Straight Walled Cartridges???

If straight walled cases like the 38-55, 375 win. 444 marlin, etc. are straight walled but have a slight taper to aid feeding. Then the characteristics of the boolit which are designed usually without a taper, (straight driving bands or at least after sizing). Then seat the boolit in the case and crimp for tubular or not crimp for single shot. The boolit wouldn't be touching inside brass at the base of the boolit, whether GS or PB, correct? Would this scenario allow for cocking or the boolit, distortion on ignition, gas cutting on the drivings bands, whatever else (disrupting lube characteristics), etc.? Which would be detrimental to accuracy and leading. Take for example the 38-55. If from the web to .072 (I am assuming for crimping)before the case mouth is 1.813 inches with a taper of from the web to that .072 point, .419 to .394, a total of .025 taper. Now if you seat a 250 gr boolit in the case it would take up about .600 of case, or about 1/3rd of the case capacity. One third the taper of the case would be about .008. Even with a .376 sized boolit. that leaves darn near .004 gap between the GC or PB and the inside of the case wall. Do you see what I am getting at? I was just pondering a re-bore and chamber. Then noticed these dimensions while looking at cartridge drawings. Any thoughts, comments, or similar threads on the subject would be greatly appreciated. Thanx :castmine: Should be in the CB, favorite cartridge forum

I thought the taper for those cartridges stopped a little bit below the mouth of the case to provide an un-tapered straight walled neck? Am I wrong about that?

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Tis why we size cases back down and then expand to several thousandths under boolit diameter. Not to worry. There is no space between the case wall and boolit base in a sized case. In an unsized case and breech seated boolit, then yes, but when using BP the explosion bumps up the boolit to seal.

and once you get that 38-55 boolit up to .380 where it belongs that case taper disappears.

From lyman and lee drawings it doesn't show those dimentions, but hornady's 3rd edt, it shows the 375 win with .220 true straight wall at the case mouth. That's the only drawing I could find with that type of characteristic.

You may be overthinking this. With the 38-55 sized with standard FL sizing die and you seat a .377" or larger boolit, the case will show a "fishbelly" bulge at the base of the boolit. With larger diameter boolits, this bulge is more pronounced.

In fact, with a hard alloy boolit, you should be able to see the lube grooves if you FL sized the case.

Then fireformed brass would be out of the question for the 38-55, 444 marlin, and the 45-70. Also, you could still just neck size the the 375 win with it's .220 of true straight neck.

Are you wanting to reload fireformed, unsized brass?
A lot of what you are asking about is determined by your particular gun and its chamber dimensions and the groove diameter of the barrel.
I load for an older Winchester 38-55 and I use .381" boolits, loaded into fireformed, unsized cases and still have enough neck tension that I have to use the seater die to seat the boolits and crimp.
If one is concerned about having a straight portion of the case neck having parallel sides to fully contact the full length of the boolit, they can order a bushing type neck sizer die and have a custom size bushing made for the same.

I was pondering, having a 94 win re-bored and chambered for the 375 win, .375 groove and probably the standard land height, depending on the drill and/or reamer available. In essence a cheaper big bore 94. I know the 375 win is a 50,000 cup round but with a 250gr boolit taking up case volume and a softer hunting alloy, I don't think I'll get anywhere close to the 50,00 cup. I'd probably be lucky if I can get a gentler push at around 35,000 cup. I just happened to notice the dimensions and was wondering how those particular cartridges went together in the neck area.

If you are full length sizing and sizing your boolits to 0.001" to 0.002" over groove diameter, imo, you do not have to worry about having clearance between the base of the boolit and the inner case walls.

If you have factory loaded cartridges for the ones you mentioned, measure the od of the loaded cartridges at the crimp area and where you think the base of the bullet should be. You may be surprised.

Do the same measurements with a full length sized case and see if there is any difference in the od of the sized case from the mouth to where the base of a seated bullet would be.

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Do you see what I am getting at? I was just pondering a re-bore and chamber.

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No and why would you want to re-engineer a caliber that Ballard introduced in 1884 and has stood the test of time for over a 100 years and going strong into the next century?

There are 2 types of bullets for the 38-55:
* Straight sided shot as a fixed cartridge reload because except for the driving band, the diameter of each GG band is the same
* A tapered bullet that is breech seated where the bullet base just kisses the mouth of the case. These tapered ones run from with a xxxx smaller diameter from the nose to the base because the nose and part of the GG bands are in the bore

OK - look at this diagram that doesn't have all the dimensions but the ID of a 38-55 is a cylinder and able to shoot straight sided bullets, either seated deep to the crimp groove or seated out which is my preference in BPC rifles. You are fiddling with the OD's:
Bullet diameter .3775 in (9.59 mm)
Neck diameter .392 in (10.0 mm)
Base diameter .421 in (10.7 mm)
Rim diameter .506 in (12.9 mm)

http://stevespages.com/jpg/cd3855.jpg

Thanx John Boy for a more detailed drawing. I see that the actual case wall thickness is tapered from mouth to web. Thus allowing the entire seated boolit to make contact with the inside case wall. I was wondering if the 444 marlin and 45-70 cases designed the same way. I wasn't trying to re-engineer the caliber. Winchester already did that with the 375 win. I don't shoot BPC. the only time I use BP is in the front stuFFer. I was thinking that the 375 would provide a greater spectrum of powders to get the 250gr boolit near the 2,000fps mark with longer case life.http://castboolits.gunloads.com/imag...7a8950f896.jpg

Check the SAAMI standard drawing here.

http://www.saami.org/specifications_...tion/index.cfm

Is it possible to re-chamber from 38-55 to 375? The 38-55 case is longer. If its higher pressure one wants then simply load it up but take care not to get those hotter loads into a rifle not strong enough for it.

There's a good reason to have a cylinder case interior and taper exterior - the case forming dies need to be able to release (aside from extracting the fired case).