On most pistol cartridge rims, the very back edge of the rim has a slight 'bevel' or angle on it.

I have heard that the rim is beveled to make the extractor in rifles 'slip' over the rim better.

It looks to me like the rim bevel is a 40 or 45 degree angle. Just wanted to know if someone could take a quick look at the angle to see if I am correct.

I know this might sound like a stupid question to ask, but I am working on a custom case for a project and it's hard for me to tell if the angle is definitely a 40 or 45 degree.

Thanks,

Buck

There are several reasons which could be listed for the bevel. These range from the usual extractor story, to the cartridge being smoother to rise up the bolt face, to nothing more than cosmetics.If you compare several samples of the same cartridge from a variety of makers you will see everything from a nearly square corner to a slight chamfer to a radius. Sometimes the radius seems to go from its beginning on theoutside of the rim clear to the primer pocket. his last is particularly common to ammunition of European manufacture.

The most realistic reason seems to be that anything other than a square corner just makes the case look more finished, it is principally cosmetic in most circumstances.

The ones which seem to be really functional are cartridges like .30-40 US, .303 British, 7.62x54mm Russian and others. These are rimmed cartridges intended to be used in box magazine military rifles. In these cases the bevel is quite deep and of a flatter angle and is intended to make "rim locking" in the magazine a somewhat less serious problem.

If the cartridge you are proposing is rimless for a box magazine, or rimmed for single shot and lever guns then the issue is back to one of cosmetics and the specific angle is not at all critical, it just needs to look good!

For cartridges for semi-automatic pistols any moderate bevel or radius will serve to assist the extractor over the rim. This also serves to reduce the rate of acceleration of the extractor as it climbs over the rim and will reduce extractor breakage

Thanks CB.

In a lever gun, say a 45 LC running through a 1892 Winchester, I figured that a slight bevel was needed to help the extractor glide smoothly over the rim.

Thanks a lot,

Buck

Buck,

As I said, mostly cosmetic. If you will seek out some old black powder cartridges for the calibers typically chambered in the 1892, 1873 Winchester and 1894 Marlins, you will find the rims are very frequently square. The extractor has to be cammed just as far out, whether or not a bevel is present. If you look closely at the rim of a fired cartridge, or even chambered & extracted, you will usually see that the extractor actually cuts the rim to some degree. This is because the extractor isn't perfectly polished (and needn't ba) and is harder trhan the brass case.

Buck,

As I said, mostly cosmetic. If you will seek out some old black powder cartridges for the calibers typically chambered in the 1892, 1873 Winchester and 1894 Marlins, you will find the rims are very frequently square. The extractor has to be cammed just as far out, whether or not a bevel is present. If you look closely at the rim of a fired cartridge, or even chambered & extracted, you will usually see that the extractor actually cuts the rim to some degree. This is because the extractor isn't perfectly polished (and needn't ba) and is harder trhan the brass case.

Depends on the extractor. That bevel does "ease" the extractor up; not such an abrupt transsition.

HAve converted cases for use in off-caliber rifles and pistols, and there has been occasions when the action wouldn't operate without that little bevel. Could be that the extractors weren't fitted just right, but as they'd been in there working fine for a long long time, and continued to work fine with ammo that matched the rim bevel of the original rounds, assumed it was an ammo fault and not an extractor fault.

I honestyly don't know if that bevel is standard or not...seems to vary between makers within the same caliber.

Have noticed that all rimmed cases now come with a little relief groove (what would be an extractor groove if there weren't a rim) ahead of the rim...old rounds often don't have this relief groove, and the rim/case body just forms a 90degree angle. So far (other than some old brass refusing to enter modern shell holders) hasn't casued a problem.

Buck1,

In a lever gun, say a 45 LC running through a 1892 Winchester, I figured that a slight bevel was needed to help the extractor glide smoothly over the rim.

Buck, I have a Rossi Puma 92 and a Winchester (USRAC) 94AE Trapper in .45 Colt.

I've put cases of most every brand, and vintage through both guns and neither of them has any problems with cases that don't have a bevel on the rim.

I have a large quantity of ancient balloon head brass, much of it without any bevel at all and it cycles, chambers, extracts and ejects from both just fine.

Although it may ease the extractor up and over the rim I don't think it's a reason to wory. Years ago I acquired some 30-30 ammo that had no bevel on the rims at all. I believe it was S&W brand. The rims looked like a machined 90* angle. At any rate, the Winchester 94 top eject extractor is the same design as the Winchester 92 and it worked fine with these non beveled cases.

As for your original question, I couldn't find any way to measure the angle of the bevel. And when I looked at the cases no two of them were the same.
In this case I agree with ALK8944, I think its mostly cosmetic.

However if you want to put a bevel on them, get an original Lee case deburing tool. It's a perfect size to slip a .45 Colt case inside and put a bevel on it.

Joe

Just a guess, but I'd bet that revolver cases need the bevel to keep the rims from hanging up on the recoil shield. Most shields have a 90 degree cut or two for the hand slot, might cause problems without the bevel.

Papajohn