Can rimmed cases give the most accurate headspacing?

[Tommie]

Full disclosure: I'm a huge fan of the Donaldson Wasp. Also, I'm just thinking out loud here. Now that we have that out of the way...

Rimless cartridge shoulders move with firing, then get bumped back, and on it goes. With the necessary "slop" between the loaded round and chamber there must be a couple thousandths variation in bullet jump (or jam). Possibly enough to affect accuracy.

With a rimmed cartridge, the rim can be machined flat and true. Headspacing off the barrel breech, it would seem that bullet jump would be much more consistent. Combine this with a tight-neck chamber bullet alignment would also be less variable.

Or so it would seem.

Looking forward to hearing your replies. Thanks!

 

[ebb]

I read of a guy over at Benchrest Central that has developed a wildcat 30 caliber on 30/30 brass that everyone said was competitive against the other 30 hunter benchrest cartridges. I think its all in what you want to accomplish, do you want to compete or tinker with a wildcat? There is so much info on the 30br or the 6PPC why would you want to reinvent the wheel if competition was your goal? However if you want to prove a point or just be different what could possibly be wrong with that? Doing something the hard way has its rewards.

 

[butchlambert]

Full disclosure: I'm a huge fan of the Donaldson Wasp. Also, I'm just thinking out loud here. Now that we have that out of the way...

Rimless cartridge shoulders move with firing, then get bumped back, and on it goes. With the necessary "slop" between the loaded round and chamber there must be a couple thousandths variation in bullet jump (or jam). Possibly enough to affect accuracy.

With a rimmed cartridge, the rim can be machined flat and true. Headspacing off the barrel breech, it would seem that bullet jump would be much more consistent. Combine this with a tight-neck chamber bullet alignment would also be less variable.

Or so it would seem.

Looking forward to hearing your replies. Thanks!

If it were that great, people would be using it and they ain't.

 

[IdahoSharpshooter]

Butch,

Seeley Masker did...

 

[vmaxpro]

I see what your saying. However, chambering with a light crush eliminates that. BUT, I will say I had a 17 bee that was boring accurate!

 

[Macropod]

Then you get variations in rim thickness to contend with.
Far easier to control headspace with a rimless case.

 

[Ggmac]

All cases even rimmed are headspaced off the shoulder. At least all accurate rifles built on rimmed cases are headspaced off the shoulder , just like rimless . The reason you don't hear anyone having to do all the bumping annealing etc is no one currently uses a rimmed case .

 

[BoydAllen]

Currently there is a set of targets in for measuring as a potential NBRSA unlimited 100 yard aggregate record that was match measured at .1017". It was shot with a 6PPC. The first rule about fixing problems is to make sure that you have one in the first place. If you like to tinker, tinker. Enjoying the process is enough reason. Come back and tell us how it went. Good luck. I hope that you have a lot of fun and make some great discovery. I would be interesting to read about.

 

[XBBR Shooter]

Full disclosure: I'm a huge fan of the Donaldson Wasp. Also, I'm just thinking out loud here. Now that we have that out of the way...

Rimless cartridge shoulders move with firing, then get bumped back, and on it goes. With the necessary "slop" between the loaded round and chamber there must be a couple thousandths variation in bullet jump (or jam). Possibly enough to affect accuracy.

With a rimmed cartridge, the rim can be machined flat and true. Headspacing off the barrel breech, it would seem that bullet jump would be much more consistent. Combine this with a tight-neck chamber bullet alignment would also be less variable.

Or so it would seem.

Looking forward to hearing your replies. Thanks!

I have a rifle with a rimmed cartridge - the headspace is -0.002 (light crush). I have never had headspace management problems with it. The shoulder stays where it is... forever !!

They are not used often in bolt rifles because of feeding problems.

P.S... I love the 219 DW The .225 Win ain't too shabby either.

 

[butchlambert]

Butch,

Seeley Masker did...

Rich, you're right "DID".

 

[butchlambert]

I have a rifle with a rimmed cartridge - the headspace is -0.002 (light crush). I have never had headspace management problems with it. The shoulder stays where it is... forever !!

They are not used often in bolt rifles because of feeding problems.

P.S... I love the 219 DW The .225 Win ain't too shabby either.

Has nothing to do with rimmed or not.

 

[XBBR Shooter]

Has nothing to do with rimmed or not.

The OP's original comment was about headspace. With rimmed cases, it is easier to control headspace.

 

[butchlambert]

The OP's original comment was about headspace. With rimmed cases, it is easier to control headspace.

I understand his post. You still need proper dies, set up right or you can have a head space problem with rimmed or rimless cases.

 

[XBBR Shooter]

I understand his post. You still need proper dies, set up right or you can have a head space problem with rimmed or rimless cases.

Rimless cases headspace on the shoulder - the shoulder is always moving, and people are always debating what is the best way to manage the headspace.

Rimed cases headspace on the rim. If properly set up (not a 30-30 Winchester lever gun )... the rim is forced against the barrel face.
- the space between the bolt face, or breach block, being 1 or 2 thou LESS than the thickness of the rim... that space can never change. So the head space can never change, no matter what happens to the shoulder.

 

[DaveTooley]

Seely did, I did and many others did and still do use a rimmed case after myself and a couple of other guys came out with the 30 American case. All done on bolt guns not falling blocks. In a bolt gun it's impossible to head space off of anything but the shoulder.

 

[DaveTooley]

Shameless plug here. For all you 219 Donaldson fans I have a set of Red Elliot reamers I'd sell. Red was arguably one of the best reamer makers ever.

 

[Tommie]

Shameless plug here. For all you 219 Donaldson fans I have a set of Red Elliot reamers I'd sell. Red was arguably one of the best reamer makers ever.

Dave,
I have copies of reamer prints you had drawn up back when you, Masker, Young and others were playing with the 30 American. I spent countless hours studying those diagrams! You guys were true innovators.

Actually, a bolt action rifle can headspace off the rim. I own two that do.

 

[Eddie Harren]

I still have an IBS Hunter class rifle chambered in 30 Aardvark. It is based on a 30-30 case. It has a shoulder and rims are turned to fit a PPC bolt face. As Dave Tooley already explained, in a bolt gun the rimless case headspaces off of the shoulder.

 

[Ggmac]

I have a few aardvarks , and some other 30-30 based or 225 win based rifles . As accurate as any other , just a little more work now a days .
And like I said before , they headspace off the shoulder.

 

[IdahoSharpshooter]

Dave,

good to see your name here. I just sold (here) the last three boxes of 30 American brass I had. I finally shot out the barrel on my 6mm SMW a few years ago. He made me 50 cases to go with the barrel he fit to an old 40X single shot, and I only lost five or six over the years.
One nice thing about a rimmed case, you don't need a bump die.