Chamber shoulder and case shoulder gauge for .303?

[NuJudge]

I'm not inquiring about a Headspace gauge, I'm inquiring about a gauge that looks at the dimension to the shoulder of the chamber and to the shoulder of the the case. Has such ever been made?

There was formerly a Stoney Pointe case gauge, now something similar made by Hornady, which would appear to work for measuring where the shoulder is, but I am looking for a steel gauge.

CDD

Information

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[Parashooter]

I'm unsure exactly what you're looking for, but measuring a normal fired case will give the bolt face to shoulder dimension of the chamber (plus any action stretch). Nothing fancy is required - a 9mm pistol case works about as well as anything if we're looking for comparative rather than absolute dimensions. A more durable version can be made from a 1" section of 1/2" steel rod bored with an inside diameter appropriate to the cartridge neck and shoulder - but will not yield results visibly different when using a .001" caliper.



Use the same setup on a sized case to see what change has occurred during sizing. Or compare fired cases from two rifles to measure any difference in the face-shoulder dimension. A similar arrangement can be used to measure differences in action stretch at varying pressures, but it may take a good .0001", 3" jaw micrometer to register the small amounts involved.

[Mk VII]

Nobody ever worried too much about it; the rim, they thought, took care of most of the problems this would have caused with a rimless case. Of course they did have to increase the dimensions in WW1, to take care of dirty or indifferently made ammunition. Reloading, of course, was not considered (nor should it have been).

[Edward Horton]

Yes they are called “Wilson Case Gauge BUT they are for a SAAMI commercial chamber BUT they tell an interesting story, the cases rest on the shoulder for gauging purposes.

Below is the Wilson gauge with a new unfired Remington .303 case inside the gauge, as you can see Remington and Winchester do NOT know where to put the shoulder of the case and the case is a ¼ inch below where it should be.

The gauge has a slight groove milled in the top and bottom, the top represents min & max headspace and the bottom groove is min & max case length



Next is a fired case in the gauge and now it is sticking above the top of the gauge, this represents how far the military chamber was reamed and lengthened to allow for dirt and mud in the chamber. The gauge is still usable with a vernier caliper but the milled groove for head space can not be used.




Below in the top photo is a South African PMP surplus please note that they know where to put the shoulder of the case, this case is perfectly made and is .002 below the min headspace line on the gauge.

NOTE: the American Remington and Winchester cases average .058 on rim thickness on the cases I have, the South African PMP .303 has a rim thickness of .062 again .002 below minimum headspace as it should be.



Our American made .303 cases leave a lot to be desired, the are designed for a lower pressure than military standard which is approximately 45,000 CUP, our American ammunition is loaded to pressures lower than 43,000 CUP due to the older No.1 or SMLE still being used and shot (lawsuits) and these cases do not stand up well during reloading.

On the other hand Prvi Partizan cases are some of the best commercially made cases that can be used for reloading, they have thicker rims and larger base diameters than our American cases do.





Below base diameters of the Privi and Greek HXP cases, this is just one reason I give the Privi cases high marks.

[Jim K]

Some folks believe that they can obtain the best accuracy if the case fits the chamber tightly in addition to the headspace being tight. I can see that it might be true, but have never seen any solid data to show that it is. If anyone has, I am sure the folks here would appreciate seeing it.

From a purely functional viewpoint, of course, the position of the case shoulder in a rimmed case like the .303 or the .30-30 is pretty much irrelevant as long as it doesn't interfere with chambering.

Jim

[Edward Horton]

Some folks believe that they can obtain the best accuracy if the case fits the chamber tightly in addition to the headspace being tight. I can see that it might be true, but have never seen any solid data to show that it is. If anyone has, I am sure the folks here would appreciate seeing it.

From a purely functional viewpoint, of course, the position of the case shoulder in a rimmed case like the .303 or the .30-30 is pretty much irrelevant as long as it doesn't interfere with chambering.

Jim

Jim K

Headspace is governed by the cartridge cases you shoot and not the rifle, the .303 British is a perfect example, commercial cases can be stretched beyond their design limits in the Enfield chamber and self destruct in just a few reloadings.

On the other hand a rifle with a tight chamber and tight headspace settings will strain the cartridge case far less.

If I remember correctly cartridge cases are made from five different grades or specifications of brass and American .303 cases are one or two grades below what would be used in the upper pressure category as in the .308 Winchester and above.

I was taught the finer aspects of reloading by a benchrest shooter and machinist and benchrest shooters like tight chambers for preserving their brass and accuracy.

By my standards a 30-30 has a loose chamber and longish headspace, I stopped counting how many times I have reloaded my 30-30 cases 20 years ago, on the other hand three reloadings from a Winchester case in the .303 is extremely short lived.



It boils down to chamber diameter and headspace and chamber pressure for case longevity, with long life going to the tight chamber.

My bottom line here is the Enfield Rifle gets blamed for our poorly made American .303 cases which the factory downloads to a lower pressure to avoid law suits, I believe these American made cases are made from brass in the 30-30 and 30-40 class or spec.

This book tells you to set your headspace .003 over your rim thickness, on my Remington and Winchester cases the rim thickness averages .058, this puts your headspace at .061.

[NuJudge]

I don't know how I missed the .303 case gauge on the Wilson website.

I looked at the RCBS website, and saw their cartridge gauge, but saw they did not offer it in .303. I believe what you are telling me is that I can get .303 shoulder movement information from using the .308 RCBS Cartridge gauge. Is this true?

I am familiar with the differences in backthrust based on chamber conditions. I recently saw a series of pictures of .30-30 cartridge case heads with pressure indicating film on them: oiled cartridges showed the most pressure, followed by cartridges with the precise headspace of the chamber, the least pressure shown by chambers .010" over cartridge headspace. When studying action springyness, I'm going to have to pay particular attention to maintaining several standard chamber conditions: not just oil, but the same headspace.

[Edward Horton]

I use the .308 precision Mic on my 7.62 Ishapore 2A1 and NOT on the .303 British, if you know how long your .308/7.62 case is you can get your headspace with feeler gauges or an unfired case and a spent primer and not need headspace gauges.



On the Enfield you can insert feeler gauges between the right locking lug and the receiver to get your headspace (head gap clearance) with a unfired case in the chamber. You can also insert a fired primer in the same empty case to get your head gap clearance by starting the primer in the primer pocket and then chambering the case. Measuring the case length before and after inserting the primer gives you head gap clearance and this added to your rim thickness gives you your actual headspace measurement.

[ireload2]

EH posted

>>>If I remember correctly cartridge cases are made from five different grades or specifications of brass and American .303 cases are one or two grades below what would be used in the upper pressure category as in the .308 Winchester and above.<<<<

Do you have any citations to back this up?

[cary m2a]

I dont have data. But I can say that it sure helps the .303 Enfields that I have to just neck size, cuts group size down alot.

Cary