How far off the lands?

[916dude!]

I bought a hornady o.a.l. Gauge and ogive gauge. According to the hornady direction, a normal hunting rifle's bullet needs to be seaTed .02-.04 off the lands and to be closer than .02 is getting dangerious. Do you guys have any other suggestion, or is that correct?

 

[vman]

Re: How far off the lands?

Not all rifles, barrels and projectiles fit the same formula.

For example, VLD projectiles made by Berger like to actually touch the lands.

It all depends on a number of different factors.

What projectiles are you using?

Search around, perhaps others here using the same projectiles could shed some light on their experience using that same bullet.

 

[eleaf]

Re: How far off the lands?

Start with manual COAL. Then move it out by .010" to .005" until you find the sweet spot.

 

[JSTARSZ]

Re: How far off the lands?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: eleaf</div><div class="ubbcode-body">Start with manual COAL. Then move it out by .010" to .005" until you find the sweet spot.</div></div>

or I do it the opposite as I find the length to the lands and start at .20 off and work forwards for my bolt rifles and for semi's I go to magazine length and work backwards to see what it likes.

It also depends on the bullets - for example, if I run a 155 SMK if I load it to close the lands the bullet would almost fall out of the cartridge. You have to work individually with each bullet but when you are doing testing only change one thing at a time. More then that and it can get confusing.

 

[916dude!]

Re: How far off the lands?

I am using 175 smk hpbt. I'm gonna start about .02 off the lands and go from there. I think I'm going to stick with that and play with the amount of powder first. I'm a total newbe so I'm just trying to go by the book for now. I'm starting With the min charge in my reloading book and working up by 1/2 gn. Doest that sound like a good idea?

Ps- what's coal?

 

[krw]

Re: How far off the lands?

Cartridge overall length. I seat my Sierra 175gr HPBT's at .010 off the lands. 43.3gr Varget, Lapua brass, CCI BR-2 primers. Chambered with a Palma95 Match reamer. Shoots way better than I can shoot it. Good luck!

 

[JSTARSZ]

Re: How far off the lands?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 916dude!</div><div class="ubbcode-body">I am using 175 smk hpbt. I'm gonna start about .02 off the lands and go from there. I think I'm going to stick with that and play with the amount of powder first. I'm a total newbe so I'm just trying to go by the book for now. I'm starting With the min charge in my reloading book and working up by 1/2 gn. Doest that sound like a good idea?

Ps- what's coal?

</div></div>

Catridge Overall Length - COAL

I would start at .20 off the lands for example - if your catridge to the lands is 2.870 I would start at 2.850 and work forwards and some backwards.

read this to get a good understanding of one load development method:
http://www.6mmbr.com/laddertest.html

 

[916dude!]

Re: How far off the lands?

Thanks for the 6mmbr link. That was a very helpful article! I have a little more reloading to do before I head to the range.... And some sharpys to buy!

 

[Fuzzball]

Re: How far off the lands?

"(Hornady says) a normal hunting rifle's bullet needs to be seaTed .02-.04 off"

Hornady knows what they're talking about. In fact, it's not uncommon to get best hunting rifle/bullet accuracy even further off than that.

 

[Kzone]

Re: How far off the lands?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 916dude!</div><div class="ubbcode-body">I bought a hornady o.a.l. Gauge and ogive gauge. According to the hornady direction, a normal hunting rifle's bullet needs to be seaTed .02-.04 off the lands and to be closer than .02 is getting dangerious. Do you guys have any other suggestion, or is that correct? </div></div>
It could be getting dangerous...
The key to using the gauge and comparator is a clean throat and lightly touch the lands with the bullet.Use several bullets measure to the lands at least five times take an average.The # u come up with should give u an accurate to the lands measurement.Now u can work under .020 knowing your not going to push the bullet into the lands from a wrong measurement or one bullet being slightly longer than another causing to much pressure which could be dangerous.If u keep a .010 cushion u should never have a problem. With 85 SGK's at .021 my tikka shot in the .5's took it down to .015 and now shoots in the .4's @3063fps.

 

[916dude!]

Re: How far off the lands?

Well I set it about .02 off and with 175 smks and a bunch or charges from 39.5-44gn of imr4064 and shot some nice sub 1moa groups and think I found a good charge at43.5gn. I might play with the seating depth next month after riflesonly class. Thanks again for all the help guys!

 

[cali_tz]

Re: How far off the lands?

in my previous 338LM rifle, a Rem 700, I ignored whether the round would fit in the magazine. At 0.020" jump, that rifle seemed to work fine, minimal pressure indications.

In my new 338LM rifle, I elect to fit rounds in the mag, so it works out that the bullet jump now must go higher, to 0.050".

It's apples to oranges for many different reasons, so we can compare the two rifles, which only share the caliber in common. But at 0.050" off the lands, the new rifle shoots quite well. I tried single feeding rounds to the new rifle at 0.020" and it didn't seem to necessarily shoot any better.

I think with long bullets like 300 gr Scenar, there may be an argument to have a higher jump. You get less peaky pressure at just post ignition, saving a bit of recoil jump and brass wear, and the bullet is got tons of bearing length to engrave and be fully in grooves by the time the boat tail exits the neck of the brass.

I think I'll stick with my mag fit bullet seating...

Anything in error with my line of thought above?

 

[RandyM72]

I reloaded for target/long range varmint shooting 220 swift, 22-250, 243 Win. and found 10-15/1000's of an inch a good place to end up. You'll find a sweet spot of about a 3-5/1000 variance. Then, experiment in 3/1000's inch increment in or out. I was using primarily HPBT match bullets with long ogives. It can be difficult to determine to accurately the land contact (zero point) - especially with long ogives. Thats where a bullet seating depth tool comes in very handy to find that measurement with some degree of accuracy. There are several brands - some better than others. Bullet seating depth/"jump" to the lands is critical to accuracy. Touching the lands will increase cartridge pressures - try to avoid this with maximum powder loads when starting off. You may wish to start 20/1000's of an inch jump and then increment closer to add safety to your load development.

 

[diggler1833]

 

[longrange772]

Here is a pretty good article comparing vertical displacement vs jump.

Bullet Jump: Is Less Always Better?

About 2 years ago, Mark Gordon shared some preliminary research he’d conducted with the Applied Bal...

precisionrifleblog.com

 

[straightshooter1]

Long ago when I started precision reloading, as my .308's throat eroded I tried to maintain the same jump, but that resulted in having to change my powder load to try and get the accuracy I had. I was "chasing the lands" and it was a royal hassle. Then I was listening to a couple top champion shooters that stated once they found their precision load, they never changed the seating depth for the life of the barrel as the throat eroded. And they were able to maintain their accuracy. I decided to give that a try. Once I got my accuracy load and seating depth (which started out at ~.010 off the lands), I kept the same seating depth for just over 2000 rounds where the throat had eroded just over .030". I was still getting really good results. With a little additional research on how seating depth effects precision, it became clear to me that distance from the lands is very minor compared to the importance of seating depth.

Bullets with secant ogives do better close to the lands and may need some adjustment after less erosion than bullets with tangent ogives. Tangent and hybrid ogives can pretty much ignore distance to the lands and maintain a seating depth for a long time.

 

[RandyM72]

Re: How far off the lands?

in my previous 338LM rifle, a Rem 700, I ignored whether the round would fit in the magazine. At 0.020" jump, that rifle seemed to work fine, minimal pressure indications.

In my new 338LM rifle, I elect to fit rounds in the mag, so it works out that the bullet jump now must go higher, to 0.050".

It's apples to oranges for many different reasons, so we can compare the two rifles, which only share the caliber in common. But at 0.050" off the lands, the new rifle shoots quite well. I tried single feeding rounds to the new rifle at 0.020" and it didn't seem to necessarily shoot any better.

I think with long bullets like 300 gr Scenar, there may be an argument to have a higher jump. You get less peaky pressure at just post ignition, saving a bit of recoil jump and brass wear, and the bullet is got tons of bearing length to engrave and be fully in grooves by the time the boat tail exits the neck of the brass.

I think I'll stick with my mag fit bullet seating...

Anything in error with my line of thought above?

I don't think there are any hard and fast rules for seating depth - simply experiment. There's often variables like throat wear, barrel cone configuration, bullet shape, cartridge OAL (if it will even fit in the magazine - that is a limiting factor you can't escape) , etc. that can alter whats considered a good seating depth. Short necked cases used together with HPBT long slender ogive shapes reduce the neck bearing contact and and can cause concentrically problems where the bullet is out of alignment at the start. Having a tool to find the zero where the bullet just touched the lands is very helpful at the start of the process. From there on it is simply experimentation to see what works best. I never had a tool set for this before as I am not sure they were even available 40 years back, back when bullets and powder were relatively cheap and plentiful. Bench shooters often made their own tools/instruments out of necessity back then. Now I think differently and want information and results more quickly/cheaply and I purchased a set for multi-calibres to help take out the guesswork. Regardless, time experimenting at the range produces results that doesn't always follow what you might expect.

 

[DubfromGA]

I reloaded for target/long range varmint shooting 220 swift, 22-250, 243 Win. and found 10-15/1000's of an inch a good place to end up. You'll find a sweet spot of about a 3-5/1000 variance. Then, experiment in 3/1000's inch increment in or out. I was using primarily HPBT match bullets with long ogives. It can be difficult to determine to accurately the land contact (zero point) - especially with long ogives. Thats where a bullet seating depth tool comes in very handy to find that measurement with some degree of accuracy. There are several brands - some better than others. Bullet seating depth/"jump" to the lands is critical to accuracy. Touching the lands will increase cartridge pressures - try to avoid this with maximum powder loads when starting off. You may wish to start 20/1000's of an inch jump and then increment closer to add safety to your load development.

Solid first post.