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Cooperman

1:8 twist 6mm (.243) but won’t accurately fire >75g puzzle

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Dear wise experts of UKV,

Hoping you can help. I bought a second hand rifle that looked the business from a shop in Shropshire - BAT action, Krieger match  barrel, Sheehane thumbhole laminate stock, Jewell trigger,  all looked great with a little used barrel. It’s been made with a reputable gun smith 8 years ago.  It is definitely a 1:8 twist. I was hoping to use 103 eldx in it. Bore scope shows little use and a good throat. It’s 7 tho’ shorter than a new sako factory  barrel rifle when comparing OAL with SST. 

It will shoot 58g vmax to within 1/2 MOA with careful handloads, slightly worse with 75g Nosler, just about MOA with 95g SST, and about the same with 103 eldx.

I then had it bedded at the front, as the BAT didn’t fit the aluminium bedding block. Accuracy similar as was before, but now doesn’t put 2 of the the three shots together, just neat triangles. Reduced the barrel from 25 to 24 and recrowned. 

Is it possible to deliberately make a rifle to shoot light bullets at the expense of shooting heavy bullets, even with a fast twist? The build spec was for light factory loads.

I tried to contact the original owner to no avail....

Thanks for all suggestions or knowledge,

Cooperman.

 

 

 

 

 

Edited by Cooperman
Update to 243

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Cooperman

 If it is definitely 1:8 then I’m not sure what to say? How have you determined the twist?

I had a 1:8 6mm Swiss Match (similar to 6-6.5x47) and it ran the 115g DTA’s with no issues.

Laurie or the Gun Pimp might have some ideas?

T

 

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Hi Terryh,

I rodded it with tape, used a marker pen on the red, and finally asked a gunsmith to check - it is definitely a 1:8.

Bizarre indeed. 

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If the spec was to shoot light factory loads i would have thought 1:10 or even 1:12 would of been the twist fitted . 

Anyhow , the 1:8 should still shoot the heavy loads as well as the light loads , i have a 1:8 twist 6x57Lapua and it shoots every weight of 6mm bullet as well as each other . 

What 6mm is it ?

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What actual calibre is it ?

6PPC ?  6mmBr ?

Even if the rifle has a short throat, a true 1-8" should still shoot heavy bullets, unless it hasn't got the engine room. The BR has, but I doubt the PPC would shoot anything much heavier than 75's. You would be pushing the bullet so far back in the case, it wouldn't leave much powder room.

At that age, its unlikely to have any info on the proof marks. These days, if they have under saami/cip spec length throats, the proof house want to know, and mark the barrel accordingly.

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I hd some 1:8 .223 barrels from Walther years ago, they should've shot anything but wouldn't stabilise anything heavier than a 69, and I know someone else that had a 1:9 that would only stabilise 55's

It happens and it's possible that the bore is slightly oversize

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.243 cartridge, correct??..But if different I stand corrected...Had a similar problem as yourself attempting to get a consistent accurate load with the .243. By that I mean putting pill-on-top-of-pill, or a least achieving ragged hole consistency - rarely could I do that 😡 and this was with a brand new rifle. 

Every time I thought I had an accurate load, as soon as conditions altered the POI changed. I also found barrel-heating a serious barrier to achieving consistent accuracy, even after allowing to cool. Never could get that .243 shoot like a .223 or /308...By the time I would have achieved getting the .243 to shoot like I wanted, I'd have reached barrel-burnout, and would have had to start all over. 

Decided it was best to be happy with what I could achieve, which was .75MOA @ 100yds (85g pill) and use as a dedicated fox tool and nothing more....a great cartridge but way too finicky to faff around reloading for....

Just my experience but ATB

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Hi snakeman,

yes 243.  It’s a thick barrel, probably remmy varmint. I’ve two 243’s, a sako 75, which likes 90g, but fancied trying the heavy bullets in 6mm. The sako shoots in the .4’s when I do my bit with my very carefully made  loads.

Thanks Bradders - I wondered if funny barrel. 

If it helps, The magneto says the first shot is always c50-60 FPS slower than the others. If it fire four, the third three aren’t any more accurate but the SD is close.

weejohn - it’s definately a 1:8, which I agree  is bizarre given the build spec. 

Thanks all

 

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Another horrible result this weekend was trying different SST loads at 200 yards and it managed a 6 inch group :( first was through the middle? Worst group I’ve ever seen. A bedded BAT! 

the 100 yards were normal😜 at fair to crap near MOA.

rebarrell seems the most likely option long term.  Tremo sold me 200 58s which work well enough until the frustration reaches that point.

ive reloaded for 5 years now, and the other 243 and 270 I shoot are great.

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I’ve tried the SST to 3300 FPS, where the bolt was stiff, but no real pressure signs at 3200,  so it’s not lack of speed. The 58s go well at 3600.

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