How far off the lands?

[roysclockgun]

I am asking these questions in all seriousness and not just because I have nothing else to do! <8^)) Over the past two days, I have preped many hundreds of rifle cases and loaded about half of them.
I have an E. Brown Model 97D single shot rifle in 6mm Bench Rest Magnum. For those who do not know, the 6BRM is a wildcat cartridge. One has to first neck down 30-30 cases by running them through a 7-30 Waters resizer, then again through the 6BRM resizer. This gets a case that can be fire formed. Because pressures are kept low, I am on my fourth firing without needing to trim cases.
Not too long ago, I learned here, that one could set the bullet back off the lands, in order to get "jump" and therefore, lower pressures and higher velocity. I had loaded for years by the rule of "get the bullet as close to the lands as you can and test by trial and error, until the optimum OAL is attained".
Today, I begin 0.010" off the lands and work forward.
My question is: Should my start point be further off the lands than 0.010"?
I determine the point at which the bullet touches the lands, but loading a bullet very long, coating it with fiber tipped pen, and closing the action until the ink on the bullet is not marked by the lands. That gives me my start point in OAL from which I subtract 0.010" to begin the test.
The Model 97D shoots consistant groups under 7/8" at 100 yards. I want it to shoot under 1/2".
Best,
Steven

 

[joelkdouglas]

Steven,

I have heard two theories on Cartridge Base to Ogive/seating depth away from the lands.

German Salazar says "A good place to begin (and frankly to stay unless you're already at the Master level in NRA Highpower) is to jump 0.020" for conventional tangent ogive type bullets such as the Sierra MatchKing line or Berger's new designs and to jam 0.015" for VLD type bullets such as Berger VLD, Hornady AMAX, JLK VLD, and others of the secant ogive design."

Salazar reference below:
http://riflemansjournal.blogspot.com/20 ... depth.html

Bryan Litz, chief ballistician at Berger, talks about seating depth during load development: "In general, the seating depth of a particular bullet in a particular rifle tends to be more static than what powder charge will work best. In other words, it's probably best to start with a low to medium powder charge and find the best seating depth. Then, using that estabilished seating depth, start working on changes in powder charge."

Litz says for Berger secant ogive bullets to run a test, making groups of rounds that are 0.010 off lands, 0.050 off, 0.090 off, and 0.130 off. One of these groups will shoot better than the others, and then you can make small adjustments from there.

For what it's worth, Partitions shoot best in my 30-06 when 0.07 off the lands. Custom Competitions seem to like 0.02 off the lands, once again in my rifle.

Good luck!

 

[rick smith]

In some cases you can't be close to the lands due to magazine length or freebore. Several things you need to remember when dealing with mag boxes, the rounds have to feed into the chamber from the mag box, you should not be jammed into the lands, the bullet should not be so far out as to move when going from the mag box and a loaded round should clear the action on extraction.
Now with your single shot most of these are a mute point. Instead of a sharpie to color the bullet I run a piece of 4/0 steel around the bullet. I can see the land marks much clearer. Once you find the lands, check that distance several times. If you are into the lands, the bullet can be moved forward on extraction and give you a false reading. Measure base to ogive not to the bullet tip.
I would start the search with the bullet set 0.010 off the lands, test some loads and move the bullet deeper into the case as necessary. There is no magic being close to the lands, just a starting point.Rick.

 

[300WSM]

It really is 6/5 and pick em.

I don't follow the Berger way as I find the velocity/pressure ok signs, accuracy, and then tweak from there.

Moreover most rifles out there are repeaters of some sort. Unless you are going to designate your repeater as a single shot, you have to contend with the magazine. In basically every situation you can never get near the lands and still have a cartridge able to fit in the magazine.

 

[SJB358]

In basically every situation you can never get near the lands and still have a cartridge able to fit in the magazine.

I don't necessarily agree with this 300. I can get to the lands on just about every Model 70 I own and still have a functioning cartridge. My problem rifles that I run into are the Remington's in the safe. Those have long leades or short mag box's that will not allow me to start near the rifling.

My 35 Whelen, which I can get out and touch the rifling, and still fit the cartridge in the mag box, BUT, I have so much bullet out of the neck, I don't feel there is adequate neck tension.

The other Remington, even with 105 Amax's will allow me to get out and touch the rifling and still function through it's 2.8" box. So, 1 outta 2 of them does okay in that regard.

 

[HomerOz]

G'Day Fella's,

Roysclockgun, unless I'm restricted by magazine length etc, I usually seat most of my field/hunting rifles bullets, between 0.020" and 0.030" off the lands!
It works for me!!!

Hope that helps

Doh!
Homer

 

[woods]

Not too long ago, I learned here, that one could set the bullet back off the lands, in order to get "jump" and therefore, lower pressures and higher velocity. I had loaded for years by the rule of "get the bullet as close to the lands as you can and test by trial and error, until the optimum OAL is attained".
Today, I begin 0.010" off the lands and work forward.

Lower pressure means lower velocities

Questions:

Do you set your seating die at the start of loading and then do not touch it

Do you check your seating depth by measuring to the tip of the bullet or with a comparator to the ogive

Have you ever checked each bullet when seating several to see what kind of variance you are getting


IME seating depth variance is hard to keep below +-.005" unless you are taking extensive steps to reduce that variance. So you may be seating some bullets .005" off and others .015" off

Also IME when seating close to the lands any variance has a greater effect on pressures and velocities than when seating further off. When I run a seating depth test I will start at .015" off and vary by .015" further (i.e. .015", .030", .045", .060", .075", .090") to look for best group, lowest velocity standard deviation and lowest velocity extreme spreads in order to get the most consistant performance and reduce flyers. Most of the time the sweet spot will be from .030" to .060". The variance of .015" or even .020" is necessary to get any consistant repeatable definitive differences.

YMMV

 

[rick smith]

Don't feel like I am taking extensive steps and I measure all my rounds after I seat the bullet. 98% or more are within 0.001". I spot check concentricity and take corrective steps if rounds are 0.002 or higher.Rick.

 

[300WSM]

In basically every situation you can never get near the lands and still have a cartridge able to fit in the magazine.

I don't necessarily agree with this 300. I can get to the lands on just about every Model 70 I own and still have a functioning cartridge. My problem rifles that I run into are the Remington's in the safe. Those have long leades or short mag box's that will not allow me to start near the rifling.

I don't doubt your reloading ability but I am first and foremost a model 70 guy. I like remington too. Having said that I have 5 Model 70's right now that are all repeaters but if you get close to the lands, and I'm talking .010 or closer they will not fit in the magazine. I have one that will get close to that distance and will fit in the magazine. It fits in there so tight that the weak follower spring may not do its job properly

May I ask how you are measuring this to get your actual OAL to the lands with specific bullet "a"?

Again I'm not suggesting you don't have an accurate way of doing this, but it is astonishing the amount of people who think they are getting a cartridge to the land measurement and don't understand that bullet "A" max OAL will be different than bullet "B" because of the differing bullet geometry.

There are ways of finding the max OAL for a specific bullet without using a comparator and was curious the method you use.

 

[SJB358]

300, I use the Stoney Point gauge, with the corresponding Hornady Case. That's odd you have such trouble getting near the rifling in yours, the only rifles that I would have issues with is my older Model 70 7mm Rem Mag and some of the shorter bullets, and maybe 264, but both of those get there, and still fit in the magazine with all the Nosler 160's and 175's for the 7 and the 130's and 140's for the 264.

The Stoney point is pretty easy, as if you work with a clean barrel when doing the measurements, you push the bullet into the rifling, till it touch, lock it down, retrieve the bullet and measure? How do you measure yours?

 

[300WSM]

300, I use the Stoney Point gauge, with the corresponding Hornady Case. That's odd you have such trouble getting near the rifling in yours, the only rifles that I would have issues with is my older Model 70 7mm Rem Mag and some of the shorter bullets, and maybe 264, but both of those get there, and still fit in the magazine with all the Nosler 160's and 175's for the 7 and the 130's and 140's for the 264.

The Stoney point is pretty easy, as if you work with a clean barrel when doing the measurements, you push the bullet into the rifling, till it touch, lock it down, retrieve the bullet and measure? How do you measure yours?

Sounds like something similar. I use a dummy case with the neck split in a few area thanks to a dremel tool. Split just enough to offer a good firm hold of the bullet but not too much that I cant retrieve the bullet. Regardless I just load the dummy cartridge with the subject bullet into the chamber, then eject. When entering the chamber it pushes the bullet back into the dummy case. Upon extraction I have a dummy cartridge with that particular bullet sitting at the absolute maximum length the chamber will allow. I can work backwards from there and more times than not I have to work back from that because the magazine will not permit this type of OAL.

I don't have a single 70 that will permit magazine use with this much OAL. One is close but its so tight I have zero confidence in the magazine working proper as those follower springs are not that powerful.

 

[rick smith]

Just be aware that the bullet could be moved forward as you extract it, the lands grip on the bullet could give you false readings.Rick.

 

[SJB358]

Just be aware that the bullet could be moved forward as you extract it, the lands grip on the bullet could give you false readings.Rick.

That was the issue I had with that method, so it eventually drove me to the Stoney Point Gauge.

 

[joelkdouglas]

Yep, I use the Hornady Gauge. Same thing as the Stoney Point--I think Hornady may have even purchased it from Stoney Point. Works well.

The throat length varies in every rifle--a way to make sure you can reach the lands AND have a round feed well through a magazine is to call a barrel maker and order a barrel, call Dave Kiff at PTG and order a reamer specifying the freebore you want, and have a gunsmith do their magic.

 

[300WSM]

Just be aware that the bullet could be moved forward as you extract it, the lands grip on the bullet could give you false readings.Rick.

That could happen if you make the neck too loose for sure.

Again having a sense of feel with things really pays off. If you went this method and weren't sure if your OAL was disturbed when extracting, It's not very difficult to double check your measurement.

Seat a bullet to the depth you feel is the max OAL and mark it...re-do the chambering. Re-do it a few times. If it has moved you will see the evidence right in front of you. Are you guys slamming these things in the chamber with the utmost speed and thrust?

I'm all for supporting useful vendors in this industry so lets not get off course on this one...

Regardless on the model 70's and these magazines, the several rifles here won't hold loaded rounds with an OAL that long. I will measure a couple tonight and try and do a picture or two. If memory serves me correctly the closest I can get is about .025 to the max oal the chamber will allow and still have the magazine function.

 

[roysclockgun]

But I thought that more recently, the idea was to get more jump than .025? Most shooters are recommending dropping back more than that in order to get better groups. I am no expert, but I try to listen to those who are.

 

[SJB358]

But I thought that more recently, the idea was to get more jump than .025? Most shooters are recommending dropping back more than that in order to get better groups. I am no expert, but I try to listen to those who are.

I usually end up around there or up to .1 off the rifling, but I always start up close and work back...

Unless it is a monometal.

 

[longrangehunter]

For what ever it's worth I'd invest in a Sinclair Seating Depth Gage P/N 09-400. I measure 10 bullets off the ogive length; divide by ten for the average; use the gage with five different fired rounds and five bullets; take those measurements from the gage and add the average bullet length you found; you'll have five different OAL measurements, divide them for an average and/or look at those measurements and use the shortest measurement as a starting point to work from. This measurement is into the lands. No special cases to buy and you'll use a fired round from your gun.

 

[roysclockgun]

Yeah, I agree with everyone who spoke of more expensive equipment that will cut my group size. However, I have killed deer at a measured 400+ yards with my 280Rem. and while not world class, it is my own personal limit for taking game. My bull elk was just over 300 yards head on, coming up a mountain toward me. Three shots hit the boiler room with the fourth dropping him from a shot just under his left eye and exiting the right side of his neck. So, for my purposes the ancient tools that I am using to handload are getting me what I need and want.
Paper punching and varmint shooting is different for me and I strive to get tiny clovers. I do not get it with every rifle, but with a number of them, I do.
At 70, I just don't want to plunk more money down on hand loading, state of the art tools, when I can put that money into one more rifle to play with at the range, or in the field.
I will however, not use the pilot on my case trimmer and see how doing that helps.
I just today, showed a friend of mine, now 67 years old, how to handload for his new 308Win. chambered rifle. He got the bug very quickly and wanted to know when he can "try again!" So, I believe that I have another convert.
Thanks for all the responses,
Steven L. Ashe

 

[DrMike]

I just today, showed a friend of mine, now 67 years old, how to handload for his new 308Win. chambered rifle. He got the bug very quickly and wanted to know when he can "try again!" So, I believe that I have another convert.

That has to qualify as one of the most gratifying aspects of hand loading. Good on you, Steven.