6CM testing Results

[Jourdan_D]

Well went out and formed some brass this weekend and did some tests loads. below is a pic from my FF load

i've got 3 promising loads with my formed brass

1st: ES 15, SD 7.5
2nd: ES 7, SD 4
3rd: ES 16, SD 9

all three where 1/3 moa groups but think i can make them better so going to play around with seating depth on all three this coming weekend.

 

[rcw3]

47 gr of H1000 is typically a "bread and butter" accuracy load with that set up whether you are shooting the 95 VLD's or anything up to the 115's. Not a real high velocity load, but typically a good solid performer accuracy wise.

 

[Dgd6mm]

I shoot the 115 DTAC at 48.7 out of my 27" and 49.0 out of my 30" and have had the same accuracy that you show on your target at 100 yards. Mine were 5 shot groups, and no this does not happen everytime. I have not shot either 6CM in a while but I did check the 27" last time out at 100 yards, 5 shot group slightly under .250 with 3900 rounds down it. I'm not saving it, I've got another 6CM barrel ready to screw on when it gives up.

 

[boltfluter]

I shoot the 115 DTAC at 48.7 out of my 27" and 49.0 out of my 30" and have had the same accuracy that you show on your target at 100 yards. Mine were 5 shot groups, and no this does not happen everytime. I have not shot either 6CM in a while but I did check the 27" last time out at 100 yards, 5 shot group slightly under .250 with 3900 rounds down it. I'm not saving it, I've got another 6CM barrel ready to screw on when it gives up.

Very impressive barrel life and great shooting. I need one. ;D

Regards, Paul

www.boltfluting.com

 

[Pax]

Working on my first 6CM and having some problems with light primer strikes not firing on my fireform loads. I am jamming the bullets enough that when I get a FTF and eject the round the bullet is stuck and I spill powder in my action. This happens 1 in 15 rounds or so. I have not had any problems on full sized loads, just fireforming. Am I not jamming enough? I have .003 neck tension. Should I create a false shoulder like I'm making a PC of BRX brass?

Dave Kiff made the reamer for Lapua brass and 105 hybrids and Chad Dixon did my metal work. Not sure if this makes a difference, but in case you want to know.

Thanks in advance for the answers. The good news is I can tell this is going to be a shooter. Even the fireform loads are sub half-MOA.

 

[teele1]

What is your firing pin protrusion? I had just the opposite with my first 6CM loads. Mine were too long.

 

[Pax]

.05" as best I can measure. I pulled out my other prone rifle, same action (Pierce) and the firing pin protrusions match. This rifle has never had an light strikes.

 

[teele1]

What about undersized brass on those that failed to fire?

 

[Dgd6mm]

What about undersized brass on those that failed to fire?

Verywell may be the culprit. I had this in one of my 6CM's that Dave Bruno chambered with a shoulder. I took the FTF rounds and put them in my Tac rifle which is on a Savage action that I headspaced with a go gauge a little tighter and they fired. This was new unfired - unsized brass. Since then I size new brass before the first firing, haven't had it happen since.

 

[J Fogg]

I just started using my 6cm this year, had the same ftf problem a false shoulder remided it and formed the cases nicely. First match shot was a mid range prone, shot a 200, 199, and 197, which is well above my master card, Chad Dixon also did my metal work.
Joe

 

[Jourdan_D]

I had 2-3 per 50 rounds that this happened to me while FF. Just turn the bolt handle to recock and pulled the trigger again and they went boom.

 

[Hoser]

I normally neck up my 243 brass to 6.5 and then use a bushing to bring it back down to 243. But just barely enough to close the bolt. First firing is with pistol powder and cream of wheat.

Kinda like making dasher brass.

 

[Changeling]

No, the 6mm AI is a heavyweight and can do things the 6 CM and 6 SLR cannot. Like, drive 115 grain bullets over 3300 fps and burn up a barrel in 800 rounds.

No Steve that's not quite true! A whole lot depends on how one shoots, to fast = HOT barrel, to slow and the barrel gets to COLD, medium and the barrel stays just right. Sorta like the the little chic trying out the 3 bears "porage/soup/beans".
There is not a doubt in my mind that my 6mmAI will hopefully make it to 829 rounds give or take.

 

[Pax]

Thank you all for the advice. I am thinking that the brass might have been a hair undersized.

Rounds that dont fire in my rifle will fire in my brother's AIAX chambered with the same reamer (go figure).

Anyway. I have 12 rounds loaded up that I formed a false shoulder on. I used a 6.5mm mandrel and then sized back down with my .243 die just enough to close the bolt.

If this does not work then ill fire-form all my brass in his AIAX! Haha.

The full sized loads are shooting as good as I have ever seen in one of my rifles. I had a ragged hole 10 shot group slung at 200 yds. yesterday. That at least is encouraging.
Seems that this rifle likes them hot. The 105 hyb are clocking 3286. My 10 shot SD is 12, which could be better, but other primers and velocities did not net anything better.

 

[Steve Blair]

No, the 6mm AI is a heavyweight and can do things the 6 CM and 6 SLR cannot. Like, drive 115 grain bullets over 3300 fps and burn up a barrel in 800 rounds.

No Steve that's not quite true! A whole lot depends on how one shoots, to fast = HOT barrel, to slow and the barrel gets to COLD, medium and the barrel stays just right. Sorta like the the little chic trying out the 3 bears "porage/soup/beans".
There is not a doubt in my mind that my 6mmAI will hopefully make it to 829 rounds give or take.

[br]
I shot crows with my 6mm Rem., 58 V-Max at ~4020. There was no getting the "black buzzards" to present themselves slowly and singly, while the barrel cooled. However, with careful barrel temperature management, I think your goal is attainable.

 

[Pax]

False shoulder method is working as intended.

 

[rcw3]

I normally neck up my 243 brass to 6.5 and then use a bushing to bring it back down to 243. But just barely enough to close the bolt. First firing is with pistol powder and cream of wheat.

Kinda like making dasher brass.

Why the heck go through all that just to make 6CM brass?

Way Way too much work!

I have a 6CM barrel and a few 243 Imp 30Ëšbarrels (they are very similar cartridges and brass is made the same way for both) and I have never had to do anything like that to make brass and I have never had a failure to fire with fire forming rounds. It just seems like a solution for a problem that does not normally exist (unless it's a problem somewhere else in the set up of the rifle, the chambering or making of the initial fire forming ammo).

If the cartridge has any benefit, it's based on the simplicity of things, it's on the basis that you just load up .243 Win ammo or use factory ammo and just shoot it in the gun and you've made brass just like that - - Done!

Robert Whitley

 

[rcw3]

FWIW - - if you have to use special brass prep techniques for the 6CM to keep from having the fire forming cartridges from going too deep in the chamber that it causes a failure to fire, then IMO there's a head space problem.

For the 243 Imp 30Ëšwe use a regular 308/243 Win "go" gage as the "go" for the chamber, and we keep the chamber on "go" with that (i.e. not sloppy), and that makes it so head space is focused in the neck shoulder junction area, and for the fire forming rounds, I've never had a situation (with multiple barrels) where 243 Win loaded ammo goes too deep in the chamber that there is a failure to fire. IMO - - after working with the 6CM, the cartridge head spacing can be done the same way using a 308/243 Win "go" gage. The cartridge head spacing on the 6CM drawing (at the neck/shoulder junction) is close enough that you could chamber it that way too. Looking at the 6CM reamer drawing, I would be surprised if the chamber was not originally intended for use with a 308/243 Win "go" gage.

Robert

 

[Hoser]

Why the heck go through all that just to make 6CM brass?

Because I can.

I dont have to do it that way, and I have had good luck just loading up 243 brass with 47 gns of H-1000 and shooting it.

It is just the way I do it now.

 

[brasscow]

Ive fire formed 300 pieces of Lapua brass so far and today i decided to take 5 pieces of that brass and run a quick pressure test to see what kind of velocity i would get. Rifle is an AIAX with krieger barrel, chambering by very reputable smith

Reamer: My own, done by Kiff for Lapua brass
Load: 47.5gr H1000 in 243 win case jammed .010" into the lands. Fireformed load was 51gr H1000, with the only pressure signs being a very very slight ridge around firing pin strike barely felt by fingernail, but this is pretty typical for the large firing pin hole on an AI. I've actually seen quite a bit worse.

Fire-formed brass measures 1.681" from base of case to a point on shoulder that is .4" diameter, so it doesnt seem like its over-headspaced.

My 1x fire-formed brass I noticed had some imperfections but I wasn't too worried about it as the shoulder is moving forward i figured a little stretch marking was no big deal.

Photo below of two pieces of typical and above typical fire-formed virgin brass.

Another photo of two pieces of five pieces I have fired that have four firings on them with just neck sizing

Another Photo of a sectioned case with four firings.

Is this a bad batch of Lapua brass? I would think maybe its over pressure or something but the virgin brass has similar markings and there are basically no pressure signs at 51gr and definitely not at 47.5.

Any idea what is going on?

https://www.dropbox.com/s/7rsc7w5o0kf98se/Photo%20Jul%2013%2C%203%2047%2008%20PM.jpg

https://www.dropbox.com/s/xulqaasf96lhdwl/Photo%20Jul%2013%2C%203%2048%2005%20PM.jpg

https://www.dropbox.com/s/c2mpbchup9ih9qa/Photo%20Jul%2013%2C%205%2009%2030%20PM.jpg