6CM clickers

[solarshooter]

Hi all, I have a new Tikka build with an 18" Bartlein chambered in 6CM (with a SAAMI spec reamer) by @Unknown Munitions. I bought 1x fired Gunwerks brass, and am on the first reload of this brass, and encountering pretty frequent clickers that have to be "smacked" open. I'm shooting 43.0gr H4350, Berger 108 EH, CCI 200, 2.800" COAL, no pressure signs (ejector marks begin at 43.5, very clear at 44.0, so I consider this just below max pressure load). I am using Redding dies, standard FL sizing die, micrometer seater. This barrel was ordered as a prefit, and measured 1.542" max headspace after installation (measured by taking a "short" headspace case that chambered easily, and adding layers of tape to the base until the bolt didn't close or barely closed with alot of pressure. This is 0.001" over SAAMI minimum headspace. I'm aware of the general principle of what causes clickers, basically that the case is not getting resized enough at the 0.200" line to fit the chamber, and I'm aware that this can be resolved by some combination of:

• Opening up the back of the chamber (or picking a different reamer that is a little larger at the base, too late for that)
• Shortening the die such that it can resize further down on the case (at the expense of also driving the headspace shorter
• Using different brass

Has anyone else encountered and/or solved this problem? @UM GM warned me this could happen going the prefit route, since exact ideal headspace might be hard to hit. They are great to work with and I'm sure would help me if chamber mods are needed, but I was curious if I can fix this with dies or brass. Thanks!

 

[BBob]

Opening up the back of the chamber (or picking a different reamer that is a little larger at the base, too late for that)

This is your answer. Send the barrel back and have UM open up the back end. Easy peasy. I can do it in 15 minutes. If they won't do it find someone that will.

Shortening the die such that it can resize further down on the case (at the expense of also driving the headspace shorter

This will never (almost never) work. See previous answer.

Using different brass

This will never (almost never) work. See first answer.

 

[Lawnboi]

I’d bet this is happening cause you’re shooting an extremely hot load.

Especially if it’s a new rifle I wouldn’t be suprised if that barrel sped up 100 + fps.

Personally for the first 200 rounds of 6 creed I’d be starting around 40 grains of h4350.

Not being able to size the shoulder may just be your chamber/die. And other than a trip back it your going to have to mess with shell holders and dies.

 

[solarshooter]

I’d bet this is happening cause you’re shooting an extremely hot load.

Especially if it’s a new rifle I wouldn’t be suprised if that barrel sped up 100 + fps.

Personally for the first 200 rounds of 6 creed I’d be starting around 40 grains of h4350.

Not being able to size the shoulder may just be your chamber/die. And other than a trip back it your going to have to mess with shell holders and dies.

43.0 didn't seem unreasonable based on searching I did, but agreed, it certainly isn't "cool". I can test this with some lower loads, but I'd hate to be significantly limited on MV (3gr is alot) due to something that might be fixable with the chamber.

 

[Harvey_NW]

I bought 1x fired Gunwerks brass

This isn't helping either. Sometimes fired brass gets sized enough to function in a different chamber, sometimes if the OG chamber was dimensionally bigger you can have interfering tolerances.

 

[BBob]

This isn't helping either. Sometimes fired brass gets sized enough to function in a different chamber, sometimes if the OG chamber was dimensionally bigger you can have interfering tolerances.

Absolutely!

Missed it too in my speed reading

 

[Lawnboi]

This isn't helping either. Sometimes fired brass gets sized enough to function in a different chamber, sometimes if the OG chamber was dimensionally bigger you can have interfering tolerances.

I didn’t see that either initially reading.

New barrel=new brass. Sometimes it works but sometimes it dosnt. Even if they spun it on themselves you can’t guarantee that brass fired in another chamber will work in yours, even if full length sized.

Try again with new brass and a below max charge, would be what I would personally do.

 

[solarshooter]

Great, I will try and find some new brass and back the charge off a bit before I send the barrel off to the chamber modified. On that note, is necking down 6.5CM in my FL die a viable path to get fresh brass? I'd like to use Lapua but I can't find any 6CM.

 

[Lawnboi]

Great, I will try and find some new brass and back the charge off a bit before I send the barrel off to the chamber modified. On that note, is necking down 6.5CM in my FL die a viable path to get fresh brass? I'd like to use Lapua but I can't find any 6CM.

Alpha or Peterson is near lapua and what I would choose.

I’d bet money it’s the used brass and not a chamber problem.

One way you could confirm too is to buy some factory ammo, Berger makes 6 creed in lapua brass and you could have some lapua that way.

Let us know how it shoots as well, more tikka prefit options is good.

 

[solarshooter]

OK well this brings up another question, LRP or SRP? Upside of LRP for me is that 95% of what I shoot and reload for is LRP, so I'd like to maintain commonality with the stock I have. But I could be swayed if there's a performance benefit to SRP. I'm aware there are many more SRP in stock typically, so maybe the common components argument isn't that strong.

 

[Lawnboi]

OK well this brings up another question, LRP or SRP? Upside of LRP for me is that 95% of what I shoot and reload for is LRP, so I'd like to maintain commonality with the stock I have. But I could be swayed if there's a performance benefit to SRP. I'm aware there are many more SRP in stock typically, so maybe the common components argument isn't that strong.

For hunting, LRP. Better ignition, thicker cup resists some of the issues with field conditions.

The only benefit to the small rifle primer creedmoor brass is a little more material in the case head making pockets last a little longer, and that you can use cheaper more available primers. On a 6 creed I wouldn’t be super worried about case life, with alpha, Peterson or lapua you could likely burn a barrel with one or two hundred cases.

Most of those brass makers also make thicker brass so just be warned before stuffing 43 grains of h4350 in. Personally I normally end up around 40-41 grains for a bullet like that.

 

[ID_Matt]

43.0 didn't seem unreasonable based on searching I did, but agreed, it certainly isn't "cool". I can test this with some lower loads, but I'd hate to be significantly limited on MV (3gr is alot) due to something that might be fixable with the chamber.

Hogdon website has 41.7 as a max and hornady book shows 41.7. That is with the 108 eldm, so maybe the berger is different but 43.0 sure seems like it might be on the spicier end and could be contributing to the clickers.

 

[solarshooter]

Hogdon website has 41.7 as a max and hornady book shows 41.7. That is with the 108 eldm, so maybe the berger is different but 43.0 sure seems like it might be on the spicier end and could be contributing to the clickers.

I started at 40.0 and stepped up in 0.5gr increments looking for ejector marks. I only remember one or two clickers in that test (out of 30 or so rds), and I don't think they correlated with pressure. I've found book max can be conservatively low in many cases, so I'm not afraid of going 2 or more gr over book provided I find max and can maintain a safe distance from it. And again, I found many folks online shooting 42-43 or more, so I didn't get any alarm bells when that ended up being useful max.

I got 10 boxes of 20rds of Gunwerks brass, and I'm starting to think maybe some were fired in a larger chamber, and some smaller, and that's why the clickers are inconsistently happening, even all at the same powder charge. I went against my better judgement since this brass was extremely affordable for what I think is ADG 1x fired, but that may have been a mistake!

 

[Lawnboi]

I started at 40.0 and stepped up in 0.5gr increments looking for ejector marks. I only remember one or two clickers in that test (out of 30 or so rds), and I don't think they correlated with pressure. I've found book max can be conservatively low in many cases, so I'm not afraid of going 2 or more gr over book provided I find max and can maintain a safe distance from it. And again, I found many folks online shooting 42-43 or more, so I didn't get any alarm bells when that ended up being useful max.

I got 10 boxes of 20rds of Gunwerks brass, and I'm starting to think maybe some were fired in a larger chamber, and some smaller, and that's why the clickers are inconsistently happening, even all at the same powder charge. I went against my better judgement since this brass was extremely affordable for what I think is ADG 1x fired, but that may have been a mistake!

I’m cautious putting any once fired (in a different rifle) brass in a custom barrel. Most factory barrels have the clearance to mix and match.

 

[gbflyer]

You might beat the clickers with a small base die.

 

[B23]

How close to touching the lands are you at 2.800 COAL ? If you're touching or real close to touching that'll spike up the pressure and take a load that is on the edge of overpressure if it was 10-15 thou off touch but send it well overpressure if that same load is touching the lands or real close to touching.

 

[Wrongside]

This isn't helping either. Sometimes fired brass gets sized enough to function in a different chamber, sometimes if the OG chamber was dimensionally bigger you can have interfering tolerances.

Yep. The only time I’ve had clickers was with used brass. SB die helped, but didn’t cure it. New Alpha brass for that rifle and the problem went away. The used brass and over pressure load aren’t a great combo. The barrel/chamber are probably fine.

OP, I didn’t see it mentioned, do you know your velocity?

 

[solarshooter]

How close to touching the lands are you at 2.800 COAL ? If you're touching or real close to touching that'll spike up the pressure and take a load that is on the edge of overpressure if it was 10-15 thou off touch but send it well overpressure if that same load is touching the lands or real close to touching.

0.040" off the lands, shouldn't be an issue there. I think in order of ease/cost I'm going to do the following:

1. Back the charge off
2. Get new brass
3. Get a smaller base die
4. Send the barrel back to UM to have the chamber opened up

 

[solarshooter]

Yep. The only time I’ve had clickers was with used brass. SB die helped, but didn’t cure it. New Alpha brass for that rifle and the problem went away. The used brass and over pressure load aren’t a great combo. The barrel/chamber are probably fine.

OP, I didn’t see it mentioned, do you know your velocity?

2930fps avg over 3 shots. The full pressure/MV test results look like this, 3 shots at each charge:

Charge weight (gr)	Avg MV (fps)
40.0	2715
40.5	2741
41.0	2774
41.5	2823
42.0	2858
42.5	2905
43.0	2932
43.5	3008
44.0	3038

 

[B23]

I think ADG makes the brass you're using and their brass typically has a little less case capacity then many of the others. From what I've read ADG 6CM brass holds around 49-ish gr H20. Reducing the case capacity down to 49.5 and running your load through QL shows 2920 which is pretty close to what you're getting but it also shows it as a 72,500 PSI load which is pretty hot. Before I did anything else I'd back it down at least one full grain and see if that cures your heavy bolt lift problem.