6UM alternative

[RockCreekGuy]

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

 

[Tanner]

I’d probably go 6-284 if I was after an easy button as far as brass and dies go. Not as much gas as the 6 UM for sure, but you’d still be pumping 108s over 3200 easily and 115s well over 3100.

Anything to avoid using WSM brass would be a bonus to me.

 

[hereinaz]

I like easy, so I have gone with the Sherman and paid the “premium” for everything. Seems like you can do what you want with this.

 

[RockCreekGuy]

I’d probably go 6-284 if I was after an easy button as far as brass and dies go. Not as much gas as the 6 UM for sure, but you’d still be pumping 108s over 3200 easily and 115s well over 3100.

Anything to avoid using WSM brass would I could see it

The 6.5prc has the same case capacity and less neck to reduce. I could see it if you're not running a mag bolt face and already have dies and brass.

Are you averse to the wsm case design or winchester brass?

 

[Slick8]

Let's narrow it down to Lapua brass and go from there.

Of those, I'd say the 6.5 PRC would be a great fit. IMO, any capacity beyond that holds a lot of diminishing returns.

 

[Ryan Avery]

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

I would look hard at doing a 6PRC.

In the initial testing, the 6-7PRC and 6 WSM seemed finicky and needed more powder to hit a similar velocity as the 6.5 PRC or 6.5 SAUM cases.

 

[Tanner]

Let's narrow it down to Lapua brass and go from there.

Of those, I'd say the 6.5 PRC would be a great fit. IMO, any capacity beyond that holds a lot of diminishing returns.

The 6.5prc has the same case capacity and less neck to reduce. I could see it if you're not running a mag bolt face and already have dies and brass.

Are you averse to the wsm case design or winchester brass?

Agree, if you’re starting from scratch it’s a wash between PRC and 284. But if you’re already working with a .473 bolt I’d go 284 before having it opened up.

I was never super happy with the way my WSM’s fed and the WW brass was not great either. Alton now that you can get ADG brass that would make it slightly more attractive.

284/PRC seems to be a sweet spot velocity wise for the 105-115gr 6mm bullets as I’ve heard of more than a few reports of them getting zooky on game when started at the 3350-3400 range, but it does seem the 115 DTAC nose ring is doing much better at those speeds.

 

[RockCreekGuy]

I would look hard at doing a 6PRC.

In the initial testing, the 6-7PRC and 6 WSM seemed finicky and needed more powder to hit a similar velocity as the 6.5 PRC or 6.5 SAUM cases.

It's funny how that little voice in the back of my head kept reminding me of the stories you've told on the podcast about your friend's daughters crushing elk with 6 creedmoors and keeps asking why the 6prc wouldn't be a good enough step up. It's hard not getting sucked into the game of grinding through the various cases to wildcat in Quickload and being woo'd into larger cases.

 

[hereinaz]

Sherman has 6mm in his universe of SAUM or PRC based cases. Here are rentals for reamers.

6mm Sherman PRC/SI 0.140" FB - 4D Reamer Rentals

Premium Reamer rentals from 4D Reamer Rentals include headspace gauges in addition to the reamer.This all in one package is the best way to get started in these cartridges from Sherman Wildcat Cartridges.

4drentals.com

 

[rharbaugh]

I would look hard at doing a 6PRC.

In the initial testing, the 6-7PRC and 6 WSM seemed finicky and needed more powder to hit a similar velocity as the 6.5 PRC or 6.5 SAUM cases.

Ryan, or anyone, can you please help me with some parlance?

Is the 6PRC a 6.5PRC necked down to 6? (6-6.5PRC?)

and the 6-7PRC is never referred to as 6PRC?


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[realunlucky]

Ryan, or anyone, can you please help me with some parlance?

Is the 6PRC a 6.5PRC necked down to 6? (6-6.5PRC?)

and the 6-7PRC is never referred to as 6PRC?


Sent from my iPhone using Tapatalk

Correct 6/6.5 prc is commonly known as the 6 prc

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[Ryan Avery]

It's funny how that little voice in the back of my head kept reminding me of the stories you've told on the podcast about your friend's daughters crushing elk with 6 creedmoors and keeps asking why the 6prc wouldn't be a good enough step up. It's hard not getting sucked into the game of grinding through the various cases to wildcat in Quickload and being woo'd into larger cases.

Yes, it's hard to know when to say when. But it seems anything much bigger than the 6.5 PRC and 6.5 SAUM case has diminishing returns for the 6mm bullet options we have right now.

 

[TaperPin]

What a fun project! You can’t go wrong with any of your choices. I just noticed 300 WSM Lapua brass at Scheels for the first time in a long while, so that’s a good sign.

I’ve never had major issues with necking down cases - worst case a light pass turning the neck down slightly. In case you’re looking for a decent tubing mic as you check and turn necks, I have the Shars and it measures .0001” (ten thousandths) accurately and repeatably. For $30 it can’t be beat. Mine had a weak spring on the torque limiting knob, but just using it with a light touch made dozens of accurate measurements. For twice the money it looks like RCBS rebrands the Shars.

 

[GoatPackr]

6 prc would be the easy button. No fire forming. Just load and shoot.
I shoot the 6-7PRC.
Things are changing and becoming more available like brass and dies. The 6PRC wasn't as easy 6 months ago and in another 6 months will be even better.

Each of the other cases mentioned are slightly different other than neck size even though they have same name. Example... 6.5 PRC is NOT the same as 7 PRC. 270 WSM is not the same as other wsm cases or SAUM.
Any can be made into a 6mm but probably not going to be as easy as the 6UM 30 deg (6 PRC) when their brass does arrive.

 

[TaperPin]

I have a 6mm-06 and while it isn’t bad, it would be nice to have more speed/bigger case. I don’t know that a 6.5 PRC case is any larger.

 

[ACHILLES]

Have friend that just finished up loading for a 18” 6mmPRC Imp 40*. 108bergers @ 3300fps. I think he said with n565.

 

[Justin Crossley]

I feel that the 6 CM, 25 CM, and 6.5 CM are better overall than burning extra powder for speed you don't need. If you want to hunt farther than those are effective, you can move up to 6.5 PRC or 7 PRC without all the gymnastics.

I used to really like wildcats but not anymore. Now I want the simplest tool that will do the job.

 

[wyosam]

I’ve been thinking of my next 6 as well. Since I like to be different and avoid the easy button, I think I’m going with a 6 Swede (Probably improved). Lapua brass, rhymes with what the cool kids are shooting, should be spicy enough for my needs, and I think I have some Swede 40* bushing dies on a shelf somewhere.


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