6mm SLR vs. 6mm XC

[Brave Echo Niner]

Afternoon All,

I came across a new calibre (to myself) while scrolling through various articles, the 6mm SLR. It has made me consider which calibre I will rebarrel my match rifle to next time.

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The rifle will be used for PRS/long range plinking, so a heavy bullet in 6mm (115 Nosler RDF most likely) at circa 3000FPS with a 26-28” barrel will be the most suitable end result IMO. I am not bothered about factory ammunition availability as I reload but case availability would be a consideration.

Initially I was convinced a 6XC would prove to be the best option, particularly having seen how well some of @Ronin ‘s XC builds shoot. However I am now curious if a 6 SLR would be able to get the velocities mentioned with much lower wear on the brass while keeping a long neck to aid accuracy/consistency.

Any thoughts or first hand experience of the 6mm SLR - is the additional effort in forming cases worth it?

Ben

 

[jcampbellsmith]

I remember reading about the 6mm SLR 15 years or so ago. Clearly it has never caught fire anywhere and I've not heard mention of it in the last five years.
Regards
JCS

 

[Buchan]

Get a .270 Blaser to annoy someone we both know!

 

[Brave Echo Niner]

Get a .270 Blaser to annoy someone we both know!

Unfortunately I have too much self respect!

 

[Laurie]

There are more than a few around. I have one. Dave Wylde (Valkyries Rifles) has the match (long throat) reamer and gauges.

For those who don't know this wildcat, it is a 243 Winchester given a single resizing in the SLR version die which reforms the top end to an identical shape to the XC - ie long neck and 30-degree shoulders. There is also a 6.5 SLR - identical process, but using the 260 Rem or 308 Win as the donor case. (I have a friend who has had a lot of very high F-Class scores and match wins shooting this version with the latest generation of heavy 6.5mm bullets.

Returning to the 6mm version, its designer Robert Whitley (author of a load of hot 6.5 Grendel based wildcats for use in AR-15s) designed three chamber versions - long-throat heavy bullet match version for 115s, (but thanks to the very long case-neck) are still ideally suited to 105-110gn match bullets; a shorter-throat match version for bolt-action 'tactical' / PRS rifles where the cartridges have to fit short-action magazines; an AR-10 version of the second type with large clearances for semi-autos.

As to applications and usability, pros & cons etc are exactly as per the 6XC, but with a bit more case capacity and performance (around 1gn water less than the same brass in standard 243 Win). Its proponents say it gives far less 'throat torching' than the shallow-angle / short-neck 243 case so you get great barrel life plus performance. I'll concede it'll be better than standard 243 loaded to the same pressures shooting the same heavy bullets (but by how much is the question - IME marginal), and poorer than the 6XC as it's a larger case burning more powder at similar pressures.

So, it's a simple trade-off against the XC - a wildcat which you may have trouble sourcing dies for, capable of say an extra100 fps MV, but with an inevitable reduction in barrel life if you use the performance fully. Although case reforming is simple with thin-walled Winchester and R-P brass, reforming Lapua and similar is harder, requires neck-turning and annealing whilst there is excellent ready to use XC brass available.

Whitley's website (AR.com) has gone offline and nobody is saying if his gunsmithing business is still up and running. SLR dies were only made by Redding in the expensive bushing Competition version with Whitley retaining ownership of the design. If Whitley has retired or died, that'll likely be the end of the SLRs.

 

[Border]

There are more than a few around. I have one. Dave Wylde (Valkyries Rifles) has the match (long throat) reamer and gauges.

For those who don't know this wildcat, it is a 243 Winchester given a single resizing in the SLR version die which reforms the top end to an identical shape to the XC - ie long neck and 30-degree shoulders. There is also a 6.5 SLR - identical process, but using the 260 Rem or 308 Win as the donor case. (I have a friend who has had a lot of very high F-Class scores and match wins shooting this version with the latest generation of heavy 6.5mm bullets.

Returning to the 6mm version, its designer Robert Whitley (author of a load of hot 6.5 Grendel based wildcats for use in AR-15s) designed three chamber versions - long-throat heavy bullet match version for 115s, (but thanks to the very long case-neck) are still ideally suited to 105-110gn match bullets; a shorter-throat match version for bolt-action 'tactical' / PRS rifles where the cartridges have to fit short-action magazines; an AR-10 version of the second type with large clearances for semi-autos.

As to applications and usability, pros & cons etc are exactly as per the 6XC, but with a bit more case capacity and performance (around 1gn water less than the same brass in standard 243 Win). Its proponents say it gives far less 'throat torching' than the shallow-angle / short-neck 243 case so you get great barrel life plus performance. I'll concede it'll be better than standard 243 loaded to the same pressures shooting the same heavy bullets (but by how much is the question - IME marginal), and poorer than the 6XC as it's a larger case burning more powder at similar pressures.

So, it's a simple trade-off against the XC - a wildcat which you may have trouble sourcing dies for, capable of say an extra100 fps MV, but with an inevitable reduction in barrel life if you use the performance fully. Although case reforming is simple with thin-walled Winchester and R-P brass, reforming Lapua and similar is harder, requires neck-turning and annealing whilst there is excellent ready to use XC brass available.

Whitley's website (AR.com) has gone offline and nobody is saying if his gunsmithing business is still up and running. SLR dies were only made by Redding in the expensive bushing Competition version with Whitley retaining ownership of the design. If Whitley has retired or died, that'll likely be the end of the SLRs.

So reading between the lines go for a 6XC.

 

[scotch_egg]

I would go with a 6mm creedmoor Ben. It’s a hair more powerful than the XC and there is plenty of lapua brass available. @Ronin (who I believe you know ) has a reamer.


As for the 6mm SLR I made something similar by running the top of a .243 through a 6mmbr die. Stopped myself building the rifle my shooting more 6mmbr and just loving the soft recoil of 29gr of powder.

 

[Laurie]

So reading between the lines go for a 6XC.

As I said, it's toss-up depending on your needs and how you rate barrel life vs performance.

That assumes the Redding dies remain available though. The SLR has a lot of off the shelf competition these days - 6mm Creedmoor as @scotch_egg suggests; the XC; coming soon from Lapua the highly-praised in the US 6mm GT (case capacity between 6 Dasher and the 6-6.5X47 Lapua). All four should be capable of superb precision. They all have their merits, but for simplicity and getting tools / components, the SLR comes below the others. I bought my SLR with the dies included basically to have a play with an easily formed wildcat and to try it in mid-range BR and club F-Class. I've yet to see how well it does in those roles.

 

[ColinBr]

I've just had a 6mm XC made by @Ronin

Picked it up last week and even with just the initial first few (13) rounds thru the chamber it is showing very promising results and that's just from factory ammo.

I'm off to the range tomorrow to put a few more rounds down with factory ammo and then start the load development.

I went with 6XC over the Creed due to the barrel and brass wear you get with the Creed, having heard it'll do the cases in 6 loads compared to the XC which has been stated to do well in excess of 12 loads.

 

[308tikka]

Dont wish to hijack your thread, but which powder do you intend using to shoot 100/105/108/115 gn projectiles from either 6SLR or 6xc ?

I pick my 6xc up this weekend and will start looking at load dev. I chose 6xc as I have an excellent source of once fired norma brass in tight chambers - and the brass life is meant to be excellent.

 

[ColinBr]

Dont wish to hijack your thread, but which powder do you intend using to shoot 100/105/108/115 gn projectiles from either 6SLR or 6xc ?

I pick my 6xc up this weekend and will start looking at load dev. I chose 6xc as I have an excellent source of once fired norma brass in tight chambers - and the brass life is meant to be excellent.

RS62 is my go to.
Shows optimum burn rate with a good show of speed

I'm using 108gr ELDMs

RS70 is also recommended

 

[Brave Echo Niner]

@Laurie - Ace post and seems to me to indicate the additional performance is unlikely to be worth the effort of sorting the brass etc.

I'm a bit of a snob with brass, so would want to use Lapua, Alpha or Peterson ideally, so neck turning would definitely be a reality of the SLR.

 

[Laurie]

Dont wish to hijack your thread, but which powder do you intend using to shoot 100/105/108/115 gn projectiles from either 6SLR or 6xc ?

Viht N165 and Lovex S071 in SLR. As, internal ballistics wise, the SLR is no different from a common or garden 243 Win, the same powders work for any given bullet weight, so anything in the Viht N160 / H4831 class is usable.

The XC is a smaller capacity cartridge with a lower capacity to bore area ratio, so uses faster burners. When I had one years ago, I got some good results with Viht N550, but pressure kicked in before I hit the 3,050 fps I wanted with 105s (30-inch barrel). Alliant Re17 / RS60 got me there with excellent MVs and results, but ultimately did nothing good for barrel life. If I were working up a load for the cartridge today, I'd probably try the fairly new Viht N555 first.


Edit:

RS62 is my go to.
Shows optimum burn rate with a good show of speed

Yes, agree - it would be an obvious choice for the XC

 

[Brave Echo Niner]

I would go with a 6mm creedmoor Ben. It’s a hair more powerful than the XC and there is plenty of lapua brass available. @Ronin (who I believe you know ) has a reamer.


As for the 6mm SLR I made something similar by running the top of a .243 through a 6mmbr die. Stopped myself building the rifle my shooting more 6mmbr and just loving the soft recoil of 29gr of powder.

Not sure I'm quite at the point in my life I need a creed just yet @scotch_egg!

Although if it's made by @Ronin I have no doubt it'd shoot lights out!

 

[308tikka]

Viht N165 and Lovex S071 in SLR. As, internal ballistics wise, the SLR is no different from a common or garden 243 Win, the same powders work for any given bullet weight, so anything in the Viht N160 / H4831 class is usable.

The XC is a smaller capacity cartridge with a lower capacity to bore area ratio, so uses faster burners. When I had one years ago, I got some good results with Viht N550, but pressure kicked in before I hit the 3,050 fps I wanted with 105s (30-inch barrel). Alliant Re17 / RS60 got me there with excellent MVs and results, but ultimately did nothing good for barrel life. If I were working up a load for the cartridge today, I'd probably try the fairly new Viht N555 first.


Edit:


Yes, agree - it would be an obvious choice for the XC

Many thanks. I have a few thousand 105/108 to get through and its for deer primarily so wont need stonking speeds. Have plenty of rs 60 and can get 555 easily enough-much appreciated chaps.

 

[ColinBr]

Many thanks. I have a few thousand 105/108 to get through and its for deer primarily so wont need stonking speeds. Have plenty of rs 60 and can get 555 easily enough-much appreciated chaps.

Go for the 555 if you can then mate. Keep that barrel sweeter for longer.

 

[Malxwal]

555 works a treat in my 8 twist 243 under 107smk and 103 eldx

 

[swagger700]

I've got enough 105amax and H4350 to last me out. 6xc has impressed me

 

[jcampbellsmith]

Dont wish to hijack your thread, but which powder do you intend using to shoot 100/105/108/115 gn projectiles from either 6SLR or 6xc ?

I pick my 6xc up this weekend and will start looking at load dev. I chose 6xc as I have an excellent source of once fired norma brass in tight chambers - and the brass life is meant to be excellent.

N160 was David Tubb's pick.
Regards
JCS

 

[Ronin]

rS 70 - 105-115 perfect VO and not high energy