Typical headspace

3

338lm

New member
My questions below pertain to custom chambering a barrel/not factory barrels.
When reaming a chamber, what is the least amount of headspace that a person should use? What is the typical headspace used when custom chambering?
Does proper headspacing vary with different calibers?
 
proper head spacing is just that, proper or correct. There is no "close is good enough". There are industry standards and tolerances so that ammo matches up to rifles.
When you talk about wildcats and custom dies then you can fireform brass to match the chamber dimensions. After that the brass conforms to the chamber and the dies are matched to that chamber. Unless you have a lot of experience you should always have a go gage made and use it when chambering. Tolerances of .000" +.002" are very very easy to work to.

Right is right and wrong is wrong, there's very little grey area in between.

Dave
 
I prefer to use a steel go gauge and chamber so you can feel the stripped bolt close firmly on it at the bottom of the bolt throw. That is a minimum head spaced chamber.

If you can not feel it close on a go gauge, it should not close on a no-go gauge and that would be acceptable for a hunting rifle.

If it closes on a no-go gauge but does not close on a field gauge, that is acceptable for a military rifle using military ammunition.
 
I just do chambers for myself, mostly..... I like chamber depth to be such that when I FL size a fired case with the dedicated shellholder contacting the FL die, it bumps the shoulder about .002. This can be done with micrometers, die and a headspace gage.
I made up a bunch of round shims, .001 to .005 thick, that I put between the H.S. "go" gage and the bolt face to determine actual headspace when chambering.
Works for me but YMMV, and opinions differ.
 
in competition rifles, me thinks. most want to see thier headspace at the basic number( this is listed in saami drawing for common chamberings, and on the specific reamer print).

me also thinks you are refering to clearance, not headspace. as in how much clearance is there between my (min spec) chamber and my (sized) brass ?

mike in co
 
Headspacing/SAAMI

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This is a shooting industry standard that is recconized by the Insurance industry. It makes sure factory guns will load and fire factory ammo made by other manufactures. It allows a safe tolerence between different manufactures. The difference in steel go and no go gauges most frequently is .0035 headspacing length.

SAAMI is here to protect us against our selves.
Rustystud
 
Yes, the question that I am actually asking is how much clearance does a person typically use between your brass length and the chamber length (between shoulders) on a competition rifle when you have to bump the shoulder back with a die?

From the responses already received I now also understand how a competition chamber is sized (reamed) using a "go" gauge.
 
338lm said:
the question that I am actually asking is how much clearance does a person typically use between your brass length and the chamber length (between shoulders) on a competition rifle when you have to bump the shoulder back with a die?
Click to expand...

I bump my shoulders .0015" when sizing.
 
388

I feel safe in saying that the vast majority of Benchrest Shooters, when speaking of "headspace', are talking about the distance between the bolt face and the head, (face), of a chambered round. I know that we are using the term in slang, but that is what it means to us.
Typically, the number .001 inch is used. If my brass is getting a little tired toward the end of a Two Gun event, I might even go as far as .002 so they go in and come out easy.. Accuracy does not seem to suffer.
When doing this, be sure and use tools that allow you to measure with extreme accuracy just how much you are moving the shoulder back. DO NOT use the feel method, as there are other variables that can give you a false indication as to just what is happenning......jackie
 
Headspacing

Jackie has brought up a very good point. We need to be talking about the same measurement. The "correct measurment" of head spacing. The case length, the gap between the bolt face and the case head are often misused as meaning "headspacing".

There are three different types of case, rimless bottle necked, belted magnum, and rimmed. Each is measured differently.

Rimless bottle neck cases are measured from a datum line half way between the neck shoulder juncture and the shoulder body juncture back to the case head. Belted cases are measured from the front of the belt to back of the case head. Rimmed cases are measured from the front of the case rim to the back of the case head.

Actual headspacing is set with steel gauges. A go gauge and an no go gauge. The SAAMI spec for these gauges requires that the go gauge is .0035shorter than the no go gauge. A properly headspaced rifle will allow the bolt to close on a go gauge and not close on a no go gauge.

A chamber is cut and the action fitted to allow enough space between the case head and the bolt to smoothly close without being forced shut. Target rifles are typically fitted tighter than hunting rifles. SAAMI is the accepted industry standard. Properly fitted barrels will exhibit between .0015 and .0035of gap between the bolt face and cartridge head.

Dies should be set to resize fired cases to fit the chamber without having to force the bolt closed. Brass has a memory and when sized it springs back. Dies form the brass slightly smaller than desired size but the case springs back a small amount. Dies are set to properly size the case to a minimum amount. One can "work" their brass, this term means to over size the brass and re-fire form with every sizing and firing.

In essence any chamber is a custom chamber and fired brass custom forms to that chamber.

If you will find Frank de Haus last edition of THE BOLT ACTION RIFLE and read Wayne Van Zwolls adendum about head spacing it is the most complete definition I have ever read.

Rusystud
 
Rustystud

Good post!:)

When I first saw 338lm's question I thought, "Oh no, here we go again." Another discussion of what "headspace" means to different shooters.

I know that each of us may have his/her own idea of what headspace is but I think it's important that, on a technical forum like this, we should all be using the correct terminology. We experienced guys know what we are talking about even when we each use our own terms and definitions but it's not fair to new guys trying to get answers to basic questions.

And, as we know, it doesn't stop with "headspace". How about "jam", "throat", "lead", "freebore", just to name a few others. :mad:

Ray
 
jackie schmidt said:
ITypically, the number .001 inch is used.


When doing this, be sure and use tools that allow you to measure with extreme accuracy just how much you are moving the shoulder back. DO NOT use the feel method, as there are other variables that can give you a false indication as to just what is happenning......jackie
Click to expand...
I think what Jackie means is that the amount of headspace is expressed in thousants of an inch (in the US where the inch measuring system is used).

The standard definition if headspace, regardless if it is a rimmed, belted or rimless cartridge, is "the distance between the face of the bolt and the base of the cartridge with the cartridge fully seated in the chamber". If the firearm is not a bolt type action, say for example a revolver or semi-auto pistol, then the definition is "the distance between the face of the breech and the base of the cartridge with the cartridge fully seated in the chamber".

If you are buying a new custom or benchrest rifle or having a custom or benchrest rifle built the gunsmith can use the chambering reamer and a short section of the barrel to make a gage to aid in setting back the shoulder if headspace becomes negative, being determined by the bolt being hard to close when inserting resized fired brass that is still not primed or loaded, and using a stripped bolt.

There are aftermarket products like the one shown by Al Nyhus in his post on annealing brass http://www.benchrest.com/forums/showthread.php?t=54166 .
The trouble I have with this type device where it has only a single contact point is that your chamber shoulder may not be the exact same angle as the sizing die shoulder. That is why many experienced reloaders use the stripped bolt "feel" method.
 
JerrySharrett said:
I think what Jackie means is that the amount of headspace is expressed in thousants of an inch (in the US where the inch measuring system is used).

The standard definition if headspace, regardless if it is a rimmed, belted or rimless cartridge, is "the distance between the face of the bolt and the base of the cartridge with the cartridge fully seated in the chamber". If the firearm is not a bolt type action, say for example a revolver or semi-auto pistol, then the definition is "the distance between the face of the breech and the base of the cartridge with the cartridge fully seated in the chamber".

If you are buying a new custom or benchrest rifle or having a custom or benchrest rifle built the gunsmith can use the chambering reamer and a short section of the barrel to make a gage to aid in setting back the shoulder if headspace becomes negative, being determined by the bolt being hard to close when inserting resized fired brass that is still not primed or loaded, and using a stripped bolt.

There are aftermarket products like the one shown by Al Nyhus in his post on annealing brass http://www.benchrest.com/forums/showthread.php?t=54166 .
The trouble I have with this type device where it has only a single contact point is that your chamber shoulder may not be the exact same angle as the sizing die shoulder. That is why many experienced reloaders use the stripped bolt "feel" method.
Click to expand...



standard definition of HEAD CLEARANCE..........(not headspace)....and further of a headspace gage not a cartridge...nice soft brass moves around...

ducking...mike in co
 
Mike, I believe the term "headspace" is evolving whether that is a good thing or not...

Right or wrong... very few people refer to "head clearance" when they think of the space between the back of the shell and the bolt face... headspace is what they think of... and they know they can correct an actual headspace problem by reloading to correct the head clearance...

Definitely confusing to a person new to reloading and firearms...:)
 
dennis,
i'm on a one man crusade to "try" and get it in accordance with the SAAMI lexicon.

its a loosing battle....most times i just bite my lip, but here on the gunsmith forum...i figured i can step up.
"everyone" "knows" what we are talking about...clearance.....but when the new guy walks in, he learns wrong, and the problem grows.

thanks
mike
 
One little point that goes back to the question, I believe that one should not gage bump from a once fired case, but from one that has been fired until a little tight, and that the primer should be removed as well. It takes a few shots for the head to shoulder measurement to reach maximum. I bump .001.
 
I definitely know whats going on now as per chamber reaming for a competition rifle, and also how much to bump the shoulders back on my brass.
Thanks for educating me.
 
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