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

[wannabee]

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.

[Randy in Va]

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.

[wannabee]

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.

[rjb]

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

[Brent]

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?

[rjb]

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]images/icons/frown.gif[/img]

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.