Bullet touching the lands or 2000th back?

[Rflshootr]

In a recent same subject thread I put up this picture of some recent LDI was doing for a new rifle.
I start all my LD at .010 off the lands.
This was my second rounds of LD after finding in the 1st that 58gr was around the right powder charge but I also wanted to check the 56 & 57gr as well.
For this projectile you can see even at all 3 powder charges that .005 out performed the .015 CBTO depth & were also better than the .010 as well.
View attachment 140654

I was also testing a Speer 150gr SPBT projectile & the opposite occurred, all the 0.015 seating depth groups were better.

I think there are a lot of factors like ogive shape for one, but yeh you just have to shoot em & find out what they like!

Every time you change bullet weight or manufacturer, you will most likely have a different bearing surface length to some degree. This and jacket toughness and thickness change pressures which in turn throw the load out of tune. SO, you have to retune by either changing the seating depth or the powder charge.

 

[aushunter1]

Every time you change bullet weight or manufacturer, you will most likely have a different bearing surface length to some degree. This and jacket toughness and thickness change pressures which in turn throw the load out of tune. SO, you have to retune by either changing the seating depth or the powder charge.

Thanks, I think?
But I do understand whats involved when you start changing components, I have been reloading for about 15 years now.

 

[Pine Lakes Bob]

I just purchased a Nosler Long Range Carbon Rifle, chambered in 28 Nosler, and have started working on a load using the 175 ELDX bullet. I tried Norma 217 powder but was unable to find a consistent charge weight. The velocities were all over the place. I tried Retumbo and have a good velocity node around 81 grains and velocity just over 3200 fps.
Having read the discussion above, I can see it may take many rounds to find the right jump. Does anyone have experience with this bullet, powder, and cartridge combination that may be helpful in minimizing the number of rounds down the barrel and still find an accurate load.

 

[Don Titus]

A .300RUM w. 215 Hybrid. But it likes the 230 Hybrid @ .015" jump. Go figure. I have a few others that like .080" as well.

Sometimes, mag length dictates OAL, and therefore jump to lands.

That's the situation with my Remington 700 in 300 WM. Mag limits COAL to 3.675", which requires me to jump the 181 Hunter Hammer .121"...which consistently shoots <1/2" groups at 2850 FPS ... (sometimes <1/4") with 74.7 gr. of H4831SC and Fed 215 primers.

 

[Don Titus]

Touching. I don't like any movement that isn't straight down the pipe!

Check out Dave Emry's article in current issue of Guns & Ammo...about the importance of the round being aligned with the bore...I.e., PAT or "principal axis tilt"...

 

[Don Titus]

The only advice I can give you on this is the slug when it is touching the lands and grooves exponentially increases the pressure of the cartridge. to verify this just look in either the Speer or Hornady reloading manuals. Hornady MAnual #9 page 25, it seems Speer manuals now do not have the same two pages they used to. the bare minimum I use is 0.010" off the lands and grooves (the lead). most of my rifles love the slugs 0.025" to 0.030" off the Lead. another bit of advice I can give you if this is not a hunting rifle and it is a target rifle, neck size only your brass for best accuracy. if you wish to get the best accuracy out of a hunting rifle, set your sizing die 0.002" less than the headspace (length of your chamber). if you need simple way to do this, then let me know it is pretty simple it keeps you from having to buy expensive measuring devices and works very well.

I am getting ready to set up my die to bump the shoulder .002" on my 300 WM cases and would be interested in your simple method. Thanks...

 

[wsq]

Loading close to or touching the lands with accuracy takes good equipment hope no one gets hurt trying to achieve these velocities and accuracy. It didn't take me long to learn that $35 dies at a local sport store wasn't what was needed for accuracy loads with the vld's I still like to start at .010 and go up to find a load for hunting. Good hunting and shooting it's a lot of fun.

 

[jbruehl]

The only advice I can give you on this is the slug when it is touching the lands and grooves exponentially increases the pressure of the cartridge. to verify this just look in either the Speer or Hornady reloading manuals. Hornady MAnual #9 page 25, it seems Speer manuals now do not have the same two pages they used to. the bare minimum I use is 0.010" off the lands and grooves (the lead). most of my rifles love the slugs 0.025" to 0.030" off the Lead. another bit of advice I can give you if this is not a hunting rifle and it is a target rifle, neck size only your brass for best accuracy. if you wish to get the best accuracy out of a hunting rifle, set your sizing die 0.002" less than the headspace (length of your chamber). if you need simple way to do this, then let me know it is pretty simple it keeps you from having to buy expensive measuring devices and works very well.

 

[jbruehl]

How do you set sozing fie 2000 less than headspace?

 

[jbruehl]

How do you set sozing fie 2000 less than headspace?

Sorry. Sizing die

 

[Lenny Foffa]

Hi, In my experience , every rifle will have a different and nearly perfect COAL and OGIVE length, with a particular Brand and weight of Bullet, and those measurements will change with different bullets . This is the fun of experimentation and load development testing. I shoot Bench Rest some times , and the common terms used are Jump and Jam. So somewhere between 15/1000 th Jump and 3/1000th Jam into the Lands and Grooves , is usually the ideal spot for the best accuracy, with that particular bullet, in that particular Rifle. In order to accomplish this you need to know where the lands and grooves are , so the Hornady ( or other brand ) OGIVE Measuring Gauge Kit will tell you the exact OGIVE length with any bullet you wish to try . In many case's this will be longer than the Factory COAL for that cartridge. In all my target rifles the COAL and OGIVE lengths that are best for accuracy , means the loaded rounds are too long for the Magazine Well ,or clip. So my target guns are shot in Single Shot mode. The Ogive Tool and a really good Micrometer Seating Die ( Forester , ect ) are a MUST, for making accurate loads. This is just my personal opinion, and I enjoy the search for the best possible accuracy loads. Hope this was helpful, Have fun with it!!! Lenny

 

[JimmyCP]

There seems to be a question of varying opinion on whether to have a 2000 th jump to the lands and option of bullet touching the lands for best accuracy. What's everyone's thoughts here?

Where ever it times right with the barrel for the tightest group. Never had 1 in any rifle have a magic number.

 

[misterc01]

The right answer is: "it all depends." With the rifle, different bullets, the accuracy and seating depth is different for each. So, find the depth to the lands, then seat depths starting on the lands I f you like (I do not), then .001 under, .015, .002 under, etc., to whatever max you want to try. Then go and shoot them to see which gives you the best accuracy. I set up six rounds at each depth, then shoot a series of three shot groups see which is the more accurate. IF two look really close, I set another six and reshoot. Takes time, but the process gets you there. Like others here, I am usually there at .015 -.002. One surprise, in one caliber and bullet weight, the most accurate was from Hornady A-Max Black right out of the box!

 

[misterc01]

Hi, In my experience , every rifle will have a different and nearly perfect COAL and OGIVE length, with a particular Brand and weight of Bullet, and those measurements will change with different bullets . This is the fun of experimentation and load development testing. I shoot Bench Rest some times , and the common terms used are Jump and Jam. So somewhere between 15/1000 th Jump and 3/1000th Jam into the Lands and Grooves , is usually the ideal spot for the best accuracy, with that particular bullet, in that particular Rifle. In order to accomplish this you need to know where the lands and grooves are , so the Hornady ( or other brand ) OGIVE Measuring Gauge Kit will tell you the exact OGIVE length with any bullet you wish to try . In many case's this will be longer than the Factory COAL for that cartridge. In all my target rifles the COAL and OGIVE lengths that are best for accuracy , means the loaded rounds are too long for the Magazine Well ,or clip. So my target guns are shot in Single Shot mode. The Ogive Tool and a really good Micrometer Seating Die ( Forester , ect ) are a MUST, for making accurate loads. This is just my personal opinion, and I enjoy the search for the best possible accuracy loads. Hope this was helpful, Have fun with it!!! Lenny

Excellent post!