The 6UM

[khuber84]

@Ryan Avery what will this improved version net over a standard 6 Saum? Reason I'm asking, a friend has a standard 6saum reamer, and I already have 65 Saum bushing dies. My fired adg 65 Saum hold near 73gr capacity, so there isn't a lot of capacity gained here, but I'm aware of the geometry of less taper and 40° shoulders do hide pressure. I'm just curious if there is much advantage re-tooling with new dies/reamer.

 

[Nbowlin]

Have your guy leave the barrel on the unfinished long side. Test and cut until you are happy with the achieved speed.
Barrel length vs fire forming.

 

[khuber84]

Have your guy leave the barrel on the unfinished long side. Test and cut until you are happy with the achieved speed.
Barrel length vs fire forming.

It's a Bartlein carbon, so finished length isn't very adjustble. I'd probably have him cut the muzzle as short as possible to carbon shoulder and finish around 25". I also have a 4 groove 3b steel 7tw, but I fear that'll be a jacket smoker. Gonna have to get me some these deep ringed dtacs, prob gonna order a few k of them. Should we organize a group buy to get then at the desired dpeth cut?

 

[Ryan Avery]

@Ryan Avery what will this improved version net over a standard 6 Saum? Reason I'm asking, a friend has a standard 6saum reamer, and I already have 65 Saum bushing dies. My fired adg 65 Saum hold near 73gr capacity, so there isn't a lot of capacity gained here, but I'm aware of the geometry of less taper and 40° shoulders do hide pressure. I'm just curious if there is much advantage re-tooling with new dies/reamer.

I will have to look, but when I measured the SAUM case necked down to 6mm before FF, I think it was 70g of H2O from what I can gather from the internet. It looks like it beats the 6 PRC by 150 FPS. Please don't quote me on that; I don't have first-hand numbers.

You AI for more than just case volume. You also get a better case design. You slow down case stretch, and if you believe PO Ackley, you get a better combustion process.

 

[khuber84]

I will have to look, but when I measured the SAUM case necked down to 6mm before FF, I think it was 70g of H2O from what I can gather from the internet. It looks like it beats the 6 PRC by 150 FPS. Please don't quote me on that; I don't have first-hand numbers.

You AI for more than just case volume. You also get a better case design. You slow down case stretch, and if you believe PO Ackley, you get a better combustion process.

Better combustion may have had something to do with the prehistoric powders from his era. I understand the less stretch, the square ish design, chamber grip, I've had a few Shermans.....unfortunately. The case's squared off case geometry may be worth 50-75fps, nothing more, I choose to no longer get my hopes up, or have expectations. I will call jgs Monday and order a reamer. That's a 3 month wait, how long to wait on a sizing die? I'm sure my old 65 Sherman max seater will do just fine with a 6mm stem. In fact, I do have 200x pcs or adg 65max brass sitting new in box, will test some of these to fireform with.

 

[Ryan Avery]

Better combustion may have had something to do with the prehistoric powders from his era. I understand the less stretch, the square ish design, chamber grip, I've had a few Shermans.....unfortunately. The case's squared off case geometry may be worth 50-75fps, nothing more, I choose to no longer get my hopes up, or have expectations. I will call jgs Monday and order a reamer. That's a 3 month wait, how long to wait on a sizing die? I'm sure my old 65 Sherman max seater will do just fine with a 6mm stem.

I also knew I would +P them in the future and wanted a little more volume... I am building a 16" now that will be +Ped I hope to get 3200+.... that poor barrel. HAHA!

 

[khuber84]

I also knew I would +P them in the future and wanted a little more volume... I am building a 16" now that will be +Ped I hope to get 3200+.... that poor barrel. HAHA!

N570 will turn that shorty into a blow torch. Even with a can it'll be a fire hazard.

 

[Mountainrancher]

N570 will turn that shorty into a blow torch. Even with a can it'll be a fire hazard.

Anything you shoot inside 100 yards with it will be tenderized by that soft splashy match bullet and cooked to medium rare but the fireball leaving the barrel.

 

[khuber84]

What's the taper after the Ackley treatment? Traditional 0.010/inch? I know the Sherman designs are 0.0068/inch.

 

[PathFinder]

6 UM +P is alive. Still a lot of finishing touches to put on the rifle. Bedding, paint, adjust bottom metal, bolt handle, etc. But it's alive and showing lots of promise. It will stay like this through bear season and then I'll put the finishing touches on.
The big dot is two sighters with a FF load.
Below that is 67-69 grains in 1/2 grain increments. 67 is the one top left. All left faint ejector marks, 69 cratered the primer a bit. Right bottom dot is 3 at 68.3 grains. No chrono right now but I'll take it to 1k tomorrow and get a good estimate.
Loads are N570 with CCI 250 primers.
So far it's been very easy to load for. Necks need a swab of graphite or One Shot for their first seating or two.
Recoil is basically negligible. Shooting at 100 I was able to watch hits on 14x.

Sent from my Pixel 6 using Tapatalk

 

[Deerfield]

6 UM +P is alive. Still a lot of finishing touches to put on the rifle. Bedding, paint, adjust bottom metal, bolt handle, etc. But it's alive and showing lots of promise. It will stay like this through bear season and then I'll put the finishing touches on.
The big dot is two sighters with a FF load.
Below that is 67-69 grains in 1/2 grain increments. 67 is the one top left. All left faint ejector marks, 69 cratered the primer a bit. Right bottom dot is 3 at 68.3 grains. No chrono right now but I'll take it to 1k tomorrow and get a good estimate.
Loads are N570 with CCI 250 primers.
So far it's been very easy to load for. Necks need a swab of graphite or One Shot for their first seating or two.
Recoil is basically negligible. Shooting at 100 I was able to watch hits on 14x.

Sent from my Pixel 6 using Tapatalk

I like! I’m becoming more and more convinced that I need a 6UM.

 

[Ryan Avery]

6 UM +P is alive. Still a lot of finishing touches to put on the rifle. Bedding, paint, adjust bottom metal, bolt handle, etc. But it's alive and showing lots of promise. It will stay like this through bear season and then I'll put the finishing touches on.
The big dot is two sighters with a FF load.
Below that is 67-69 grains in 1/2 grain increments. 67 is the one top left. All left faint ejector marks, 69 cratered the primer a bit. Right bottom dot is 3 at 68.3 grains. No chrono right now but I'll take it to 1k tomorrow and get a good estimate.
Loads are N570 with CCI 250 primers.
So far it's been very easy to load for. Necks need a swab of graphite or One Shot for their first seating or two.
Recoil is basically negligible. Shooting at 100 I was able to watch hits on 14x.

Sent from my Pixel 6 using Tapatalk

Yes!

 

[4th_point]

Thanks for sharing, Ryan and formi.

I appreciate the outside the box thinking compared to preconceived notions that exist in the hunting community. You've got improvement aspects in terms of internal, external, and terminal ballistics all rolled into one project.

And Ryan, I thought that you were a medium bore magnum proponent?!

 

[khuber84]

Reamer ordered, 7.5tw hawkhill rem varm blank en route. Will be on a zermatt origin medium, McMillan game warden 2.0 long range, hawkins hunter dbm. Have some the components in hand already, reamer will likely be longest wait. Would like to run suppressed so will probably finish around 23". Has anyone tried ramshot LRT, Rl33, Retumbo, or 8133 in the 6UM? I do love N570 but man that stuff is like a cutting torch to chamber throats.

 

[IrkedCitizen]

1500 Deep cut 115gr DTAC TBN coated bullets ordered. Smith is waiting on reamer. Should be 3 weeks. Barrel is in stock and ready to go once reamer arrives.

My build will be:
Zermatt TL3 long action
Trigger Tech Diamond
Osprey/PVA barrel 18" 7tw 6 groove 1.200" straight, LRI Murder Hornet fluting
MDT HNT26 Folder/ARCA chassis
MDT 300prc 5 round magazines
Atlas bipod
Might throw a Ti Pro muzzlebrake on there until I get my suppressor approved. Especially since they just came out with a 1.200" straight 6mm.

I'm going to use n570. Let's burn some barrels!

 

[khuber84]

1500 Deep cut 115gr DTAC TBN coated bullets ordered. Smith is waiting on reamer. Should be 3 weeks. Barrel is in stock and ready to go once reamer arrives.

My build will be:
Zermatt TL3 long action
Trigger Tech Diamond
Osprey/PVA barrel 18" 7tw 6 groove 1.200" straight, LRI Murder Hornet fluting
MDT HNT26 Folder/ARCA chassis
MDT 300prc 5 round magazines
Atlas bipod
Might throw a Ti Pro muzzlebrake on there until I get my suppressor approved. Especially since they just came out with a 1.200" straight 6mm.

I'm going to use n570. Let's burn some barrels!

Feeding the 2.9" case from a 3.85 mag could be tricky. I do believe hawkins makes spacers for the long mags for short mag use in the 3.25" max coal range. These were intended for wsm and Saum cases with heavy long bullets with proper freebore.

 

[IrkedCitizen]

Ryan said it shouldn't be a problem. We will see how it goes.

 

[Rooggvc]

6 UM +P is alive. Still a lot of finishing touches to put on the rifle. Bedding, paint, adjust bottom metal, bolt handle, etc. But it's alive and showing lots of promise. It will stay like this through bear season and then I'll put the finishing touches on.
The big dot is two sighters with a FF load.
Below that is 67-69 grains in 1/2 grain increments. 67 is the one top left. All left faint ejector marks, 69 cratered the primer a bit. Right bottom dot is 3 at 68.3 grains. No chrono right now but I'll take it to 1k tomorrow and get a good estimate.
Loads are N570 with CCI 250 primers.
So far it's been very easy to load for. Necks need a swab of graphite or One Shot for their first seating or two.
Recoil is basically negligible. Shooting at 100 I was able to watch hits on 14x.

Sent from my Pixel 6 using Tapatalk

What stock is that your running?

 

[Ryan Avery]

Reamer ordered, 7.5tw hawkhill rem varm blank en route. Will be on a zermatt origin medium, McMillan game warden 2.0 long range, hawkins hunter dbm. Have some the components in hand already, reamer will likely be longest wait. Would like to run suppressed so will probably finish around 23". Has anyone tried ramshot LRT, Rl33, Retumbo, or 8133 in the 6UM? I do love N570 but man that stuff is like a cutting torch to chamber throats.

Tried
RL26
RL33
RL 19
RL 16
RL 23
IMR 4831
H 4350
VV560
VV565
VV570

Nothing touches 570 in speed. I might try RL 19 again in a +P.


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[Ryan Avery]

Ryan said it shouldn't be a problem. We will see how it goes.

It fed fine in a Tikka LA, 3.95 in UM bottom metal and standard LA mag in M5 bottom metal.


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