The 6UM

[ElPollo]

DO NOT RUN NR DTACS or 108 ELD-Ms in a 7 Twist 6UM.

They can't take it. I blew up another suppressor. I thought I was good with the standard NR Dtacs, but one randomly came apart yesterday. I inspected them, including this one, before loading them. It's not worth the risk. The ELD-M was just for shit and giggles. A few made it down the barrel, then one grenade. Wildcattin is fun

That definitely falls outside of any definition of a good day of shooting.

 

[B23]

UM, Ryan Avery, or whoever else builds or has one of these have any of you ever given any consideration or talked to guys like Frank Green w/Bartlein about using a gain twist barrel?

I wonder if there would be any advantage, with regard to preventing bullets from coming apart, if the bullet starts out with a bit slower twist rate then progresses and exits at the desired twist rate to stabilize whatever bullet/s you're shooting.

 

[amassi]

Read on the reloading post of clicker issues.
Anyone else seeing this?


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[amassi]

UM, Ryan Avery, or whoever else builds or has one of these have any of you ever given any consideration or talked to guys like Frank Green w/Bartlein about using a gain twist barrel?

I wonder if there would be any advantage, with regard to preventing bullets from coming apart, if the bullet starts out with a bit slower twist rate then progresses and exits at the desired twist rate to stabilize whatever bullet/s you're shooting.

I think the answer is just dropping to a 1:8, at um velocities and sea level it has a 1.41 “marginal” stability per bergers calculation. You go to 3,000’ asl and it’s stable


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[ID_Matt]

Read on the reloading post of clicker issues.
Anyone else seeing this?


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I get it TERRIBLE on my 7SAUM with ADG brass. Lot of talk about it being a chamber spec issue. I am switching dies and bought new ADG brass to see if that helps. Next step is trying new brass, if peterson or whoever would ever start making some.

 

[amassi]

I get it TERRIBLE on my 7SAUM with ADG brass. Lot of talk about it being a chamber spec issue. I am switching dies and bought new ADG brass to see if that helps. Next step is trying new brass, if peterson or whoever would ever start making some.

Brass won’t fix if if the reamers too tight. That’s why Sherman had to redesign all his saum based reamers. ADG brass is tough and dies can’t size the web down enough
Alex wheeler made an improved aw2 reamer for the 6.5 prc case (works great btw) increases web clearance from .003 (saami) to .005-.006. Once the chambers cleaned up (can be done by hand with a t handle) you can shoot brass that previously wouldn’t chamber and the clicker issue is gone.


if the 6 UM is a clicker issue the reamer might need to be redrawn.


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[Kurt]

My 6 UM does not have any “clicker” issues. 24” Proof 7.5 twist barrel. 66 grn of N570 with 115 DTAC.

 

[Tullis94]

Read on the reloading post of clicker issues.
Anyone else seeing this?


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Where did you see that? I looked on that thread and didn't see where there were clicker issues?

 

[Lawnboi]

@Ryan Avery are you seeing bullets come apart down range? Odd that it would happen in the suppressor as I assumed that it happened down range a ways. I’ve got a couple 7 twist barrels that I run suppressed, though 3k is about the most velocity they see.

Curious if it’s possible the suppressor just couldn’t handle the pressure? Odd that the bullet would come apart an inch out of the muzzle, first iv head of that.

Curious what you have learned. From the bullet or barrel maker; if anything

 

[amassi]

My 6 UM does not have any “clicker” issues. 24” Proof 7.5 twist barrel. 66 grn of N570 with 115 DTAC.

Round count and # of reloads?


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[amassi]

Where did you see that? I looked on that thread and didn't see where there were clicker issues?

Post #2

6 UM Reloading Thread

6 UM Reloading Thread

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...

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[Kurt]

Round count and # of reloads?


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180 rounds total, 100 fire form, 80 reloads with current load. That being said, no “clickers” up to 67 grain, 67.3 saw pressure signs. 66 was most accurate.

 

[Ucsdryder]

180 rounds total, 100 fire form, 80 reloads with current load. That being said, no “clickers” up to 67 grain, 67.3 saw pressure signs. 66 was most accurate.

My 7saum started clicking on 4th reload. I was running it hot. When I backed off the clicks stopped. I bet you’d see the same in this scenario.

 

[Kurt]

My 7saum started clicking on 4th reload. I was running it hot. When I backed off the clicks stopped. I bet you’d see the same in this scenario.

Perhaps I didn’t word that correctly. I have not had any issues with “clickers” with any of the loads I shot through load development or my current load, but did start to see slight signs of pressure at 67.3 and declined accuracy. At that point I reverted to the 66 grn load that shot the most accurate.

 

[Ryan Avery]

@Ryan Avery are you seeing bullets come apart down range? Odd that it would happen in the suppressor as I assumed that it happened down range a ways. I’ve got a couple 7 twist barrels that I run suppressed, though 3k is about the most velocity they see.

Curious if it’s possible the suppressor just couldn’t handle the pressure? Odd that the bullet would come apart an inch out of the muzzle, first iv head of that.

Curious what you have learned. From the bullet or barrel maker; if anything

Possibly a suppressor failure, but talking with DD it doesn't sound like it. I think the tip above the NR is coming loose in the barrel and catching a baffle. The ELD-Ms were out of the barrel when they popped.

 

[Ryan Avery]

UM, Ryan Avery, or whoever else builds or has one of these have any of you ever given any consideration or talked to guys like Frank Green w/Bartlein about using a gain twist barrel?

I wonder if there would be any advantage, with regard to preventing bullets from coming apart, if the bullet starts out with a bit slower twist rate then progresses and exits at the desired twist rate to stabilize whatever bullet/s you're shooting.

It is just as easy to use a 7.5 or 8 Twist. Kurts is pushing the NR dtacs hard(3460) with the 7.5 twist with zero issues.

I think the 7 twist combined with the +P is causing this issue.

 

[Ryan Avery]

My 7saum started clicking on 4th reload. I was running it hot. When I backed off the clicks stopped. I bet you’d see the same in this scenario.

Could you tell me your case measurement on the 200 line on the "clicker" brass?

 

[PathFinder]

Brass won’t fix if if the reamers too tight. That’s why Sherman had to redesign all his saum based reamers. ADG brass is tough and dies can’t size the web down enough
Alex wheeler made an improved aw2 reamer for the 6.5 prc case (works great btw) increases web clearance from .003 (saami) to .005-.006. Once the chambers cleaned up (can be done by hand with a t handle) you can shoot brass that previously wouldn’t chamber and the clicker issue is gone.


if the 6 UM is a clicker issue the reamer might need to be redrawn.


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By firing 2-3, all of my brass are nothing but clickers. Doesn't matter the pressure, everything from very mild loads with H1000 and 105 hybrids up to max pressure with N570/115 DTACs. I'm still hunting with the rifle, just takes a second longer to reload. Brass that are fireformed without projectiles give me one more full firing before it's a problem.
UM is working on a reamer revision, seems to be what is needed. They have been really good about communicating with me on the issue and started working on it a while back.
.547" on the .200 line is where it becomes a problem. .546" is borderline, anything below that isn't a problem.

 

[Ryan Avery]

Here are the PVA Cayuga’s

650 yards with retumbo, 65, 66, 67 grains. The speed with the far right group is 3280

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[The Guide]

Here are the PVA Cayuga’s

Those the 100 grain ones?

Jay