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    • #24942
      goody
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      I have been enjoying my son’s handsome Winchester 54 in 270, very late serial number and shooting Ly 122 gr cast with 872 in nice little clusters. So if this gun does this good with light weight what will it do with Ly 150’s. They are 16 inches from the 122’s and really all over the place. I tried some unique powder and the bullets were tumbling. I was shocked and decided to check the twist and was more shocked at the 11 12 inch twist. Never heard of that(normal for me) and I ask from those of you that do know what does this twist mean for shooting cast and jacket bullets?

    • #24944
      Goodsteel
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      My first question is, how did you check the twist on that rifle?
      If you are using the old cleaning rod trick, remember that any error at all will give you SLOWER twist measurements. Never faster. All it takes is a very slight slippage to give you a false reading.

    • #24953
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      Always check both the push and pulled twist measures.

      On that note the standard twist in the 6.8 SPCII is 1-11 with at least 2 makers offering 1-11.25 . The 11 twist will shoot most 130 gr projectiles down to 2200 fps . With the 270 you should be able to overcome the twist with 140s with speed.. the tumble doesn’t surprise me,I had a 7mx57 that did the same with 289 sized lovern bullet . I suspect that if the 11.5 is correct that your load is just to slow to stabilize. A 130 cast should be ok it that twist but it also may be right at the edge.

    • #24956
      goody
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      trust me it is a 11 and half twist. I use a bronze brush a size smaller and wrap cloth around till it fits tight and rotates the same for a few passes then I put scotch tape around rod at barrel end and leave it long like a flag pointing up and pull thru till it makes a complete rotation. I do it again and when the tape is out of barrel not where the excess tape is and pull for a full rotation. Measuring it each time.Do it again and again. This is likely the wrong way to do it but it works for me. So, do I here that this twist is better with lighter Jacketed bullets around the 130 gr and is trying to get the cast 150’s worth burning powder for? I don’t need to shoot heavy lead but I was trying and wanted a answer why they (the cast 150’s) shot so different.

    • #24959
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      I suspect that the 150 is justout of the limit/usable twist length of both twist and bullet. I want to try a 150in the 6.8but I don’t have enough sizers to make it happen with the 7mm bullets.

    • #24961
      Goodsteel
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      Must be a custom barrel. I know of only two rifle manufacturers (both European) that twisted the 270 Winchester anything other than 1-10 (and both of those were faster). All American manufacturers went with the standard 1-10 twist rate.
      In fact, I can’t think of a custom barrel manufacturer that offers any twist slower than 1-10 either?
      Using a brush is a very dodgy way to get your twist rate. A slug is much more reliable.

    • #24986
      goody
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      I will try a slug because the rifle looks original. It must wait because I am having a hernia fixed today. I sure hope I am wrong so the gun is valued as a original. Thanks for your input.

    • #24995
      Larry Gibson
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      goody

      What is the length of the 122 and 150 gr cast bullets? Let me know and I’ll run them through a stability calculation for you.

      Larry Gibson

    • #25084
      uber7mm
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      Larry,

      Is your offer good for 7mm bullets?

      I have a 130 grain Lee C285-130-1R @ .882″ and the 160 grain Lyman 287641 @ 1.096″. The lengths include gas checks. If it’s not too much trouble, I’d like to know stability for 1:10″ & 1:9.5″ twist barrels.

      Thank you,

      Charlie

    • #25095
      Larry Gibson
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      uber7mm

      Glad to help out. You shouldn’t have stability issues with either bullet in either twist. The C285-130-1R should be stable a 200 fps with either twist. The 287641 should stabilize at 400 fps from the 10″ twist and at 300 fps from the 9.5″ twist. Those would be some real mouse fart loads!

      Larry Gibson

    • #25107
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      Larry
      Since we’re on a roll. Will the RCBS 7mm 168 stabilize in a 1-11 down to .270 or .278? It should be golden in the 9 and 9.5 at 284 .

    • #25113
      uber7mm
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      Larry Gibson;n3410 wrote: uber7mm

      Glad to help out. You shouldn’t have stability issues with either bullet in either twist. The C285-130-1R should be stable a 200 fps with either twist. The 287641 should stabilize at 400 fps from the 10″ twist and at 300 fps from the 9.5″ twist. Those would be some real mouse fart loads!

      Larry Gibson

      Use mortar calculations to get on target? LOL

    • #25114
      Larry Gibson
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      Harter;n3422 wrote: Larry
      Since we’re on a roll. Will the RCBS 7mm 168 stabilize in a 1-11 down to .270 or .278? It should be golden in the 9 and 9.5 at 284 .

      Sizing a .287 cast bullet down to .277 will lengthen the bullet a bit. Not sure how much but for the 11″ twist if the length elongates to 1.2′ it needs 1500 fps to be fully stable. If the bullet elongates to 1.25″ it would need 2050 fps to be fully stabilized.

      Larry Gibson

    • #25121
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      There is hope for the heavy in the 6.8 . The 2050 may be the dooming factor .

      Thanks Larry .

    • #25184
      goody
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      Goodsteel, a dufus I am. Feeling a little better from the hernia op and rechecked this twist but this time I wrapped some fine steel wool around patch instead of cloth and after multiple passes it is a 10 inch twist! Makes me happy to no longer be an ignoramus of these things and to know the gun has proper twist for a factory unit. Now I am wondering how many other “misdiagnosed” twists I have!! Live and learn
      Goody​

    • #25191
      Goodsteel
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      goody;n3518 wrote: Goodsteel, a dufus I am. Feeling a little better from the hernia op and rechecked this twist but this time I wrapped some fine steel wool around patch instead of cloth and after multiple passes it is a 10 inch twist! Makes me happy to no longer be an ignoramus of these things and to know the gun has proper twist for a factory unit. Now I am wondering how many other “misdiagnosed” twists I have!! Live and learn
      Goody​

      You’re not a dufus. You had a bad technique that resulted in a bad measurement and the internet is full of information like that.
      You were humble enough to test it again and post your corrected readings, and it’s things like that that will make GSF different.

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