OAL, lands and other conundrums for the apprentice reloader.

Pond, James Pond · November 23, 2012, 03:12 PM

I've frequently read the same type of remark over the last few weeks: guns end up liking different things and each one is unique.

Now another thing I'd read was stick to the OAL quoted: too long and it'll touch the lands, too short and you'll have pressure spikes etc...

Yet, once more, I've found out that the manuals are a set of rules meant to be broken it seems as a number of people have talked of adjusting their OAL to suit their rifle: a bit closer to the lands, a bit further away, better accuracy and so on.

So this begs the question: how do you know if your not-to-be-deviated-from OAL actually suits your rifle or not?
In fact, how do you even know exactly how far the lands are down the barrel, compared to the ideal for that calibre?
And finally how much adjustment is too much?

Dan Newberry · November 23, 2012, 03:36 PM

Most load recipes can be made to show good accuracy at different seating depths. In my opinion (and many others share it) there is no magical "one" distance to the lands that is necessarily best. You could, for instance, get good accuracy at .010" off the lands... and again at .025" off... and again at .040" off... I've at times had a hard time making up my mind which OAL I wanted to go with after shooting a DTL test, as groups tend to tighten up at various depths on the continuum. When there's a tie, I always go with the deeper seating depth as I believe this aids neck tension uniformity, and makes the cartridges a little more "field friendly" in case they're dropped (the deeper the bullet, the less likely you'll knock it off axis if you drop the cartridge)...

Changing the seating depth of the bullet changes *barrel time*... it does this by altering pressure one way or the other, and of course making the trip through the barrel either longer or shorter by a tiny amount.

Many folks begin with an arbitrary distance to the lands and tinker with the powder charge in order to make that specific distance to lands (DTL) work.

This is like beginning with an arbitrary set of jets in the carb on a racing engine, then tinkering with different piston compressions until you find *just* what works best with that set of jets!

In other words, you're working backwards, and depriving yourself of the best fine tuning adjustment for the load--the DTL.

We know that DTL is not nearly as important as the actual coarse adjustment, which is the powder charge. We can know this simply be looking at match loads, such as Federal's GMM or Black Hills or whatever. Those factory produced loads will actually have a different DTL in every rifle they're fired in. But they still shoot great!

Why is that??

It's because the load recipes that the various manufacturers have come up with are what I call OCW loads (Optimal Charge Weight). They have found the correct amount of powder to match that bullet in the cartridge--and the load is so deep into that accuracy groove fine tuning adjustments can be forgone (to some extent) and accuracy still holds.

That is not to say that DTL is not important. If you could take some of that match winning Federal GMM ammo and adjust the seating depth to your specific barrel, then you'd find that it would be 1/2 MOA, rather than 1 MOA, for example.

My main reason for working with the DTL *after* identifying the OCW powder charge is to not only increase the accuracy of the load, but also to "tune" the cold, clean bore shot to stay in the group. Many folks have hunting rifles that they tend to want to shoot a couple foulers though before going hunting; this because they have learned that their cold clean bore shot (CCB) is well off the final point of impact the scope is set at. But if you tune your load properly by adjusting the DTL, you will be amazed at how close the CCB stays to the rest of the group. And you stop wasting ammo...

Dan

mehavey · November 23, 2012, 03:37 PM

Quote:

... Q1: how do you know if your not-to-be-deviated-from OAL actually suits your rifle or not?
Q2: how do you even know exactly how far the lands are down the barrel, compared to the ideal for that calibre?

A1: The only way to "know" is by trial & error -- Baseline on the most accurate load that's ~20-thou off the lands, and then take it toward & away from the lands to see where it's most accurate. Re-baseline there for THAT load.

A2: There is no "ideal" (That I've ever run into). There can be "way too short" to the point that bullets must be seated so deep as to be counterproductive; and waaay too long to where 20-thou off the lands puts the bullet 20-thou outside the case mouth. "Nominal" lands will put the bullet ~1/2 -2/3rds of a caliber deep into the case at mid-range bullet weights

1stmar · November 23, 2012, 03:52 PM

I wouldn't view loads in a manual as rules but rather guidelines. Rules are not meant to be broken, hand loading virtually invites tinkering. Every rifle, barrel etc is different so pressures will vary. Once you start on your way based on manuals, you will start to tweak settings, as you do, do so safely, monitor for pressure signs and be aware of how far you are deviating from the manuals. Some pressure signs are subjective so certainly question yourself if you feel you are deviating to far seek help to make sure you are looking at all possible signs (primer cups, bolt lift..). Always use the manual as a starting point and work from there.

Pond, James Pond · November 23, 2012, 06:21 PM

Thanks for explaining that folks, but...

always a but!!

If I take mehavey's comment:

Quote:

Baseline on the most accurate load that's ~20-thou off the lands,

How do I know that, in my rifle, the standard OAL puts the bullet .020" off the lands? How do I know it is not actually .010", or .030"?

How do I even know if I end up touching the lands already when I chamber my round?

I need to know the exact length of my change from bolt face to lands if I then want to know which OAL gives which DTL...

Quote:

Rules are not meant to be broken

OK, broken was an exaggeration on my part. But certainly the rules seem to be more guidelines in that experienced reloaders intentionally veer away from them, this way and that from time to time.

mehavey · November 23, 2012, 06:36 PM

Quote:

how do I know the standard OAL puts the bullet .020" off the lands? How do I know it is not actually .010", or .030"?

You do NOT know by any "book" measurements such as in those in a manual. Every rifle is different.

Short of using a specific Hornady OAL gauge,** I recommend you use the CLEANING ROD METHOD to get a (fairly good) idea what OAL corresponds to a given distance off the lands and go from there.

NOTE: That distance is for that bullet in that rifle only. Other bullets/other rifles will be different.

jwrowland77 · November 23, 2012, 07:46 PM

The only way to tell how far you are from the lands is to get and OAL gauge. Along with that, you need a comparator that way you can measure to the ogive not to the tip of the bullet. The ogive is where it will touch the LnG.

mehavey · November 23, 2012, 07:50 PM

Quote:

...need a comparator...

+1 with soft points... although a "reasonable" OAL can be determined/loaded if (1) the tips are not substantively deformed, and (2) the cartridge is off the lands by 20-thou+

(Note that a standard paper clip diameter is 30-thou)

November 23, 2012, 03:12 PM	#1
Pond, James Pond Senior Member Join Date: July 12, 2011 Location: Top of the Baltic stack Posts: 6,079	OAL, lands and other conundrums for the apprentice reloader. I've frequently read the same type of remark over the last few weeks: guns end up liking different things and each one is unique. Now another thing I'd read was stick to the OAL quoted: too long and it'll touch the lands, too short and you'll have pressure spikes etc... Yet, once more, I've found out that the manuals are a set of rules meant to be broken it seems as a number of people have talked of adjusting their OAL to suit their rifle: a bit closer to the lands, a bit further away, better accuracy and so on. So this begs the question: how do you know if your not-to-be-deviated-from OAL actually suits your rifle or not? In fact, how do you even know exactly how far the lands are down the barrel, compared to the ideal for that calibre? And finally how much adjustment is too much? __________________ When the right to effective self-defence is denied, that right to self-defence which remains is essentially symbolic. Freedom: Please enjoy responsibly.

November 23, 2012, 03:36 PM	#2
Dan Newberry Senior Member Join Date: October 3, 2012 Location: Wytheville, VA Posts: 216	Most load recipes can be made to show good accuracy at different seating depths. In my opinion (and many others share it) there is no magical "one" distance to the lands that is necessarily best. You could, for instance, get good accuracy at .010" off the lands... and again at .025" off... and again at .040" off... I've at times had a hard time making up my mind which OAL I wanted to go with after shooting a DTL test, as groups tend to tighten up at various depths on the continuum. When there's a tie, I always go with the deeper seating depth as I believe this aids neck tension uniformity, and makes the cartridges a little more "field friendly" in case they're dropped (the deeper the bullet, the less likely you'll knock it off axis if you drop the cartridge)... Changing the seating depth of the bullet changes barrel time... it does this by altering pressure one way or the other, and of course making the trip through the barrel either longer or shorter by a tiny amount. Many folks begin with an arbitrary distance to the lands and tinker with the powder charge in order to make that specific distance to lands (DTL) work. This is like beginning with an arbitrary set of jets in the carb on a racing engine, then tinkering with different piston compressions until you find just what works best with that set of jets! In other words, you're working backwards, and depriving yourself of the best fine tuning adjustment for the load--the DTL. We know that DTL is not nearly as important as the actual coarse adjustment, which is the powder charge. We can know this simply be looking at match loads, such as Federal's GMM or Black Hills or whatever. Those factory produced loads will actually have a different DTL in every rifle they're fired in. But they still shoot great! Why is that?? It's because the load recipes that the various manufacturers have come up with are what I call OCW loads (Optimal Charge Weight). They have found the correct amount of powder to match that bullet in the cartridge--and the load is so deep into that accuracy groove fine tuning adjustments can be forgone (to some extent) and accuracy still holds. That is not to say that DTL is not important. If you could take some of that match winning Federal GMM ammo and adjust the seating depth to your specific barrel, then you'd find that it would be 1/2 MOA, rather than 1 MOA, for example. My main reason for working with the DTL after identifying the OCW powder charge is to not only increase the accuracy of the load, but also to "tune" the cold, clean bore shot to stay in the group. Many folks have hunting rifles that they tend to want to shoot a couple foulers though before going hunting; this because they have learned that their cold clean bore shot (CCB) is well off the final point of impact the scope is set at. But if you tune your load properly by adjusting the DTL, you will be amazed at how close the CCB stays to the rest of the group. And you stop wasting ammo... Dan __________________ *www.BANGSTEEL.com* Practical Long Range Rifle Courses... Optimal Charge Weight handload consulting

November 23, 2012, 03:52 PM	#4
1stmar Senior Member Join Date: March 21, 2012 Location: Connecticut Posts: 2,378	I wouldn't view loads in a manual as rules but rather guidelines. Rules are not meant to be broken, hand loading virtually invites tinkering. Every rifle, barrel etc is different so pressures will vary. Once you start on your way based on manuals, you will start to tweak settings, as you do, do so safely, monitor for pressure signs and be aware of how far you are deviating from the manuals. Some pressure signs are subjective so certainly question yourself if you feel you are deviating to far seek help to make sure you are looking at all possible signs (primer cups, bolt lift..). Always use the manual as a starting point and work from there.

November 23, 2012, 07:46 PM	#7
jwrowland77 Senior Member Join Date: March 23, 2012 Location: Conway, Arkansas Posts: 1,398	The only way to tell how far you are from the lands is to get and OAL gauge. Along with that, you need a comparator that way you can measure to the ogive not to the tip of the bullet. The ogive is where it will touch the LnG.