seat vld's to the lands or off a bit?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by wannabee, May 25, 2003.

  1. wannabee

    wannabee Active Member

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    seat vld\'s to the lands or off a bit?

    I have posted a liitle about this subject but have gotten little response. I had a gun rechambered to 6-284 by a smith in MT. During load development, I found that I could not reach the lands w/ the 107 gr MK(barrel has a 1-8 twist) . Accuracy was less than desirable when I seated the bullets out as far as I could(neck tension .001-.002). Last Sat we shot some loads that I made up that were seated a lot further-and I went to .004 neck tension. These shot reasonably well- 6 shots in 3/4"@100yards(4 touching).
    Here's my ? Would I be better off to have the barrel set back and the throat shortened so I could reach the lands, or just be happy the way it is. I haven't shot this rifle beyond 200 yards yet, as ranges like this is few and far between.
    I was never under the impression that 1/4" of freebore was conducive to extreme accuracy. The rifle was assembled for a long range varmint truck gun(it weighs right at 20 lbs w/bipod and NF12-42x scope). As this is my first dabble into LR stuff please advise. Much thanks.
     
  2. Randy in Va

    Randy in Va Well-Known Member

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    Re: seat vld\'s to the lands or off a bit?

    Several things:

    Only change one thing at at time *changed neck tension and overall length*

    Dont wear your barrel out on load development. 3 shot group is plenty to figure out a varmint gun.

    Report on the 3 shot groups before changing anything. VLD's almost always require touching to even .030 into the lands for optimum accuracy.
     

  3. wannabee

    wannabee Active Member

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    Re: seat vld\'s to the lands or off a bit?

    Just got done loading some ammo for tomorrows range session- I'll report results tomorrow. I'll have cut the barrel back a little and rechamber to shorten the throat.
     
  4. rjb

    rjb Member

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    Re: seat vld\'s to the lands or off a bit?

    WB be carefule what you ask for. The throat
    cut when barrel is chambered is usually by that same reamer. So just facing off barrel and using same reamer will not change bullet seating. I had a custom reamer made with short throat in another caliber to suit lighter bullets. Then 107s were seated pretty
    deep but only boattails stuck below the neck/shoulder junction. Recently there were some VLDs that blew at long raange (>500yds)
    out of this 1:8 twist. So I ordered a throater reamer in 6mm from Dave Manson. With
    it the bullet seating to lands was advanced
    another 0.100". This moved 105s and 107s into neck an they can still touch lands if wanted. Many factory or SAMMI spec chamber
    reamers have the "safety" free bore you found. A complete custom reamer might be necessary. Some gunsmiths cut chamber and throat (bullet seat) separately to tune for
    particular loads on request. Hope that helps, rjb
     
  5. Brent

    Brent Well-Known Member

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    Re: seat vld\'s to the lands or off a bit?

    RJB,

    What was wrong with just the boattail below the shoulder if the shank wasn't? Sounds like that would have been optimal the way it was, leaving plenty of room to seat them out farther when the throat erroded more?
     
  6. rjb

    rjb Member

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    Re: seat vld\'s to the lands or off a bit?

    Sorry this took a while to answer. When seating heavier boattails so only boattail stuck inside the neck / shoulder was thought to be ideal. However experience prooved that
    location also puts the pressure ring of bullet jacket (largest dia. spot, usually where boatail joins the body dia.) Right at the area of brass case that thickens into the dreaded Donut.More time was spent checking and returning case necks and still it was suspected a few tight conditions slipped by that tossed shot out of groups. I run a tight neck chamber in that rifle so it
    became an issue until the chamber throat wore and the bullets were seated further out.
    rjb [​IMG]
     
  7. Guest

    Guest Guest

    Re: seat vld\'s to the lands or off a bit?

    Seating bullets into the lands will produce better long range accuracy in a properly designed chamber with properly prepared brass. Out of 30 different cartridges I have done load devlopment on, across hundreds of rifles, not one gun shot better with the bullets off the lands than it did with the bullets into the lands. Some shot near as well, but they are few. Even if you get better groups at 200 yards, if your deviation in velocity gets too large, you will see vertical stringing at long range. Vertical is BAD.
     
  8. Varmint Hunter

    Varmint Hunter Well-Known Member

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    Re: seat vld\'s to the lands or off a bit?

    I have gotten measurably smaller groups when loading bullets into the rifling on my 22-243AI (8 twist) and my 7STW (10 twist). Other rifles either wouldn't allow the bullets to be loaded out that far or did not benefit from loading that way.
    Just my 2 cents
    VH
     
  9. Guest

    Guest Guest

    Re: seat vld\'s to the lands or off a bit?

    Rufous.... I like a 30 degree angle from a parallel neck to a parallel free bore area leading to a 1 degree throat. The amount that you place a bullet into the lands is affected by several things, whether you have a 3 groove, 4 groove, or six groove barrel. The angle of your throat, and how tight your free bore area is, will all affect how far into the lands your rifle will prefer the bullet to be.

    I look at neck tension as an either/or situation. Either your hunting dangerous game and need significant neck tension along with needing to not stuff a bullet into the lands, or you're in a pure accuracy situation where you may optimize neck tension and bullet seating depth to maximize accuracy. In the ultimate accuracy scenario I think light neck tension is the way to go. I like about .0012 press fit into the neck. With light neck tension and the bullet seated about .005" longer than the round is if it is extracted before firing. In other words, chambering the round pushes the bullet back about .005" into the neck. This works very well with light neck tension.

    I do my own machine work, and occasionally do machine work for friends. I have several interesting designs and products that are sold through my company "A.R. TACTICAL", My companies web site will be up and running in about 4 weeks. There will be loads of technical information available along with some products like Titanium Rings and Bases that just can not be found anywhere else. The quality of the things I machine is untouchable, we go to great lengths to engineer the PROCESS of making things properly, including better materials selection, and stricter design criteria that takes into account dynamic stress and heat management. Hope to have a semiauto .338 lapua in Titanium for next years Shot Show, light weight, low recoil, low torque, and 1/4 MOA accuracy! Of course the wildcating opportunities will be endless. [​IMG]
     
  10. rufous

    rufous Well-Known Member

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    Re: seat vld\'s to the lands or off a bit?

    S1, please elaborate on your comments. What do you mean by a properly designed chamber and what do you mean by into the lands? Would into the lands be 0.005" into them or 0.010" or what? I imagine it would be a matter of experimenting how much to go into the lands like we are used to varying how far off the lands. Also can you comment on neck tension. This is something I have not messed with, except that I have been using a Lee Factory Crimp Die on my 300 Win Mag. When seating into the lands would one want more neck tension? Finally does your statement that all guns with proper chambers should shoot their best with bullets into the lands apply only to target/varmint/vld type bullets or are you finding that it also applies to big game bullets? Are you a gunsmith? If not who does your gunsmithing? Thanks, Rufous.

    [ 06-12-2003: Message edited by: rufous ]
     
  11. wannabee

    wannabee Active Member

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    Re: seat vld\'s to the lands or off a bit?

    Thanks for the input. I just got home from Tacoma,WA. Work took me there for 2 1/2 weeks and I'm glad to be back. Next week I leave for SD to shgoot some P-dogs. Before I left to Tacoma, I shot some groups w/ the 6-284. 107 gr SMK's mollied w/ 56.5 gr rl22 gave me 2 3-shot groups of 3/4" @200 yards. Neck tension was right at .003, and runout out was .0015 or less. The only thing I can't test for is seating into the lands, as my chamber won't allow it. So, after my trip to SD, I'll address it again. My smith is Dennis Olsen in Plains MT. Very well respected from what I understand. I will bring it up w/ him first, and then go from there.
     
  12. rufous

    rufous Well-Known Member

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    Re: seat vld\'s to the lands or off a bit?

    S1, thanks so much for the info. This is most interesting stuff. It brings up some more questions though. You mention a 30 degree angle from neck to throat (freebore). Is 30 degrees standard or are chambers cut with a wide range of transitional angles? Also you prefer a 1 degree leade. Is there that much difference between a 1 degree and the more standard 1.5 degree leade? What difference would there be between the two leade angles? Am I envisioning it correctly that a 1 degree leade would be a gentler transition to the lands than a 1.5 degree leade? You said that the number of grooves the barrel has will affect the amount the bullet should engage the lands. Do you have a normal amount into the lands for a 3 groove and 4 groove and 6 groove? Let us assume we have a 300 Winchester Magnum with a 1.5 degree leade and a parallel throat that is 0.3083” in diameter on a 4 groove and on a 6 groove barrel. How much into the lands would you likely see these setups shooting at their best? What kind of range in seating depths do you experience with the various parameters? Are we talking that you have found all your rifles shooting best at just touching the lands to as much as 0.015” into the lands or is the range more than that? When I say just touching the lands I should specify that I determine that depth by use of the Stoney Point tool.
    How far can one seat the bullet into the lands without the lands seating the bullet into the case? I suppose that would depend on neck tension. I do not understand what you mean by 0.0012” press fit of neck tension. Does that mean that the inside diameter of the neck is 0.3068” after resizing and before seating the bullet? I am using standard dies, not the Redding bushing dies so I can only decrease neck tension by turning necks (I am not confident that I could grind the expander ball accurately in order to reduce neck tension). Again my major application is for a big game rifle so I need more neck tension than a benchrest shooter would and of course my accuracy needs are no where near as great.
    Finally I am still wondering if this all applies to match bullets only or do you find that the big game bullets (Nosler Partition, Barnes X etc) also shoot best when seated into the lands?
    Thanks again for offering your experience to the rest of us, Rufous.