Full Length or Neck Only; What's Best Resizing for Accuracy?

[25WSM]

Like afp1 says. Setting your brass back creates a slightly smaller volume.
Shep

 

[Bart B]

A 30 caliber bullet needing 5 pounds of force to push it out of the case neck needs about 65 psi in the case to do that. Several hundred psi to push the bullet full into the bore past the throat.

 

[25WSM]

From what I'm told by the guys that have been doing this for way more time than me is small brass give a slightly slower ramp up of pressure. A neck sized case doesn't need to expand any and the pressure ramps up faster. They say that's why some fireforming loads are more accurate than once they are sized. They claim the bullet gets a softer start. I don't have any scientific data to prove or disprove this. Just what I've been told by guys doing this for 50 yrs. Maybe PO Ackley wrote about it somewhere. They also say brand new brass shoots better because it's small. The turd in the violin case.
Shep

 

[Bart B]

Isn't a 65 psi start pressure to move a bullet a soft start?

What about a 13 psi starting pressure to apply a 1 pound force? I've shot such loads.

 

[Rich Coyle]

Like afp1 says. Setting your brass back creates a slightly smaller volume.
Shep

In that case one should see higher velocity. But that's not what happens. Neck sized cases produce higher velocities.

 

[25WSM]

Rich the smaller case expends some energy to expand the brass to full chamber size. The neck sized brass already fits and doesn't need to expand much to get the bullet going. The speed difference is not much between the 2 if using the exact powder charge but both will be the same speed when tuned correctly. Full length sized brass may need a few 10ths of a grain to match the same tune. I can't even tell you how much on my new rifles because I haven't bought or owned a neck die in a long time. I do have a few Lee collet dies but they are used on full length sized cases.

Shep

 

[Rich Coyle]

Shep,

The loads would no longer be the same. Therefore the neck sized cases exceed full length sized cases with all things being equal. Facts are facts. But so what. Who really cares. I did my test for fun and never gave it a thought others would argue about the info.

 

[25WSM]

Depends on what you mean by exceed. If it is purely speed per exact same powder charge then yeah by a smidgen. But full length sized brass has other advantages. Like they actually fit in the chamber properly for more than 3 firings. The bolts on my guns close with no resistance from brass that's too long. My brass extracts easy on full pressure loads. Neck sized brass can cause verticle in your groups. When you don't control the length of your shoulder some rounds chamber harder than others. This will absolutely cause verticle. Plus it just sucks having to crush the bolt handle down all the time. These are just plain facts. So if it cost me a couple tenths of a grain more powder to eliminate all that I'm in.
Shep

 

[INTJ1]

Depends on what you mean by exceed. If it is purely speed per exact same powder charge then yeah by a smidgen. But full length sized brass has other advantages. Like they actually fit in the chamber properly for more than 3 firings. The bolts on my guns close with no resistance from brass that's too long. My brass extracts easy on full pressure loads. Neck sized brass can cause verticle in your groups. When you don't control the length of your shoulder some rounds chamber harder than others. This will absolutely cause verticle. Plus it just sucks having to crush the bolt handle down all the time. These are just plain facts. So if it cost me a couple tenths of a grain more powder to eliminate all that I'm in.
Shep

All this can be hard to understand for those who don't compete at long range. Working up a load for my 33-28 Nosler elk rifle, it can't be shot fast. The rifle recoils completely out of the front rest and the rear bag is moved out of place. It is very slow between shots and even with that I managed a 1/2" 3-shot group at 100 yds.

That was my perspective for years. The idea that rifle upset and slow shooting could increase group size didn't even compute. It wasn't until I started competing that I saw that a tight fit in the chamber actually wasn't good.

What would be interesting would be to have a 600 or 1000 yd indoor range. There would still be micro currents in the building but that could be mitigated. In that environment then maybe a tight chamber fit might be better.

 

[25WSM]

The recorder holder I talked about doesn't make his brass small so it is faster to run the gun, he does it because he says small brass allows brass movement in the chamber to help bullet get straighter. Once again the turd in the violin case reference from the Sierra ballistics guy. He said make it small to be more accurate. He wasn't referring to running the gun fast. It was based on a pure accuacy observation. Have you read the Houston warehouse expirment. It's a pretty cool read about shooting long indoors.
Shep

 

[INTJ1]

He must view it like my friend, the 2018 NBRSA LR BR Champion, that the slightly expanding case helps keep things more consistent. I guess my own experience sort of backs that up as when I small based and had no difference in accuracy.

If only the Houston warehouse was 1000 yds. I know if a guy who has access to a 200 yd indoor range, and my fiend up the road is always sending him stuff to try in the blind. That is how the Bullet Genie was validated.

 

[25WSM]

1000 yard warehouse would be ginormous. It would have to be tall too.
Would be fun to shoot in one. Our club has an 8 pm curfew so you can't shoot right at evening. Normally that last half hour of daylight is the calmest. I know people who shoot at night on private ranges to help mitigate wind and mirage. They say one flashlight near the target is plenty of light to shoot.
Shep

 

[Rich Coyle]

"Depends on what you mean by exceed. If it is purely speed per exact same powder charge then yeah by a smidgen. But full length sized brass has other advantages. Like they actually fit in the chamber properly for more than 3 firings."

What is wrong with you neck sizers? The higher velocity is higher. I didn't have to full length size until I fired the case seven times. You sound like an evolutionists who is trying to claim abiogenesis happened several times.

 

[Bart B]

Has anyone actually measured rimless bottleneck case neck centering in the chamber neck when the case is in its firing position? I have and full length sized ones are better centered. Not much difference, a thousandths or so is typical. Cut the barrel off at the chamber mouth so it's able to be measured with a calibrated loupe.

Regarding a 1000 yard indoor range, 308 Winchester maximum ordnate is about 11 feet at about 560 yards for a 1000 yard zero. About 8 feet for the 300 Win Mag.