Measuring your length to lands
Good video, I’ve never actually seen it done like that. May have to give that a try.
mamalukino last edited by
Great video Greg!
I am a proponent of that method; the results are consistent, unlike the various other methods I've used.
painless last edited by
Great video Greg! I just did the same thing with the DT rifle, just used the sharpie method. It’s a pretty slow and tedious process but very precise.
pizfiz last edited by
@orkan - another extremely useful, thoughtful video. Thanks as always.
@painless For the DT, you can pull the barrel out and use the bolt without stripping the firing pin spring out of the bolt.
Though if you leave the barrel in the chassis, you'll need to pull the guts out of the bolt so there's no pressure there.
martino1 last edited by
Thanks for taking the time to do that video.
7david7 last edited by
Excellent video! A couple more interesting things about this are; with the length to ogive measurement of one bullet it will be the same for all bullets ie, the ogive to lands will be unaffected by ogive shape. Also, with this reference measurement you can keep track of throat erosion by periodic rechecks.
with the length to ogive measurement of one bullet it will be the same for all bullets ie, the ogive to lands will be unaffected by ogive shape.
This is not entirely true. The lead angle in the rifling will interface with different bullets ogive differently. Also, the bullet comparators will interface each bullet in a different location based on ogive shape. Thus if you try to just seat a new bullet to the measurement you made on a different bullet, you're definitely going to be off.
So, the only real way to be precise here is to create a dummy cartridge for each bullet.
steelbanger last edited by
Great job Greg,Thank's for sharing that video.I also love the color of that stock,do you remember what the color mix is.
bigfoot last edited by
Speaking of dummies. I engrave mine as well as do some recording in my notebook for that caliber with that particular bullet. It's easy for me to get things scrambled up and have to go back through the process of either the dropping the bolt method or the Hornady swizzle stick. They are handy when setting up your seating die so you don't punch the first one in too deep. There's a long story behind those 308 dummies with all the different numbers.
For the most part, that's the technique I've used to get the measurement. I've been jamming the bullet into the lands where the bullet is seated in a case neck that is only just firm enough to hold the bullet in place so it doesn't take much pressure to close the bolt. So, not doubt I'm not getting the accuracy that can be gotten from the video's method. But, I'm wondering if that much accuracy provides enough return for the effort???
The lands is essentially is in constant movement and one would have to go through this process after X-number of rounds to make the adjustment to maintain that accuracy. And, wouldn't one also have to short their bullets in any particular lot to be sure the ogive measurement on each bullet is the same to get the benefit of measuring the lands this way?
@straightshooter1 Take caution. This is not sniperforums. The expansion of knowledge here is not dependent on whether "you" or anyone else needs it or not. We do not cater to the lowest common denominator, but rather push for the best and most efficient way to do things. Based on what I've seen of your rifles and your targets, it's entirely plausible that your needs are not the barometer for success here on Gunhive.
Measuring the lands location to the bolt face precisely is desirable no matter if you are chasing the lands or not chasing the lands. ... and the lands most often do not erode nearly as fast as people think or claim they do. The measurement must be known during load development, as a matter of proper technique as well as a matter of shooter safety.
People's inability to accurately and precisely measure their location inexorably removes the ability to discuss the topic intelligently.
Arguing this level of precision being "necessary" or not, is an individual mandate and irrelevant. Being as precise as one can be is the goal for most. If you want to know if this level of precision helps or not, do your own work, and find out. Those of us that have done the work know that some bullets are finicky and will require much more intimate measurements than those that are forgiving. These discussions will not be reduced to the "is it needed" drivel that preoccupies most forums.
I just tried this method on my Bighorn 223 and came up with exactly the same number I did with the hornady gauge 1.9235. I didn’t expect to get the exact number down to the 4th decimal. That goes to show how precise the feel is. It was actually just as easy and as quick as using the hornady tool on this particular action. With hornady tool I’d take like 10 measurements and then average them together so that took some time. With the bighorn TL3 the firing pin and shroud come out with no tools and there isn’t an ejector on the bolt so it was no big deal. A bolt with a plunger type ejector may take a little more time to disassemble. Also I’ll note that it’s much easier to “feel” the lands on some barrels using the hornady tool than others. I’m not sure why unless it has to do with the lead angle or something. This particular barrel is very easy to feel the bullet contact the lands so the hornady tool works very well on this one. I have a few other barrels that it’s much harder to feel the contact as precise in which makes the hornady tool a pain in the ass. I’m impressed with this method and will definitely start using it more often.
Got it. So, thanks for your response. . . . sincerely.
I really was't trying to marginalize anything, but was simply curious as to how far you or anyone here might draw the line when it comes to precision.
Knowing @orkan for the short time I have known him, there will be no end to striving for precision. If he gets every rifle shooting 1/8 moa he will still want to find a way to do it better, faster, and more consistently. He will never be satisfied...and it is people like him that are always on the cutting edge because of their continual desire to be better.
Besides his vast experience, that's what I really appreciate about him.
Having been an aircraft mechanic (long time ago now) and working to what was then high tolerances when looking at .0005 in for things like turbine blade concentricity, precision is paramount. Today, those tolerances are much greater (like around .00001 - .00002 in. or better) thanks to the advances in tools and electronic technology. Maybe one day @orkan and the guy that builds the Prometheus and others like them will develop more tools to get such extreme precision. :-)
His vast experience is a direct result of the desire for perfection. And yes...I have no doubt that it will lead to more awesome tools.
bear9350 last edited by
When you say "finicky" what kind of tolerances are you talking about. I am just trying to wrap my head around tolerance values used here. Depending on application a precise measurement can mean something different. I am just wanting to understand what kind of precision we are talking about here.
Rem700 are talked about all the time as having long throats and not being able to chase the land while keeping with in mag lengths. How far off the lands are some of those? (I know that different guns/ different bullets will be different. Just trying to get a feel for what is a lot and what is tight.)
When you are loading what king of tolerance do you expect to hold from base to ogive? In the video you measure the lands at 1.8220". If your are loading for 10 thousandths off the lands that give you 1.8120" as your nominal. What do you consider and acceptable/ repeatable tolerance?
My remington 700 (SPS-V) that I sold had a ridiculously deep throat. I actually never got an accurate measurement to the lands because I couldn't find them. A 175 SMK would fall out of the brass before reaching the lands...so I grabbed a 220 smk just for the fun of it...and it would fall out of the brass before touching the lands as well.
Another SPS-V that I worked with...the 175 smk would be about .010" off the lands at 2.950" OAL. In my experience, the remington chambers are all over the place and not consistent by any imagination of the term. Inconsistencies like these are why some people can get a rem 700 to shoot somewhat well...and others have trouble getting a group less than 1.5"
@bear9350 There are two separate issues here. One is how precisely you can measure the lands. The other is how precisely you can seat bullets.
As it pertains to staying in your node with a really finicky bullet, both can be required to be very precise. I've seen rifles with bullets that needed to be within 5 thousandths. This is usually a function of a finicky rifle. One of the many reasons I use TS Customs is that they create rifles which are forgiving as it relates to load development and component selection.
A caliper can hold a tolerance of a couple thousandths. They will often read the exact same measurement, but some tolerance must be there. So it is not unreasonable to say you can get +/- .002 of your desired adjustment fairly easily. This will suffice for most rifles and bullets. When I measure a bunch of loaded rounds, I'll typically be within .001 on all, measured via caliper. So ACTUAL tolerance is likely larger. How tight you can hold this tolerance is hugely dependent on brass neck condition and press operation technique. This is where finely treated neck-turned brass will often shine. Though sorting during bullet seating will go a long way. Suffice it to say that a bullet that seats hard will be long, and a bullet that seats soft will be short.
The other issue you are talking about is whether long jump to the lands is acceptable. It is, in many instances. In others, not so much. It's very rifle, bullet, and load specific. I've achieved beneath half-moa with a huge amount of jump. Jump to lands is not detrimental, on its own. Sometimes, it's required, as is most notoriously evident with some Berger VLD's.
What he means by finicky is some bullets/barrels will be very sensitive to seating depths. They will shoot poorly if the seating depth or relation to the lands is not consistent. Some bullets are very tolerant to seating depths and are easier to tune. It’s always a good practice to know the bullets relation to the lands even if you can’t get to them at mag length. Now obviously in @dddoo7 case when the lands were so far away the bullet feel out the case it’s not possible. Also tuning the seating depth can’t increase and decrease your ES and SD’s while not affecting your group size. It generally doesn’t make a drastic difference but every little bit helps. As for consistency or variance in base to ogive lengths, I usually get to within .002. Depending on what I’m using that batch of am I for I’ll measure each one and sort them if needed. For Fclass matches I sort out anything that’s more than .002 and use the ones that are greater than that for sighters. For most everything else I don’t sort them. There is always a handful that will be .003 to .005 out in a batch of 100 rounds and I’ve never been able to completely eliminate those few odd balls.
I don’t like a bullet to be jammed into the lands so I usually start with a .010 jump and work backwards from there.
Your replied as I was typing so I didn’t see it. Wasn’t trying to answer his questions twice
tackyp last edited by
One of the many reasons I use TS Customs is that they create rifles which are forgiving as it relates to load development and component selection.
What aspect of building a rifle makes it forgiving? Is that a function of the chamber and components or the tolerances the gun is built to?
@tackyp Lots of things.
... but you won't see me divulging trade secrets. ;)