factor is bullet stability. If the bullet does not exit your muzzle with a perfect true spin it will not fly as expected. Some of the better (More Expensive) low drag bullets, (Higher BC number = VDL Bullets) come out of the muzzle with a wobble. That is the tip of the bullet is conning. The bullet does not go to sleep until it is far down range, say 300 yards. When the bullet is conning the BC is much less that printed on the box. The bullet present a large front and side profile. Due to the larger effective side profile he wind in the first 10 yards, 25 yards and 50 yards impart additional motion to the bullet. And the larger frontal profile slows the bullet down more.

Bottom line is if the bullet is conning after leaving the muzzle it varies in drop at longer ranges and there is more wind drift. Not Good.

Destabilization of the bullet at launch is mostly determined by three factors: Uneven, non square or non perfect muzzle (See your gunsmith), High gas pressure as the bullet exits the muzzle (Faster burning powder can some times help. Longer barrels are usually the better solution) and low drag bullets with longer boat tails are more subject to destabilization because the gas out of the muzzle passes the bullet while part of the tail is still inside end of the barrel. Shooting a load that gets the same velocity with less muzzle pressure when the bullet leaves the barrel does make a positive difference. Remember if the bullet is conning the BC is bullet's velocity at the target is different shot to shot so the group will be larger. This will be true even if each bullet leaves the barrel at exactly the same velocity.

One way to check for this is to shoot in difficult winds at short range, say 100 yards. Shoot your VLD bullet and shoot a similar quality and weight flat base bullet. If the FB bullet shoots smaller groups and makes smaller rounder holes in the target it is likely that your VLD bullet is conning or wobbling when it leaves the barrel. If you have good target paper you can sometimes see that the VDL bullet is making a larger hole with indicates the bullet is conning and not spinning true.

We shoot a lot at 485 yards, the limit of our private range in TN. Most often shooting with 26" and shorter barrels we have seen better groups at this range with FB bullets. Flat base bullets stabilize much faster than the VLD bullets and do not seem to be pushed into conning as easily as the VDL bullets.

To shoot tight groups you have to get all the error factor either reduced or eliminated. Wind is always a big factor.

I had a 31" 6.5 X 284 barrel with a muzzle brake that did not shoot the Berger VLD 140 bullets as expected. Muzzle brake on or off did not make a difference. The same load in a matching barrel shot much better at 100 to 485 yards. I refinished the Muzzle with a piloted had reamer, (From Brownels) and the barrel then would shoot equal to it's mate. It was difficult to tell the difference but I suspect the accuracy was slightly better over all with the Muzzle brake on.
 
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Contrary to popular belief excess coning motion DOES NOT measurably increase BC (see Vaughn and McCoy) and the biggest contributor to excess coning is inbore cant or yaw. The largest contributor to inbore yaw is neck clearance on the loaded round.

al
 
Al,

Very interesting. However this does not match with my personal observations. Maybe the BC does not change much but I have clearly see the conning or bullet wobble increase the wind drift. An then after tuning up the muzzle the same barrel improved.

I do agree with the inbore cant or yaw. Neck clearance on a loaded round can be significate also an off center chamber. However, with the match grade chamber we mostly shoot these are no usually an issue. Mostly we are all shooting tight neck chambers fitted with .0015 or .0020 clearance on a loaded round. A few years ago I made up a set of brass with .004 clearance and with the OAL short by .125 as an experiment. With the bullet into the lands about .004 (Meyer's moly coated 6 PPC bullets) these shot about the same as the tighter necks. However, when the bullets were not into the lands the neck tension came into play and I could see a difference. If one goes up to the much larger neck clearance that is common to some of the factory barrel chambers I am sure the results would be difference.

I think one thing going on now days is the new bullets have better BC numbers. They need more spin to stabilize and they are more likely to be destabilized by muzzle blast.

Try some of the good quality flat base bullets at mid range, out to 600 yards. I think you may be impressed just how good they perform. And you shoud find the FB better out to 300 yards in most barrels.
 
We shot 69gr SMK's for years at 600yds with a NM M16 service rifle because that was all that was available. A lot of good scores were shot in those days, and we were able to be comepitive against the .308 and .30-06 crowd. the only drawback for me to the M16 was the shorter sight radius.
 
I have a Remington 5R rifle with 1-9 twist. It stabilizes the 69 Sierras and 70 Bergers fine at 300 yards (the maximum distance of my range). I've tried 77 Sierra and 80 Bergers and clearly (at 300 yards) these two bullets weren't stable in the 1-9 twist. My barrel likes lighter bullets like the 53 gr. Sierras but as suggested by others you're better off with 69 Sierra and 70 Bergers for long distance in the wind with your rifle.

Jerry
 
Gina, I've got a Savage with a 1 in 9 barrel that shoots 75 gr Hornady's well, but your barrel might not like bullets that long. I'd try the 75 gr Hornady HPBT and 77 gr Sierra MK with a slow powder for the .223 like 4895 (either IMR or H), Varget, Reloder 15, TAC, or 748. You won't get the velocity that you get with the lighter bullets, but with no flags on a range with twitchy, switchy winds I can get 3" ten shot groups with them from an AR and 12X scope, not to mention terrible eyesight.
 
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