OAL measurement - how hard do you push the bullet?

[patriot07]

Using the Hornady straight OAL gauge, I've gotten significantly different readings trying to find the lands based on whether I just barely push the rod til I feel any resistance, or I push a little harder, or if I push even harder than that and the bullet barely sticks in the lands. My readings have shown as much as .070" variation purely based on how hard I push the bullet.

My assumption is that the most proper way is the medium pressure route - more than the first sign of any resistance, but not enough to stick it in the lands. But I was wondering what the SH gurus thought.

 

[spife7980]

That depends, do you want to know where the lands start or some arbitrary amount of jam?

So long as you don’t have a savage

 

[Xander3Zero]

I would carefully double check all your steps, .070" sounds like a large variance based solely on how much you push the bullet into the lands. I think it takes considerable force to jam a bullet .070" into the lands even using a bolt, let alone the little hornady tool.

 

[supercorndogs]

Did you clean it really well before measuring? That will help. I like to put a cleaning rod down barrel. That way I can push it from both ways while feeling for the lands. You want it just to touch, not to jam.

 

[patriot07]

That depends, do you want to know where the lands start or some arbitrary amount of jam?

So long as you don’t have a savage

Thanks for the video. I'll try this.

 

[patriot07]

I would carefully double check all your steps, .070" sounds like a large variance based solely on how much you push the bullet into the lands. I think it takes considerable force to jam a bullet .070" into the lands even using a bolt, let alone the little hornady tool.

I agree, seems like a ton of variation. I probably took 20-30 measurements last night. It really isn't much force difference between the lightest touch versus the bullet sticking in the lands. I just got wildly different readings.

I was headed to the range today anyway so I loaded a few at .030" off the 'medium' force number, which was fairly consistent. They loaded and extracted/ejected without issue, so I know I'm not jammed into the lands or anything like that. But I'm going to try what was shown in the other video to see if I can get some more consistent results.

The problem, IMHO, is the inherent friction in the Hornady tool. It seems difficult to perceive the increased force of touching the lands without jamming the bullet into the lands.

 

[patriot07]

Did you clean it really well before measuring? That will help. I like to put a cleaning rod down barrel. That way I can push it from both ways while feeling for the lands. You want it just to touch, not to jam.

I did clean it before measuring. I had a cleaning rod in anyway, since I had to push the bullet back out of the lands quite a few times.

 

[supercorndogs]

It can be tough to feel a slight jam when running the bolt, but it will spike your pressure and velocity.

 

[Blackedout12v]

I have ran into this same situation, one rifle I can tell where the lands start exactly regardless of how much pressure is put on the tool, like hitting a wall. Another rifle has what is best described as a first stage of friction that the bullet can be forced through then hits the lands where it will stick. I just used the first stage measurement to be on the safe side. I don't recall at the moment what the difference in measurement was.

 

[Sheldon N]

When I use the hornady tool I gather both measurements... push the bullet HARD into the lands and measure where the full stop is. I use a few different bullets and measure each a few times to confirm consistent readings. Then switch over to a light touch method using a cleaning rod down the barrel. Push the bullet back and forth between the Hornaday tool and the cleaning rod to get a feel for where if first barely touches the lands. Again multiple measurements with multiple bullets to get an average. The two numbers can be closer or farther apart depending on bullet shape. Long sleek bullets have a bit more of a wedge effect that can spread out the measurements. Stubbier bullets are more consistent between touch and hard jam.

The video method above works too, and is more precise for finding the "touch" point.

Either way I pick a starting point for seating depth that's off the lands and then do load development and refine seating depth. Once I have the number that shoots the best I run that. Doesn't matter how you quantify how far "off the lands" you are, as long as you choose the load that shoots best and replicate those dimensions.

 

[patriot07]

When I use the hornady tool I gather both measurements... push the bullet HARD into the lands and measure where the full stop is. I use a few different bullets and measure each a few times to confirm consistent readings. Then switch over to a light touch method using a cleaning rod down the barrel. Push the bullet back and forth between the Hornaday tool and the cleaning rod to get a feel for where if first barely touches the lands. Again multiple measurements with multiple bullets to get an average. The two numbers can be closer or farther apart depending on bullet shape. Long sleek bullets have a bit more of a wedge effect that can spread out the measurements. Stubbier bullets are more consistent between touch and hard jam.

The video method above works too, and is more precise for finding the "touch" point.

Either way I pick a starting point for seating depth that's off the lands and then do load development and refine seating depth. Once I have the number that shoots the best I run that. Doesn't matter how you quantify how far "off the lands" you are, as long as you choose the load that shoots best and replicate those dimensions.

I agree. I had just heard that my particular loaded on 6.5 CM tended to run best at .030 off the lands and I was going to try to save some testing time/money.

 

[patriot07]

Update: I tried to do the method in the video and it didn't work for me. Didn't ever get a free-running bolt throw no matter how far back I seated the bullet. I tried a piece of virgin brass with no bullet in it too, and got the same result, so I'm not sure what the issue was. I had removed the ejector and firing pin.

On the other hand, I was able to figure out what some of my issue was with the Hornady tool. The inherent friction in the tool was making it difficult to feel the first touch, and I realized it was because the plastic seems along the side of the push rod were scraping against the red metal housing. After sanding the sides of the rod down with some 320 grit sandpaper, it moved much more freely and it was much easier to figure out where it was first hitting the lands and then feel the bullet being pushed down into the rifling. Ultimately, it was just poor manufacturing quality from Hornady that was causing problems. I got fairly consistent measurements after that by not pushing the bullet too hard, so I feel pretty confident in having a decent starting point.

Thanks to all for the help!