Whitley Creates Accurate 6mm Cartridge with 22-250 Lapua Brass
Our friend Robert Whitley of 6mmAR.com has come up with a new, accurate 6mm wildcat based on the new Lapua 22-250 brass that has just started arriving. Robert provides this report:
“I just received a box of the new Lapua 22/250 cases — beautiful brass! My real desire with it was to make it into a 6mm version, preferably something that was ‘no neck-turn’ with a .308 Win-type body taper that would work well in bolt gun and semi-auto magazines and would have a capacity to allow superior velocities. I considered the 6XC, but since you have to bring a whole lot of the shoulder of the brass up into the neck (when you re-form the brass from 22-250 to 6XC) that would necessitate neck-turning it because with Lapua brass the shoulder metal is thicker than neck metal of the brass.
I wanted a simple ‘neck it up and shoot it’ approach so I made up a 6mm-250 Improved 30 cartridge (i.e. 6mm-250 Improved with a 30 degree shoulder) and this thing works great — just neck up the brass, load it and shoot it! The case is like a 6XC with a .030″ longer body and a .030″ shorter neck, which works out fine if you are going to be shooting mainly the 105-108 gr bullets (which it will do very well shooting 2950 – 3000 fps). If you want to hot-rod things, which I do not, I am certain the case can push the 105-108 gr bullets a fair amount faster.
I set it up and throated the reamer for the Sierra 107s and the Berger or JLK 105 VLDs (i.e. a .090″ free bore on the reamer) and it works great with them. If I was going to use it with the Lapua 105s or the Berger 108s I would add about .025″ – .030″ to the freebore of the reamer (i.e. make the freebore around .115″ to .120″).
The great thing is you can use a 6XC die set for it without modification, and all you need to do is keep the dies about .030″ up off the shell holder from their normal position and use them as is. You can make a spacer washer about .030″ thick that you can put on and take off the 6XC dies and use the dies for both cartridges (i.e. 6XC and 6mm-250 Imp 30).
6mm-250 Imp 30 Shows Great Accuracy
Fire-forming loads are real accurate. Here is a 10-shot group I shot prone at 100 yards shooting fire-forming loads with it — the group is the size of a dime. For fire-forming I use a milder, but still very accurate load: 32.0 grains of N140 with a Sierra 107 and a BR2 primer. For fire-formed cases you can jump up to N160 (around 38-40 grains — depending on lot) and it will push the 105-108 gr bullets real accurately in the 2950-3000 fps range, with low ES and SD. This cartridge has a neck length of .268″ which is plenty long for a 6mm shooting bullets with varying bearing surface lengths. The reamer diagram (link below) leaves about a .003″ neck clearance over a loaded round, which seems to work out very well for a ‘no-turn neck’ set-up.
So there you have it … the 6mm-250 Imp 30 is simple, easy to make, accurate as all get out, there are available factory die sets you can use, and it uses great new Lapua brass — what’s not to like!”
CLICK HERE to download Whitley 6mm-250 Imp 30 Reamer Print.
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Tags: 22-250, 6mm, 6XC, Lapua Brass, Wildcat
That is very very close to the 240NMC
Why didn,t you use the 240 NMC? Hornady makes dies for it. A bunch of people have been shooting it for years.
I’m rather new at this, but I couldn’t help but wonder why not use .243 brass?
When it comes to the 6mm cartridge, the BRX is head and shoulders above everything else. It provides the perfect combustion chamber for the 105-108 bullet weight and does it so efficiently that you never need to clean the primer pockets. Plus, and no offense meant here but if my BRX shot a group like that I would be trying to figure out what was wrong.
The article states that 10 shot group was shot prone, that more than likely means with a sling. How could you complain about that kind of accuracy? Man!
This cartridge isn’t very original, but it is a good design for high power guys. I don’t think he’s trying to set the world on fire with his brand of cartridges but just tweak existing ones that suit for what highpower guys need. Lapua brass should hold up great too.
Rick–
I’m also a fan of the 6 BRX, but Robert is looking for a highpower cartridge that can feed well from a magazine. As far as accuracy goes, Robert typically tests the way he shoots matches — prone (no rest), with iron sights. I don’t know if he was using irons here.
With all due respect to everyone, Rick Curtis is one of the very best prone shots in the USA. He shot a 1600 clean within a moth of taking up smallbore prone. He is is a Distinguished Rifleman in smallbore, and a High Master in Long Range.
Robert is a fine long range rifleman, and so am I on a given occasion. But, we are not even in the same league with the prone knots that Rick Curtis can lay down. Having said that, Robert’s prone group is a mighty fine one.
Jim Hardy
Sorry if I offended anyone with my lack of tact! I just got excited cause’ all I seen was criticism of the efforts of a fellow long range shooter trying/experimenting, I thought that was what this was what our sport was all about? I sure don’t have the track record as some of you guys, but maybe your constructive criticism may help, if its directed in a helpful way.
Tanner:
I just wanted to explain who Rick is to the BR community as some on this board may not have heard of him. He is an exceptional prone/sling rifleman on an International level.
Of course, Robert is a regular contributor to this board, and he needs no introduction as a rifleman or cartridge tester.
And you are correct, the cartridge described may not be new at all, but thanks to Robert for bringing attention to this fine old wildcat. It sure got my attention, and I have a barrel in the safe that may like it.
I remember when a few competitors used to shoot this version of the .243 in 1000 yd BR at Hawks Ridge (as an alternative to the 243 AI), and they did very well indeed.
In fact, it seems like all of the chamberings based on the original 6BR and the 243 have done very well. Robert has made some other twists to the basic 243 which may be even better.
Favor center,
Jim Hardy
Wow that posting of Rick Curtis is bizarre! A 56 year out of shape guy with bad eyesight (me) takes a new wildcat and with fire forming loads with almost no load work up in a Remington 700 magazine feed high power match rifle, in prone with a sling shoots a perfect 10x clean (actually I shot 2 in a row with it for a 200/20x but the second group was slightly looser due to more pulse and body movement) and Rick says the new wildcat’s a loser to a 6mm BRX – New one on me!
Robert Whitley
This cartridge should make an outstanding varmint/predator hunting rifle. With the exception of utilizing a shorter freebore for lighter varmint bullets (65-87 gr.) with a 1-12 twist barrel. I belive Robert Whitley has come up with a most excellent cartridge design which is easy to make and should give long case and barrel life and excellent accuracy. Kudos to Robert on this cartridge design. It will probley be my next long range varmint rifle.
I have a Fred Sinclair 6×250 with a 270 neck sitting on a Sako L579 receiver. I have learned how to create the shells from Nora brass thinning the neck to fit the 270 neck. To my understanding there are a few of these exact riffles that were made in the 70s by Fred Sinclair & his apprinteses. Ive been told that one of Mr. Sinclairs apprinteses to this day still does long range competition with this exact same riffle. I’m looking for bullet and powder loads for the best accuracy. I believe my Barrel is an 11 & 1 twist. I know that’s odd but doing the tape on a gun cleaning Rod that is what I ended up with. Would appreciate someone’s help to be able to create really good varmint and possibly deer bullets or long distance shooting bullets for this riffle. Thank you