6 UM or 6-7PRC?

[BjornF16]

@Ryan Avery @Formidilosus @UM GM @Unknown Munitions

What are the pro/cons of 6 UM vs 6-7PRC in a Tikka action?

As of today, have to fire form for 6 UM, but will that be changing soon?

Has a 6-7PRC been built and tested yet?

Magazine issues?

My future Rokstok wants to know…

 

[Ryan Avery]

Good Questions

We don't have the 6-7PRC reamer yet; it should arrive by the end of January. I am going to build one.

We will be talking to Peterson and ADG about 6UM brass at SHOT.

6um Pros
Less Recoil
Short Action
Short case
Very efficient

Con
Brass availability
Fire forming
Custom Die


6-7PRC Pros
Brass availability
No fire forming
7PRC Die

Con
Long Action(Remington)
Minimal velocity increase??

 

[Axlrod]

For dies you can use a 7 prc bushing die with a different bushing in a 6-7 prc.

The 6 UM requires a custom die.

C.O.L. for the 7 prc is the same a 30/06 so definitely LA. Will work in a Tikka.

The 6UM has a cooler name for now...

 

[Ryan Avery]

For dies you can use a 7 prc bushing die with a different bushing in a 6-7 prc.

The 6 UM requires a custom die.

C.O.L. for the 7 prc is the same a 30/06 so definitely LA. Will work in a Tikka.

The 6UM has a cooler name for now...

Ahh, I added it to the list. But the 7PRC die might make clickers with the reamer having a fat butt, so a custom die might be needed.....

 

[B23]

We don't have the 6-7PRC reamer yet; it should arrive by the end of January. I am going to build one.

You generally go 22 inches or shorter so will your 6mm-7PRC build be a shorty too?

It'll be interesting to see if you get much velocity gain over your 6UM and if you do will it cause accuracy issues with the bullet trying to launch them faster. Only time will tell and you'll be the first to know. I have a couple long actions sitting on the shelf along with a Broughton 8tw 6mm barrel that have been collecting dust waiting to be turned into something so I'll be interested in following this along.

 

[Ryan Avery]

You generally go 22 inches or shorter so will your 6mm-7PRC build be a shorty too?

It'll be interesting to see if you get much velocity gain over your 6UM and if you do will it cause accuracy issues with the bullet trying to launch them faster. Only time will tell and you'll be the first to know. I have a couple long actions sitting on the shelf along with a Broughton 8tw 6mm barrel that have been collecting dust waiting to be turned into something so I'll be interested in following this along.

Going to be a 20" barrel.

 

[BjornF16]

The 6UM has a cooler name for now...

I dunno…Sixum prick has a good ring to it

 

[ericmcd]

Not to muddy the waters especially since I'm a boring reloader for common cases but theirs also a 6 Sherman short tactical, I know nothing about it but seems similar to the 6 um and I know they sells brass and dies for some of their cartridges on the site.

 

[Jimbee]

Going to be a 20" barrel.

Any reason not to go shorter?

 

[Axlrod]

I dunno…Sixum prick has a good ring to it

Nice! I was thinking
6mm PRK
or
6mm ROK

 

[Neverenoughhntn]

Nice! I was thinking
6mm PRK
or
6mm ROK

6it

 

[UM_Blaine]

Ahh, I added it to the list. But the 7PRC die might make clickers with the reamer having a fat butt, so a custom die might be needed.....

Ryan,

I am ordering all the PRC based reamers with the Wheeler butt, so there shouldn't be any clickers.

 

[Ryan Avery]

Ryan,

I am ordering all the PRC based reamers with the Wheeler butt, so there shouldn't be any clickers.

Hmm, I guess we’ll see.


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[UM_Blaine]

Hmm, I guess we’ll see.


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Well, we kinda have already seen it works without clickers............though I am sure someone can load even a Wheeler chamber hot enough to get clickers.....................

 

[khuber84]

Well, we kinda have already seen it works without clickers............though I am sure someone can load even a Wheeler chamber hot enough to get clickers.....................

Clickers can form on the AW 535 chambers too, it's important to find a die that sizes small at the base in conjunction with the AW reamers if you're going to run warm hand loads. Not all dies are created equally. The best I've found for the prc cases is the Bullet central Micron. They have the smallest base sizing followed by a RCBS matchmaster. The Hornady, redding and Forster ones I tried in 65prc didn't do as well. This was prior to 535 spec chambers, fighting clickers in my first 65prc. My redding 300prc type S die however, sizes quite well on the lower side of the case.

 

[eoperator]

Not all dies are created equally. The best I've found for the prc cases is the Bullet central Micron. They have the smallest base sizing followed by a RCBS matchmaster.

Short action customs modular sizing dies also

 

[wind gypsy]

Clickers can form on the AW 535 chambers too, it's important to find a die that sizes small at the base in conjunction with the AW reamers if you're going to run warm hand loads. Not all dies are created equally. The best I've found for the prc cases is the Bullet central Micron. They have the smallest base sizing followed by a RCBS matchmaster. The Hornady, redding and Forster ones I tried in 65prc didn't do as well. This was prior to 535 spec chambers, fighting clickers in my first 65prc. My redding 300prc type S die however, sizes quite well on the lower side of the case.

not related to clickers but I assume the BC Micron dies dont size all the way to neck/shoulder junction like other FL bushing dies? They dont do anything different in that regard do they?

 

[UM_Blaine]

Currently, with the Wheeler chamber, if you get clickers you know it's most likely either a hot load, an out of spec die, oversize brass, etc. You know it's not likely an undersize chamber. I am sure the standard PRC chambers were fine at first, nominally .004 to .005" over the size of new brass. However, brass makers seems to change specs more than we would like.

I have fought that for many years, and am in fact rechambering a 300 WSM I had built 20 years ago (before I had my own lathe) because the brass dimensions have changed over the years and my old reamer is too tight for modern brass. That can still happen, and if they do change the specs again we have to adapt.

Micron dies are very nice. I have a sizer for my 6 BRA and it matches my Wheeler 6 BRA reamer perfectly. However, most dies work with the PRC Wheeler chamber. I have used so many different brand's of dies over the years that I don't really have a favorite anymore. I think the ultimate answer is to have custom dies made for your chamber. Or maybe you can find someone who has already had a custom die matched to a particular reamer, which is what Alex has done for for his 300 SAUM IMP reamer.

 

[khuber84]

Short action customs modular sizing dies also

Haven't tried those gucci ones yet, thought I was ballin' with the micron! Lol I find the theory of a neck bushing incorporating

Not to muddy the waters especially since I'm a boring reloader for common cases but theirs also a 6 Sherman short tactical, I know nothing about it but seems similar to the 6 um and I know they sells brass and dies for some of their cartridges on the site.

6sst holds only 1.5 gr more than a prc, 2 gr less than Saum, 4-5gr less than 6um. The supposed extra performance from any Sherman case is from elevated chamber pressure. Not the improved case capacity. Improving a case by 1-2gr nets 40-80fps at the same psi level. Not 150-200fps like advertised. That's just running high pressures.

 

[eoperator]

Haven't tried those gucci ones yet, thought I was ballin' with the micron! Lol

-Sac dies are $300 with bushing

-BC Micron dies are $275 + $35 bushing