The 6UM

[Clownbuster]

From Kurt,

My daughter shot this buck with the 6 UM at 540, one shot, entered right behind right shoulder, no exit or damage on offside, first 115 I have had not exit, hit a rib on the way in. Took out most of the lungs, tore the diaphragm in half and even damage the liver. Pretty unbelievable damage inside.

Sent from my iPhone using Tapatalk Pro

Were these DTAC NRs with the standard cut depth, or a deeper cut NR?

 

[Clownbuster]

Put this one together in the 6 SAUM chamber, 16.5" barrel. Wondering if N570 or RL26 will work, or if something faster burning like N560, H4350 or RL16 would work better. Anyone have short barrel load development intel to share?

 

[PathFinder]

Whitetail buck, distance was 730 yards. Somewhere around 2300 fps impact. Deep cut NR DTACs.
First shot was 13 degrees below me and quartering hard away. Entrance around the last rib. The rest is a little muddled...the buck went down, got up and went about 10 yards, and then went down again. Last couple of shots were through brush to make sure he was going to stay down as he was still trying to move. Deer was mostly broadside at this time, one shot while half-standing, others while laying down. This spot takes a while to get to animals so we try to make sure they aren't going anywhere before we leave to recover them. One shot ended up underneath the ribcage mid-body. Didn't attempt to recover that bullet. One ended up in the offside shoulder and shattered it. That's the small bullet fragment picture. One ended up (I assume) taking a hard turn and exited up through the backstrap with basically zero energy left when it did, that's the stereotypical looking mushroom lying under the hide. Not sure which shot that was, being in a hurry I didn't take the time to figure it out. One neck shot only hit the windpipe and a tiny bit of muscle, it basically penciled through and I believe the deer was already expired when that one hit.
Conclusions: At this velocity the deep cut NR DTACs appear to be fragmenting/expanding well. The bullet that hit the offside shoulder was very fragmented. Probably should have taken the time to do a full necropsy but I had an 18ish hour drive home ahead of me and was itching to get started.

1st shot entrance:


Strangely located exit in backstrap. Typical mushroom that probably weighs less than 50 grains

Entrance through onside shoulder

Exit in offside shoulder. This shoulder was completely shattered from the top of the scapula all the way down through the main joint. Lots of small bullet fragments and a pea sized chunk of the core were found.

Small exit hole in offside shoulder

Offside shoulder exit wound again with small bullet fragment referenced above

 

[Ryan Avery]

@Ryan Avery how’s the brass testing going??

Great, ADG is doing a two day run of 6UM in March.

 

[Ryan Avery]

Were these DTAC NRs with the standard cut depth, or a deeper cut NR?

Standard

 

[khuber84]

Can any of the 30° 6UM adg brass testers tell me how much longer the shoulder is on this brass VS the shoulder on their 65saum brass they we're using prior? I'm not wanting to wait till April to cut my barrel to this new brass, if it's 0.006 or 0.008 longer I'll just have my smith go past the go gauge by the difference.

@Unknown Munitions you've likely got prints for 6.5 Saum since you build rifles, I know you've got prints now for the 6saum 30° chamber based on this new brass. What's the difference between the two shoulder datum lines?

 

[andarch]

So brass in the middle of next year, which is no big deal. 6.5 SAUM brass is available, but with no word on the dies, I'm ready to get off 6UM train and just go straight 6 SAUM or PRC.

 

[khuber84]

So brass in the middle of next year, which is no big deal. 6.5 SAUM brass is available, but with no word on the dies, I'm ready to get off 6UM train and just go straight 6 SAUM or PRC.

I will say the 5gr capacity increase of the Saum, gives it a noticeable edge if you're going to run N570. I was only able to get 115 dtacs going 3130 w/ 62gr from my 20" 6prc, 12" drop tube, very full case, minor crunch. My 24in 6saum w/ 66gr N570 goes 3460 with dtacs, but I run it at 3350 with 63.6gr. Yes 4" of barrel and a 5-6gr capacity advantage, but a 330fps difference. Of course these are different barrel manufacture. The saums a hawkhill 237 bore 4gr 7.75tw, the prc is ace 237 bore 4gr 7.5tw. Both using adg brass. I know there aren't a lot of Saum brass options. But the new Hornady stuff isn't bad, I ran one with 147 eldm for 8 firings with H1000 at 3080 from a 26in barrel, and pocket was still holding primers after 8 reloads.

 

[PathFinder]

So brass in the middle of next year, which is no big deal. 6.5 SAUM brass is available, but with no word on the dies, I'm ready to get off 6UM train and just go straight 6 SAUM or PRC.

Order them straight from Whidden. They should show up around the same time or slightly before the brass.

Sent from my Pixel 6 using Tapatalk

 

[Ryan Avery]

So brass in the middle of next year, which is no big deal. 6.5 SAUM brass is available, but with no word on the dies, I'm ready to get off 6UM train and just go straight 6 SAUM or PRC.

SAUM case is the way.

You can order from Whidden.

But ADG is coming out with their own die line at SHOT and will have both 6UM 30 and 6UM 40 degree dies.

 

[Ryan Avery]

Can any of the 30° 6UM adg brass testers tell me how much longer the shoulder is on this brass VS the shoulder on their 65saum brass they we're using prior? I'm not wanting to wait till April to cut my barrel to this new brass, if it's 0.006 or 0.008 longer I'll just have my smith go past the go gauge by the difference.

@Unknown Munitions you've likely got prints for 6.5 Saum since you build rifles, I know you've got prints now for the 6saum 30° chamber based on this new brass. What's the difference between the two shoulder datum lines?

Email [email protected], they will tell you.

 

[khuber84]

SAUM case is the way.

You can order from Whidden.

But ADG is coming out with their own die line at SHOT and will have both 6UM 30 and 6UM 40 degree dies.

View attachment 805666

Is that an 1-1/4" die body or a midget holding a 7/8" die body? Things looks girthy!

I'll contact rifles@Unknownmunitions

 

[Ryan Avery]

Is that an 1-1/4" die body or a midget holding a 7/8" die body? Things looks girthy!

I'll contact rifles@Unknownmunitions

They will all be 1.25

 

[bielenbm]

SAUM case is the way.

You can order from Whidden.

But ADG is coming out with their own die line at SHOT and will have both 6UM 30 and 6UM 40 degree dies.

View attachment 805666

Are they going to be available to buy right after shot show? What is the target price going to be for a 6 um die set?

 

[switchback270]

I reached out to Whidden. 6UM dies were to be shipped to Unknown Munitions this week. So we’ll see.

 

[khuber84]

Any beta testers have a piece of unfired 30° 6um brass that I could borrow to get a shoulder datum measurement on? I'll pay shipping both ways.

I requested info from UM on the shoulder datum line of the 6um 30° chamber print, so I could compare it to my 6/6.5/7/300 Saum prints. They all use the same exact 0.460 datum line, all the same Saum go gauge. All in wanting to know is how much deeper I need to set a standard Saum chamber to fit the 6um 30 brass. Here's UM's response:

"The reamer specs are still in flux. So I can't comment on that at this time. Having said that, those details will likely remain private unless you buy a 6UM reamer.

The 6UM 30 is not just a 6 SAUM. 6UM 30 brass will not fit in a 6 SAUM chamber.

The reamer is now and the dies will be available shortly! We sincerely appreciate your interest.

Thank you"

So from sounds of it, nobody will know the actual difference in headspace between Saum and um30 unless you buy from UM.

 

[IrkedCitizen]

Which is weird since they were open and posted the 6um reamer print from the very beginning.

 

[Clownbuster]

Any beta testers have a piece of unfired 30° 6um brass that I could borrow to get a shoulder datum measurement on? I'll pay shipping both ways.

I requested info from UM on the shoulder datum line of the 6um 30° chamber print, so I could compare it to my 6/6.5/7/300 Saum prints. They all use the same exact 0.460 datum line, all the same Saum go gauge. All in wanting to know is how much deeper I need to set a standard Saum chamber to fit the 6um 30 brass. Here's UM's response:

"The reamer specs are still in flux. So I can't comment on that at this time. Having said that, those details will likely remain private unless you buy a 6UM reamer.

The 6UM 30 is not just a 6 SAUM. 6UM 30 brass will not fit in a 6 SAUM chamber.

The reamer is now and the dies will be available shortly! We sincerely appreciate your interest.

Thank you"

So from sounds of it, nobody will know the actual difference in headspace between Saum and um30 unless you buy from UM.

Same here, would pay for shipping both ways for one piece if someone would be willing. I have 6UM 30° brass on backorder thinking it would chamber fine in my 6 SAUM, but it sounds like I need to cancel it if I can't get a piece to compare to 6.5 SAUM.

 

[wind gypsy]

 

[andarch]

Order them straight from Whidden. They should show up around the same time or slightly before the brass.

Sent from my Pixel 6 using Tapatalk

I ordered the dies back in August from UM, I don't think ordering them from Whidden directly would get them to me faster. However, I've pretty much decided to bail on the 6UM and go 6 SAUM.

I started the project trying to get a DTAC going over 3200 since I couldn't get there in my .243 AI. Looks like the 6 SAUM will easily do what I want and I can use the same dies with a different neck bushing if I decide to do another SAUM down the road (I think 25 SAUM would be fun and I already have a 6.5).

As far as brass I thought the 6 UM brass was just a 6.5 SAUM necked down to 6mm, I'd bet that's the case as that's a relatively simple change to the process compared to a whole new set of case dimensions. A run through the sizing die would fix it anyway.

The whole idea of the 6UM was great when it first came out, buy the reamer (which was not proprietary at first) and take it to your local gunsmith and have them cut a barrel. Now that it's all proprietary it's a tougher proposition.