6 UM Reloading Thread

[PathFinder]

Welcome to the official 6 UM reloading thread. This is the place to log and gather data for the new 6 UM cartridge. Content can range from fire forming to load data to long range external ballistics. The purpose of this thread is to become the reloading data center that will allow new adopters of the 6 UM to get up and running efficiently.
Let's do our best to keep this thread on track and uncluttered. When adding additional load data, contributors should continue to update their original post to make data easier to sort through. Questions are welcome but the primary purpose of the thread is to document data. Terminal data and general discussion should continue on the thread in the Long Range Hunting forum.
When posting, please include rifle specs including barrel maker, chamber type (+P or not), round count, etc.

 

[PathFinder]

I'll kick this off with some fire forming data. I've used two methods so far.

• The first is the same recipe UM has been using. 55 grains of 7828 SSC, with any 105-110 grain 6mm bullet seated at or very near the lands. This results in a very well formed case, with dimensions equal to sized cases from full pressure loads with nice sharp shoulders. This is my recommended method if you don't have a separate fire forming barrel!
• The next method doesn't use a bullet or any case fill whatsoever. I DO NOT RECOMMEND FIRING THIS IN ANYTHING BUT A DEDICATED FIRE FORMING BARREL! 20 gr of Titegroup, and a standard primer. It's very clean and low cost, and can be done at home.
  • The case must remain upright until fired
  • The trick to this method is to lube the case very lightly with a light oil. This allows uniform stretching of the case, rather than stretching at just one spot. See picture below for a case that stretched in just one section because it was inadequately lubed.
    • Be certain to completely degrease both cases and chamber after this method, before firing a round with a projectile! Lubed cases/chamber will increase the shear load on the bolt lugs when a projectile is loaded!
  • This method will cause the barrel to heat up, I ended up cooling mine about every five rounds.
  • Wear ear & eye protection and point it in a safe direction!
  • This results in a case that is 98% fully formed. Shoulder-base measurement matches sized cases from full pressure loads, but shoulders won't be as sharp.
  • When using a dedicated fire forming barrel, 50 cases can be formed in 10-15 minutes.

Pictures in order:

1. Case that wasn't adequately lubricated with no projectile method.
2. Projectile FF case vs no projectile case
3. Measurements of no projectile case, projectile FF case, and case that was projectile FF and then fired with a full load.
4. Cutaway of the improperly stretched case. Surprisingly the stretched section wasn't thinned much. Results look good overall, the brass seems to be handling the fire forming well.

6 UM +P 22" Osprey (6 groove, 1:7) Workup/Velocity Data Summary:
Both magnum or standard LR primers work. Early data suggests that standard primers allow higher powder charges and slightly wider nodes.
Nodes are generally .5-.7gr wide.
N570 is the velocity king. Max charges have very high fill volume, a drop tube is necessary.
H1000 is a great, stable option to put the 6UM cruise control at excellent velocity.
N568 shows some promise at slightly lower velocity than N570. High fill volume.
Staball HD didn't show any obvious nodes and spiked suddenly and somewhat dangerously once compressed at the top end of its spectrum. Be careful with this stuff anywhere near max.
The 108 ELD M will withstand launch from a 7 twist, 6 groove barrel
Workups are in the Excel screenshot below. Green text highlights nodes.

6 UM 24" Bartlein 5R 7.5tw

• This barrel looks to be ok so far. Accuracy is very stable 1MOA-1.5MOA, it's almost completely insensitive to changes in powder charge and seating depth. I'm honestly not impressed with overall accuracy on paper, but these are 10 shot groups and it's ready to go hunting.
• 61 gr of H1000 and a 105 Hybrid is a great cruise control load that should give some more barrel life. Somewhere 61-63 grains with any 103-108 grain bullet should net similar results. It puts the cartridge at or above the upper reaches of a 243 AI at very comfortable pressure and excellent accuracy. Should be somewhere in the mid 3200s.
• It's somewhat dependent on N570 to reach its true potential. N570 really is the magic fairy dust for this cartridge and 115s. Retumbo is the only other powder I'd like to try but haven't yet.
• UM is working to resolve the issue with smaller body sizing dies, but I've got clickers galore by the second firing. Every single round, even low pressure loads. They can be sized and used again. .547" diameter at the last part of the case that the die hits is the cutoff. They really need to be .545" to avoid this issue.
• Fed 215M primers seem to be the ticket. CCI200 let me work up to higher charges and gave higher velocity, but 215M were more accurate and resulted in lower pressure/less severe clickers.
• At just over 100 rounds the barrel should be fully broken in/sped up.
• 

 

[Ryan Avery]

Saved to upload data next week.

AB PDM for the 115 DTAC NR Deep Cut

 

[PathFinder]

Updated with info for the 24" Bartlein. Going to take this load to 1k tomorrow.

 

[amassi]

Why didn’t you +p the second barrel?


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[PathFinder]

Shawn Carlock and Blaine thought it may have been part of why that barrel died so fast.
My own thought was that taking half the rifling out of the throat on a 6 UM wasn't a great idea. Other hot rod cartridges have done fine on barrel life with +P throats so I don't know for sure that it was a problem.
There are others in the wild now so we'll have more data soon. If others don't have any issues I'll +P the next one. I'm convinced my fire forming method was the primary culprit.

Sent from my Pixel 6 using Tapatalk

 

[amassi]

I’d think the clicker issue would be solved with a new reamer print, like the AW2 for the prc and the b series dies for the Sherman wildcats based on the saum cartridges.
Small base dies didn’t work on the prc problem


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[wind gypsy]

Shawn Carlock and Blaine thought it may have been part of why that barrel died so fast.
My own thought was that taking half the rifling out of the throat on a 6 UM wasn't a great idea. Other hot rod cartridges have done fine on barrel life with +P throats so I don't know for sure that it was a problem.
There are others in the wild now so we'll have more data soon. If others don't have any issues I'll +P the next one. I'm convinced my fire forming method was the primary culprit.

Sent from my Pixel 6 using Tapatalk

Lines up with that bartlein thread about a RUM +P dying early.

 

[Doddse1]

Any more updates to the 6 UM so far? Really excited to see some more data/field results.

 

[PathFinder]

Mine is going hunting soon, that is my only update until I start my 18" UL build. I'm waiting on 6mm Ace blanks to do that.
@Ryan Avery may have some updates for his 16.5" barrel.
@Kurt posted his load data in the 6 UM thread.
Long story short, feed it 66 gr N570, 215M, and 115 DTAC in a 7.5 or 8 twist. Chrony, check actual data, and go hunt.

Sent from my Pixel 6 using Tapatalk

 

[wilkup]

Mine is going hunting soon, that is my only update until I start my 18" UL build. I'm waiting on 6mm Ace blanks to do that.
@Ryan Avery may have some updates for his 16.5" barrel.
@Kurt posted his load data in the 6 UM thread.
Long story short, feed it 66 gr N570, 215M, and 115 DTAC in a 7.5 or 8 twist. Chrony, check actual data, and go hunt.

Sent from my Pixel 6 using Tapatalk

Are these shorties to be suppressed or just to keep weight down?
If suppressed is the goal, have you had any issues with the higher velocity blowing out the internals?

 

[Doddse1]

Mine is going hunting soon, that is my only update until I start my 18" UL build. I'm waiting on 6mm Ace blanks to do that.
@Ryan Avery may have some updates for his 16.5" barrel.
@Kurt posted his load data in the 6 UM thread.
Long story short, feed it 66 gr N570, 215M, and 115 DTAC in a 7.5 or 8 twist. Chrony, check actual data, and go hunt.

Sent from my Pixel 6 using Tapatalk

Thanks for the update. I’m really excited to hear about how it goes this season. Very curious about performance on deer/elk at ranges 600-700 yards. I have a tikka donor action and I’m very tempted to do this cartridge or the 6.5 UM.

I’m also really curious about the recoil on an UL build for that cartridge. Listening to the S2H podcast got my mind thinking differently about bullet and cartridge choice for sure as far as shootable cartridges at distance with a lighter recoiling hunting rifle. Obviously lighter than a 9lb scoped 300 PRC but still curious.


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[Jimbee]

If I'm using a 115 dtac nose ring in a 6cm should I put .292 g7 bc in my strelok?

 

[Ryan Avery]

Yes


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[amassi]

Anyone shooting coated Dtacs out of their 6um?


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[Ryan Avery]

Anyone shooting coated Dtacs out of their 6um?


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With the last two rifles I have shot coated DTACS

 

[Formidilosus]

The UM I have is a 20” Benchmark barrel, new UM reamer.

115gr DTAC
66gr N570
Fed 210 primer
2.890” coal
3,250fps MV


112gr Barnes MatchBurner
66gr N570
Fed 210 primer
2.915” coal
3,250fps MV

 

[RogerPa]

I'll kick this off with some fire forming data. I've used two methods so far.

• The first is the same recipe UM has been using. 55 grains of 7828 SSC, with any 105-110 grain 6mm bullet seated at or very near the lands. This results in a very well formed case, with dimensions equal to sized cases from full pressure loads with nice sharp shoulders. This is my recommended method if you don't have a separate fire forming barrel!
• The next method doesn't use a bullet or any case fill whatsoever. I DO NOT RECOMMEND FIRING THIS IN ANYTHING BUT A DEDICATED FIRE FORMING BARREL! 20 gr of Titegroup, and a standard primer. It's very clean and low cost, and can be done at home.
  • The case must remain upright until fired
  • The trick to this method is to lube the case very lightly with a light oil. This allows uniform stretching of the case, rather than stretching at just one spot. See picture below for a case that stretched in just one section because it was inadequately lubed.
    • Be certain to completely degrease both cases and chamber after this method, before firing a round with a projectile! Lubed cases/chamber will increase the shear load on the bolt lugs when a projectile is loaded!
  • This method will cause the barrel to heat up, I ended up cooling mine about every five rounds.
  • Wear ear & eye protection and point it in a safe direction!
  • This results in a case that is 98% fully formed. Shoulder-base measurement matches sized cases from full pressure loads, but shoulders won't be as sharp.
  • When using a dedicated fire forming barrel, 50 cases can be formed in 10-15 minutes.

Pictures in order:

1. Case that wasn't adequately lubricated with no projectile method.View attachment 565517
2. Projectile FF case vs no projectile caseView attachment 565518
3. Measurements of no projectile case, projectile FF case, and case that was projectile FF and then fired with a full load.View attachment 565519
4. Cutaway of the improperly stretched case. Surprisingly the stretched section wasn't thinned much. Results look good overall, the brass seems to be handling the fire forming well.View attachment 565520

6 UM +P 22" Osprey (6 groove, 1:7) Workup/Velocity Data Summary:
Both magnum or standard LR primers work. Early data suggests that standard primers allow higher powder charges and slightly wider nodes.
Nodes are generally .5-.7gr wide.
N570 is the velocity king. Max charges have very high fill volume, a drop tube is necessary.
H1000 is a great, stable option to put the 6UM cruise control at excellent velocity.
N568 shows some promise at slightly lower velocity than N570. High fill volume.
Staball HD didn't show any obvious nodes and spiked suddenly and somewhat dangerously once compressed at the top end of its spectrum. Be careful with this stuff anywhere near max.
The 108 ELD M will withstand launch from a 7 twist, 6 groove barrel
Workups are in the Excel screenshot below. Green text highlights nodes.View attachment 575478

6 UM 24" Bartlein 5R 7.5tw

• This barrel looks to be ok so far. Accuracy is very stable 1MOA-1.5MOA, it's almost completely insensitive to changes in powder charge and seating depth. I'm honestly not impressed with overall accuracy on paper, but these are 10 shot groups and it's ready to go hunting.
• 61 gr of H1000 and a 105 Hybrid is a great cruise control load that should give some more barrel life. Somewhere 61-63 grains with any 103-108 grain bullet should net similar results. It puts the cartridge at or above the upper reaches of a 243 AI at very comfortable pressure and excellent accuracy. Should be somewhere in the mid 3200s.
• It's somewhat dependent on N570 to reach its true potential. N570 really is the magic fairy dust for this cartridge and 115s. Retumbo is the only other powder I'd like to try but haven't yet.
• UM is working to resolve the issue with smaller body sizing dies, but I've got clickers galore by the second firing. Every single round, even low pressure loads. They can be sized and used again. .547" diameter at the last part of the case that the die hits is the cutoff. They really need to be .545" to avoid this issue.
• Fed 215M primers seem to be the ticket. CCI200 let me work up to higher charges and gave higher velocity, but 215M were more accurate and resulted in lower pressure/less severe clickers.
• At just over 100 rounds the barrel should be fully broken in/sped up.
• View attachment 587359View attachment 587361View attachment 587362

Just tagging in, as I now have a 6-7PRC (UM) now being built. 20” carbon, Vesper, Rokstk. Should be interesting!

 

[Axlrod]

Just tagging in, as I now have a 6-7PRC (UM) now being built. 20” carbon, Vesper, Rokstk. Should be interesting!

The 6 UM is a different cartridge than the 6-7PRC (6 ROKUM).

 

[RogerPa]

The 6 UM is a different cartridge than the 6-7PRC (6 ROKUM).

I know it’s not the same parent cartridge, but I do assume some of the information being shared here will be interesting. For example, I now know it has been tagged “6 ROKUM”. Thanks for that! I liked the idea of not fireforming, and simply necking the 7 PRC down to 6mm. Again, it should be interesting!