Primer pocket web thickness

[pacowboy]

I'm looking for a dimension on a pc of brass for the thickness of the web between the primer pocket and the inside of the case. I'm getting .094 by my calculations after primer pocket uniforming a Nosler 300 win mag case. I read a lot of information on here and I can't recall anyone asking this. After multiple firings and cleaning and uniforming brass can this web get smaller and unsafe? Is there a minimum thickness for this dimension?

 

[dok7mm]

If you have a depth gauge that will fit inside your neck, measure from case mouth to inside of web, then measure case OAL.

The difference is web thickness. You can measure a bunch of brass to find average thickness.

Be interesting to follow a couple of cases through their life.

 

[pacowboy]

I measured overall length of the case then the depth of the internal portion from the mouth to the flash hole and the depth of the primer pocket itself. I subtracted those 2 numbers from the overall case length and got to my .094 web thickness. I was pulled away so I didn't have time to measure more last night. I plan to check more.

 

[Tiny Tim]

Your doing it right. I have no knowledge of what the spec might be. Keep us posted on your findings. And your right, I don't think I've ever heard it asked.

 

[243winxb]

After multiple firings and cleaning and uniforming brass can this web get smaller and unsafe

Short answer- Watch for loose primer pockets.

Many maximum loads may stretch the web and appear as loose primer pockers.
I dont know if the .094" will thin as it stretches a few thousandths?

SAAMI has nothing on web thickness. I seen a 5.56 drawing that had listed a web thickness. The big magnum should have thicker webs.
When the 338 lapua magnum was being designed, the web and side walls were made thicker to handle the pressures.

When the primer fires, it makes its own pressure in the pocket. No powder needed.

 

[pacowboy]

I'm familiar with with loose primer pockets. The primer pocket tool I have to true them up to the proper depth takes some material from the "floor" of the primer pocket. I sometimes use the same tool to clean them out as well. It works nicely in my drill as opposed to the old hand tools I've had for 30 years. If it takes material out on more than one occasion and instead of just removing the dirt will that make the "floor" or web too thin to be safe? I have to check it again when I get home but originally for the large rifle primer pockets it was set at .125 depth of cut. It does not remove anything from the walls just the depth.

 

[MagnumManiac]

Web thickness varies brand to brand.
Norma has the thinnest and Winchester or Herters have the thickest.
It is the web thickness that determines how long a primer pocket will last and secondly how hard the case head is.
To answer your question, yes, removing material will weaken the pocket/web over time.
This is why I DO NOT uniform pockets, BUT, I DO de-burr flash holes on EVERYTHING.

Cheers.

 

[pacowboy]

Web thickness varies brand to brand.
Norma has the thinnest and Winchester or Herters have the thickest.
It is the web thickness that determines how long a primer pocket will last and secondly how hard the case head is.
To answer your question, yes, removing material will weaken the pocket/web over time.
This is why I DO NOT uniform pockets, BUT, I DO de-burr flash holes on EVERYTHING.

Cheers.

Ok. Then my next question would be what extra benefits does uniforming primer pockets give you.

 

[Rardoin]

Ok. Then my next question would be what extra benefits does uniforming primer pockets give you.

Excellent question! You will get many answers as well. I've tested this question in 3 different cartridges off of F-open platforms (22lb rifle/fully rested) at 100yds in as dead of calm as I could get and in 600 and 1000yd competition and 965yds on my test range in calm conditions. The result is my pocket uniforming tools collecting dust and more time on my hands . I don't even clean primer pockets any longer. There are many tools I 'had to have if I was going to get good groups' at long range. Many of them share the same dusty box. As far as thinning the web with uniforming tools it should not happen if the tool is designed to bottom out as a preset depth referencing off the case head.

 

[MagnumManiac]

Excellent question! You will get many answers as well. I've tested this question in 3 different cartridges off of F-open platforms (22lb rifle/fully rested) at 100yds in as dead of calm as I could get and in 600 and 1000yd competition and 965yds on my test range in calm conditions. The result is my pocket uniforming tools collecting dust and more time on my hands . I don't even clean primer pockets any longer. There are many tools I 'had to have if I was going to get good groups' at long range. Many of them share the same dusty box. As far as thinning the web with uniforming tools it should not happen if the tool is designed to bottom out as a preset depth referencing off the case head.

Ahh, but as the case head expands, the primer pocket shortens a few tenths. This is why those primer pocket cutter things remove material each use.
If I find a problem pocket, which happens from time to time, I seriously debate whether to get my swager out.
As stated I don't touch pockets, but if I have 100 pieces of brass that won't take a primer, I'm more inclined to send them back rather than d*ck around with them.

I found the biggest difference to CONSISTENT group size was not from primer pockets, but HOW the primers are SEATED and whether the flash holes are clean and free from burrs.
If you look closely at pockets, you will find they are concave on the bottom, this is how they were designed to be, making them flat restricts the primer flash, sure they are all uniform, but I can't see how this is beneficial.

Cheers.

 

[243winxb]

This 》 As far as thinning the web with uniforming tools it should not happen if the tool is designed to bottom out as a preset depth referencing off the case head.

The primers should be flush to .008" below the case head, when fully seated (SAAMI) I have some .012" below, works fine.

 

[243winxb]

Ahh, but as the case head expands, the primer pocket shortens a few tenths. This is why those primer pocket cutter things remove material each use.

If the pockets are not uniformed, then primers should be sitting proud. Higher then the case head after many firings?

I have 223 & 243 brass fired over 20 times. Factory pockets, no uniforming. Primers still seat as they should.
Maybe i need to load to 65,000 PSI?
I used a small uniformer on some 38 special brass that had shallow pockets from the factory.
Cleaned some LC 5.56 brass with it. Reddings as a stop. Cant go to deep.

 

[pacowboy]

If the pockets are not uniformed, then primers should be sitting proud. Higher then the case head after many firings?

I have 223 & 243 brass fired over 20 times. Factory pockets, no uniforming. Primers still seat as they should.
Maybe i need to load to 65,000 PSI?
I used a small uniformer on some 38 special brass that had shallow pockets from the factory.
Cleaned some LC 5.56 brass with it. Reddings as a stop. Cant go to deep.

My primer pocket uniforming tool is Set at .127

 

[MagnumManiac]

If the pockets are not uniformed, then primers should be sitting proud. Higher then the case head after many firings?

I have 223 & 243 brass fired over 20 times. Factory pockets, no uniforming. Primers still seat as they should.
Maybe i need to load to 65,000 PSI?
I used a small uniformer on some 38 special brass that had shallow pockets from the factory.
Cleaned some LC 5.56 brass with it. Reddings as a stop. Cant go to deep.

A few tenths over 20 firings is not gonna make a primer proud of the case head. And as you know, case head expansion gets to a point and almost stops, unless you keep using higher and higher pressures, but then the case head expands laterally, opening the primer pocket.
If the case head was completely inside the barrel, no expansion would take place. Alas, it isn't.
So, I should have said, until case head expansion becomes stable, as it does as it hardens with use, the web does move into the primer pocket and the pocket expands outwards.
Having trouble explaining this, lost my job today and the old brain is having trouble releasing technical info.

Cheers.