6UM alternative

[rifletuner]

The 6-284, 6-6.5 PRC, 6-06, 240 Wby all have pretty much the same case capacity right around 66-67gr H2O depending on brand of brass and if you measure it new unfired or after its been fired. The 6-06AI has a little more then those others and is real close to the same as a 6 RSAUM they hold about 71-72gr H2O. The 6UM and 6-6.8 Western are near twins at about 75gr H2O then the 6 WSM has a little more boiler room at 78-79gr H2O.

The SAUM, UM, WSM, and Western will all need a mag bolt face while those others use a standard bolt face size. Most of them will work in a short or Tikka size action but except the 240 Wby or anything based off the 06 case, those two need a long action.

Generally, more case capacity means more velocity but once you get to a certain point of overbore, unless you plan to run exceptionally long barrels, there is a point where you start seeing little increase in velocity for the amount of powder being used.

IMO, the 243Win/6 CM size cases which is right around 51-53gr H2O is kind of the "easy button". They do everything pretty well, are easy to load for, and have pretty decent throat/barrel life. If you want more velocity then either of those the 6-284 and 6-6.5 PRC are also pretty easy peasy. That's not to say that any of the others are difficult per say but like most things it's all about trade offs.

With ADG making quality brass for the 6.8 Western I can see that becoming a very popular case to build 6mm, .257 and .264 wildcats off of.

Why wont a 240WBY or 6-06 fit in a Tikka action? Or are you just saying it will limit the seating depth of the bullet in these actions?

 

[B23]

Why wont a 240WBY or 6-06 fit in a Tikka action? Or are you just saying it will limit the seating depth of the bullet in these actions?

You can certainly use a Tikka you'll just have to seat the long heavy for caliber bullets deeper in the case.

 

[Formidilosus]

You can certainly use a Tikka you'll just have to seat the long heavy for caliber bullets deeper in the case.

What’s the coal of a 6-06 with a 115gr DTAC, 108gr ELD-M, etc. seated with the boattail at the neck/shoulder junction?

 

[eLightfoot]

I think the sweet spot is 6rem. But the brass situation sucks. The most over looked opportunity is a wildcat off 6.5x55 lapua brass. Widely available and just a tad over $1 a piece. 22 and 6mm improved versions would haul ass. If you’ve got a tikka or LA donor

 

[AZ_Hunter]

I think the sweet spot is 6rem. But the brass situation sucks. The most over looked opportunity is a wildcat off 6.5x55 lapua brass. Widely available and just a tad over $1 a piece. 22 and 6mm improved versions would haul ass. If you’ve got a tikka or LA donor

The x55 or x57 Mauser cases improved with modern bullets…. It’s funny you posted that, I was thinking about that yesterday. That would be neat.

 

[B23]

What’s the coal of a 6-06 with a 115gr DTAC, 108gr ELD-M, etc. seated with the boattail at the neck/shoulder junction?

I don't have either of those but if I recall the Berger 115's were right around 3.35 in my 6-06AI which is built on a LA Stiller. Are those 115 DTAC's longer then the Berger 115's?

You probably know the answer to this better then me but aren't the 06 length Tikka factory mags somewhere around 3.3 OAL? Using UM's detach mag setup would give plenty of length though.

 

[3gunyotehtr]

112 Matchburners are 3.42 in my 6mm-06, neck/shoulder junction.

 

[wyosam]

I think the sweet spot is 6rem. But the brass situation sucks. The most over looked opportunity is a wildcat off 6.5x55 lapua brass. Widely available and just a tad over $1 a piece. 22 and 6mm improved versions would haul ass. If you’ve got a tikka or LA donor

I’m thinking improved to 30* and calling it the 6 Swedemoor.


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[eLightfoot]

I’m thinking improved to 30* and calling it the 6 Swedemoor.


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30 or 35 and leave the taper for slick feeding. I read about people doing this and they just ran a 6br reamer extra deep. But a straight 6swede wouldn’t require custom dies and still be plenty fast.

 

[DangerRanger]

Is the recoil of the 6prc/6um etc really this close to a boring old 6.5prc with a 130?

 

[roosiebull]

I've been following most of the 6UM scuttle, as well as 6-6.5prc, 6 saum, 6-7prc and 6UM 30⁰. I've read the pros and cons and variations of them. It's all a lot of fun. I find myself wanting to build a fast 6 but I find myself more willing to loosen the reigns on some of the constrictions on its design parameters. Cutting to the chase how about a 6-270 wsm?

ADG produces the brass.
35⁰ degree shoulder out of the box.
Not much more to neck down than the 6.5.
ADG lists case capacity essentially the same as their 7PRC at about 80 grains.
Only .085" longer case than the 6.5 SAUM and is .180" shorter than the 7prc.

Being ADG the brass is the same quality as all of the other chamberings being discussed. To those opting for the 30⁰ shoulders to avoid forming, the 35⁰ should be desireable. You're starting out with as much capacity as you'll need. I do like the shorter fatter cases myself. I don't care if it fits in a short action and I'm not a short barrel guy so with this kind of capacity a 22-24" barrel should provide more than enough speed and still carry suppressed. 270 wsm brass availability isn't as good as 7prc but at any given time it's not like 6.5saum brass availability is much better. Find 200 pieces and you have enough for the expected barrel life and I can buy 270wsm in ADG right now. Like those who have saum or prc bushing dies if you already have wsm bushing dies, you buy a few more bushings and you're off. The recoil calculators will report a higher numerical value of recoil from the 6-270wsm than the 6UM. With a brake or can would you know the difference without having both rifles in front of you?

To wrap it up, I want 6UM performance without having to form and I dont want custom dies. I first gravitate to the "regular" 6 saum with a 24" barrel but I don't own saum dies so I dug through ADG and Lapua's website to see what other chamberings are being offered if I'll be starting from scratch and ran into the 270wsm. I already own 300wsm bushing dies, the 35⁰ shoulder is improved over the 30⁰, brass quality is equivalent, case capacity is there (albeit perhaps a tad wasteful) and the neck down is less than the 7mm. Can't wait to here some comments.


Adam

6RC (rock creek) starts off with a viable name at least

The hot rod 6’s is certainly hard to ignore, but my practical side makes me realize I’m not a great candidate because of the ranges I shoot/am willing to shoot.

I do enjoy the whole 6mm conversation though, and the really quick 6’s have made me forget about the rifle I’ve always wanted, but there is no factory rifle i want it in (257wby)

If I can’t shake the speed bug, I will be going with one of the quick 6’s, probably the creed for simplicity. First I need to get an arc so my daughter has a good elk option, but my next personal rifle will be one of the quick 6’s

 

[6mm Remington]

I think the sweet spot is 6rem. But the brass situation sucks.

Amen to that. My son has two rifles in 6mm Remington and I have one which is a Ruger 1B. Love the rifle and the cartridge. My son shot his first elk with his 6mm Remington. He was a pretty tickled young man that day. Hornady is making excellent 6mm Remington brass. I just saw that Scheels here in Missoula has several hundred rounds of 6mm Remington brass. I purchased 150 rounds.

It would be nice if us 6mm Remington fans started pimping Peterson Cartridge company to start making some 6mm brass. Theirs is excellent stuff and I've been trying to wear them down. They chamber some stuff that I cannot imagine is more sought after than 6mm Remington brass, but I guess I am wrong. Help me out you 6mm Remington fans maybe we could make it happen! They have just started producing some 300 WSM brass also. I cannot wait to get my hands on some. I have purchased 280AI and 30-06 from them and it is excellent stuff.

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[Grizzle]

A 6 rem ai would be pretty sweet but unless someone made good brass it's probably not worth the squeeze over 6cm

 

[khuber84]

A 6 rem ai would be pretty sweet but unless someone made good brass it's probably not worth the squeeze over 6cm

6x55 lapua improved, yes brass is available. Custom dies may be needed, but lapua brass is available, will have you around 55-56gr powder cap with a nice long neck.

 

[eLightfoot]

6x55 lapua improved, yes brass is available. Custom dies may be needed, but lapua brass is available, will have you around 55-56gr powder cap with a nice long neck.

I was very interested in this. Lapua x55 is available and cheap. Just too much work to get custom dies n reamers. I’d love a 22 cal with 35degree shoulder on a 55swede case.