Bullet seating depth and Free Bore

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BJung

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Is there a relationship between the seating depth and free bore for accuracy?

I finally have been able to determine my chamber dimension for my T99 Arisaka and make brass that was long enough to extend a seated bullet long enough to touch the rifling. Now I can seat a bullet ogive from a distance I was unable to do. A seated bullet to magazine length is much shorter. Could this be as accurate as a an accuracy load longer than the magazine length?
 
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Rule of thumb (only)
20-thou off the lands to start for default.
Closer/Farther may be better... experimental at that point for accuracy.

But remember.... God made magazine lengths by default as well.
:D :) ;)
 
Is there a relationship between the seating depth and free bore for accuracy?
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Maybe. I find cartridges shoot best when the bullet is seated with the bullet about 0.020-0.030” off the lands and about a calibers length into the neck. Those are usually 2 different seating depths unless the rifle is highly matched ammo to chamber.

In your case, I would start at seated a calibers length into the case or mag length. Whichever is shorter and work shorter until I find a sweet spot. First get it shooting the best it can with powder changes at this length and then shorten.
 
In my opinion no. Weatherby uses a long freebore in their rifles and they are quite accurate. Plus, the lands are always eroding do your trying to measure a moving point.

When i test my final test is seating depth. I usually shoot 5-7 groups varying each one by 0.003. Within that spread i have taken a 0.5moa group down to 0.75moa and back up.

As best i understand it, you are adjusting the bullet back and forth to regulate how long its in the barrel total and time it so it comes out at the top or bottom of the barrel whip. Kind of like a pendulum there is less barrel travel over all in that spot. Total time in the barrrel as regulated by changing the distance traveled.
 
Thanks for the measurements from the lands. If the lands erode, has anyone experienced a loss in accuracy or size of their printed groups for the COAL determined when their test base based on the previous uneroded condition of their lands?

I think of the distance from lands is a good reference point. It has worked for me before.

I suspect that seating depth will print groups like the OCR ladder test. There are Nodes. And so a handloader might find a Node at the Lands or close to it and then further the bullet is seated, the printed groups open and then tighten up as Shadow9mm mentions. Thinking while writing here, I think a good test would be to find the most accurate load from the lands and then find one from the OAL from the magazine and work in, then compare the groups. Does anyone have knowledge or experience of what I'm thinking is true?
 
Case Prep Theory

I have a theory about case preparation to handload the best cartridge for a rifle. Can you comment about my theory based on your knowledge and experience.

First, I'm resizing 30-06 brass to make a new casing. And so, I bought once fired Norma cases. If there were Lapua cases I would buy them. ideally I'd like to shoot my lead wad straight up by am afraid the wax will hit the ceiling of the indoor range of our quanset hut. How high might that wax plug go? Shooting straight up will ensure the case will be more concentric when fire formed, yes?

I set my seating die so the resized case line between the neck and shoulder meet and line that up with a fire formed case so brass flow is minimalized. Maybe if I trimmed a newly sized case and chambered it for fit, the better. In the future, I will resize the case so the case chambers snug and not expand the neck initially with the sizing button because it will affect neck concentricity and then bullet runout.

Then, I deprime my case only without using the sizing button. I expand the neck with a mandrel and measure runout on the neck. I then mark the highest point so I know where the case is thickest and thinnest. And, I mark down the thickness of the neck or separate them by concentricity. I turn then necks and clean up the primer flash holes. Turning the neck might not be necessary because I use a mandrel to expand my neck and ensure a constant neck tension. Last, I'll debur the case mouth. From there I will measure the weight and volume of each case. I'll do tests later to see if groups with brass of the same weight or volume make a difference.

When I chamber my rounds, I take into account the concentricity of the case body and the bullet runout.
 
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So the way i look at it, measuring from the base of the case to a point on the ogive is a much more consistent measurement thsn trying to figure how much i pushed the bullet into the lands and keep track of a moving point.

If a given load that was already worked up begins to shoot poorly, i will generally load test loads on 0.003 either side of where i was currently seating and shoot those to see if the groups tighten back up. If not id look at the crown, and or do a deep cleaning with a copper remover.

I do measures the bullets to see where they engage the rifling. But thats only to make sure im a safe disance away, usually 0.020 is as close as i want to he. After that i seat deeper in 0.003 increments until i find a good spot.
 
T99 Arisaka
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The Type 99 Arisaka 7.7x58mm is service grade rifle. What modifications have been done to your T99 that would allow you to shoot it more accurately than can be done with the service sights and trigger??

Accuracy in the ammo, or the barrel doesn't mean much unless it creates accuracy in the shooter's hands.

Load for, and shoot ammo made to run from the magazine, and see what your best groups are. That's your baseline.

If you are using a service grade rifle, in its GI trim, its not impossible you won't be able to shoot better groups with ammo loaded to X off the lands.

Only testing in YOUR rifle with YOUR loads can tell you is this is the case, or not.
 
The joy of handloading

I enjoy handloading to try to get the most out of my rifles. The most enjoyable is finding a good load for a service grade rifle. My first HP rifle was an Enfield. I scoped it and shot a group the size of a quarter. I was hooked. Another rifle was my M96 Target rifle. I had Lapua brass for that and shot Sierra 142gr MK the size of quarter twice in a row the size of a dime with that. I haven't been so luck with my SKS. I might have to expect that to not shoot MOA at 100 yards. Then there's this T99. The sights are a challenge to use but I designed a good target to line up the sights. Some people have assembled some good loads and are shooting past 600 yards with what looks like a service grade rifle. This is my goal.
 
See my post here from a couple of years ago. Scott Satterly has been winning matches using 0.125" (1/8") jump. The whole close-to-lands thing seems to be helpful if you are having trouble loading concentric cartridges. However, a lot of the perceived benefits are due to poor statistical sample size rather than actual improved performance.
 
(No two rifle - bullet combos are the same. One of my rifles prefers the bullets almost touching while another does better with .055" jump (which is mag length).
This is from the Berger site:
https://bergerbullets.com/vld-making-shoot/)

agreed ^ and also the sample size matters ^^ .

i have had one rifle that liked about .090-.100 off the lands, and another that likes "jammed" about .005 so i have to agree, just test and see what works best for you.
 
BJung said:
I have a theory about case preparation to handload the best cartridge for a rifle. Can you comment about my theory based on your knowledge and experience.

SNIP.
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Friend what does your reply have to do with the OP question of seating in reference to the lands? You make an interesting post but I think it really needs its own thread.


Now for my reply to the OP question, if you have a magazine rifle seat to the magazine, and if through experimentation you find shorter works better go with that. In some cases driving the bullet into the lands increases accuracy, to wit the national records of the Cast Bullet Association for plain base bullets PBB. These are seated in the lands and a "sealed" cartridge containing powder is chambered behind the bullet. Pretty damn sure most that visit this site would be thrilled to have the accuracy these folks have. Fixed ammunition is allowed by the rules but no one uses it in this class. If you missed it the point I am making is that sometimes seating into the lands is the best way. Not always though. Every single rifle is different and what works for my .308 Win Ruger hawkeye with a cast bullet may not be the same as your .308 Win Remington model 788 with a 150 grain soft point.

The beauty of hand loading is how easy you have the ability to experiment to find what your choice of rifle and components will give you the best accuracy. There are no universal rules.
 
In my opinion no. Weatherby uses a long freebore in their rifles and they are quite accurate.
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I wouldn't say Weatherby rifles are quite accurate. They're generally pretty mediocre.
Consistent, yes. But proper groups (5+ rounds) are not worth bragging about.

Even the rifles that Weatherby "guarantees" to meet various MoA standards over the years are only guaranteed to do so with a 3-shot group of "premium ammo". So Weatherby can prove that the rifle met their standards by shooting whatever ammo they want, for however many groups they want, until one of them falls under the threshold. (With useless 3-shot groups.)
And if, during questioning about the issue, you admit to ever doing anything in contrast to their prescribed break-in, cleaning, handling, etc., they can just claim that the lack of performance was user-induced (or abuse) and the guarantee is void.
 
But proper groups (5+ rounds) are not worth bragging about.
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We have different opinions about how many rounds make a "proper" group.

For some rifles I think 5 shot groups are excessive, and a waste.

For big game hunting rifles, 3 shot groups make more sense to me, (if you're using a repeater) as in you haven't put down the game by shot #3, odds are high, you're not going to.

I have some light barrel bolt guns for deer and other big game hunting. If they hold 5 (some don't) and you fire them rapidly you don't get "good" groups, but you almost always get "minute of game" groups. IF you let them cool completely between shots, you get smaller groups, but they aren't target guns and were never made to be.

I've got single shots, again, what's the point of looking at 5 shot averages when the gun only holds one??

I've got some varmint rifles where 5 shots just barely warms up the heavy barrel, so for them, 5 shot groups make a bit of sense.

Weatherby makes hunting rifles, pretty fine ones, overall. Sub MOA isn't what they're going for.

I grew up shooting in an era when a MOA rifle was "a pearl of great price", something sought after, and worked for, and rarely obtained. Unless the maker guarantees it, I don't expect MOA or less. Happy when I can get it, but I don't consider it an entitlement the way some seem to do today.
 
I suspect that seating depth will print groups like the OCR ladder test. There are Nodes. And so a handloader might find a Node at the Lands or close to it and then further the bullet is seated, the printed groups open and then tighten up as Shadow9mm mentions.
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I suspect you are often correct with 3-5 shot groups. Increasing the number of rounds fired often causes this to get muddy and one end or the other of the range may be a hundredth of an inch better, but not very significant. It depends on the load, rifle and the depth you are evaluating first.

Scott Saterly has been winning matches using 0.125" (1/8") jump. The whole close-to-lands thing seems to be helpful if you are having trouble loading concentric cartridges. However, a lot of the perceived benefits are due to poor statistical sample size rather than actual improved performance.
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I would agree that until you have 20-40 rounds down range at a particular “node”, it is hard to know what we really have.

We have different opinions about how many rounds make a "proper" group.

For some rifles I think 5 shot groups are excessive, and a waste.

For big game hunting rifles, 3 shot groups make more sense to me, (if you're using a repeater) as in you haven't put down the game by shot #3, odds are high, you're not going to.
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I always find one shot groups look the best. I prefer 25 shot groups to tell me my loads capability. After all, I want to know my probability of hit on shots 1-3, not my 3 shot group size.
 
My 3 shot OCR ladder targets look very messy. Each ladder is dotted with a bingo marker and each hole is marked off from the first shot #1, #2 and so on. Afterwards I look at both the best cluster with the same charge and printed holes with the next charge close to it.

I like one hole ladder tests too because I don't like wasting powder and have a lot of test loads to shoot in a day. I'm on my third type of powder because I ran out before testing, couldn't find another of the same powder, and had to start all over again with testing. The 3-5 group OCR test looks like a combination of a 1 shot ladder test and just loading 3 (preferably 5) shots of powder charge weights and finding the best load like the "old days".

I suspect that the 20-40 rounds down range is for farther distances when you're dialing in your load. I'm wondering, is a 600 yard accuracy load the same as a 100 yard accuracy load or slightly different. I've read of shooters talk about bullet stabilizing down range?
 
Black Walnut. I think handloaders in general are people that like to tinker on things. Thanks for your reference to cast bullets. I have 7.7-185 cast bullets to test with 2400 too.
 
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