I am baffled

[Johnch]

I was out tonight with the GF plinking at the range
She was working on a brick of 22's , ventalating pop cans

I had a bunch of the 165 gr 30 cal modifyed silouete bullet loaded in the 308 with 11 gr of Promo
I am guessing around 1400 fps

I was shooting paper mainly at 50 and 100 yds , getting about 1.25" and 2" , 5 shot groups at the 2 ranges


An other shooter left , leaving some clean targets at 200 yds
So I figured I would see how much drop I was getting at 200 with a 100 yd zero

When I went down to see , I was shocked , by seeing the 2 groups I had shot
To be 1.75" and 1.875"
So I shot 2 more 5 shot groups at both 100 and 200 yds

100 yd groups were just smaller than 2" and the 200 yd groups were both just over 1.75"

Not going to say these are great groups
But how am I shooting smaller 200 yd groups
With everything the same , as I was just randomly picking rounds out of a 100 rnd box
No changes other than shooting into a different backstop

Any ideas ??


John

[DLCTEX]

Boolits are stabilizing as velocity comes down, fewer rpms, I think. DALE

[mooman76]

Aim small, mis small.

[NSP64]

I go along with Dale, They are 2" accurate @ 100yrds and then go sub-sonic somewhere past 100yrds and become 1.75" accurate then kind of like when they shoot good @100 then keyhole @200

[Bill*]

Nah....Those were "special" targets. I've seen em on ebay. The further you shoot, the better the group. At 500 yards I shot a 5 shot group with a 22 that measured .11 (offhand....including a called flyer )

[rvpilot76]

As mentioned earlier, the boolits are stabilizing. They are what some refer to as "going to sleep".

Kevin

[bushka]

neat,going to sleep,that is cool,must stay sub sonic.

[DLCTEX]

Going to sleep is a term used back in the 50's when we played "tops". A wooden top with a metal point was wound with string and made to spin. When trown hard, the gyroscopic forces multiplied unbalance forces and the top would wobble on its axis until the rpm's fell below the point where the energy in the imbalance reduced enough that the top would spin true on it's axis and stand motionless except for the spin, thus "going to sleep". DALE

[Boerrancher]

It is quite common for my 6mm-284 to shoot smaller groups at 200 yds than at 100. As has been pointed out it is do to the bullet becoming more stable further down range, but I am not sure I agree with the sub-sonic theory, because I am starting out with a muzzle velocity of 3950 fps with a 100 gr bullet. I don't think that at 200 yds I am subsonic. Also, as a caveat, I don't have that problem of smaller groups at 200 yds with the 85 gr bullets, they seem to stay at 0.75 in for a 5 shot group. The 100 gr will consistently shoot 1 in groups at 100 yds then shrink to an average of .75 in at 200 yds. I will also note that the rifle was made from a 244 Rem barrel which has if I remember correctly a 1 in 14 twist where a regular 243/6mm is a 1 in 10 twist.

Best Wishes from the Boer Ranch,

Joe

[Johnch]

Thanks for the insite

John

[felix]

244 Remmie barrels were 12 twist; 6mm Remmie barrels are 10 twist. ... felix

[Scrounger]

244 Remmie barrels were 12 twist; 6mm Remmie barrels are 10 twist. ... felix

I believe the 6MMs are 9 inch, Felix, .243s (Winchesters) were 10 inch.

[felix]

Yep, you're correct, Art. ... felix

[NSP64]

It is quite common for my 6mm-284 to shoot smaller groups at 200 yds than at 100. As has been pointed out it is do to the bullet becoming more stable further down range, but I am not sure I agree with the sub-sonic theory, because I am starting out with a muzzle velocity of 3950 fps with a 100 gr bullet. I don't think that at 200 yds I am subsonic. Also, as a caveat, I don't have that problem of smaller groups at 200 yds with the 85 gr bullets, they seem to stay at 0.75 in for a 5 shot group. The 100 gr will consistently shoot 1 in groups at 100 yds then shrink to an average of .75 in at 200 yds. I will also note that the rifle was made from a 244 Rem barrel which has if I remember correctly a 1 in 14 twist where a regular 243/6mm is a 1 in 10 twist.

Best Wishes from the Boer Ranch,

Joe

Hey, your cheating.Using those condom coated bullets I would say you are probably correct,subsonic was a poor choice. How about they reached a better balance between rpm, shape & forward movement. Given any particular boolit diameter/weight/speed there are probably several speeds that they shoot accuratly. In this case the boolit may have been slipping into subsonic flight, Cast boolits (for the most part) don't have sharp tapered points, and may fly better in subsonic.

[Tom Herman]

Thanks for the laugh, Bill!

Nah....Those were "special" targets. I've seen em on ebay. The further you shoot, the better the group. At 500 yards I shot a 5 shot group with a 22 that measured .11 (offhand....including a called flyer )

[OBXPilgrim]

I've heard other folks talking about the .303 british doing the same thing at 500-600 yards.

When you first hear of one doing it, sounds hard to believe.

[Ricochet]

The RPMs don't come down much as the boolit flies. Linear speed drops off rapidly, rotational speed slowly.

[jackley]

The bullet may stabilize at a slower speed. BUT what makes it stabilize at the same spot every time a new bullet is shot? I've heard of this happening all my life but it just doesn't make much sense. The bullet would have to stabilize at the exact same spot every time, to print the same size or smaller groups at 200. And I just don't think this would happen. I can't remember the formula now but a gun that prints an inch at 100 yds does not necessarily print 2" at 200 yards. There are other factors at work here.

Jerry

[Tiger]

Ask Larry Gibson. He seems to have all the answers. He and his crew will tell you it is not possible to shoot smaller groups at further distances.

Ralf

[JSnover]

I wish I could remeber the details now but one of my old Sierra manuals offered some insight on this. On leaving the barrel the bullet enters what's called the Modus Violentus, where it is unstable as it makes the transition from your bore to the atmosphere. They claim this zone or portion of it's flight can print larger groups as far out as 100 yards, smaller ones after that. This is something we can argue for years and I'm not sure if I can believe or understand it, but Sierra claimed it to be a fact.