Accuracy of OAL Gauges?

[Golfer]

I have a Stoney Point,now Hornady) OAL gauge and use it to find where each of the bullets I load for a particular rifle touch the lands. I tried measuring some 6MM Berger 108 Match BT HPs and never could get consistant readings. I can feel by tapping the plunger when the bullet disengages the lands but when I try to gently tap it back to the lands it feel like I am back into them a couple of thousandths. My readings vary as much as .008 so I amnot sure just where the kissing the lands point is.
Should I just try to use a measurement that I know is actually into the lands as my reference point?

 

[rayjay]

I have about decided that the inconsistency of the Stoney Point tool comes from using a case that is not fireformed to the chamber. I used a fireformed case that I bump the shoulder back about a 'thou and then slit the neck.

 

[billmo]

I have a Stoney Point,now Hornady) OAL gauge and use it to find where each of the bullets I load for a particular rifle touch the lands. I tried measuring some 6MM Berger 108 Match BT HPs and never could get consistant readings. I can feel by tapping the plunger when the bullet disengages the lands but when I try to gently tap it back to the lands it feel like I am back into them a couple of thousandths. My readings vary as much as .008 so I amnot sure just where the kissing the lands point is.
Should I just try to use a measurement that I know is actually into the lands as my reference point?

golfer, Ray is correct. I read somewhere that using the modified case could net a variance of @ .005. I normally slide the tool in the chamber and hold it firmly while pushing the plunger with my other hand til I feel the bullet touch the lands fairly hard.
Then tighten the thumb wheel screw down real snug and retrieve the bullet. I hope this helps. Bill

 

[284driver]

I have about decided that the inconsistency of the Stoney Point tool comes from using a case that is not fireformed to the chamber. I used a fireformed case that I bump the shoulder back about a 'thou and then slit the neck.

Rayjay,
Does that keep enough neck tension to pull the bullet back out of the lands?

 

[treeman]

i use this tool a lot and know its not 100% reliable but it's a lot closer than any other method. the way i use it get fairly con sistent results. if a bullet gets stuck i just drop a smaller [dia.] bullet down the barrell to dislodge it and catch it at the back of the action. i have a tap to modify the casses and always use fire formed casses. _____treeman

 

[NorCalMikie]

If you guys use a "midified case" from Hornady,,Stoney Point) you don't have to deal with "neck tension". If you are making your own cases, make sure you get the neck ID big enough that the bullet will fall out. My bullets stick in the lands and slide out of the modified case so I use a cleaning rod to bump them out.
When they stick in the lands, I know that I get the same reading every time.
The Hornady,Stoney Point) modified case is reamed aprox. .002 larger than the chosen bullet. No neck tension involved.

 

[rayjay]

The slit neck method doesn't jam the bullet into the land, it just touches the lands. I can't remember having a bullet stick. If I check a chamber 5 times, 4 will be exactly the same length and the other will be a thou difference.

 

[NorCalMikie]

rayjay: One of the questions was asked about "neck tension"?
There should'nt be any resistance between the case neck and bullet. In my way of thinking, resistance could cause a difference in measurements because it's a "feel thing" as you're pushing the bullet into the lands.
And I'am no expert, just the way I do my measurements.

 

[rayjay]

As in many things a person should 'TRY IT'. I own a Stoney Point tool and several of their cases. Like many people [ re all the threads about the inconsistency ], I couldn't get the SP tool too give me the same reading twice so I started looking for some other method. I read about the split neck method so I

TRIED IT

I found it gave me the consistency I was looking for and the cost for each new caliber was the price of one fired case.

As far as I can tell, using my split necks the bullet does not get marked by the lands. It just touches the lands. I can see this being one area of inconsistency with the SP tool. It would be very hard to place the exact same pressure on the 'pushrod' each time you remeasure with the SP tool.

 

[NorCalMikie]

reyjay: At least we're not stuck on one thing!
Something else that came up was a batch of Berger VLDs that had 2 different bullets in the same box that were cut from different dies. The readings would come out with up to .015 difference in readings??? That really makes you scratch your head.
Finally got that figured out.
If your split case necks gives you a consistent reading, keep it up. The more you use a tool, the better you get with it.
I'am always into trying something different so I won't rule that out. Might come in handy someday. And thanks for your input.
Different ideas makes it easier to learn a different methods to doing something and that's what we're here for. :thumb:

 

[Golfer]

Thanks for all the replies guys.
Let me make a few points. I am using a Davidson 6mm nose piece on my caliper not the Stoneypoint unit.
The modified case is an unfired case from Stoney point.
The case neck is expanded enough that the bullet slides freely in the case mouth.
I have a minimum spec chamber so the case fits snugly without any wobble.
It sems to me that a once fire split neck case would fit the chamber tighter but since the bullet would be held more firmly you couldn't tell if you were just touching the lands or into them a couple of thousandths.
I am thinking that I will just use the push rod to advance the bullet until I first feel any contact and then lock the push rod in place rather than tap the rod back and fourth trying for that exact "kiss" point.

 

[rayjay]

With the split neck case there is no 'feel'. You seat the bullet just barely in the case, place the case under the extractor and close the bolt. They you open the bolt and measure the oal. All of my rifles have the ejector removed so I don't have any issues with that.

Good luck

 

[Golfer]

rayjay
Sems to me that with the split neck method you describe it is the land contact that is pushing the bullet back into the case mouth. If that is the case, wouldn't the amount the bullet is pushed depend on how much tension the case neck applies to the base of the bullet? With the very slender Berger bullets I am using the ogive makes very gradual contact with the lands verses the more abrupt contact that a stubbier bullet would make. Even with the modified case applying no resistance and only the very light pressure I am putting on the push rod I am getting several thousandths differences in length.

 

[jo191145]

For practical load development I must ask.
Does it make any difference if your DTL measurement is correct?

Pick a number. An average if you get different readings and stick with it. After you choose a powder charge you'll do a seating depth test anyway.
In the end will it matter if your favorite load is .008 into the lands when you think its .005?
Just wondering.