So I've been reloading .303 brit for a while now and I know that case life is going to be reduced shooting military rifles and to get a bit more life out of the cases I neck size my brass and so far its its been working just fine. However I recently acquired a 1915 Ross Mk 3 and after a trip to the range shooting factory loads I noticed what looks to be the beginnings of case head separation (lighter coloured ring on the outside and a visible ring on the inside of the case) when I was going through the brass. When I first got the rifle I went through it and checked the headspace and while it was a tad on the excessive side it still was within acceptable tolerances, I'm also aware that during ww1 they opened up the chambers to accept the poorer quality British ammo and upon inspection of the brass it appears that it was done to this rifle but its only slightly larger than that of my No.4's. So I'm wondering is this rifle just going to eat brass or could I increase case life by using the o-ring trick to tighten up the headspace and hopefully instead of having the head want to separate it moves the shoulder instead.
.303 brit case head separation question
- Thread starter Lucite
- Start date
The rubber o-ring holds the rear of the case against the bolt face preventing the case from stretching. The added benefit of the o-ring is as it is compressed it centers the rear of the case in the larger military chamber.
Below fire forming cases with reduced loads and a rubber o-ring. This makes the brass butt plate softer when forming 100 or more cases.
Below I use Hornady 100 grain 312 pistol bullets and SR 4759 or Trail Boss powder. You can also use the rubber o-ring with full power loads.
Below showing the case stretching with excessive head clearance. At max military headspace of .074 with a rim thickness of .058 you can have .016 head clearance. And with a normal case with with .002 shoulder bump you would only have .002 head clearance and no case stretching.
Below the o-ring holding the case against the bolt face.
And below the fired case now headspacing on its shoulder and the shoulder holding the case against the bolt face.
NOTE, some reloaders use small ponytail rubber bands that are thinner than the average o-ring if you can't find one thin enough. And make sure you grease the rear of your locking lugs to prevent galling.
The case on the far right below was reloaded and full length resized three times with the die touching the shell holder and the case started to separate.
The case on the left shows the shoulder location on a new unfired case and this varies greatly between brands.
Below fire forming cases with reduced loads and a rubber o-ring. This makes the brass butt plate softer when forming 100 or more cases.
Below I use Hornady 100 grain 312 pistol bullets and SR 4759 or Trail Boss powder. You can also use the rubber o-ring with full power loads.
Below showing the case stretching with excessive head clearance. At max military headspace of .074 with a rim thickness of .058 you can have .016 head clearance. And with a normal case with with .002 shoulder bump you would only have .002 head clearance and no case stretching.
Below the o-ring holding the case against the bolt face.
And below the fired case now headspacing on its shoulder and the shoulder holding the case against the bolt face.
NOTE, some reloaders use small ponytail rubber bands that are thinner than the average o-ring if you can't find one thin enough. And make sure you grease the rear of your locking lugs to prevent galling.
The case on the far right below was reloaded and full length resized three times with the die touching the shell holder and the case started to separate.
The case on the left shows the shoulder location on a new unfired case and this varies greatly between brands.
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The method suggested by Neilm is called the false shoulder method of fire forming cases. And necking up the diameter of the case neck creates a false case shoulder the case can head space on and preventing the case from moving forward. Another method if you have a fairly new barrel without cordite throat erosion is to jam the bullet into the rifle to hold the case against the bolt face. With this method you should reduce the load to a mid-range load. Reducing the load prevents a pressure spike because the bullet does not get a running start before hitting the rifling.
Bottom line, any of these methods is OK and the point is to not let the case stretch on the first firing and then neck size and let the case head space on its shoulder.
You have to be careful with Rosses, particularly if you partially resize cases to headspace on the shoulder. If done imprecisely, the bolt head will not fully rotate and the gun wont fire. Acquiring this knowledge cost me a deer a few years ago... The o-ring trick might cause the same issue if not done properly.
buzzmagoo
CGN Ultra frequent flyer
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Pharmacys sell them little rubber bands for kids dental braces , they are smaller than dollar store hair rubber bands . Check art and crafts stores or Isles for bags of brightly colored bands kids Weave them into bracelets and necklaces they will be larger . Three different Diameter ( thickness when stretched ) never heard of this but if it works , hey ! Why not .
Thanks I'll keep that in mind.
I've used those kids craft rubber bands when fire forming cases for my Martini Henry, they work well enough.
maple_leaf_eh
CGN Ultra frequent flyer
It's OK to admit using the elastic bands yourself. It's allowed nowadays to be whoever you want to be.
