6XC vs 6x47 vs 243 - survey for quick twist set up

[65BR]

Looking for those to chime in, how much better accuracy and case life will I see with the XC and 47?

Looking to run at least an 8T w/105-108s and likely considering 7.5" thru 115s.

When set up for 115s, how light of bullets can you use on the bottom end? Will 70s work? I imagine you'd need about an 85-87 if not 95 to touch lands.

Use will be a sporter weight hunting rifle, game thru deer/hogs and paper/plinking steel, etc. for fun.

Thoughts and experience?

Thanks all.

 

[Yellow11]

On the heavy side, the DTAC 115g will work in 8 twist... assuming you are runnnng around 2900 fps.

If you use a lighter bullets, you will reach a stage where, if too light, they will centriifugally self distruct, as they need a slower twist and are manufactured with that in mind.

For example, Berger 88g will produce about a 1.5 GS in a 9 twist barrel, but I can relate to using the same bullet in a 7 twist (2.5 GS) and they just never reached the other end if the range - they vapourize.

 

[65BR]

Thanks for that info, looks like I'd need to start with bullets of 85gr as my 70 TNTs might not hold up.

Appreciate the info. Odds are I'd run one or two preferred bullets so an Amax or DTAC may be 'dual purpose' - paper-varmints.

 

[HPMike800]

Unless your long range target shooting, I would skip 115's and go an 8 twist. Chamber for 107's.

 

[CT10ring]

65BR, I just had a 6X47 Lapua built. Surgeon repeater action, Krieger LV 1/8 tw. I have shot maybe 50 rounds thru
& it shoots 88g Berger varm match HP into small holes & handles 105 amaxes really well, once I got OAL & powder weight figured out. think the leade was .100. Works great with these 2 bullets, IMHO. Some great advice & load work ups from the super folks posting on this site

 

[Mudcat]

1-8 for XTC
1-7.5 for LR if you want to run 115s. 7.5s, at least kreigers, will stabilize 115VLDs with no problem and will shoot them well too....if you find the seating depth they like. My 7.5s didnt like light bullets so I wont use them xtc any more.

 

[spclark]

On the heavy side, the DTAC 115g will work in 8 twist... assuming you are runnnng around 2900 fps.

I had a new rifle built in 2008 (Quadlite, Bartlein 30" 1:7.8 twist, stocked & 'smithed by Carl Bernosky) chambered with the latest 6XC reamer profile (at that time) from Hugh Henrickson, intending to shoot the DTAC 115's at 1,000 yards.

During it's first range outing for load testing I was throwing the 115's (hBN-coated from D. Tubb) up to 3,200 fps with RL-17, not quite as fast with a couple of other propellants. Brass was toast after one firing at that speed so don't go there. Accuracy was not up to expectations either, even at lower speeds.

I'd been able to shoot the same 115's with great accuracy (at least at 600 yards) out of a Pac Nor 1:7.5 twist 26" barrel on my T2k. Conversely, in the original Schneider 1:8 25" I blew up a few Berger 115 VLD's trying to shoot 600 yards. They need 1:7 at minimum to work, according to Berger. The DTAC's will like this twist too, maybe 1:7.5 but I wouldn't go much slower... or faster, for that matter.

Late last year while doing load testing in the Quadlite with then-new IMR 8208 XBR at 600 yards I achieved 3,125 fps with Berger 105 VLD with loads that don't ruin brass and provide excellent accuracy. At 3,000 fps the B105 VLD is every bit as capable of great results as the 115.

Last Saturday up at Winnequah Gun Club (Lodi, WI) in the afternoon I shot a 142-4x at 1,200 yards (24x 'scope & sling, off a mat) hitting the spotter twice in the X-ring. Admittedly that afternoon the conditions for this were near perfect (78°, virtually NO wind AT ALL, 55% humidity). When we went to the pits to pull for the next relay I had a fellow shooter take a picture of my target. Pic arrived just after I posted this, attached in next post.

 

[spclark]

My target at 1,200 yards last Saturday, 6XC & Berger 105VLD @ 3,125 fps. 15 shots for score, 142-4x.

 

[flatlander]

I've built several 6x47s for myself & others. Two of my bbls. are Krieger 1:7.5 .236"s, while another one is a Bartlein 1:8 .237". One of the Kriegers is on a LR prone rifle, and is shot exclusively with DTAC 115s, while the other two have been used in BR varmint silhouette matches, and thus are used with bullets from 65 custom BR FBHPs up through 115 DTACs.

I've had no issues with lighter bullets in either Krieger .236" or Bartlein .237" bbls., but then I'm not running the lighter bullets as fast as possible. The thing that surprised me was that the 1:8 Bartlein has been the most consistently accurate with 115s of the three bbls. I've experimented with Berger 115VLDs in this bbl. & the Krieger on the prone rifle, and the 1:8 Bartlein is the best of the two with that bullet also.

The only conclusion I've reached with this limited sample of bbls. is that there's no cut & dried or absolute standard for which twist rate works best for a wide range of bullet weights. My gut feeling is that a combination of bore dia./twist rate - along with a strong dash of individual bbl. characteristics - has more effect on determining whether a given bbl. will work well with a wide range of bullet weights.

Most recent experience was a Bartlein 5R 1:7.8, .237" bbl. in 6x47 for a friend who tends to run the warmest loads w/DTAC 115s he can get away with. He's running them at well over 3100fps w/RL17 out of this bbl., and at least to date hasn't squawked about losing any cases to loose primer pockets. The next 6mm bbl. I do for myself (whether it winds up being chambered for the Dasher or 6x47) will be one of these .237" 1:7.8 5R bbls. just because I'm curious and want to see if his bbl. is a fluke, or ??

 

[scott_at_vortex]

The absolute fastest twist I will use for the 115's(beergers ,dtacs,or 117 matrix) is a 7.7 or even 7.8. I currently run a 8 twist and it shoots all the 115's great. I have had a 7 and 7.5 and could never get rid of pressure, even with minimum loads. In the 7 I was in the upper 3100's no matter if I had 43gr of powder or 46grs. It really made no sense. I finally just gave up on it, plus after less than 600 rds I looked at it with a bore scope and it was the worst fire cracked barrel I have ever seen, not much throat erosion ,but fire cracking like you wouldnt believe. I have also talked to numerous highly respected gun smiths that have seen similar things happen. Most of them also say that they have never seen an 8 twist not stabilize the 115's as long as it was indeed a true 8 twist and so far I have had no problems with mine and it shoots great.

This is strictly my experience and opinion's, YMMV



Best Regards
Scott