Tailstock Misalignment?

[LVLAaron]

^ I'm a checkride away from being a pilot!

 

[Henryrifle]

You got that image from a Teslong? It must be connected to a laptop because I am getting garbage out of the WiFi version I am using connected to my phone. Nice plane(s). I used to fly Bonanzas, Barons, a Duke! and King Air 90s & 200s for an insurance company. Enjoyed those days a lot. I bought a Vans RV6 that I flew for several years.

 

[Henryrifle]

Aaron, I know you will love the freedom that comes with flying. It is amazing how much faster you can personally get to distant places, and on YOUR schedule. A plane makes the world seem like a smaller place.

Hank

 

[DonkeyHote]

Just a note, and to put your mind at ease about your tail stock being out .
Just take a good indicator , mount it in your chuck and sweep the tail stock spindle, do the inside taper.
If it is out adjust it.

 

[V35]

You got that image from a Teslong? It must be connected to a laptop because I am getting garbage out of the WiFi version I am using connected to my phone. Nice plane(s). I used to fly Bonanzas, Barons, a Duke! and King Air 90s & 200s for an insurance company. Enjoyed those days a lot. I bought a Vans RV6 that I flew for several years.

Its the Wifi version to my phone, I phone 13 if that even matters? The teslong is fiddly to me, I had to play with the mirror distance some to get good pics. I have found that the smaller the diameter of the bore, the harder it is to clear it up. Beech makes good planes, my cousin used to fly a Beechjet until the owner upgraded to a G450 and he got to take that all over the place until he couldn't pass the medical.

And Aaron, best of luck to you on the check ride, hopefully it wont be the last, the instrument rating is helpful in more ways than you know.

 

[INTJ]

1. There is no freedom in flying. Just work and dissatisfaction and expense. That's why after having flown C-130s, T-38s, T-1s, and a nice Navajo; I am working my azz off to become qualified in all the pilot quals that Civil Air Patrol has to offer. My unit has a 2021 C-182 with a G-1000. Most of the time I get to fly it for free. When I do decide to pay for one myself it's about half or two-thirds of what such a plane would rent for.

2. It took me a lot of convincing that the weird shapes I was seeing with the Hawkeye, on everything but 4 and six groove cut barrels, weren't my fault. It took two master machinists/action makers and a bunch of sub 1/2 minute 650 yd groups from hunting rifles to convince me.

The worst one was a button rifled 375 CheyTac. It had ridges on the edge of each land that extended all the way to the throat. That rifle shot a 3/4" group at 500 yds.

So @Henryrifle, it's not your fault that they look weird. One day you will become convinced of that.

 

[Tad_Earhart]

The original pictures look very similar to how a Shilen Ratchet typically does with a fresh chamber. Aaron's demonstration and pictures is about the best way I have seen it shown before. With all of the odd/non-normal rifling patterns used with the rimfire stuff a person will see some very funky looking shapes in there around the leade area. Maybe someone following this thread can post a picture of a good polygonal rifled barrel with a fresh cut chamber and how much different it can look.

Tad

 

[clowdis]

It's not polygonal but the photo posted by V35 shows a generous radius at the bottom of the groove. Definitely not square. Used to own a Cessna 177RG, great little airplane, but a money pit if there ever was one. Finally sold it and never went back. Cross country flying was the kind of boring to me and the thing I enjoyed most was learning how, from my private license to my instrument license. Reckon I enjoyed to look of terror on my instructor's face.

 

[Henryrifle]

Lots of hours in a Cardinal--great plane! It does stink to have to pump the gear down, however. As a follow-up to this I am on day two of load development for the rifle with the smeared-looking throat. The rifle is in tune and responding normally to both tuner and power charge changes. So, ugly but functional:


Thanks all,
Hank

 

[Alex Wheeler]

I have seen a few barrels cut different than I think they should, and after checking my setup. It still was concentric to the spindle. Not all blanks have lands that are perfect, some seem to appear that they are.

This is a Shilen barrel I chambered in 300 PRC. The lands looked funny, each one looks identical, but my setup was double checked as good, and when looking in the chamber with a loop the lead and throat looked great. I suppose the button pushed the material unevenly. Its not the prettiest chamber I have cut, but the rifle shoots great, so Im pleased. It was chambered by pre boring and using the same reamer holder the OP mentioned he used. I had a lot of questions I asked myself on this one, and before I removed it from the lathe, I ran my long stem indicator in there and by slowly turning it, I could see that the lands were not flat so to speak. I always indicated in the groove, but from this day forward, I indicate in the grooves and then check the lands and make notes of any irregularities I see. I have gained nothing by doing so, but there may be a lesson in it someday.
View attachment 1462719

Thats very typical in a button rifled barrel. The button creates a land thats cupped. The middle of the land will usually measure about .0003 lower than the edges. And one edge is always higher which you can see in your picture.

 

[Alex Wheeler]

All of this stuff is what I call "bore geometry". Because the reamer cuts a round hole you can tell a lot about the shape of the lands or grooves by how the cut looks. I should say that you can cut an out of round hole in a 5r though. Anyhow, those shapes dont really play a role in the accuracy of a barrel. They do make it harder to dial in though. Unless you have dialed in a lot of barrels and bore scoped them after you just wont know how much those shapes are worth in inches. But from experience, I can say that the previous picture of the cupped land is only .0003-.0004 deeper in the middle than it is on the edge. But it looks like a mile. Keep this in mind. The cutters used in a cut rifled barrel are tiny. Imagine trying to grind those angles. And they have to be resharpened often. So you will always see different shapes in barrels. Its amazing how good they are actually.

 

[jackieschmidt]

PacNor Barrels have, or used to have lands that were concave, inducing a convex shape at the top of the lands.

Through the years, I have seen all sorts of strange shapes of lands and grooves. Some years back, we started noticing on our Krieger 6mm blanks that the grooves were not a perfect circle as the indicator swept the arc.

The throats looked weird, but the barrels shot pretty darned good. Charles Huckeba even shot a potential record with one.

Krieger made up a name for this shape, not many bought into it. Turns out, the grooves were the result of their resharpenning their rifling hook tool by simply grinding the face. However, due to the back clearance, this left the tool in a shape that was not a true radius.

Or at least that is the story that was floated.


Soon after, all of our barrels started having true circle grooves again.

Go figure.

 

[Acyr]

All of this stuff is what I call "bore geometry". Because the reamer cuts a round hole you can tell a lot about the shape of the lands or grooves by how the cut looks. I should say that you can cut an out of round hole in a 5r though. Anyhow, those shapes dont really play a role in the accuracy of a barrel. They do make it harder to dial in though. Unless you have dialed in a lot of barrels and bore scoped them after you just wont know how much those shapes are worth in inches. But from experience, I can say that the previous picture of the cupped land is only .0003-.0004 deeper in the middle than it is on the edge. But it looks like a mile. Keep this in mind. The cutters used in a cut rifled barrel are tiny. Imagine trying to grind those angles. And they have to be resharpened often. So you will always see different shapes in barrels. Its amazing how good they are actually.

As someone who grinds those angles in cut rifle cutters for the barrels I make, do you see any pattern in groove geometry that may yield better results other than a perfect radius?

 

[Alex Wheeler]

No. I much prefer as close to a perfect radius as possible. Not because I think the shape of the groove plays a role in accuracy, but because I know a concentric throat does and so does the volume of the barrel. I have ordered barrels from .2430-.2440 in groove diameter to see what happens. Theres a sweet spot for velocity and accuracy, smaller gives up velocity and larger gives up accuracy. When the groove is not an even depth from the centerline of the bore its really hard to control the volume. When the groove is high or low in the middle or edges, or if it has ratchet your going to get different diameters depending on where you measure. This also makes dialing the barrel in much more tedious and if not done properly, can have you thinking its dialed but its not. From my experience this plays out in real life. The manufacturers that do the best job with the groove radius also have the most consistent barrels. You will see them tune up in the same spot over and over again.

 

[Acyr]

Thanks for the input Alex. I have often wondered if a "slight" rachet on the leading edge would provide some benefit in BC at 1000 yards.

 

[Alex Wheeler]

Thanks for the input Alex. I have often wondered if a "slight" rachet on the leading edge would provide some benefit in BC at 1000 yards.

Maybe. I have been told about testing done with land types and it does have a small bc effect. But not in accuracy.

 

[LVLAaron]

It would make sense that any type of ramped/ratchet shape would be better for BC than a sharp edge cut into the bullet

 

[Henryrifle]

I don't know, Aaron. The bullet is spinning at over 250,000 RPM and initially traveling at 2.5-2.7 time the speed of sound. None of that is as intuitive as it may seem...

Hank

 

[DaveTooley]

Hornady did, still does, extensive testing when they got their dopplar radar system. Everything, twist rate, land profile, land to groove ratio, etc. had an affect on BC. Very small but enough that it could be measured.

 

[xr650rRider]

Drag coefficient is a function of velocity, so every velocity change, changes BC. So published BC values are a guesstimate at best anyway.