Headspace

[B78-22250]

Hello I have just joined this forum but have been reading posts here for many months. I started reloading shotshells back in 1972. Built my first gun from a kit in 1977 TC hawkin.50. Have gotten into many benchrest techniques but don't shoot competively. Just like to shoot like most of you. I try to be honest and put my money where my mouth is. I have read a lot of questions about headspace and measuring this in bolts levers and pumps I think i have a tecnique and answer that will help the old as well as the new. Of course that pertains to reloading experience not age. We all know Headspace is a measurement from the case head to a datum point on the shoulder of the case. The shoulder of the case is always on a angle IE it starts out small at the neck and gets larger depending on calibre and case thickness till it reaches nominal body taper at the junction of shoulder and case body.I have found the Sinclair nut with 6 different calibres cut with chambering reamers perform several measurement . Remember angled shoulder and datum point. As long as you use the same diameter every time for your measurements you will be ok.I will use my Sinclair nut to measure headspace. Say I use a hole in the gage that goes over the neck of a .224 case but still will not go over the shoulder of the cartrige i want to measure say .224 cal.I will use the .30 cal hole. I measure my fireformed brass from the chamber of this unique and one of a kind firearm. By using the nut with careful feel I now have a measurement of headspace for that firearm.I can now use this measurement to set up Fl or bump dies and have proper headspace for this firearm.

[GeauxTide]

Sounds complicated. After first firings of brass in my rifles, I put the edge of a penny between my sizing die and shell holder. For my 6.5-06 and .338-06, I size '06 cases up or down full length for the first firing. This will not disturb the newly created and exactly correct headspace in that rifle with that batch of brass.

[B78-22250]

Sir I will not dispute your method. What you are doing is fireforming your brass to your chamber then backing off FL die .050-.062. I measured 10 pennys from my retirement stash ,effectivly neck sizing your cases to within .050- .062 short of neck shoulder junction.This is a good method and works well with bolt guns. I was trying to give people a way to measure base to datum point so they can obtain more accurate measurements for setting up dies for headspace for all types of actions using once fired brass from their chambers.If you do not have a sinclair nut you can make your own gage for any calibre you shoot and can measure your headspace with accuracy to + -.002. I will be glad to give information to anyone interested.

[Shoney]

B78-22250

WELCOME TO TFL!

In reading your post, I think you have a pretty good grasp of headspace. SAAMI's Compendium of definitions says:

Headspace - The distance from the bolt face (when the bolt is closed) to that surface in the cartridge chamber which stops the case’s forward movement. For bottle-necked cases, the measuring point is centered on the shoulder and is known as the datum line. For belted magnum cases, the headspace is measured from the front of the belt to the head of the case. In practical terms, the amount of free movement a cartridge has in a closed chamber. This dimension is critical for the safety of the shooter, as well as the accuracy of the weapon system. Insufficient headspace hinders complete chambering; excessive headspace permits case stretching, separation or rupture, endangering the shooter.

I am unsure of what your term "bump dies" refers to. It sounds like Neck Sizing Dies I presume.

Once you have fireformed the cases in your chamber, you really don't need any measurements of the case to proceed, unless you are going to send in measuremnts to have a die made. To have dies made for a one of a kind cartridge, they usually prefer a chamber cast. With a sizing die, you adjust the die down until it will just touch or "bump" the shoulder so there is no setback or just minimal setback to the shoulder. This can be done quite accurately with eyeball adjustments.

With a neck sizing die, you do approximately the same adjustments, but there is no shoulder in the neck die to setback the shoulder of the case. You simply watch the neck as you progressively turn the die down to size the neck.

You must also remember that as you continue to reload the cases, they will get very difficult to chamber at some number of shots (usually 5-6) and the case will need a full length resizing.

Good Shooting!

[B78-22250]

Sir I am refering to a die made by most major die makers. A bump die sets the shoulder of the case back and does not effect the neck or body dimensions only headspace dimensions. Without proper measurment one cannot set up dies with any real accuracy. Remember I am talking about a way that will be precise for levers.autos.pumps and bolts.I have my own lathe and milling mach. So I tend to roll my own out of need.I am not trying to refute anyones method or opinion but just give my opinion and knowlege from spending money and learning lessons the hard way.

[B78-22250]

Sir I am refering only to non belted brass. You can neck size with a Fl die also with a neck die and a neck sizing bushing die IE wilson or redding or others. I am talking about measuring the true headspace of your rifle. setting up your dies correctly having a reference that you can measure and repeat accurately and cheap. Redding sells a bump die which sets back the shoulder without changing any other dimension of the case.You can measure and set up your dies for lets say .002 headspace. If that is close enough for you i can tell you how to make your own gage save some bucks and gain some hard earned knowlege. this is simple and requires 1/2 a brain and a little knowlege a few hand tools and i will do my best to explain and help anyone interested in learning something simple and new.

[Shoney]

B78-22250

I wasn't trying to be flippant or know-it-all in my post. Sorry if I offended. I tried to read your post three times with great difficulty.

When there are more than 4-5 lines together, my old tired dyslexic eyes have trouble connecting with my brain. You may get comments like mine from other irreverent members. Perhaps I should have taken more time to absorb your post.

Since you are making your own dies, my comments

don't need any measurements of the case to proceed, unless you are going to send in measuremnts to have a die made. To have dies made for a one of a kind cartridge, they usually prefer a chamber cast.

are exactly what your are doing and how you take those measurements.

As far as the term bump die, I have coppied the following from 6MM BR magazine>

Dies Made from Chambering Reamers--Why They're Not a Good Concept
You may have heard of "bump" dies. These are made with the same reamer used to cut the chamber. They won't resize the sides and base of the brass, but they will bump the shoulder back, decap, and resize the neck with a bushing. In my opinion, they are a waste of money. After very few firings, the brass will start getting tight, and there's nothing to be done about it. You could bump the shoulder back an excessive and dangerous amount to ease chambering, but then a case separation is imminent.

If the action bolt is clicking or popping at the top of the bolt lift, it indicates that the brass is too big near the base. Once you start getting this, you might as well throw the brass in the garbage, as it will be impossible to stop when using full power loads. I think this is the most common complaint with 6mm BR or 6 PPC chamberings. If the bolt closes and opens hard throughout the whole stroke without the pop at the top, this indicates the shoulder needs to be pushed back.

Is this what you are referring to as "bump dies"?

[B78-22250]

Shoney I am not saying certain calibers have unique problems. Many do.All I am saying is if you have a accurate measurement of headspace. Head to datum line you can set up your dies for minimum headspace and maximum case life no more no less. I have taken 25-06 lapua and created a way to make formed 22-250 brass. I don't have to size or anything but deprime/reprime charge and seat bullit. It fits chamber perfect to .002.in all dimensions. No trim no streched case . i do not exceed elastic limits of my brass. Ie no sizing no streched cases.No trimming these are benchrest tecniques and not for everyone. I know the difference in dies and their applications.I know what each dies funcion is. I am trying to give information that is useful to many and free to all who care to listen.

[impalacustom]

Isn't this basically what your doing? https://www.hornady.com/shop/?ps_ses...0ac87ed0c3ee5b
The datum line is a given for any caliber, wildcat or not, for example my 20 Dasher uses the 6mmbr case as a parent and has the .375 datum. I use the .375 bushing. After I fire my brass that I formed I measure my headspace. Reading off of my reamer print I know where it should be and compare, then I bump my shoulder back 0.001" and I am off to the races. The same thing can be done with standard cartridges. Get the SAMMI specs and compare to your fired brass and see where your at. I always bump my shoulders back on my wildcats and standard cartridges, but I use the Hornady gauge to measure with.

If this isn't what your doing I am kind of confused then.

[brickeyee]

After very few firings, the brass will start getting tight, and there's nothing to be done about it. You could bump the shoulder back an excessive and dangerous amount to ease chambering, but then a case separation is imminent.

While a bump die COULD set back the shoulder excessively if not set up correctly, they have their place.

As for "there's nothing to be done about it," annealing is useful if the brass has hardened up.
It is very worthwhile for hard to get or highly prepped brass.

A pass through a bump die after a few neck sizings works for some calibers, but you may need to use a full length sizer also.

[snuffy]

Not to criticize your efforts B-78, but I'm with shoney, I almost didn't read your L-O-N-G paragraph because there's no breaks in it. Hit enter twice to put a break in the words.

That said, I use the RCBS precision mic to figure out actual headspace for my rifles. They're expensive IF you have a bunch of different calibers, because they're caliber specific. The Hornady LNL headspace kit does the same thing, I may get one so I can compare readings.

I figure it this way, different strokes for different folks, in other words, whatever works for you. I DON'T have access to a machine shop, wish I did. So I have to buy measuring tools from those that sell them. If others here have the machines, and the skill to operate them, I'm sure it would be fun to make some loading gizmos. If you figure the cost for a mill and a lathe into the making of a few dies, it would be MUCH cheaper to just buy whats out there!

[B78-22250]

Impalla you are very close to my meaning. I am doing the same thing with a simple homade guage. It lets you take a reference line on the shoulder and read with your calipers to the case head. You have a reference measurement that is repeatable.