[Darkker]

So I understand that this is an unanswerable for a variety of reasons.
However, What is your most common jump space to rifleing?
I have Long used Richard Lee's 1/32" amount, and an considering going longer for my long range target work.

Mostly I want to know what you use, and if there is a paticular reason for it, or just something to use.

 

[leverite]

Check out the latest Gun's Magazine. Barsness tackles this topic w/ his usual mix of common sense and experience.

 

[EWestbrook]

Usually just load them to a length that will feed proper from the magazine and go from there. What caliber are you wanting to do long range work with?

 

[MikeG]

I'm not either of those two but here is what I use:

Jacketed:

For hunting rifles, I start out 0.020" from the lands, and go deeper if needed for accuracy, or if there isn't enough neck to hold the bullet. Of course they have to feed through the magazine. I have a few guns that can't seat bullets near the rifling and frankly it doesn't seem to bother either of them. But I start at 0.020" if I can.

Caveat, for the times I use Barnes "X" bullets, I start at 0.050" per Barnes' recommendation.

Note also that if you don't get the bullets seated straight in the case, then fiddling with seating depth probably isn't the best use of your time.

I don't shoot benchrest or formal competition so can't comment on what might work for those folks.

Cast:

I seat them to touch the rifling when the bolt or lever closes, such that there are marks on the bullet if it is withdrawn without being fired. They are crimped, o course.

Hope that helps.

 

[Rocky Raab]

I'm like EWestbrook: I neither know nor care where the lands are. I begin by loading to the maximum length that will feed (or chamber) and seat deeper until I get best accuracy. Then I measure the case-head to bore-diameter (not groove diameter) datum line on the bullet. I can then load ALL bullets to that same overall cartridge length with no further testing.

Here's that datum line. This is a .25-caliber, so the datum line is the first point on the bullet where the diameter is .250". Measure from there to the case head and that is my "best seating depth" for that cartridge in that rifle.

 

[kdub]

Yep - what Rocky said.

Main concern is proper functioning from the magazine, then progressively seat deeper until accuracy or sometimes pressure signs indicates the need to stop.

 

[Rocky Raab]

The datum line trick allows you to repeat the best length without starting over every time you load a new kind of bullet. Simply scribe a line at the same diameter on the new bullet, and seat to the same base to datum distance. You'll be at the same "off lands" distance no matter what bullet nose shape. The only time it won't work is if you switch to an extremely long and pointy bullet that won't fit the magazine at the "best" seating depth.

 

[pruhdlr]

Trying To Understand

When would it not be best to seat the bullet as close to the lands as possible ??

I understand the pressure thing(bullet jammed hard into the lands). And I understand the load to mag length thing. Given that......put the forward part of the bullets bearing surface as close to the lands as possible.....why would this EVER be a bad thing ??

Is this over simplification ?? -----pruhdlr
P.S. This is why I love to work with single shots with allot of freebore and heavy(long) bullets.

 

[Rocky Raab]

Square One: what is the goal? If the goal is best accuracy at acceptable pressure, then it doesn't matter if the bullet is .0000001" off the lands, or a quarter-inch. As long as that is the most accurate spot in that rifle, what we are actually trying to do is reproduce that distance. It matters not what that distance is, as long as we know it and can put every bullet there.

 

[MikeG]

When would it not be best to seat the bullet as close to the lands as possible ??

I understand the pressure thing(bullet jammed hard into the lands). And I understand the load to mag length thing. Given that......put the forward part of the bullets bearing surface as close to the lands as possible.....why would this EVER be a bad thing ??

Is this over simplification ?? -----pruhdlr
P.S. This is why I love to work with single shots with allot of freebore and heavy(long) bullets.

Barnes says to use a minimum of 0.050" for their solid bullets (X, TSX, etc.). Could they be seated closer? I suppose so if one were to work up the load carefully, but seating them to 0.050" and deeper has not presented a problem so I have not tried.

Also, it is my personal preference to have jacketed hunting loads a minimum of 0.020" from the rifling, to avoid one inadvertently sticking in the field. If seated closer, it might be prudent to chamber them individually before going hunting? Just a thought.

I will agree with Rocky's general principle, to just find the depth the rifle likes and don't worry about the actual figure (as long as you have some way to reproduce it for future loadings).

 

[Darkker]

I appreciate it gents. Rocky, thanks I hadn't thought of the Datum line trick. And how did I know you were going to plug a 25 cal?

I'm fooling with 168 gr. BTHP's in my 308. My FP has an incredibly long throat, and mag. I found at max I can have a coal of 2.915" and still function and not touch.
Now to fool with it and find the sweet spot for accuracy. Oh yes, the 1200 yard gong WILL be mine!!!

 

[Rocky Raab]

You're welcome. It came to me as a blinding light when I was boning up on headspace. I read that they use a datum diameter on the shoulder to establish a set distance from the breechface, and suddenly realized that I could use the identical method to set bullet distance as well. Bone obvious - in hindsight!

 

[spitfire_er]

That looks like a good setup if you don't have a bullet comparator. It seems for precision reasons that you may not get an exact measurement every time using this method. You are basically just eye balling it which to me would seem like you could get ~0.001-0.007" variation in your readings. May not be life or death, but could be an inch or two out at 1,000.

To me I think that a comparator, as long as the bullets are good quality will give you the best most consistent measurement.

Even with the comparator I sometimes get variation, but they are never more than 0.003" and that is most likely due to bullet variation and the non-competition dies I usually use.

I also start most long range loads into the lands and work them in deeper.

 

[spitfire_er]

Then I measure the case-head to bore-diameter (not land diameter) datum line on the bullet.

Don't you mean "(not Groove diameter)".....isn't the land diameter and bore diameter the same thing? You had me confused there for a minute.

 

[Rocky Raab]

Oh, for cheese. YES! Thanks. I'll go correct that. It should read (not groove diameter) as you point out.