RE 6xc

[hellraiser]

Hi anyone shooting this round `looking for info good or bad all help welcome thanksim lookin at a 26 inch barrel with 1-8 twist

[Scotch_egg]

Calling John M-H Calling John M-H

 

John owns an original Tubb 2000 and is a true advocate of the round.

[jcampbellsmith]

Hi anyone shooting this round `looking for info good or bad all help welcome thanksim lookin at a 26 inch barrel with 1-8 twist

 

I bought a set of Tubb dies for the 6XC and I sold them again. Have you read this? http://www.accurateshooter.com/cartridge-guides/6xc/

 

I have a 6XC project that's been work in progress for about a year and I think it's got another year to go before I will fire a shot.

 

Regards JCS

[Scotch_egg]

I would also consider the 6slr.

 

No fireforming required. You may need to neck turn if using lapua .243 brass.

 

I am still waiting for a review from the likes of Baldie and DanPD. Who I think have rifles chambered.

[gbal]

Hi anyone shooting this round `looking for info good or bad all help welcome thanksim lookin at a 26 inch barrel with 1-8 twist

See 6br site.It's the current favoutite USA ''across the course'' round,which has some special requirements.Nothing much wrong with it's parents(243 short reamer and 22/250 brass),but it's the 115g DTAC bullet that makes it shine,and with less powder,more barrel life-Tubb et al shoot a lot of rounds in this discipline. Of course the cartridge is a competent medium 6 mm for other uses,and more exclusive than the (yawn) 6x47,so why not?

george

[1967spud]

I would also consider the 6slr.

 

No fireforming required. You may need to neck turn if using lapua .243 brass.

 

I am still waiting for a review from the likes of Baldie and DanPD. Who I think have rifles chambered.

+1 mine is but a week or so away

[Scotch_egg]

I have run a piece of lapua .243 through my 6mmbr body die to create a 6slr case. 6mmbr on steroids IMHO.

 

Just need to borrow/hire a reamer for my preferred rifle fettler to use.

 

I've got 2,600 DTAC'S on route

[gbal]

+1 mine is but a week or so away

Another fine reinvented wheel,perhaps? Just take a 243 case- and run it through the FL 6slr die,and the extra powder compared to 6XC gives you 243 performance,and you are not limited to the pricey 6XC brass! There may be marginal throat improvement. If only there was more choice of 243 brass.....but why spoil the fun.

george

[hellraiser]

Is the 6 mm xc old news am i looking at a phased out round is there better in 6mm for longrange shooting

[Danpd]

1354135353[/url]' post='137616']

I would also consider the 6slr.

 

No fireforming required. You may need to neck turn if using lapua .243 brass.

 

I am still waiting for a review from the likes of Baldie and DanPD. Who I think have rifles chambered.

 

No 6SLR from me yet I'm afraid, I'm a big advocate of the 6x47 Lapua though, and don't really see the need for the 6xc or the 6SLR, but I'm always open to new things if I see they genuinely serve a purpose.

[Laurie]

I shoot it - nice cartridge, accurate and will give a 105 over 3,100 fps from 28" with reloder 17. Being a smaller case / powder charge, it'll give a longer barrel life than 243 Win / 6SLR, but a bit less performance.

 

Tubb developed it for 115s, which just work with a 1-8" twist barrel but are better used in 1-7.5", and I've had better results with 105s and the 107 SMK (in a 1-8" Bartlein).

 

I managed to get Norma brass at a good price - very good, consistent necks, weights etc, all except for too shallow primer pockets which need reaming before first use or the primer sits slightly proud. Now at seven / eight firings and primer pockest are still tight. You can easily enough make 6XC from 22-250 Rem brass though and that's OK since Lapua started making this calibre.

 

Nobody speaks well of the original Tubb dies. I bought a Redding Type S bushing sizer and a Competition seater - very good, no complaints.

 

It's a nice efficient cartridge, but nothing magical. It's debatable if it's better than, or even equal to, the 6mm Dasher improved variant of the 6BR in straight precision terms - unless of course magazine feed is needed which was essential for Tubb's original purpose for the XC as an 'Across the Course' job for the match variant of US Service Rifle. Certainly, the Americans are winning more 600 yards BR matches with the Dasher than almost any other cartridge and have won more than the occasional 1,000 match too!

 

There's not a lot of difference between 6XC, 6SM (Swiss Match) and 6-6.5X47 Lapua performance and accuracy-wise except the Lapua design uses the small rifle primer, the other two large rifle.

[John MH]

Not had any trouble with my Tubb Dies since I've had the T2k (2006). The 6 XC is an accurate round if put together well, I've had good results with 107 SMKs and 105 Scenars. Norma Brass is excellent and I only paid 25 Cents per case but that was some time ago. Norma also make factory ammuntion in 6XC. I have a stash of 115 DTACs but honestly find the 107 SMKs shoot well enough unless the wind is playing up.

 

Sailing home in a few hours so will be off line for a few weeks.

[jcampbellsmith]

Is the 6 mm xc old news am i looking at a phased out round is there better in 6mm for longrange shooting

 

6XC is discussed on a regular basis in this forum - http://forum.accurateshooter.com/index.php?board=6.0 Regards JCS

[gbal]

I shoot it - nice cartridge, accurate and will give a 105 over 3,100 fps from 28" with reloder 17. Being a smaller case / powder charge, it'll give a longer barrel life than 243 Win / 6SLR, but a bit less performance.

 

Tubb developed it for 115s, which just work with a 1-8" twist barrel but are better used in 1-7.5", and I've had better results with 105s and the 107 SMK (in a 1-8" Bartlein).

 

I managed to get Norma brass at a good price - very good, consistent necks, weights etc, all except for too shallow primer pockets which need reaming before first use or the primer sits slightly proud. Now at seven / eight firings and primer pockest are still tight. You can easily enough make 6XC from 22-250 Rem brass though and that's OK since Lapua started making this calibre.

 

Nobody speaks well of the original Tubb dies. I bought a Redding Type S bushing sizer and a Competition seater - very good, no complaints.

 

It's a nice efficient cartridge, but nothing magical. It's debatable if it's better than, or even equal to, the 6mm Dasher improved variant of the 6BR in straight precision terms - unless of course magazine feed is needed which was essential for Tubb's original purpose for the XC as an 'Across the Course' job for the match variant of US Service Rifle. Certainly, the Americans are winning more 600 yards BR matches with the Dasher than almost any other cartridge and have won more than the occasional 1,000 match too!

 

There's not a lot of difference between 6XC, 6SM (Swiss Match) and 6-6.5X47 Lapua performance and accuracy-wise except the Lapua design uses the small rifle primer, the other two large rifle.

Thanks Laurie,most of these close performance clones are developed for two reasons-one,to fit a specific purpose(use up 22/250 brass,feed in A the C rifle etc),and two-just plain fun.No harm in either,though it can get extreme/almost contradictory- for example,go to some trouble and cost to avoid having to use lapua brass eg,though it is initially more expensive.Not sure now lapua is always noticably better,without BR conditions/equipment,anyhow,but it does last longer,especially wrt primer pocket stretch.For most shooters,if they must dabble,best to see what is really winning after a season or two,of shooting,and think about that eg Dasher,in this context. ( this shooting/rifle etc has to be similar to their needs,of course.)Sometimes,its easy-load a 58 Vmax in a 243 case and you have effectively,a 22/243 middlestead,so I'm gratefull to the developers of the lighter bullets-wish they come earlier!Or the 6.5 grendel to 'improve' the 223 ar15 ,but opinions may diverge here....!!

george

[Laurie]

Having had my interest in the XC jolted, I thought I'd look at the load tables in the new Berger Reloading Manual (thank you Spud!) just to see how it compares ballistically to the other sixes.

 

Now, here's a strange thing! Despite them using 24" barrels and 6-284 26", the XC supposedly produces higher MVs (significantly) than say the 243 Winchester while using less powder (equally significantly!). In fact ..... if you believe the data (I don't) ..... 6XC outperforms 6-284 marginally with 105gn bullets, and that's despite having two inches less barrel to play with!

 

Highest maximum load MV

 

6XC ....... 42.8gn Ramshot Hunter ..... 3090 fps (105gn + 108gn combined)

243 Win ... 45.6gn Re25 ............... 2938 fps (105gn, 108 has separate table)

6mm Rem ... 47.1gn AA-Magpro .......... 2997 fps (105gn, 108 has separate table)

6-284 Win . 49.6gn IMR-7828ssc ........ 3080 fps (105gn, 108 has separate table)

 

All are shown as 24" barrels bar 6-284 which is 26"

 

Wow - what a wonderful cartridge, only it CANNOT be correct. My assumption is that the XC was tested in a much longer barrel, but there could be several reasons for these strange results. I'll email Berger in due course and query them.

[gbal]

Having had my interest in the XC jolted, I thought I'd look at the load tables in the new Berger Reloading Manual (thank you Spud!) just to see how it compares ballistically to the other sixes.

 

Now, here's a strange thing! Despite them using 24" barrels and 6-284 26", the XC supposedly produces higher MVs (significantly) than say the 243 Winchester while using less powder (equally significantly!). In fact ..... if you believe the data (I don't) ..... 6XC outperforms 6-284 marginally with 105gn bullets, and that's despite having two inches less barrel to play with!

 

Highest maximum load MV

 

6XC ....... 42.8gn Ramshot Hunter ..... 3090 fps (105gn + 108gn combined)

243 Win ... 45.6gn Re25 ............... 2938 fps (105gn, 108 has separate table)

6mm Rem ... 47.1gn AA-Magpro .......... 2997 fps (105gn, 108 has separate table)

6-284 Win . 49.6gn IMR-7828ssc ........ 3080 fps (105gn, 108 has separate table)

 

All are shown as 24" barrels bar 6-284 which is 26"

 

Wow - what a wonderful cartridge, only it CANNOT be correct. My assumption is that the XC was tested in a much longer barrel, but there could be several reasons for these strange results. I'll email Berger in due course and query them.

 

100 fps extra seldom excites me,especially if there is any special prep needed,but D Tubb reports 115 DTAC @3000 fps before visible pressure signs (and accuracy drop off)but,as you suspect,with 27 and 29 inch barrels.(6br site). Of course,pressures are not formally measured-they never are.As he says,it's a good, competitive cartridge, given the discipline requirements,especially as it is easy to prep and not fussy.

george

[Laurie]

100 fps extra seldom excites me

 

Nor me, but this discrepancy interested me at an intellectual level. Internal ballistics results are a combination of combustion chamber capacity (fireformed case + bullet position when moved forward into the rifling by primer ignition); calibre; bullet weight; powder charge and energy; allowed maximum pressure. We'll assume that we have a powder with the optimal burning rate characteristics to suit the capacity / calibre / bullet weight combination as that is the big variable in any load combination.

 

The rule of thumb is that if everything else is equal (calibre / bullet weight / allowable PMax / optimal powder / barrel length) an x% change in combustion chamber volume (read case size / capacity) produces an x% divided by 4 change in MV. This also assumes that neither of the setups being compared are seriously under or over-bore capacity as there comes a point where increasing case capacity and powder charge weight makes virtually no change to the results because the resulting combination is so inefficient.

 

6XC has a water capacity of 49.7gn weight, 50gn in round terms. 243 Win is nominally 54gn, 8% larger, and 6-284 is ~66gn, 32% larger. You would expect 243 to produce a modest MV increase of around 2% on the divide % change by four rule, but a rather more significant 8% change in favour of the 6-284. If we take 3,000 fps as our starting point with 105s in this class of 6mm cartridge, the 243's extra case capacity only provides a modest 60 extra fps. Like GBal, that sort of change doesn't excite me one way of the other.

 

6-284's extra capacity and charge weights should provide ~8% more velocity or 240 fps, which starts to be very significant. Of course barrel wear and tear increases too - and by MUCH MORE than 8% - absoulutely no free luch here. In practical terms, we almost certainly don't get an 8% increase anyway as the 6-284 is getting rather over bore capacity and is almost certainly less efficient than the 6XC or 243. Even so, it should produce a substantially higher MV than the XC even before it's given two extra inches of barrel.

 

Taking the 'assuming all other things are equal' issue, they're not in this trio as 6XC has an allowable PMax of 65K psi, 243 is nearly 5K below that, but 6-284's parent 284 Win is only a little down at 63,817 psi. Even so, 6XC shouldn't be such a big 'winner' here.

 

Anyway, I ran Berger's fastest load combinations through QuickLOAD to see if that threw anything up. The Ramshot Hunter load in the XC was calculated to produce 3,075 fps at 59,981 psi - very much the sort of result you expect from a loading manual where they're not going to quote absolutely max right on SAAMI / CIP PMax values for obvious reasons. QuickLOAD's estimate is also impressively close to what Berger actually got.

 

Run the 243's fastest combination (N560) through and the estimate is 2,935 fps for a very modest 52,268 psi - again QuickLOAD is right on the real life money, impressively so at only 3 fps out! But if Berger's highest performing load only produces 52K psi ...... ?? I'm not a 'speed fiend', but when you run modern cartridges at pressures barely above 50,000 psi, you rarely get great results.

 

QuickOAD doesn't have the 6-284 in its database but taking the 6mm Rem Ackley and inflating its capacity to 66gn water, a load of IMR-7828 that produces Berger's 3,080 fps only produced 47,200 psi PMax - which is very much in line with what I'd expect for this size of cartridge to produce that MV. To use maximum loads in a modern high-performance wildcat whose pressures are not that much more than those of first generation 19th century military cartridges is extremely odd to my way of thinking! Run the charge weight of 7828 up several grains and QuickLOAD says to expect 3,306 fps from a 26" barrel at ~60,000 psi PMax.

 

This is very much theoretical, and you cannot rely on QuickLOAD for all the many stated reasons - especially when you have to 'adapt' another cartridge to get the internal ballistics combination you're looking for. But it does point out why the XC is apparently so 'good' in the manual - for some reason Berger loaded it up a lot more than the others, or to turn it the other way around, supplied maximum loads that are well down on the norm for the others.

 

Apart from the above caveats on putting one's faith in computer models, note that I deliberately stayed at or below 60,000 psi estimated pressures. Mik McPherson pointed out many years ago that claims for home-brewed 'super cartridges' or even some popular wildcats in regular use that allegedly get 200 fps over a similar factory model because they have a 5-degree change in shoulder angle or somesuch minor improvement - simply DON'T. Yes, they get the extra 200 fps, but only thanks to a method of load development that works charges and pressures up until the primer blows then the developer reduces the charge by half a grain saying words to the effect of 'Well, that'll be safe'. Run the cartridge and its final 'safe' load in a pressure barrel and you see any extra velocity comes from running it at proof-plus pressures.

[gbal]

Nor me, but this discrepancy interested me at an intellectual level. Internal ballistics results are a combination of combustion chamber capacity (fireformed case + bullet position when moved forward into the rifling by primer ignition); calibre; bullet weight; powder charge and energy; allowed maximum pressure. We'll assume that we have a powder with the optimal burning rate characteristics to suit the capacity / calibre / bullet weight combination as that is the big variable in any load combination.

 

The rule of thumb is that if everything else is equal (calibre / bullet weight / allowable PMax / optimal powder / barrel length) an x% change in combustion chamber volume (read case size / capacity) produces an x% divided by 4 change in MV. This also assumes that neither of the setups being compared are seriously under or over-bore capacity as there comes a point where increasing case capacity and powder charge weight makes virtually no change to the results because the resulting combination is so inefficient.

 

6XC has a water capacity of 49.7gn weight, 50gn in round terms. 243 Win is nominally 54gn, 8% larger, and 6-284 is ~66gn, 32% larger. You would expect 243 to produce a modest MV increase of around 2% on the divide % change by four rule, but a rather more significant 8% change in favour of the 6-284. If we take 3,000 fps as our starting point with 105s in this class of 6mm cartridge, the 243's extra case capacity only provides a modest 60 extra fps. Like GBal, that sort of change doesn't excite me one way of the other.

 

6-284's extra capacity and charge weights should provide ~8% more velocity or 240 fps, which starts to be very significant. Of course barrel wear and tear increases too - and by MUCH MORE than 8% - absoulutely no free luch here. In practical terms, we almost certainly don't get an 8% increase anyway as the 6-284 is getting rather over bore capacity and is almost certainly less efficient than the 6XC or 243. Even so, it should produce a substantially higher MV than the XC even before it's given two extra inches of barrel.

 

Taking the 'assuming all other things are equal' issue, they're not in this trio as 6XC has an allowable PMax of 65K psi, 243 is nearly 5K below that, but 6-284's parent 284 Win is only a little down at 63,817 psi. Even so, 6XC shouldn't be such a big 'winner' here.

 

Anyway, I ran Berger's fastest load combinations through QuickLOAD to see if that threw anything up. The Ramshot Hunter load in the XC was calculated to produce 3,075 fps at 59,981 psi - very much the sort of result you expect from a loading manual where they're not going to quote absolutely max right on SAAMI / CIP PMax values for obvious reasons. QuickLOAD's estimate is also impressively close to what Berger actually got.

 

Run the 243's fastest combination (N560) through and the estimate is 2,935 fps for a very modest 52,268 psi - again QuickLOAD is right on the real life money, impressively so at only 3 fps out! But if Berger's highest performing load only produces 52K psi ...... ?? I'm not a 'speed fiend', but when you run modern cartridges at pressures barely above 50,000 psi, you rarely get great results.

 

QuickOAD doesn't have the 6-284 in its database but taking the 6mm Rem Ackley and inflating its capacity to 66gn water, a load of IMR-7828 that produces Berger's 3,080 fps only produced 47,200 psi PMax - which is very much in line with what I'd expect for this size of cartridge to produce that MV. To use maximum loads in a modern high-performance wildcat whose pressures are not that much more than those of first generation 19th century military cartridges is extremely odd to my way of thinking! Run the charge weight of 7828 up several grains and QuickLOAD says to expect 3,306 fps from a 26" barrel at ~60,000 psi PMax.

 

This is very much theoretical, and you cannot rely on QuickLOAD for all the many stated reasons - especially when you have to 'adapt' another cartridge to get the internal ballistics combination you're looking for. But it does point out why the XC is apparently so 'good' in the manual - for some reason Berger loaded it up a lot more than the others, or to turn it the other way around, supplied maximum loads that are well down on the norm for the others.

 

Apart from the above caveats on putting one's faith in computer models, note that I deliberately stayed at or below 60,000 psi estimated pressures. Mik McPherson pointed out many years ago that claims for home-brewed 'super cartridges' or even some popular wildcats in regular use that allegedly get 200 fps over a similar factory model because they have a 5-degree change in shoulder angle or somesuch minor improvement - simply DON'T. Yes, they get the extra 200 fps, but only thanks to a method of load development that works charges and pressures up until the primer blows then the developer reduces the charge by half a grain saying words to the effect of 'Well, that'll be safe'. Run the cartridge and its final 'safe' load in a pressure barrel and you see any extra velocity comes from running it at proof-plus pressures.

Thanks,Laurie.

I can't quite remember who first noted that the availability of affordable chronographs

had set back claims for wildcat cartridge 'improvements' by several decades.I rather think the same might be true for chamber pressure measurements.Of course there can be some improvements-though just what 100 fps gives the average hunter,or isn't available in another standard cartridge,is often elusive.

 

"In theory,practice is the same as theory,in practice it isn't"

 

But that's as often as not because measures are imprecise,or absent,or assumptions overlooked,'graphs' assumed to be straight line,'rule of thumb' reliable across the range,and beyond,-as you point out very clearly,it ain't neccessarily so!Nor is it because god/physics is perverse,just sometimes complex.Thanks to a Mr A. Einstein,for this valuable insight.Proceed with care.

 

george

[Canadian F-Class Guy]

I have built two 6XC's, one of which I had with a 30" 7.5 twist and the second was an 8 twist 28" Krieger. I have been obsessed with 6mm chamberings for years and I think I have played with nearly everything "conventional", I have also had 6-6.5X47 Lapuas, a 6-22-250 and most BR variants too, so I think I am comfortable making some comparisons.

 

The 6XC is a very easy cartridge to make work, at least with 105-108 grain bullets. My experience showed that getting 105 Hunting VLD Berger bullets up to 2950 was very easy, using roughly 37 grains of H4350; as always I found the Berger VLD bullets loved 10-15 thou jam into the rifling. Precision was very good with this being a solid .2-.3 capable set up.

 

In the 7.5 twist, I also had excellent results with 105 Hunting VLD bullets, and except for different COAL, they loads were identical. However, I did the 7.5 twist with the intention of using the 115 berger VLD bullets. David Tubb extols the virtues of the 117 DTAC, but these are nearly impossible to get in Canada - or were. I have found the 115 Berger VLD to be an enigma; it has always been a difficult bullet to make work well and I cannot figure out what I am doing wrong, because I know the bullet works well for others. That being said, despite delving into numerous different powders, I was never able to make the 115 bullet produce anything better than half minute results, so I stuck with the 105's.

 

Component availability has been a challenge. Brass choices are the excellent (and expensive) Norma brass, or the Tubb brass. Both of which have been difficult to find in quantity until recently, however I did make a number of cases with lapua 22-250 brass. these worked well except there is a sacrifice in terms of neck length. I use the Redding 6mmXC Micrometer seater die and Tubb's FL/Bump/bushing die

 

My new darling 6mm is the 6mm Swiss Match. This is almost unheard of in Canada, and there are no domestic sources for brass. I had custom dies made and of course I was able to order a reamer from JGS in the US. It is the equal to the 6XC in almost every regard. It is elegant, extremely precise and it works.

 

Berger has changed things up a little with the introduction of their new 105 grain Hybid bullet. The BC on these is exceptional and comes very close to the 115 VLD. With the lighter bullet having equal ballistics to the 115, I have lost any impetus to find a way to launch 115 grain bullets.

 

So to sum up my own personal experience with the 6XC, it worked best with 105 grain bullets, it was easy to make work and it is very precise. Its ballistic near-twin is the 6mm Swiss Match. Sitting off to the side lies the 6mm Dasher. Not quite the velocity, but oh so easy to make work and so incredibly precise.

 

As an aside, I have also had two 6-6.5X47 Lapuas in a 7 twist and an 8 twist. Both drove me to drinking. I could NOT for the life of me make these produce F-Class results. Again, no idea why, because accoring to many on the internet (mind you, I have not MET anyone) this cartridge works well for others. I bashed together catrifges with 6XC brass to see if the flash hole was the culprit and it was not. Just bad mojo I guess.

 

cheers!

 

Ian

[The Gun Pimp]

 

My new darling 6mm is the 6mm Swiss Match. This is almost unheard of in Canada, and there are no domestic sources for brass. I had custom dies made and of course I was able to order a reamer from JGS in the US. It is the equal to the 6XC in almost every regard. It is elegant, extremely precise and it works.

 

 

cheers!

 

Ian

 

Hi Ian,

 

I'm a Swiss Match fan also. Forming the cases from 6.5x47 Lapua using the small primer pocket permits far higher m/v than with the genuine SM Ruag brass. I'm running a 270 neck and using 105gn Bergers at almost 3200fps using a powder we call Elcho 17 which is supposed to be close to RL 17. Huntington's supplied my FL die and I'm using Wilson dies to neck-size and seat.