6 UM or 6-7PRC?

[huntnful]

@Ryan Avery During your fire form stage what kind of accuracy were you seeing? My first 6 rounds down the barrel grouped nicely into roughly a 3/4” group. I’ve fire formed 85 pieces so far, accuracy has been poor on the other 79. It’s so hot I usually have time to shoot 6-10 in a session. They group in a 1.75”-2”. Once I get through my 100 pieces fireformed, hoping things tight up.

Picture below was 6 I had time to do this morning.

I've fire formed A LOT of brass. And that group is not a promising sign, I can tell you that much. It won't get much better once formed, especially if you're forming with your desired powder and bullet already. I'd be looking into steps to improving accuracy immediately. Make sure all your torque is correct first. Not sure on the build specs or gun builder. But is the action bedded? If everything is legit on the build itself, you may be looking into a new barrel soon.

Before I formed any more. I'd prep the pieces you have formed already and go shoot them for accuracy testing at least.

 

[longrange13]

I've fire formed A LOT of brass. And that group is not a promising sign, I can tell you that much. It won't get much better once formed, especially if you're forming with your desired powder and bullet already. I'd be looking into steps to improving accuracy immediately. Make sure all your torque is correct first. Not sure on the build specs or gun builder. But is the action bedded? If everything is legit on the build itself, you may be looking into a new barrel soon.

Before I formed any more. I'd prep the pieces you have formed already and go shoot them for accuracy testing at least.

Yeah everything is perfect on the rifle. It’s a tikka with the UM action mods and nitride, ace barrel they chambered and installed. Stockys stock, plenty of free float room, everything degreased and torqued to proper specs. Nightforce scope, um rings. I’m going to prep some brass tonight and shoot for accuracy. I’ve already tried the 108eldms and they shot worse. Might be a case where the barrel only likes monos. Ive never had great luck with overbore cartridges. I’m really surprised all the other 6um barrels and Ryan’s 6-7prc have come out slamming.

Ive done 2, 26 nosler before. Couldn’t ever get them to shoot a cup and core bullet. They liked monos a lot tho. Might be the case here.

 

[longrange13]

I don’t recall how accurate the FF loads were, but they were better than yours. I would remember those.

For the 6UM and the 6-7 PRC, I use 58 grains of 7828 and 110 SMK because I have a lot of both.

Well Sheeeeeiiiiit, sounds like bad luck on my part lol. I’m going to try the 115s with fireformed brass today. Then maybe some n565, Retumbo, and a couple other bullets. See if anything brings it in.

 

[AZ_Hunter]

Following, so please keep updated.

 

[huntnful]

Yeah everything is perfect on the rifle. It’s a tikka with the UM action mods and nitride, ace barrel they chambered and installed. Stockys stock, plenty of free float room, everything degreased and torqued to proper specs. Nightforce scope, um rings. I’m going to prep some brass tonight and shoot for accuracy. I’ve already tried the 108eldms and they shot worse. Might be a case where the barrel only likes monos. Ive never had great luck with overbore cartridges. I’m really surprised all the other 6um barrels and Ryan’s 6-7prc have come out slamming.

Ive done 2, 26 nosler before. Couldn’t ever get them to shoot a cup and core bullet. They liked monos a lot tho. Might be the case here.

Could possibly be your reloading process? Unless you’ve proofed your process on other barrels and cartridges of course. You can introduce some terrible accuracy with inconsistent ammo.

This is what I expect to see when fire forming. 30 rounds groups in the 1”-1.5” is about normal. And that’s from bigger cartridges than the 6 UM.

 

[longrange13]

Could possibly be your reloading process? Unless you’ve proofed your process on other barrels and cartridges of course. You can introduce some terrible accuracy with inconsistent ammo.

This is what I expect to see when fire forming. 30 rounds groups in the 1”-1.5” is about normal. And that’s from bigger cartridges than the 6 UM.

View attachment 739262
View attachment 739263
View attachment 739267

I’ve never wildcatted before but I do have a lot of experience and the best equipment money can buy. Here is a 6.5 creed I did a load for earlier this month. I think my process is sound.

 

[huntnful]

I’ve never wildcatted before but I do have a lot of experience and the best equipment money can buy. Here is a 6.5 creed I did a load for earlier this month. I think my process is sound.

Yep, looks like whatever you’re doing shot great there. So your process probably isn’t influencing those groups much, if at all.

I’m curious to see how the once fired, prepped brass shoots for sure. Could be a significant improvement. I’m just not used to seeing crazy big groups during fire forming either.

 

[longrange13]

Yep, looks like whatever you’re doing shot great there. So your process probably isn’t influencing those groups much, if at all.

I’m curious to see how the once fired, prepped brass shoots for sure. Could be a significant improvement. I’m just not used to seeing crazy big groups during fire forming either.

I’ll keep you posted for sure, hoping for the best but prepared for the worst

 

[Axlrod]

I’ll keep you posted for sure, hoping for the best but prepared for the worst

I have the same rifle from UM as you, except a Bartlein barrel. The one thing with mine is the neck clearance. My fired round and loaded round neck dia. are the same, and a bullet will not go in a fired case. I have seen this in other wildcats, and the only easy cure is turning necks. So I have turned some, but haven't shot them yet. After necking down the necks are a little thick anyway, so this will help with that. I have wondered if this is part of the shoulder collapse during bullet seating the first time.
My FF loads that I have shot at paper are all pretty good. But I haven't shot too many at paper either. I don't really do much load dev. until I am over 100 rounds. By then my brass is all FF and the barrel has sped up.

 

[Ryan Avery]

WTS - 6-7PRC barrel will brass

Ace #2 20” fluted by Kampfeilds Chambered and threaded by UM for a Tikka action Comes with 97 pieces of ADG 7 PRC necked down to 6mm 40 pieces of ADG 7PRC 30 Rounds have been fired through this barrel. The barrel shot great during load dev. $1000 TYD Sent from my iPhone using...

rokslide.com

Sent from my iPhone using Tapatalk Pro

 

[wind gypsy]

I didn't knowfire forming made that big of a difference. Maybe I'll try that with the rest of my brass.

I think @khuber84 is primarily suggesting that for barrel life reasons?

 

[khuber84]

I think @khuber84 is primarily suggesting that for barrel life reasons?

Fireforming virgin brass with a top end load, stresses a case in my opinion. There's a lot of stretch going on, not just the shoulder growing and doing it's things, but the base/web is expanding to grab the Chamber. Virgin brass is fair bit smaller than your once fired. I've alway been a believer in having a fireform barrel, or using a midweight load with a bullet jammed if you dont have headspace, or a false shoulder set. But yes, barrel life isn't a bad consideration either since N570 is pretty much a plasma torch for the throat.

 

[Jimbee]

Well Sheeeeeiiiiit, sounds like bad luck on my part lol. I’m going to try the 115s with fireformed brass today. Then maybe some n565, Retumbo, and a couple other bullets. See if anything brings it in.

Any updates?

 

[longrange13]

Any updates?

Not yet, haven’t had time to make it back out. All my once fire brass has inconsistent case length and is also past max trim length by .001-.003. I ordered up a 6mm pilot for my Henderson trimmer, just waiting for that to show up this week.

 

[khuber84]

Typically when a print is made on neck down case, especially 7 to 6, they add neck length in the chamber due to natural neck growth from necking down. Do you have a print to refer to? My other trick, is chamber an empty case, and put my teslong bore scope in from muzzle side, I can typically see if there's room from case neck to end of chamber.

 

[Jimbee]

Not yet, haven’t had time to make it back out. All my once fire brass has inconsistent case length and is also past max trim length by .001-.003. I ordered up a 6mm pilot for my Henderson trimmer, just waiting for that to show up this week.

I'm going to try some different bullets and or powders and put the pain back into painless load development. Maybe skim bed my rokstok?

 

[Jimbee]

Typically when a print is made on neck down case, especially 7 to 6, they add neck length in the chamber due to natural neck growth from necking down. Do you have a print to refer to? My other trick, is chamber an empty case, and put my teslong bore scope in from muzzle side, I can typically see if there's room from case neck to end of chamber.

 

[khuber84]

View attachment 746832

Nope, no extra length in there, that's saami 7mm prc case oal!

 

[longrange13]

Typically when a print is made on neck down case, especially 7 to 6, they add neck length in the chamber due to natural neck growth from necking down. Do you have a print to refer to? My other trick, is chamber an empty case, and put my teslong bore scope in from muzzle side, I can typically see if there's room from case neck to end of chamber.

I don’t, I’ll ask um for a copy of it. That’s a good idea with the boresxope. I’ll check it out before I cut them down.

 

[longrange13]

I'm going to try some different bullets and or powders and put the pain back into painless load development. Maybe skim bed my rokstok?

I’ve had the same thought as well. Going to try the 115s with n570 in fire form brass, and if that doesn’t work I’ll shift over to Berger’s and then hammer bullets. My gun HATES the 108 elem