Gunsmithing Minimum Headspace?

[Estes640]

I am looking at a rifle that is said to have minimum headspace. I understand what headspace is, but can anyone tell me if this is common practice?

I've never heard this called out before so it's just a little confusing. I don't want to get the rifle and have the chamber be tight.

Any advice is appreciated.

 

[Mordamer]

It is somewhat common on custom rifles. It means that some brands of factory brass may need to be resized to fit in the chamber. It also means that you may have trouble getting a resizing die to resize brass enough to fit the chamber without modification to the die. You might not experience either of these problems. If the rifle is a good deal and is what you are looking for then I would not let the "minimum headspace" scare me away.

Some gunsmith's seem to believe that minimum headspace is synonymous to "tight tolerances". I have heard different theories that minimum headspace saves brass life and increases precision. I don't believe there is sufficient evidence backing the claims. I prefer a barrel to headspace halfway between a go and no go set of gauges. If the barrel won't pass a go gauge test it is simply "out of tolerance" in my opinion.

 

[Greg Langelius *]

I like the SAAMI chamber specs, mainly because I'm an Elder Fart and will likely be passing my rifles on to my offspring, etc. I feel that having a rifle which can have issues with ammunition may be somewhat unkind to the uninitiated.

Yes, there can be an accuracy penalty; but I'm not the superior marksman that many others here are, and such more highly refined accuracy variances tend to go unnoticed by the likes of me.

I recently endured an episode where two bads don't make a good, they make a very bad. I had a barrel adjusted too short headspace-wise (using a fired case for a H/S Gauge), combined with a couple of overweight powder charges. I make no excuses, I screwed up.

One blown primer later, I had a go gauge on order with express shipping. It took a lot of tidying up to re-space the barrel, track down all the excessive charges and pull them, and do all the necessary case measurements and die adjustments. I have a fair number of cases which will need to be fireformed again to match the new chamber configuration.

Needless to say, I will never use a fired case for a H/S gauge again.

Greg

 

[XLR308]

The last savage rifle I built in 243 win I set up with minimum headspace, Lapua brass and all factory ammo I have tried with the exception of Nosler fit perfect.
The Nosler I tried in it you can feel a little resistance when closing the bolt but it shot great without any issues.
The main issue you may encounter has allready been stated regarding the resizing operation and may require a competition shell holder set or die modification.

 

[m1match]

SAAMI is the Sporting Arms and Ammunition Manufacturers Institute which sets the technical standards for the industry. Although you may know it already, headspace is the dimension from the bolt face to a specific point on the shoulder of the case, which SAAMI specifying what that point on the shoulder is. For every cartridge, SAAMI specifies minimum and maximum headspace.

A minimum headspace rifle is just that, headspace set at the minimum dimension. What Greg was talking about is a rifle with short headspace less than SAAMI minimum. A rifle with headspace at SAAMI minimum will work just fine and if you reload and resize your brass to work in more than one rifle, like I do, you get less case stretching upon firing, which should promote longer case life. However a minimum headspace rifle might not chamber rounds well if it's dirty and fouled.

As to accuracy, I can't say that a minimum headspace rifle will be any more accurate for the type of shooting that we're doing. Accuracy International rifles are plenty accurate, but being designed as battle rifles, my AI barrels show a few thousandths more headspace than minimum.

 

[spife7980]

I've never heard this called out before so it's just a little confusing. I don't want to get the rifle and have the chamber be tight.

A rifle with "minimum head space" is only necessarily tight in that one dimension: the distance from the bolt face to the shoulder datum highlighted in yellow. Its controlled by how far the reamer was run in/how far forward the shoulder of the barrel was cut.

A chamber could have plentiful head space and be tight or loose in many/all other dimensions . Base diameter, shoulder diameter, neck diameter, neck length are all things dictated by the reamer itself, not just how far it was ran in. As an example, if someone was going to put brass in the ppc shown above they would have to turn the necks, factory brass wouldnt even chamber in it, because it has a tight neck. Typically when things are tight like that it is noted in the barrel markings along with the caliber to alert people to the potential issue.

So when someone says a "tight" chamber: tight in what way?

The minimum head space you are looking at could still have all of those other aspects of tight, it could also just as easily not. I would ask for some more detail into what it was actually cut to or with if you are concerned about its function for you.

 

[Estes640]

Thanks for all the info guys! I ended up purchasing the rifle and will update the thread once I get some brass fired through it

 

[FishDr]

Also understand there are separate dimensions called out for headspace of the chamber and the ammunition it is designed to shoot. A minimum headspace chamber should still accept ammunition at max (factory) headspace for ammo. My 260 chamber is set at the minimum HS +.0005. I get .003-.004 total growth on new Lapua Brass across the first two firings. When I FL resize, I move the headspace back .001 from fully fire-formed.

 

[TexasUplander]

im the worlds worst at setting up a rifle at very minimum headspace when i build one. this always comes back to bite me in the ass when the brass starts to work harden and you end up with .000 headspace.

 

[Edds]

I am looking at a rifle that is said to have minimum headspace. I understand what headspace is, but can anyone tell me if this is common practice?

I've never heard this called out before so it's just a little confusing. I don't want to get the rifle and have the chamber be tight.

Any advice is appreciated.

If the only thing someone could tell me about the headspace is that it was "minimum", I would think they didn't know what the headspace was. The headspace specs don't mean anything to me unless there is a number attached.