The 6UM

[ACHILLES]

Trying to understand the gains here, maybe someone can explain this to me like i’m 5.

Background—i’ve already been convinced from this forum and my real world experiences that 77tmk 223 and heavier 22cm is absolutely lethal on medium game but I do keep a larger rifle for specific hunts where i’m required to use one.

I have an accurate and to-date reliable 6.5prc shooting 147eldm at 2900fps. Are there truly nominal gains switching to a 6um?

From an outsiders perspective I would be switching to a cartridge I have to fireform, giving up a ~.700bc for a .535bc, recoil seems to be close to a wash, would gain just a bit in flatness of trajectory but within 500 yards… I really don’t see the benefits?

For the time and money it would take to source a rifle and build ammo, I could just practice an absolute boatload with my 6.5 PRC. What am I missing?

I’m no expert so take this as opinion. Plain and simple it raises your hit percentage slightly all things being equal. The further the distance the more obvious it becomes.
A little less wind drift along with less drop which gives you more room for error ranging animals on flat terrain or in general.

All cartridges using virgin brass need to be fire formed with a mild/moderate load. Even if the shoulder angle and body taper is not changing.

The benefits of switching cartridges are up to the individual and their specific needs/wants But if your just shooting out to 500 yards like you stated then no I don’t think it’s worth changing from a 6.5prc to a 6UM.

 

[sturner88]

I’m no expert so take this as opinion. Plain and simple it raises your hit percentage slightly all things being equal. The further the distance the more obvious it becomes.
A little less wind drift along with less drop which gives you more room for error ranging animals on flat terrain or in general.

All cartridges using virgin brass need to be fire formed with a mild/moderate load. Even if the shoulder angle and body taper is not changing.

The benefits of switching cartridges are up to the individual and their specific needs/wants But if your just shooting out to 500 yards like you stated then no I don’t think it’s worth changing from a 6.5prc to a 6UM.

Thank you, Achilles. So as I see it…

Slightly less Wind Drift and Drop. We are talking less than an inch of wind drift at my max range of 500? Less than my margin of error. 147 vs 108 2900 vs 3250 mv 10mph wind

All virgin brass needs to be fire formed yet I get great accuracy from factory ammo. Marginal Gain at best from reloading.

increased component cost by switching to a new barrel, saum brass etc.

If I remember correctly, I believe Form had it at around 2lb recoil energy difference between the two cartridges in similarly weighted rifles.

I really wanted 6um to be the magic bullet for my larger rifle as I’ve seen great performance increases by swapping to smaller cartridges but I just genuinely think the cartridge was designed for someone with different ranges and priorities than mine. That or someone that wanted to go the extra marathon for a super small gain in performance that could be made up elsewhere like a more ergonomic stock or practice time.

 

[mullmann]

Thank you, Achilles. So as I see it…

Slightly less Wind Drift and Drop. We are talking less than an inch of wind drift at my max range of 500? Less than my margin of error. 147 vs 108 2900 vs 3250 mv 10mph wind

All virgin brass needs to be fire formed yet I get great accuracy from factory ammo. Marginal Gain at best from reloading.

increased component cost by switching to a new barrel, saum brass etc.

If I remember correctly, I believe Form had it at around 2lb recoil energy difference between the two cartridges in similarly weighted rifles.

I really wanted 6um to be the magic bullet for my larger rifle as I’ve seen great performance increases by swapping to smaller cartridges but I just genuinely think the cartridge was designed for someone with different ranges and priorities than mine. That or someone that wanted to go the extra marathon for a super small gain in performance that could be made up elsewhere like a more ergonomic stock or practice time.

I am trying a 6prc first since I have the brass and dies. It will be slower by 1-150FPS, but I don’t need to buy dies or brass.

I thought about a 6UM, but I did not want to buy brass and dies.

 

[ACHILLES]

Thank you, Achilles. So as I see it…

Slightly less Wind Drift and Drop. We are talking less than an inch of wind drift at my max range of 500? Less than my margin of error. 147 vs 108 2900 vs 3250 mv 10mph wind

All virgin brass needs to be fire formed yet I get great accuracy from factory ammo. Marginal Gain at best from reloading.

increased component cost by switching to a new barrel, saum brass etc.

If I remember correctly, I believe Form had it at around 2lb recoil energy difference between the two cartridges in similarly weighted rifles.

I really wanted 6um to be the magic bullet for my larger rifle as I’ve seen great performance increases by swapping to smaller cartridges but I just genuinely think the cartridge was designed for someone with different ranges and priorities than mine. That or someone that wanted to go the extra marathon for a super small gain in performance that could be made up elsewhere like a more ergonomic stock or practice time.

Sounds like your on the right track of thinking.

At 500 yards 10mph from 3cl wind drift is 1.3” or .2moa difference. Not even 1click/.25moa

Regarding fire formed brass, Il go into more detail. I also get great accuracy from certain factory ammos and while forming virgin brass with handloads. Most factory ammo is what I’d consider mild anyway. Where it can come back and bite your is if your one that runs hot loads. I’ve tested this in standard cartridges also where the body taper and shoulder angle is not changing. Testing Ive trashed brass by using hot loads on the first firing. But with 1x brass I could run the same load for 6-8firings.

Also with moderate cartridges that have decent Bbl life I use what Id consider mild/fireforming loads to break in the barrel the first 100 rounds anyway. If you’re loading for a new 7Rum that’s different. Find pressure with a few shots then run it at a proper charge while forming brass. Great accuracy can still be had while harvesting animals at distance with just a few rounds on the bbl.

If you’re running at normal pressure it may never matter and you may never notice much difference in accuracy especially with a hunting rifle that is generally lighter and shot in improvised positions. If you take a measurement at the base of a virgin case just above the web then fire it and resize it and it will never be that small again after it’s fired once and formed to your exact chamber.

And I’ve never shot benchrest but I highly doubt any of the top level shooters are competing with virgin brass. But with heavy rifles using fixed rest shooting aggregates of 5 or 10 shot groups the accuracy in virgin vs formed brass might show or be the difference between first or second place considering how small those guys shoot in that discipline.

 

[Formidilosus]

Then again, the 6um may be targeted more towards a range I currently have no business shooting at or a crowd that is significantly better calling wind/executing field shots than I am.

I’m nearly positive that the “why” of the 6UM has been written and discussed multiple times in this thread. Primarily, and in order- increased danger space, longer terminal range, less wind drift, and no more recoil than a 6.5CM with heavy bullets. The very first animal killed with it used the increased danger space (647 yards, but dialed for 580 IIRC), and an elk last year used the increased terminal range (1,106 yards).


It is not for your use.

 

[Ryan Avery]

I’m nearly positive that the “why” of the 6UM has been written and discussed multiple times in this thread. Primarily, and in order- increased danger space, longer terminal range, less wind drift, and no more recoil than a 6.5CM with heavy bullets. The very first animal killed with it used the increased danger space (647 yards, but dialed for 580 IIRC), and an elk last year used the increased terminal range (1,106 yards).


It is not for your use.

It’s was also built to shoot Giraffes…

Almost go time!

 

[B_Reynolds_AK]

It’s was also built to shoot Giraffes…

Your zero's off.











Lol JK

 

[ChrisAU]

It’s was also built to shoot Giraffes…

Almost go time!

Savvy, taping up the target upside down will help prepare you for shooting in the southern hemisphere. Science.

 

[Ryan Avery]

Savvy, taping up the target upside down will help prepare you for shooting in the southern hemisphere. Science.

You caught me.

 

[Ryan Avery]

150 yards

Violent exist

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[BjornF16]

@Ryan Avery @UM GM

I see some legs hanging off that white truck in the background...more death and destruction?

 

[BradArnett]

Damn, I can't be the only one who clicked on this excited for a giraffe pic lol

 

[Ryan Avery]

Damn, I can't be the only one who clicked on this excited for a giraffe pic lol

Tomorrow is the day.

 

[wind gypsy]

@Ryan Avery @UM GM

I see some legs hanging off that white truck in the background...more death and destruction?

See live hunt thread.

 

[Ryan Avery]

Exit on a Diker at 50 yards


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[IrkedCitizen]

Brutal. Taxidermist should be able to fix it

 

[Jfjfrye]

My 6cm. 3087 at the muzzle, and this is 5000 DA. 108 berger elite hunter and its a 9 mph rifle.View attachment 506046

Randy

Thank you. Heavily looking into a 6cm. For my next one. Shooting good bullets this thing will outshoot my abilities all day long.

 

[JBradley500]

Looks like you Lieutenant Dan'd him.

 

[omicron1792]

See live hunt thread.

Wind you been to Africa yet? I’m going back either 2025 or 26. You should join.

 

[B_Reynolds_AK]

I think Ryan really stuck his neck out this morning with his 6 UM