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Old June 22, 2022, 01:10 PM   #1
Darkwarrior
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1:11 twist barrel 300 win mag - 180 gr SST

Hey y'all!

I recently got an old Sako Finnbear A3 in 300 win mag, and I understand that rifle has a 1:11 twist barrel. I took it out to the range and shot groups with 150gr Hornady interlock bullets, 165gr Barnes TSX, and 180gr Hornady SST. The first 2 shot fine, but I couldn't get the 180gr load on paper at 100 yds. I brought my target back to 20 yards and grouped about 1.5" at 20. So I'm wondering, will a 1:11 twist barrel stabilize the 180gr SST? I can't think of any other reason it isn't hitting paper at 100.

Also, the 165 impacted about 5 inches to the left of the 150gr at 100 yards. I don't know why a different bullet would group that far left/right, so if anyone has any ideas, please let me know.

Thanks!
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Old June 22, 2022, 01:47 PM   #2
Unclenick
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Welcome to the forum.

The bullet is 1.338" long in my data and should be stable in an 11" twist barrel down to about 1200 fps MV (calculator here) in an ICAO standard atmosphere. Even lower if your air is warm and humid summer air. Usually, when I have shots go left, but still group, it is because I'm using a sling that is anchoring the front of the stock well, and as recoil increases with bullet weight, the gun pivots more to the left around the front sling swivel because the stock is shifting more to the right on my shoulder (I am not squarely behind it; my anatomy just doesn't work out to let me do that perfectly). However, stock contact with the barrel can also be responsible, as can improperly tightened stock screws. External iron sight or internal scope problems can also be involved. Make sure everything is snug. Look up the stock screw torque spec and tighten the screws with a torque wrench to get that right. Bad bedding or bedding that has gotten oily can cause some odd group placement.
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Old June 22, 2022, 02:35 PM   #3
GeauxTide
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300WM is one of the most accurate of the 2.5" Mags. Check scope mounting, stock screws, and barrel channel. I'd try a 180 Speer flat base.
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Old June 22, 2022, 02:50 PM   #4
sako2
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I have a sako model 75 with a 1:11 twist. It shoots a 190gn nosler ablr very well.
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Old June 22, 2022, 08:26 PM   #5
Darkwarrior
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Thanks for the replies!

I may have a gunsmith check it out. It's a 40 year old rifle and the person I bought it from said it may never have been fired. I imagine 40 years could have had an impact on the bedding and connections of the components. I'll also try different 180gr or maybe larger bullets and see if I get any better results.

Thanks!
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Old June 22, 2022, 10:05 PM   #6
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Welcome. I would agree with unkle nick, hes one of our resident gurus here.

It could be the bedding job. I would suspect it may need a new barel or the crown touched up. If your dropping it off i would have your smith give it a good look over
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Old June 22, 2022, 11:36 PM   #7
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What can't you kill at 300 yards with the Barnes 165?
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Old June 23, 2022, 04:26 PM   #8
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A lot of folks use 300 WM for long-range target shooting. All else being equal (ballistic drag shape in particular), the heavier bullets buck the wind better.
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Old June 24, 2022, 02:59 PM   #9
Bart B.
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The most accurate 300 Win Mag rifles I've seen had 1:12 or 1:13 twist barrels for 180 to 200 grain bullets.

Changing how that rifle's held can easily move point of impact several inches. The bore axis angle moves while bullets go down the barrel.

Last edited by Bart B.; June 24, 2022 at 03:13 PM.
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Old June 24, 2022, 03:56 PM   #10
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I have a 30-06 with a custom barrel with 1 in 12" twist. Supposedly it should stabilize 180 gr. bullets but all I can say based on shooting the rifle is, "It doesn't." However, it does a great job with the Nosler 165 gr. Accubond. I took a nice fat cow elk with the load a few years back. Average groups run about .75" when I do my part.

I recently picked up a Husqvarna 30-06 with 24" 1in 12" twist barrel. I haven't had a chance to take it out and shoot but I'll be checking out how it does with 180 gr. bullets.
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Old June 24, 2022, 05:32 PM   #11
Bart B.
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The USN 7.62 NATO Garands had 1:12 twist 24 inch barrels. They tested under 4 inches at 600 yards with Sierra 190 and 200 grain HPMKs with new cases.

All barrels whose groove diameter is a few ten-thousandths inch smaller than the bullet's diameter produce best accuracy.

Last edited by Bart B.; June 24, 2022 at 05:37 PM.
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Old June 24, 2022, 09:16 PM   #12
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I've never had an issue with 180 gr bullets not working well in my 308's. I have rifles with 10,11, and 12 twists. The one with a 12 twist shoots them just fine

And while I've done less experimenting with 200 gr bullets they seem to work too.

If someone is having trouble getting an 11 twist to shoot 180's it isn't because of the twist rate. Some rifles just don't like some bullets. Try another 180 gr bullet or shoot whatever bullet and/or bullet weight that rifle does like.
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