Straight walled vs bottleneck accuracy

[dcali]

That's a big question depending on how you go about examining it, but the chamber of a straight wall cartridge will be much longer than that of a bottle neck for the same bullet. Conventional wisdom says that if you take that too far, you will wind up with poor ignition. Imagine a straight walled 6mm with the same case capacity as a 6BR - I don't know how long it would be, but I'm guessing several inches. Now imagine trying to fit a primer in the case head, and it quickly gets silly. So there are practical limits in terms of what you can even do. Cartridges have evolved the way they have for a lot of reasons.

 

[epc308]

I built myself a 6BR a couple years ago, you know, everyone’s darling? A box of Sierra 107s, a box of Lapua brass, a can of Varget, and first firings in the 2s after breakin.
It was almost too easy.
Take any good 45/70 Shiloh Sharps, or comparable quality single shot. Buy a bullet mold, but which one? Bullet alloy- 1/20, 1/30, 1/40, or something in between? Spend hours casting. Which, or what off the shelf bullet lube, or a home brew? Pan lube or lubrisizer? Black powder from Goex, Swiss, Elephant? What granulation? Compression or not, a little or a lot? Wipe the bore between shots or use a blow tube to keep the fouling soft?
All this before you load ammo and/or load the car to shoot your new rifle the first time.
Then you have long range trajectory measured in tens of feet increments at long range distances, and yes, open sights may be required.
The lock time and barrel time alone need serious consideration compared to modern equipment.
Something tells me those guys may know a little bit about wind, mirage, and last but not least, how to shoot.

 

[epc308]

That's a big question depending on how you go about examining it, but the chamber of a straight wall cartridge will be much longer than that of a bottle neck for the same bullet. Conventional wisdom says that if you take that too far, you will wind up with poor ignition. Imagine a straight walled 6mm with the same case capacity as a 6BR - I don't know how long it would be, but I'm guessing several inches. Now imagine trying to fit a primer in the case head, and it quickly gets silly. So there are practical limits in terms of what you can even do. Cartridges have evolved the way they have for a lot of reasons.

The straight wall cases were made ever longer to get a gain in velocity. Black powder is a very inefficient propellant. It has some very definite limitations in that regard. The Express cartridges were generally longer and shot a lighter bullet to get a noticeable gain in velocity. As for ignition problems, it’s very common to achieve single digit SD readings. There has to be consistent ignition and burn to do that.

 

[dellet]

I built myself a 6BR a couple years ago, you know, everyone’s darling? A box of Sierra 107s, a box of Lapua brass, a can of Varget, and first firings in the 2s after breakin.
It was almost too easy.
Take any good 45/70 Shiloh Sharps, or comparable quality single shot. Buy a bullet mold, but which one? Bullet alloy- 1/20, 1/30, 1/40, or something in between? Spend hours casting. Which, or what off the shelf bullet lube, or a home brew? Pan lube or lubrisizer? Black powder from Goex, Swiss, Elephant? What granulation? Compression or not, a little or a lot? Wipe the bore between shots or use a blow tube to keep the fouling soft?
All this before you load ammo and/or load the car to shoot your new rifle the first time.
Then you have long range trajectory measured in tens of feet increments at long range distances, and yes, open sights may be required.
The lock time and barrel time alone need serious consideration compared to modern equipment.
Something tells me those guys may know a little bit about wind, mirage, and last but not least, how to shoot.

Yeah, but they don't know dick about neck tension or shoulder bump so they can't know anything else that matters.

 

[epc308]

Yeah, but they don't know dick about neck tension or shoulder bump so they can't know anything else that matters.

I’m howling with laughter.
PS- You’re right, I did fail to mention neck tension, crimp, or lack of, and who knows what else.
One more tire to throw in the fire- there were bottleneck BP cartridges too...

 

[dellet]

I’m howling with laughter.
PS- You’re right, I did fail to mention neck tension, crimp, or lack of, and who knows what else.
One more tire to throw in the fire- there were bottleneck BP cartridges too...

When seated depth refers to how far in front of the case your bullet starts,
neck sizing is calculated by how many .001's over bullet diameter,
compressed loads are measured by .1's,
fired brass counts reach into the 1,000's,
scope and iron sight adjustments refered to by the same .001's not clicks,
you adjust your front rest to find the sweet spot in the barrel,
and your rear rest gets an icepack after a days shooting.

It's a whole new game.

Sad part is that some of these guys with the bottle necks, joy sticks and weather meters shoot 5 shot groups at 600 yards smaller than one of my bullets.

 

[epc308]

When seated depth refers to how far in front of the case your bullet starts,
neck sizing is calculated by how many .001's over bullet diameter,
compressed loads are measured by .1's,
fired brass counts reach into the 1,000's,
scope and iron sight adjustments refered to by the same .001's not clicks,
you adjust your front rest to find the sweet spot in the barrel,
and your rear rest gets an icepack after a days shooting.

It's a whole new game.

Sad part is that some of these guys with the bottle necks, joy sticks and weather meters shoot 5 shot groups at 600 yards smaller than one of my bullets.

You have obviously played with similar things to me.
Some of those same guys need to research the shooters, no, riflemen, of the day. Dr. Hudson, Harry Pope, Horace Warner, and the like.

Sub MOA, 10, not 5, shot groups, at 40 rods.

Standing. Cast bullets, black powder. Straight wall cases, or later, the new fangled 32/40, semi, kind of, bottleneck case.

But that stuff isn't accurate.

 

[GeoffreyKolbe]

One major advantage of bottle-necked cartridges is that the powder is kept in the case, where it will burn consistently, and does not follow the bullet up the barrel, where it is spread out and so burns inconsistently. Black powder did not suffer so much from this problem as its burning rate is not so dependent on pressure and also it was pretty fast burning stuff and so the powder was all burnt before the bullet had gone far up the barrel.

The Winchester Super Short Magnums took this idea to the extreme, with short stubby cases under small bullets.

 

[bsekf]

I have a friend who shoots and wins Schutzen bench rest with cast bullets. If you shoot against him you better have your shoes laced. I believe his best 10 shot group is <.5 at 100 and < 1. at 200. He has a gain twist barrel and does use smokeless powder. I believe the action is a Baker but he has Hi-Walls and Stevens.

 

[David Milisock]

Many times to answer what is more accurate one has to define what accuracy standard you have and the shooting sport you have in mind. Then how much do you want to work to become the reloader, rifle smith and rifleman you want to be.

What targets, man sized at 2,000 yards, head shooting groundhogs at 500 yards? Maybe it's only going to be on the range work, then what kind of range work?

Do the work, research what the competitors are using and why they use it for the sport of your choice. Remember in the Civil War a 1,400 yard sniper shot was done, and as stated in these posts straight or bottleneck accuracy has been achieved by good people, enjoy the sport and don't let rhetoric define you.

 

[LHH]

Thanks for the replies and info.
Interesting topic

 

[XTR]

Another thing that happens with straight wall cartridge it is difficult to maintain pressure in the chamber when a bullet starts to move the effective chamber size or combustion chamber size grows very rapidly as opposed to the bottle necked cartridges.

there are Schutzen guys who well know Mr Pope’s lessons, there are some still shooting his rifles.

it’s not the same, and with cast or swaged bullets there are a lot more potential variables to control in the lead alloy in both and temp, casting speed, molds, etc. when casting.

The guys I’ve watched breach seat the bullets and use the same case thousands of times with a wad on top of the powder.