Question on "Fire Formed" Brass

[Hinnerk]

I have an 1891 Model Argentine Mauser (7.65x53) for which I have been starting to reloading (starting to reload, in general ... never done this before ... also never shot rifles other then .22 and .50 flintlock, previous to this year). My first reloads were full length resized with an RCBS die and shellholder. I notice that the shoulder seemed to go back quite a bit and my first loads had their primers pushed back after firing. I did not see this with factory loads. So I supposed that the die was over sizing the brass. In any case, I wondered about the possibility of excess headspace and bought a Wilson gauge. That shows that once fired factory loaded ammo is about .005" longer than the max per the Wilson gauge. With the firing pin removed from the bolt, I added pieces of newspaper behind one of these once fired cartridges to see when the bolt would close with resistance. The newsprint was .002" thick. Once piece would still allow the bolt to drop easily. Two pieces created resistance.

Is it right to consider that the "fire formed" brass is then about .005"-.007" over max spec?

My loads don't reach that point with one firing. Does that just mean that they have further to go or is it an indication of less load pressure than factory (I don't want to push it with this 120 year old rifle)?

My last loads were resized to only .003" over spec and came out mostly .004" over spec after firing (none more than +.005"). Some old Norma rounds that I fired at the same time measured .006" over spec after firing.

[bsumoba]

a wilson gauge is probably not the best way as the gauge could be completely different than the chamber in your rifle. Also, what powder, bullet, primer, and brass are you using? Most would probably not use "standard" modern loads in a rifle like that, being that old.

That being said, the best way to do it is to buy an OAL gauge like a Hornady or Sinclair Case Gauge. Hook this on your calipers and measure your fired brass and zero out your calipers. Then, measure your resized cases and see what you get. This will better tell you what your dies are doing as far as bumping the shoulders back. You can also use a fired case in a pinch like a pistol case that fits around the middle of the shoulder; it is crude, but not a bad way to do it if you don't have the right tool readily on hand.

It might also be good to measure a few other locations before and after firing as well as after re-sizing: body diameter just below the shoulder and the web area, which is just above the case head. Measure these as well to see what numbers you get and report back.

[JMP]

After one firing, the location where your shoulder ends up is generally where you should set your dies for reloading. In a bolt action, you want to fit the chamber pretty much exactly as it is and not have a bunch of excess headspace like 0.005". When you fire-form, you are generally giving yourself about 0.001" of clearance as you get this from the spring back of your brass. People shooting in the field, may do a slight shoulder bump (commonly 0.002") to get a little extra room just to make sure the cases fit easily in and out. A fire-formed piece of brass will allow the bolt to close with no resistance, and that is most likely why you didn't get any resistance until you were a bit longer than your fired rounds.

It sounds like you have a big chamber so you do not want to size based on what your FL die does with complete engagement with the shell holder unless you are getting a shell holder of a larger deck height. The right dimension is based on your actual chamber, and it is NOT based on any pre-determined gauge or nominal "maximum".

This is a very common error that people make. However, usually they will oversize by no more than 0.005". This excess amount of slop is usually not detrimental to safety, but it is detrimental to your accuracy. If you get toward 0.010" of excess head space with chamber slop, then it can be dangerous. Each case and rifle is a bit different.

[BigBronco]

^^^
Agreed with Bsumoba. Keep in mind that a Wilson gauge is cut to SAAMI spec. Seeing as SAAMI most likely did not exist when your rifle was made. SAAMI came to life in 1926.

Rely on your fire formed brass measurements for a starting point.

Neck size with a shoulder bump of .001-.002 inchs. As for the primers, it could be the light loads. You need a minimum pressure to fully expand the brass and seal the chamber. During the firing process the primer gets pushed out of the pocket towards the bolt face. The expanding brass under proper minimum pressure will received re-seat the primer. after firing. Also you may look closely at the outside of your case necks for carbon fouling. This is often a sign of inadequate pressure.

[liber]

This is a pretty good explanation of fire formed.

[pacrat]

For an old 1891 which is a ["Small Ring"] Mauser. I wouldn't bump the shoulder at all, just neck size. And stick with low pressure starting loads. Your primers will stay in the pockets and your cases will last almost forever.

Many say, that the 7.65 Argie can be loaded comparable to a .308 with commercial loads. Which is true. But only if you are dealing with a later "Large Ring" Argie Mauser on a model 1898 design. Which the Argentines designated their M1909.

IMO the 91 and 93 Mausers are the slickest of the Mausers. But they are far from the strongest.

JM2c

[fguffey]

a wilson gauge is probably not the best way as the gauge could be completely different than the chamber in your rifle

It depends on the individual using the tool, in the hands of a reloader the L.E. Wilson case gage is a very precision tool, to those without instructions and those that believe the datum is a line the Wilson case gage is a drop in gage. they drop a case in the gage and then use their thump nail.

The Wilson case gage is designed to measure the case after firing and after sizing: Meaning? A reloader knows that, then there is the chamber gage. Most chamber gages are a rip off of the Wilson case gage for those that use the chamber gage like a Wilson case gage, they use the chamber gage like a drop in gage then measure with a thumb nail.

A reloader with case forming skills can form first then fire, nothing like knowing the length of the chamber from the shoulder to the bolt face in thousnadths. I fire a case then eject a once fired case.

I have forming dies, my favorite is the 308 W forming die. If I had one forming die it would be the 308 w, if I only had 2 the second would be the 243 W forming die. I can form 7.7 Japanese cases along with the 7.65 B.M. 8mm57 and 7mm57 etc. with the 308 W forming die.

F. Guffey

[J-cat]

If your FL sized shoulders are pushed back quite a bit then why don't you adjust the die to push them back less? You have the ability to adjust the die to push them back .001" or 2 or 3 or 4 or 5, etc. I like .002" myself. That way the bolt closes easily and the case lasts a long time.

Rather than using feeler gauges and trying to figure out if the case won or the press won, use Redding competition shell holders and force the case to win every time. RCSH remove press frame flex out of the sizing equation.

Now, this "spec" you're talking of: you bought a case gauge which assumes your rifle was made to spec. Oftentimes this is not the case. That's why it's better to measure your fired cases and size them to fit your chamber, not some case gauge.

[Hinnerk]

I should explain how I am using the Wilson Gauge (I think they call it a Gage, actually).

The Wilson Gauge is a cylinder of steel with an approximation of a chamber cut into it and .005" deep 'slot' milled into each face. With a case inserted, the head is supposed to project somewhere between that slot and the end face of the cylinder. The neck end of the gauge is used to measure whether the case is trimmed properly (with the head end sitting on a flat surface, the neck of the case should project between the milled slot and the end face of the gauge).

I am using a dial caliper to measure between the neck end face of the gauge and the head of my fired cases, which protrude beyond the end face of the gauge, which is supposed to be the max. spec. It is that additional protrusion that I am measuring. So, basically, I am using it like an overall case length gauge. Of course, there could be problems if dirt or bulges, etc. prevent the case from going into the gauge all the way to the shoulder.

I tried the 9mm case trick to use as a rudimentary overall length gauge tool but found that, in my hands, it was too variable.

J-CAT, yeah, that is what I am trying to do (minimize the amount of sizing and use a precise and repeatable way to measure that). I am using the gauge as a tool in relation to my rifle's chamber and not as a measure of how it should be (specification created by SAAMI after the fact).

Continuing on my original question, how close to the actual dimensions of the chamber in such a rifle (bottle necked cartridge) will a case get after one firing?

[fguffey]

I should explain how I am using the Wilson Gauge (I think they call it a Gage, actually).

The Wilson Gauge is a cylinder of steel with an approximation of a chamber cut into it and .005" deep 'slot' milled into each face. With a case inserted, the head is supposed to project somewhere between that slot and the end face of the cylinder. The neck end of the gauge is used to measure whether the case is trimmed properly (with the head end sitting on a flat surface, the neck of the case should project between the milled slot and the end face of the gauge).



Continuing on my original question, how close to the actual dimensions of the chamber in such a rifle (bottle necked cartridge) will a case get after one firing?

All reloader assume, I don't. I measure the length of the chamber from the shoulder of the chamber to the bolt face. I have no infatuation with head space. Actual dimension? No one knows, most can use a resource like SAAMI or STEVE'S PAGE, or R. Lee's book on modern reloading, what 'it is' and what it should be can be almost anything.

The Wilson case gage is a very precision gage. I measure before and again after. To save a trip to the range I determine the length of the chamber from the shoulder/datum to the bolt face. I want to know what effect the chamber is going to have on the case when fired. I am the fan of cutting down on all that case travel. There is fire forming, there is case forming. I form first then fire.

F. Guffey

[fguffey]

(I think they call it a Gage, actually).

Actually?, I actually call it a case gage, because L. E. Wilson actually named the gage a case gage. I have instructions that go back to 1955, it was not until the Internet reloaders actually started calling every thing a head space gage because they were told everything has head space.

I have no infatuation with head space and my cases do not have head space.

F. Guffey

[J-cat]

I should explain how I am using the Wilson Gauge (I think they call it a Gage, actually).

The Wilson Gauge is a cylinder of steel with an approximation of a chamber cut into it and .005" deep 'slot' milled into each face. With a case inserted, the head is supposed to project somewhere between that slot and the end face of the cylinder. The neck end of the gauge is used to measure whether the case is trimmed properly (with the head end sitting on a flat surface, the neck of the case should project between the milled slot and the end face of the gauge).

I am using a dial caliper to measure between the neck end face of the gauge and the head of my fired cases, which protrude beyond the end face of the gauge, which is supposed to be the max. spec. It is that additional protrusion that I am measuring. So, basically, I am using it like an overall case length gauge. Of course, there could be problems if dirt or bulges, etc. prevent the case from going into the gauge all the way to the shoulder.

I tried the 9mm case trick to use as a rudimentary overall length gauge tool but found that, in my hands, it was too variable.

J-CAT, yeah, that is what I am trying to do (minimize the amount of sizing and use a precise and repeatable way to measure that). I am using the gauge as a tool in relation to my rifle's chamber and not as a measure of how it should be (specification created by SAAMI after the fact).

Continuing on my original question, how close to the actual dimensions of the chamber in such a rifle (bottle necked cartridge) will a case get after one firing?

Pretty close. You might get another .001" or so with multiple firings. That's why you want to measure several cases and pick the longest.

[LynnJr]

Hinnerk
To find the actual length of your chamber fire a round and deprime it without touching the brass at all. You can do this by placing the fired case in a shellholder and knocking out the primer while sitting on your reloading bench.
Put the shellholder back in the press and size only 1/8 inch of your cases neck.
This means you need to back the die way out.
Add your new primer and powder and seat your bullet.

You repeat these steps until closing the bolt on that piece of brass is difficult.
Your shoulder is now firmly into the chamber.

Now going very slowly you start turning that die down into the press while putting that piece of brass back into the gun and checking its length.
As you start to move the brass the case will get longer not shorter.
You keep going until you feel you are getting real close then you turn the die down in 1/8 of a turn increments until the bolt just drops without a lot of drag.
This is your chambers length. Take your piece of brass and put it into your Gage. You can now make your measurement wether it be a depth measurement or a protrusion.
If it is a protrusion they sell shellholders that will allow you to minimally bump the shoulder to your dimension.
If it is a depth measurement you can sand the shellholder with 80 grit sandpaper in a figure eight pattern on a flat surface to gain the necessary length.

[JMP]

All reloader assume, I don't. I measure the length of the chamber from the shoulder of the chamber to the bolt face. I have no infatuation with head space. Actual dimension? No one knows, most can use a resource like SAAMI or STEVE'S PAGE, or R. Lee's book on modern reloading, what 'it is' and what it should be can be almost anything.

Guffey, I think that we are all talking about the same thing as SAAMI specs mean nothing. Many people have their rifles chambered to a specific dimension with the same reamer and go-gauge each time. It is pretty standard for the one cutting the chamber to use your go-gauge then give it 0.001" of clearance. That's all you need, and when you do this, you are getting chamber dimensions extremely close to your last chamber, maybe even more so than what you can measure with an Wilson Gauge, depending on the skill of your machinist.

I like the same person to create my gauges as the reamer and that tells me it will be close if chambered correctly. Like you say, I don't care about SAAMI specs, I just want to know the dimension of my own chamber, which is why it is best to choose a starting point from which you know, then you do not necessarily need forming dies on top of your fireform process if you are close enough. If you are not close enough, which should be apparent from the reloader, then they will usually create a false shoulder before fireforming.

It seems like people are getting these wild variances in headspace when they use old antiquated rifles like Mausers. I say stick to modern machining and technology to get it right. Even if you want to shoot an old beater Mauser, you can still get it rebarreled to the dimension you would like.

I think everything is saying the same thing, but you are interpreting it differently. The only thing good about getting a near SAAMI spec minimum chamber is that folks will have an easier time getting their dies set up to size for this chamber. Most people shoot for 0.001 clearance for their shoulders, and with big chambers, it is common for novice reloaders to over-size them and end up with 0.005" slop between the shoulder and the chamber. This is all that most folks want to avoid as they want to fit THEIR RIFLE'S chamber.

[liber]

Pretty close. You might get another .001" or so with multiple firings. That's why you want to measure several cases and pick the longest.

Is this because the case contracts slightly as it cools after the pressure is released when it is fired?

It seems like what you're saying is that with multiple firings it will closer to the exact headspace in that regard, since a fired case is not the EXACT size of the chamber, and I know that is true in regard to diameter and guessing it is so for the length as well.