Weird Range Results With Partitions.Need Advice From You Resident Experts

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SAKO220

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I need some advice about what could be the cause of some weird results i am getting with the 60 Grain Nosler Partition.I have never seen this before and i have no idea what is causing it.

First i will tell you some info in case it helps.

I am shooting a Sako L579 chambered in 220 Swift topped with a Weaver V16 scope.1 in 14 twist.

Shooting 37.5 Grains of IMR 4064,Win Brass(3rd time loaded)Neck Sized,Fed Primer,60 grain Nosler Partition.

Groups were shot left handed.I waited 5 minutes between each and every shot fired.All groups were shot at 100 meters.

I was just shooting over a couple of sandbags and i will never claim to be the best shot in the world or anything so i am not expecting Benchrest rifle accuracy just good predator hunting accuracy but this result with the partition is sure not acceptable to me.

I am looking for a bullet that won't blow a bobcat in two and the 53 grain TSX shoots pretty good so i can use them but the groups with the partition have me baffled and curious.

I was thinking Twist rate was to slow but the other shots all grouped pretty good.



The first time it happened i thought i had just plainly messed up somehow although all my shots felt good.So i tried it again and produce the same results three more times.

One out of every 4-5 bullets fired goes way high and to the right.It could be the first shot fired,The last shot fired or in between.On the particular target i am putting up here it was the third shot fired out of a five shot string.Five minutes between each.

I Will put up a pic of a group shooting 55 grain HPBT Gamekings for comparison.I fired five different types of bullets from the swift and all produced groups similar to the Gamekings.

I also fired two different bullet types from another caliber with similar results to the Gamekings.

The only time it happens is when i am shooting the Partitions so i don't think it is something that i am doing.

Partition pic is a five shot group and Gameking pic is a four shot group(i lost one of the cartridges somewhere on the way to the range)

Any opinions appreciated.Pics below .Thanks.

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100_3317.jpg
 
My guess would be that the twist rate on the barrel isn't fast enough to stabilize the bullet and you are getting build up in the barrel, the flier is probably the barrel (working the turkey out!)
 
Found this at Shilen's website...

http://www.shilen.com/calibersAndTwists.html

Looking at the .224 CF (Center Fire) chart, twist rate of 14 is good up to 55 grains.

For 60 grains, twist rate of 1 in 12 is ideal.

Might not be enough spin on the 60 gr. bullet to stabilize reliably. And a partition bullet, due to its structure, might react different than a solid core like a GameKing. From what I've read, I gather that smaller bullets, .243 or less, are particularly sensitive to proper twist rates. (It was the wrong twist rate that couldn't handle 100 gr. bullets that got the 6mm Rem. off to a lousy start that ultimately doomed it...a mistake that Winchester didn't make with the .243 Win.)

According to the chart, your best performers, with 1 in 14, should be in the 55 gr or less.

(Keep in mind, Sierra Gamekings have a terrific reputation for accuracy due to high standards with which they make their bullets.)

FWIW...
 
Your rifle is telling you it doesn't like 60 gr. Nosler Partion bullets.

Your rate of twist is probably borderline to stabilize that bullet, hence the odd flier. It's kinda weird, i would have expected the whole group to open up, not put 4 shots into a dime and 5th nearly off the paper.

Regardless of the reason, that bullet doesn't work in that rifle.
 
Thanks for the replies you guys.

I was kind of leaning towards the spin rate idea myself and i wasn't actually expecting them to group at all because of this when i bought them.I knew they were not an ideal weight when i bought them but i thought i would give them a try just to see.

I have had a few rifles with a 1 in 14 twist that shot the old nosler 60 grain spitzer very well and this rifle (220 Swift) shoots the Speer 70 grain semi spitzer very,very well so i thought i would give the partitions a go.

It just really puzzled me why so many of the other ones in the group shot well and one in a group would be so wild.

Also why it would be a random shot from the firing session that does it.Sometimes first shot sometimes last sometimes in the middle like it being the third shot in the target below that did it.

The first time it did it it was the first shot i fired in the group.

I have fired some heavy for caliber bullets that it didn't like before but they basically shot all over the place.

Not four into a decent size group and one random wild one.

I will most likely abandon the idea of using them on cat and go with the TSX but i was just baffled by the results and thought i would get some other's thoughts on it.

Probably is the twist as you guys have said.I just wouldn't have expected it to shoot the other shots as well as it did if they are not stabilizing enough but then again i am not an expert.

Thanks for your thoughts.
 
Strange, indeed. I have an older tang safety Ruger 77V in 220 Swift, 1-14" twist. The 60 Partition is one of the better shooting bullets over 52 grains in mine, with ½" groups quite common. How fast are you driving your 60 Partitions? With a marginal twist rate, 100 fps can mean the difference between stabilization or not. I'm right at 3750 fps using RL 19. Regards, Eagleye.
 
I am not sure Eagleye.My chrony broke a few years ago and i never bought another one.

My manual says it is a max load allthough it is showing no signs of pressure.The book says 3633 out of a 26" tube and mine is 23".Although I realize that velocities can very widely from rifle to rifle with the same powder charge.

I haven't tried another powder as of yet.I may just for curiosity sake.

Thanks,
 
Just forgetting about them would no doubt be the smartest thing to do Mount Sweetness when the TSX does shoot well and would no doubt work fine for the odd cat that shows up when i am calling coyote.

Would save wasting time and money.

Still may have to try another powder just for curiosity sake though.
 
You are probably right about the velocity.

While the TSX doesen't shoot quite as good as some of the other bullets i have shot out of it they will hover right around 3/4 of an inch groups which should be fine for what i want to use them for.

thanks
 
My 22-250 with a 1 in 14 twist puts the 60 grain Partition into tiny little groups. It is the length of the bullet that determines twist rate not necessarily weight. The 60 Partition is shorter than the 55 grain HPBT Sierra so I don't think twist is the issue.

My bet would be you are getting excessive bullet run-out on the occasional round. (The short little 60 grain Partition can be tricky to seat squarely) Try checking your rounds on a concentricity gauge and shoot a group using the best rounds you can assemble.
 
SAKO220 said:
Thanks for the tip Boo.I do not own a concentricity gauge.I will have to pick one up and retry them.
Click to expand...

Find a small mirror and lay it on the table. Roll the assembled cartridges across it. Any wobble at the bullet tip will be readily seen. Take the ones with the least wobble and try shooting them.

Another tip is to use a VLD type reamer to chamfer the inside of the case mouths. A long gentle taper on the inside of the neck will assist in seating the bullets straighter.
 
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