Interesting results from my new Sinclair concentricity gauge...

[Mikecr]

What gauge are you using Barrelnut?

 

[barefooter56]

Can the nose of the bullet be pointing of axis, while showing concentric indication where the bullet is held by the case?

Would this situation be just as detrimental to accuracy as a bullet that ran out on an axis parallel to that of the case?

Canadian Bushman,
Do this test. Load up 5-10 rounds and purposely seat them so the run out on the bullet as measured up by the bullet/case mouth junction is over .005 run out. Load 5-10 rounds that are .005 run out or less. Check both groups all the way out to the tip of the bullet if you wish and record your findings of each group. make a trip to the range , make sure to fire enough fouling shots that the bullet strikes on the target are no longer rising but are clustering on the target. Now shoot each test group on separate targets. You can use flat base or boat tail bullets ( at 100 yards flat base would be best). Compare the group sizes and shapes. I did this on a whim just to see for myself. It was definitely an "ah ha" moment.

 

[Canadian Bushman]

The indicator gauge is not as accurate close to the tip because it is measuring on a slanting surface and the gauge tip is not 90 degrees to the measuring surface.

I just tested it. I had .001 runout on a 6.5 creedmoor with a 140 VLD. I tested at the bearing surface and got .001. I then tested closer to the bullet tip and got nothing...

Yes you should keep the indicator stem perpindicular to the tangent of the radius where you measure. On my gauge this is possible to do.

 

[Canadian Bushman]

Canadian Bushman,
Do this test. Load up 5-10 rounds and purposely seat them so the run out on the bullet as measured up by the bullet/case mouth junction is over .005 run out. Load 5-10 rounds that are .005 run out or less. Check both groups all the way out to the tip of the bullet if you wish and record your findings of each group. make a trip to the range , make sure to fire enough fouling shots that the bullet strikes on the target are no longer rising but are clustering on the target. Now shoot each test group on separate targets. You can use flat base or boat tail bullets ( at 100 yards flat base would be best). Compare the group sizes and shapes. I did this on a whim just to see for myself. It was definitely an "ah ha" moment.

Honestly i dont know how to induce a particular amount of run out, ive only ever tried to remove it completely. I have tested high run out rounds to low run out rounds and that particular test was inconclusive.

I would assume .005" run out at the neck is worse than .005" run out at the ogive since the ogive is usually a projection of the misalignment at the neck, but rarely do i see a condition like barrel nut saw with the tip running true and the bearing surface running out.

 

[barefooter56]

Canadian Bushman,
Loosen the lock ring on your seater stem and turn the stem so its off center. Tighten the lock ring and make sure the stem is still off center in the die chamber.

 

[Canadian Bushman]

Canadian Bushman,
Loosen the lock ring on your seater stem and turn the stem so its off center. Tighten the lock ring and make sure the stem is still off center in the die chamber.

I use ultra seaters with captive stems

 

[barefooter56]

Dont have any old standard style seating dies?

 

[Canadian Bushman]

Dont have any old standard style seating dies?

Maybe, ill have to look, but ive already run similar experiments with slightly different run out numbers. What realization are you expecting me to see? Ive noticed my more accurate lots of shells get marginally better when i increase their straightness but its no revelation. Also to get .005 at the case mouth juction would be pretty terrible.

 

[barefooter56]

Canadian Bushman,
Sounds like you have done some experimentation already on this just with smaller variances in concentricity between the test groups. Yes .005 is rather bad but as you have seen ( and I am assuming your test groups were in the .000-.005 TIR run out range?) that from .000 to .005 the affect of bullet run out is negligible. Its when you get above that you really start to see larger affects on accuracy. Since run out up by the bullet/case mouth junction affects the run out numbers on down the bullet. Then the .000-005 figure for an acceptable range of run at the case mouth/bullet junction out must not affect the TIR measurements enough on down the bullet to put them out of spec enough to affect accuracy. IMHO

 

[Trickymissfit]

1. I do not trust any readings that come off a "long travel gear & rack dial indicator" unless it's a digital read out or jeweled movement. 98% of them are built with 10% lag in them.

2. I also don't like a cradle that has movement (like ball bearings that turn). Yes you can build one that uses ball bearings, and make it work, but the bearings will set you back a hundred bucks or more. Plus the contact area is not good.

3. Even most wand type indicators are in the 2% lag category unless it's one that is capable of rotating 360 degrees. What this means is that when the direction of movement is reversed, you have a little built in error. I use Interrapid's and B&S Best Tests, as they are zero lag. But on the otherhand a Federal .0005" will easily get readings if used correctly.

4. The folks are correct that the gear and rack indicator needs to be 90 degrees from the surface contact. The real issue here is that most indicators come with the wrong tip. You want a ball tip. They make all sorts of tips, and they simply screw on
gary

 

[barefooter56]

1. I do not trust any readings that come off a "long travel gear & rack dial indicator" unless it's a digital read out or jeweled movement. 98% of them are built with 10% lag in them.

2. I also don't like a cradle that has movement (like ball bearings that turn). Yes you can build one that uses ball bearings, and make it work, but the bearings will set you back a hundred bucks or more. Plus the contact area is not good.

3. Even most wand type indicators are in the 2% lag category unless it's one that is capable of rotating 360 degrees. What this means is that when the direction of movement is reversed, you have a little built in error. I use Interrapid's and B&S Best Tests, as they are zero lag. But on the otherhand a Federal .0005" will easily get readings if used correctly.

4. The folks are correct that the gear and rack indicator needs to be 90 degrees from the surface contact. The real issue here is that most indicators come with the wrong tip. You want a ball tip. They make all sorts of tips, and they simply screw on
gary

Trickymissfit,
The balls on the Sinclair Concentricity gauge are fixed and do not rotate and if you buy the unit without the indicator you can put your upgrade unit on it.

 

[Canadian Bushman]

Canadian Bushman,
Sounds like you have done some experimentation already on this just with smaller variances in concentricity between the test groups. Yes .005 is rather bad but as you have seen ( and I am assuming your test groups were in the .000-.005 TIR run out range?) that from .000 to .005 the affect of bullet run out is negligible. Its when you get above that you really start to see larger affects on accuracy. Since run out up by the bullet/case mouth junction affects the run out numbers on down the bullet. Then the .000-005 figure for an acceptable range of run at the case mouth/bullet junction out must not affect the TIR measurements enough on down the bullet to put them out of spec enough to affect accuracy. IMHO

Yes i spent some time testing my run out results with live fire even going so far to index the rounds to factor out the actual disperersion caused by runout. The main reason i did them is to determine my own parameter on where my rounds needed to land.

Often i heard people say "measure here make sure they are perfect" and i just couldnt accept it.
When you say to measure the case mouth junction and keep it between .000-.005" now youve given a very specific parameter. One that i agree will have a marginal effect on consistency.

It also never sat with me to build a concentricity gauge that checked three point runout. So i built my own to actually check along the bullet as its rotated to paint an entire picture of how the bullet is being seated instead of extrapolating results.

I often asked questions and got vauge answers, i appreciate you taking the time to explain to my why you do things the way you do.

Thank you

 

[barefooter56]

Yes i spent some time testing my run out results with live fire even going so far to index the rounds to factor out the actual disperersion caused by runout. The main reason i did them is to determine my own parameter on where my rounds needed to land.

Often i heard people say "measure here make sure they are perfect" and i just couldnt accept it.
When you say to measure the case mouth junction and keep it between .000-.005" now youve given a very specific parameter. One that i agree will have a marginal effect on consistency.

It also never sat with me to build a concentricity gauge that checked three point runout. So i built my own to actually check along the bullet as its rotated to paint an entire picture of how the bullet is being seated instead of extrapolating results.

I often asked questions and got vauge answers, i appreciate you taking the time to explain to my why you do things the way you do.

Thank you

You are welcome sir! Have a great weekend!

 

[engineer40]

I'm a computer network engineer by day. It's a very detailed profession that requires me to really dig deep into technical data.

And I am still in awe sometimes when I read some of your guy's post at the level of detail you reload and test.

I love it!