What does head space have to do with the case?I can change head space on any case with the sizing die...... jim
Hornady releases 6mm ARC
- Thread starter Winny94
- Start date
JEFFPPC
Gold $$ Contributor
I have a question. Hornady has made the CM a marketing sucess and may do the same with ARC. But, why not do the long overlooked obvious and promote the 6BR with cases and factory ammo and getting the rifle manufacturers to produce factory rifles.The CM is no real gain over existing cartridges in its class such as the .260 and 6.5x47. The 6BR has nothing else like it available. Maybe its the jealousy thing because it was an original from Remington who has totally fumbled the ball with it.My point is, fill a void, we do not need more of the same things that offer no real gain. But, kudos to Hornady for slick marketing.
The tone of some posts were implying that the ARC was a 6mm Grendel. But the headspace is different enough that they are not interchangeable. Grendel 1.220, ARC 1.190. Firing an ARC case in a 6mm Grendel is an unsafe condition.
One very simple reason for not commercializing the 6BR; it's not autoloading friendly. That's where the Grendel comes in, it's MSR friendly, and MSR's is where the market is right now. MSR's are outselling bolt actions 100 to 1. I remember when a new Cheaper than Dirt store opened nearby, not only were the walls lined with AR-15's and 10's, there were several long isles full of same, and only one short isle for bolt action rifles.
The ARC is specifically designed for autoloading rifles.
LVLAaron
Gold $$ Contributor
There's "available" as in you can fireform brass or do a bunch of work, then there's "available" as in buy it at a local retailer...
I think you need to clarify your terms, head space is the clearance used in sizing. Is case length or chamber length is what you are talking about? it would have more to do with the difference in shoulder length from the bolt face. I would bet it is very close to 6mmAR. that has been around for a long time.... jim
Headspace is the datum defined as a specific distance from a diameter on the shoulder to the bolt face. You can see it in every reamer print. It is not the clearance created when sizing a case.
In the example above, you'll see a very specific dimension called out from 0.350 on the shoulder back to the bolt face with a min/max tolerance. That is the headspace.
Edit: Grendel is 1.22, ARC is 1.19, and 6PPC is 1.15 - Did anyone ever experiment with a 6 PPC +0.040?
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JEFFPPC
Gold $$ Contributor
Texas 10, your correct. MSR are hot items. .But long before the AR became civilian popular there was a void ,as there still is, for an ultra accurate small case 6mm cartridge. Great for varmints and adequate for deer with decent barrel life. 6 BR made to order but has never happened. Everyone needs a 300wsm so when they shoot a 125 yd deer poorly it still expires in a short enough distance they might find it.
So that is what is said it is a measurement nothing more, you create headspace with a die setting. I fire form and use a means to hold it tight against the bolt face after the are FireFormed now you set the HEAD SPACE by seating the shoulder back so it will go back in the chamber easy and measure it with a stub. This has nothing to do with one chamber size to an other, No Print shows head space, because that is a variable for the loader themselves to set.....I just looked at at a number of prints and the only reference to head space is the use of the gage when chambering. The next head space is up to the loader and setting it up, screw the die down too much you get excessive head space, now that is dangerous ..... jim
Feel free to misuse that word if you wish, Jim, but you will be the one clarifying your meaning to others because you are not following the technically accepted definition of headspace. Headspace is fixed when the chamber is reamed and the barrel installed on the action. Headspace is not the clearance between the brass and the chamber and cannot be changed with a sizing die. The entire reason for defining and tolerancing headspace is to ensure that off the shelf ammunition works in every rifle nominally chambered for it.
Where is fguffy, by the way? I thought that if we said headspace three times and he would appear.
Where is fguffy, by the way? I thought that if we said headspace three times and he would appear.
Riflewoman is correct but we all know what you're saying, Jim. We do much the same when referring to a "node" but technically, we want bullet exit to occur at an anti-node.
2885fps! Wow!
I have a 243LBC AR 40 and 26" barrel. I get about 2750fps with 28gr of H4895 and 105gr bullet. I had to decrease my load when I used more powder because I shed lugs in two bolts.
Was Brady using Hornady factory ammo or reloads?
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Head space in chambering has nothing to do with the case at that point only the go gage and tape on it for no go. There hell it can't be changed with the sizing die, how do you set up a sizing die ? How do get the bolt to close freely? You size the case .0015 to .002 on most so you are setting head space. it has been a term for 65 years or more. .... So what do you call the clearance between the chamber size and a sized case? all the SAMI says is where to measure .... jim
I've heard it called "head clearance" before.
Unfortunately SAAMI lists some definitions but obviously it's not a complete dictionary of shooting terms. Generally speaking, dictionaries list multiple definitions of words because that's how language is used in the real world, including "head space", but shooting jargon isn't formally documented any where that I know of so sometimes there's disagreements about how words are used.
Headspace is a fixed chamber dimension on a rifle. The SAAMI definition is quite clear that the headspace measurement is taken from the firearm and it is not taken from the case used in the firearm.
When I bump the shoulder on my cases 0.0015-0.002" so that they chamber freely, the headspace of my rifle has not changed.
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