New 6mm Advanced Rifle Cartridge

[lennyo3034]

Finally had a chance to play with the 6 ARC a little. Today was messing with the EC Tuner Brake.

Hornady Black averaged 2771
Hornady Match averged 2741

I'm thinking the two hornady loads are exactly the same brass and powder charge, just different bullets. Velocity difference due to bullet weight. I saw similar differences in velocity in my dasher when I swapped Berger 105s for 109s and kept everything else the same.

I plan to load Berger 105s for this, but it does pretty well with factory.

Sorry for only 3 shot groups, just testing tuner brake today.

 

[raptor99]

Right. What I'm getting at is unless QC slipped and they loaded hot ammo (not impossible, but fairly rare), something in your rifle is causing timing (gas system) or pressure (fouling) problems. I'd give the barrel a good scrub and try adjustable gas.

It has an adjustable gas block and was just cleaned. They were the first rounds down the barrel. l really hate it because brass is so damn hard to find!! I am thinking about pulling some bullets and checking weights.......

 

[newageroman]

Well that was fun. I see you guys have been busy, Welcome to the thread LRBuck - those results are very impressive!
Shot the ARC on Easter Sunday 200/300, but when setting the ATN BC for 500, the scope display went to shit. I'm giving it one more chance this weekend. I said screw that and brought out the IHC garand to bang steel at 500, complete with 16" bayo and the ping. I would have been on the long range but I had a guest breaking in an AI action.

Hoping to make 500 more ARC cases this weekend as well.
Cheers!

 

[Dino11]

For the folks wondering about some of the lighter weight target and hunting loads.

 

[Dino11]

And what can you folks that are in the know tell me about the 6mm Grinch, it seem to be a lot like the Hornady 6mm ARC.

From my readings about it the cartridge falls in between the 6 Dasher and the 6 PPC. Sounds alot like the 6 ARC to me. And the 6 Grinch has been winning a lot of competitions for many years. Just nobody manufactures it.

 

[SWFShooter]

And what can you folks that are in the know tell me about the 6mm Grinch, it seem to be a lot like the Hornady 6mm ARC.

From my readings about it the cartridge falls in between the 6 Dasher and the 6 PPC. Sounds alot like the 6 ARC to me. And the 6 Grinch has been winning a lot of competitions for many years. Just nobody manufactures it.

The 6mm Grinch is very similar to the 6mmAR Turbo 40 and the 6mm Fat Rat. Improved Grendel case with shoulder blown forward. Has about 3 grain more water capacity than the 6mm ARC.

 

[raptor99]

The 6mm Grinch is very similar to the 6mmAR Turbo 40 and the 6mm Fat Rat. Improved Grendel case with shoulder blown forward. Has about 3 grain more water capacity than the 6mm ARC.

What would be the advantage of more case capacity?? The bolt head is the limiting factor on all of the ARs so your limited to how fast or hard you can push a bullet anyway. If your going to use a bolt gun the BR family would be the way to go......

 

[SWFShooter]

What would be the advantage of more case capacity?? The bolt head is the limiting factor on all of the ARs so your limited to how fast or hard you can push a bullet anyway. If your going to use a bolt gun the BR family would be the way to go......

More powder, higher velocity, OR lower pressure at the same velocity. It calculates out to somewhere around 5,000psi lower chamber pressure compared to the same velocity in a 6mm ARC. Downside- The fire forming brass is an extra step.

 

[Ledzep]

What he said^^^

What the bolt "cares about" is the force/thrust exerted on it by the cartridge. In the most simplistic form (ignoring case/chamber friction, case stretch, etc..) that is simply the web area of the case multiplied by the chamber pressure.

So if you assume the same bolt force because of the same chamber pressure in 2 different cartridges of the same diameter, then you look at the effect of changing the internal volume with the same pressure. Larger volume -> more energy -> more velocity for the same projectile.

However, there are still things to consider like feeding, magazine COAL limitations vs. Ogive lengths... In some situations internal capacity doesn't change as much as you'd think because the bullet is stuck at 2.25" from the head, and the mouth location is locked at the back of the ogive. There's also powder burn efficiency, which isn't so much an issue in smaller cartridges like this, but does come into play more often when you look at big and/or overbore cartridges. You can wind up burning 30% more powder for 5% more velocity...

 

[newageroman]

Skipped shooting at long range yesterday to do this:

http://brassbucket.net/wp-content/uploads/2021/04/20210412_141432.jpg

http://brassbucket.net/wp-content/uploads/2021/04/20210411_201209-scaled.jpg

http://brassbucket.net/wp-content/uploads/2021/04/20210412_083750.jpg

I have another unprocessed box stashed for next run.

The ATN Scope actually did very well. I did get stuck on the short range due to ammo testing.
I guess I am now one of those guys that takes reloading stuff to the range...

Case disection and multiple firing tests to come.

Custom headstamp ideas welcomed.

 

[SWFShooter]

What he said^^^

What the bolt "cares about" is the force/thrust exerted on it by the cartridge. In the most simplistic form (ignoring case/chamber friction, case stretch, etc..) that is simply the web area of the case multiplied by the chamber pressure.

So if you assume the same bolt force because of the same chamber pressure in 2 different cartridges of the same diameter, then you look at the effect of changing the internal volume with the same pressure. Larger volume -> more energy -> more velocity for the same projectile.

However, there are still things to consider like feeding, magazine COAL limitations vs. Ogive lengths... In some situations internal capacity doesn't change as much as you'd think because the bullet is stuck at 2.25" from the head, and the mouth location is locked at the back of the ogive. There's also powder burn efficiency, which isn't so much an issue in smaller cartridges like this, but does come into play more often when you look at big and/or overbore cartridges. You can wind up burning 30% more powder for 5% more velocity...

Agreed. In the case of a standard 6mm ARC (AR15) reamer versus a Grinch/Fat Rat/Turbo40 (AR15) reamer, the cartridges lengths are for the most part similar. The 6mm ARC case is 0.030" shorter, and for a 108ELD, you lose 0.116 grains of water capacity per 0.01" the bullet is seated deeper, so the 6mm ARC loses 0.35 grains of H20 capacity compared to a Grinch at the same overall length. The 0.116 grains of H20 per 0.01" change in seating depth factor can be used to determine differences of varying overall lengths of the same bullet. The Grinch will typically be close to 2.5 to 3.0+ grains more H20 capacity for the AR15 platform. Bolt reamers should have a longer freebore without the mag length restrictions. (the 3.0 number would be with the Grinch using Lapua, as Hornady is about 0.5 grains smaller than Lapua/Norma/Starline brass formed for either case.)

 

[TonyTheTiger]

I keep wondering what the hell grendle is. Found it on urban dictionary: https://www.google.com/amp/s/www.urbandictionary.com/define.php?term=grendle&amp=true
It's either that or an obscure Star Wars character.

 

[SBRSarge]

I keep wondering what the hell grendle is. Found it on urban dictionary: https://www.google.com/amp/s/www.urbandictionary.com/define.php?term=grendle&amp=true
It's either that or an obscure Star Wars character.

Grendel is from the epic old English poem titled Beowulf. He is a semi-monster and was defeated by Beowulf. Or something like that, it’s been 45 years since I read it!

 

[TonyTheTiger]

Grendel is from the epic old English poem titled Beowulf. He is a semi-monster and was defeated by Beowulf. Or something like that, it’s been 45 years since I read it!

That's Grendel. Some people here insist on talking about Grendle. Totally different.

 

[SBRSarge]

That's Grendel. Some people here insist on talking about Grendle. Totally different.

Ahh. Got it!

 

[raptor99]

Skipped shooting at long range yesterday to do this:

http://brassbucket.net/wp-content/uploads/2021/04/20210412_141432.jpg

http://brassbucket.net/wp-content/uploads/2021/04/20210411_201209-scaled.jpg

http://brassbucket.net/wp-content/uploads/2021/04/20210412_083750.jpg

I have another unprocessed box stashed for next run.

The ATN Scope actually did very well. I did get stuck on the short range due to ammo testing.
I guess I am now one of those guys that takes reloading stuff to the range...

Case disection and multiple firing tests to come.

Custom headstamp ideas welcomed.

What is your process for forming 6ARC out of the blanks??

 

[raptor99]

Just thought I would throw this out there. I have a bunch of loaded 105s from Hornady and they shoot so, so but I have been getting some pressure signs with some of these factory loads. I decided to pull some of these bullets and replace them with some lighter Berger 90 and 87gr bullets to try to avoid the pressure signs I was getting. To my surprise they shot VERY well!! 90s went into a .5 and the 87s into .4 for five shot groups.......

 

[jbailey]

Grendel is from the epic old English poem titled Beowulf. He is a semi-monster and was defeated by Beowulf. Or something like that, it’s been 45 years since I read it!

Hell yeah man! Nice summary. The work is consider the 'first' work written in English. Of course the English language would go on to essentially conquer the world, literature and otherwise. As the such, we should all know "Beowulf" and read it.

I love the beer (mead) hall scenes from the poem, as they were major hubs of society back in the day, more important than the 'bars' of modern life, as major political discussion were made in these halls. The halls were major engineering feats too: huge timber frames with massive/heavy roof systems:

Why a rifle cartridge was named after Beowulf's antagonist is unknown to me. There is a fairly good book called "Grendel" written from the perspective of the monster, which turns the tide on the epic: instead of Grendel representing evil, Beowulf is a blood thirsty 'man'.

Both "Beowulf" and "Grendel" are recommended reads.

 

[Maddvaper]

You know I appreciate this guys, been reading this since page one and been shooting/building Ar's since 1991. Interesting about the pressure it can handle being determined by what the Bolt can handle while Cycling. So is that saying with an adjustable Gas Block/ Gas Key/ of even an A5 Buffer system with H1-H4 Buffers to slow the Bolt down it can be loaded hotter and still be within the realm of acceptable due to it not stressing the Bolt ? (Until the Brass itself starts showing pressure of course.)

 

[newageroman]

Excellent question vaper! I have no idea on that but I just went for the adj. gas block because it added one more step of tunability whcih I figured wouldn't hurt handloading...

Anyways here is my process for making 6ARC brass during the AmmoPacalypse of 2021:
Advanced details and photos at this linky: http://brassbucket.net/6mmarc-brass-forming-from-straightwall-blanks/
ATN target vids on steel @ 1/2/3/500 will be posted there soon as I get the edit up - It's not spectacular, but seems to make the long drive worthwile somehow.

I wouldn't even attempt this without the annealer - I believe it is key.
Basic process

• Use Pilot 01 for all annealing and RCBS #3 shell holder – the H45 was too tight and the other RCBS was too loose letting cases slip and fall in the annealer to be turned upside down and picked out. RCBS#3 just right.
• Analyze to find annealing code #A
• Anneal all brass using code #A
• Lube
• Size (single pass)
• Analyze to fine annealing code #B
• Anneal all brass using code #B
• Trim
• Champher/deburr
• Clean (if needed – blow dry chips away)
• Prime
• Drop powder
• Seat bullets (jammed)
• Fire Form
• Analyze to find final annealing code #C
• Anneal all brass using code #C
• Repeat rest of loading process as normal brass.

 

[Yondering]

You know I appreciate this guys, been reading this since page one and been shooting/building Ar's since 1991. Interesting about the pressure it can handle being determined by what the Bolt can handle while Cycling. So is that saying with an adjustable Gas Block/ Gas Key/ of even an A5 Buffer system with H1-H4 Buffers to slow the Bolt down it can be loaded hotter and still be within the realm of acceptable due to it not stressing the Bolt ? (Until the Brass itself starts showing pressure of course.)

We may be thinking/saying the same thing, but for clarity I prefer to explain it this way:

There is a limit to what the AR15 bolt can handle, not accounting for other influences that decrease that limit. This base upper limit is generally somewhat less than a bolt action, but IMO somewhat closer than many think. Consider this the upper limit that the bolt itself can handle if the rest of the rifle is set up perfectly.

Common influences that decrease bolt capacity are:
- Uneven lug contact
- Early unlocking (under pressure)

Most "off the shelf" or DIY AR15 rifles have one or often both of these issues, and that significantly degrades the capacity of the bolt; IMO this is a big factor in the lower pressure "AR15 loads" published in some load data. Also note that early unlocking adds stress to the extractor as well and can result in failures there, regardless whether it's a Grendel or x39 extractor.

Any time you add load, you can expect life to decrease, but in my own experience I've seen that the combination of a good chamber (no excessive bevel to damage brass), even bolt lug contact, and careful gas tuning can run at or close to published bolt gun data without issues. Hornady's published bolt gun load for the 105gr BTHP and Lever is basically what I settled on several years before Hornady published that, and I use it as the primary load in all three of my 243 LBC AR15 rifles. Of course a caveat to this is that I'm not expecting a bolt in this cartridge to last 30K-50K rounds; that just doesn't really match my application or needs.

edit for clarity - the three 243 LBC rifles mentioned above are all AR15 (no bolt guns) with trued and shimmed or thermo-fit receivers and careful gas system sizing and tuning. Gas system lengths are rifle for the 24" and 19", and carbine for the 12.5".

 

[Thorbeast]

What does everything think about mid-length vs rifle gas on a 16" barrel? Normally I wouldn't care, but lower chamber pressure during unlocking seems to be desired with this cartridge. I really like the proof 16" ar barrel, but I wish it wasn't so heavy. I'm having a hard time finding another 16" rifle length barrel, but the weight of the proof barrel is a show stopper for me.

 

[TonyTheTiger]

What does everything think about mid-length vs rifle gas on a 16" barrel? Normally I wouldn't care, but lower chamber pressure during unlocking seems to be desired with this cartridge. I really like the proof 16" ar barrel, but I wish it wasn't so heavy. I'm having a hard time finding another 16" rifle length barrel, but the weight of the proof barrel is a show stopper for me.

Proof seems to do the appropriate amount of R&D before releasing a product. If they think it works I'd be inclined to believe them. CMMG thinks it works also, and they have a much lighter contour RLGS 16" in stock, but they don't have the accuracy reputation that Proof does.

I wouldn't even consider mid length, and if I was apprehensive about the rifle gas 16" I'd just get and intermediate gas barrel made.

 

[Gtscotty]

I'd probably look for an intermediate length or rifle length if I was going to run a can. My ARC is a 21" with +2 and with my repurposed Saker it runs great on a low gas setting. My Grendel is a mid length 16" and with my SA bleed off block, it runs fine with a can in pretty much max bleed off with my normal powders like 8208 and AR Comp. Trying LVR loads, it's still a bit sharp in max bleed off. Given the lower expansion radio of the 6mm ARC, I'd want a longer gas system to tap at a little lower pressure levels and a little longer into the cycle. If you're not using a can, a shorter gas system might be fine.

 

[Maddvaper]

I had originally set up my 16" Rifle length Mcgowen with an A5 H1 Buffer and before it was over with went back to the standard Buffer and standard Weight and still had to open up the gas port two Size's for it to lock the Bolt back on an empty mag. I'm not running Suppressed but still food for thought.

 

[Yondering]

I had originally set up my 16" Rifle length Mcgowen with an A5 H1 Buffer and before it was over with went back to the standard Buffer and standard Weight and still had to open up the gas port two Size's for it to lock the Bolt back on an empty mag. I'm not running Suppressed but still food for thought.

I haven’t used a 16” in one of these (mine are in either side of that) and don’t have a dog in the fight, but:

A little over-gassed is way better than under-gassed, and over-gassed is a lot easier to fix.
(And keep in mind that gas port sizing affects timing along with gas system length; the BCG can take in a trickle of gas over a longer time with a shorter gas system or a quick dump of gas with a longer system and get the same job done when it builds enough pressure to cycle.)

Ive learned this the hard way with gas systems that were too long for the barrel; it’s a PITA to fix and can make the rifle really finicky about what it runs.

 

[david walter]

Is the only case difference the shoulder bumped back 0.003”?

Otherwise the same?

 

[Ledzep]

I forget exactly, it's something like .028-.030 not .003".

Of the few Grendel cases I've got in the mix that I've accidentally resized to 6mm ARC, I had to trim quite a bit more off of them to get them to ARC length so case length may be different, too... Or necking down made them grow a little.

But body and rim diameters and shoulder angles are the same. It was pretty easy to go from 6.5 G to 6 ARC. Hell, I did it on accident Feels way different from the standard 6 ARCs obviously when you size them.

 

[newageroman]

Keeping this thread alive!
Made more fireformed brass Sunday. Loaded them long to jam the lands @ 2.322" Single fed them and all GTG. Only ~200 more to go - yeah...
I will take one of those cases and load it multiple times to see failure point.

Anyone else have any rounds down or any new loads going on?

http://brassbucket.net/wp-content/uploads/2021/04/20210425_131913-scaled.jpg

 

[George Mac]

I’d just like to say thank you to everyone for sharing so much knowledge regarding this cartridge. I tried a 12” 1/7 from Six5Arms. I went off Gundoc’s data for an 11.5 and took it out to 700 after a quick zero. 7 mils to 700 yards with factory 108’s was ridiculously easy And fun.

 

[2c1fr]

I am very excited about this round and it’s potential I have built an ar for it using a 24
Inch shilen barrel so far I am seeing good results with it I haven’t had a chance to load for it yet so we shall see what it does

 

[LRBuck]

These prices are a crime and I hope others are not paying this much for Black or the ELDs. In the past their ammo prices have been pretty reasonable but now...geez!

https://www.outdoorlimited.com/rifle-ammo/6mm-arc/

 

[GONE BAD]

I got 8 boxes of Hornady 6 ARC 108 match for less than $25 a box about 2 months ago just to break-in my new ARC. That will be the end of loaded factory ammo for me unless I can't get brass!

 

[godofthunder]

Got mine out to the range today finally after BA replaced the barrel. Shoots 108 ELD match right at 1 MOA. Looking forward to finding some primers and bullets that I want and doing some load development.

 

[GONE BAD]

1st time out with mine today also.
Just popped about 20 down range. Wanted to shoot it more but didn't have enough time. Did notice some ejector swipes. Brass laid in a nice little pile about four feet from me at 4 o'clock.
1 fail to feed and one mag fail to hold open on last round.
Need to have more time to play with it and burn up factory ammo. It seemed to want to shoot nice groups but I was rushed. The illusion to me is that I'm not shooting a 6mm. Feels kinda weird. Didn't install the magneto speed. It is definitely a smooth shooter.

Anyway I now have some fired brass that I can work with, check some numbers and see what develops.

 

[LRRPF52]

1st time out with mine today also.
Just popped about 20 down range. Wanted to shoot it more but didn't have enough time. Did notice some ejector swipes. Brass laid in a nice little pile about four feet from me at 4 o'clock.
1 fail to feed and one mag fail to hold open on last round.
Need to have more time to play with it and burn up factory ammo. It seemed to want to shoot nice groups but I was rushed. The illusion to me is that I'm not shooting a 6mm. Feels kinda weird. Didn't install the magneto speed. It is definitely a smooth shooter.

Anyway I now have some fired brass that I can work with, check some numbers and see what develops.

Sounds like you’re under-gassed.

Tell more about gas system length, barrel, port diameter, and gas block installation details if you will.

 

[GONE BAD]

Sounds like you’re under-gassed.

Tell more about gas system length, barrel, port diameter, and gas block installation details if you will.

Maybe but a few more rounds through it and might come together?
20" with rifle length gas. Gas block is set screws and port is .085
Carbine buffer system. I have a couple different weight buffers, might try one a tad lighter? Only have 30 rounds through it at this point in time.
First 4 AR platforms switched gas blocks to AGB last 3 stayed with just regular old low profile blocks.
I don't run suppressed and really hate messing with AGB's.

Anyway this is a last minute through together from stuff I had laying around. Only thing I purchased was the barrel and BCG.
Might go somewhere with this or might not. All depends
Just playing around

 

[trdjohn]

I've got the proper bolt head for the Savage, thinking of having savage pre-fit barrel made up for 110 tactical SA bolt rifle.

@Ledzep I see you have 28" bolt gun. Are you running SAAMI chamber, or something else w/ regards to neck, freebore, or throat? You shooting 108 ELD-Ms it seems, where are you seating the end of boattail/bearing surface in relation to neck/shoulder? What is your OAL length? What magazines are you running?

Or anyone else that has bolt 6 ARC I'd like to hear your experiences too

(I know this is semiauto forum, but other ARC threads aren't nearly as active as this one)

 

[Ledzep]

I have 2 ARC bolt guns. Cz527 (7.62x39 rebarreled) 18", and an ARC nucleus with a 28" bartlein.

The CZ works with factory magazines. The Nuke (and most any other 'standard' short action) works really well with MDT BR magazines. No real modification needed that I've experienced.

SAAMI chamber in both. I run 110 ATips at 2.35" coal. I have run 108s when I started with the ARC but I believe I kept them at 2.245". I don't know if you can get much longer with 108s without hitting rifling. Maybe .030-.050? I don't know for certain. The 110s have longer ogives.

 

[trdjohn]

Thanks Ledzep. I currently have Odin 18" gasser. My notes show when barrel was new, the 108 ELDM pushed to lands has COAL ~ 2.260" Factory 108 match is ~ 2.250. I had a box of 105 Berger Hybrid target, those with ogive push to lands, the COAL on those were 2.315"-ish. Those were the longest of the bullets I tried pushing to the lands. Your 110 ATips at 2.35", roughly how far off the lands are those?

 

[tomcatfan]

Question for the reloaders, I finally got my reloads out and they are way fast. I started my loads at 29.0 gr of lever evolution. This was 0.5 gr less than Hornady‘s max load. I was pushing a 105 gr Berger around 2780 out of my 21” Odin works barrel.

It had the same signs as factory Hornady 108 eld ammo. A slight ejector mark, but it didn’t have enough gas port pressure to cycle the action. My adjustable gas block was set up for the Hornady match.

would you guys back off and just open the gas block, or would you run until you can cycle both the reloads and factory ammo? Should I back up on the powder charge or just embrace that I have a fast barrel. I don’t want to be way over gassed for factory ammo.

 

[Ledzep]

I believe it was 2.37-.238 to the lands with 110 A-tips.

 

[lennyo3034]

How much shoulder bump is everyone using for their gas guns? I started loading today and started with the headspace comparitor. Using the B .350" bushing:

Factory Ammo: 1.184"
Once fired factory brass: 1.191"

Does .007" growth seem high? It's out of a gas gun so I'm expecting it to stretch a little more.

I just resized the brass to 1.189" for a .002" shoulder bump, but I'm wondering if that's too little. Being a gas gun the case stretches a bit during extraction so the measured 1.191" may not be representative of actual chamber dimensions.

 

[eddie102870]

most say .003-.004 for gas guns from what ive read, have you tried any through the gun with the .002 bump?

 

[Ledzep]

.007" from new to fired is pretty normal. For gas guns I aim for .002-.003" bump, followed by a check with empty cases to make sure the chambered case doesn't stick when I try to un-chamber it. If it sticks, run the die down a thou and try again.

 

[lennyo3034]

Just did.

Once fired brass would not rechamber. Not even close
.002 would chamber, but seemed to take a little bit of effort. It also came out .0005 - .001 shorter than going in.

I ended up bumping a total of .004 and it chambers and extract without effort.

 

[Triple D]

I ended up bumping a total of .004 and it chambers and extract without effort.

That’s what I go with, .004-.005. It also helps to ensure there aren’t issues when running high round count between cleanings and suppressed.

 

[GONE BAD]

I just resized mine today. New brass .007 shorter than once fired. Bumped back .002 and chambered fine. New brass my not have fire fromed to chamber (.001 spring back). I'll load these up and see how it goes.
Didn't anneal this time as it was easy to bump back. I'll anneal next firing. Brass being as hard to come by, I don't want to over work it! Probably got to make this batch last till sleepy joe gets out of office !
I'll run loads just hot enough to allow the rifle cycle properly at this point in time

 

[LRRPF52]

How much shoulder bump is everyone using for their gas guns? I started loading today and started with the headspace comparitor. Using the B .350" bushing:

Factory Ammo: 1.184"
Once fired factory brass: 1.191"

Does .007" growth seem high? It's out of a gas gun so I'm expecting it to stretch a little more.

I just resized the brass to 1.189" for a .002" shoulder bump, but I'm wondering if that's too little. Being a gas gun the case stretches a bit during extraction so the measured 1.191" may not be representative of actual chamber dimensions.

I’ve found most factory ammo to be undersized relative to base-to-shoulder datum as a rule so it will run in a wide range of chambers.

So yes, you’ll typically see a lot of shoulder growth upon firing. You don’t have to re-size to that short factory dimension though.

I use a stripped bolt with the same face depth and lug lengths to determine how far I need to move my shoulders back, along with the Stoney Point/Hornady headspace gauge set. When setting up my sizing die, I incrementally turn the die down until I get reliable bolt lock-up with the stripped bolt in the chamber I’m loading for.

For those that are trying to make sense of what we’re talking about, we’re measuring the distance from the base of the cartridge/case to a middle point on the shoulder as a way to set headspace. Too long...and it won’t chamber. Too short with repeated re-sizing to that length, and you over-work your brass, which reduces its life.

Unfired factory Lapua brass:

Fired:

 

[alamo5000]

I scored some 6mm ARC ammo. Hornady 105's @ Palmetto. I probably got screwed a little but I got them to the door for $1.75 p/r shipping and tax included.

All I really wanted to do is have some on hand for when I get my barrel and to also be able to harvest some brass.

After I get these in hand I will be able to at least reload. Got a bunch of powder and primers. I just need some 6mm bullets.

Note: I was just going to buy brass only but if you can find it it's almost a buck per piece.