Moving An Accurate Load Closer To The Lands

[Brandon05_88]

I've worked up a load using the OCW test, and it shows pretty good accuracy, ES and SD. I loaded for an OAL to fit the magazine, and it is approximately 0.045" off the lands. This load is 41.3 gr RL22. I've chronographed loads up to 48.0 grains and noticed some pressure signs. I want to move closer to the lands to see if accuracy improves. Is it safe to run a test at 0.020" off the lands with 41.3 grains and single feeding? Will the velocities be different from more internal case volume? Has anyone tried this, and what were the results? Thanks.

Rifle is .243 Win, 26" tube, 95 gr SMK, 41.3 gr RL22 2,750 fps...kinda slow.

 

[gcoulsey]

Re: Moving An Accurate Load Closer To The Lands

Your at 41.3 grns, but have been as high as 48 grns? Is that a typo?

Either way, moving the bullet out should reduce pressure, until you hit the lands, then it can spike up again,
How much this will affect the velocity depends on powder burn rate blah blah blah.. Shoot it and see.

As long as your confident you know your .020" OFF the lands it will be fine, if your getting to within .010" then move slowly, to allow for a little 'fudge factor' on your lands readings

 

[Brandon05_88]

Re: Moving An Accurate Load Closer To The Lands

Nope, no typo. I ran the OCW test from 38.5 gr to 42.4 gr. Then, I seen on Alliant's site that I could go up to 46.5 gr per their suggestions. I loaded up to 48.0 gr and borrowed a buddy's chrono just to test pressure/check velocity. 48.0 gr yielded 3,280 fps with a 95 grainer. I did get an ejector mark on the case head, slightly cratered primer, and stiff bolt lift, so I stopped. I didn't have the chrono available when I ran the OCW, so I wanted to chrono some 5 shot groups. I am going to shoot 41.1 to 41.5 gr in 5 shot groups and 0.1 gr increments. This Sunday I will be shooting in a match where I can shoot 20 shots in 20 mins if need be. I don't have to use the magazine. I'm just curious if seating the bullets 0.025" longer will improve accuracy or throw me out of the 'node.' I'm sure I'll at least be 0.020" off the lands; the last time I measured the OAL to touch the lands was 100 rounds or so ago. I'd really like to shoot it to compare at both seating depths, but, due to work, weather and flooding, that may not be possible.

 

[vman]

Re: Moving An Accurate Load Closer To The Lands

Any significant change to seating depth IMO should be followed by some load development tweaking.

 

[gvanhyning]

Re: Moving An Accurate Load Closer To The Lands

I normally work up loads and vary the seating depth at .003 to .005 increments. Seating a bullet deeper in the case can and will create more pressure and could lead to problems with a load that is at or near max. Whatever seating depth you decide on will need to be run through the chronograph again.

 

[jwoolf]

Re: Moving An Accurate Load Closer To The Lands

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gfunkUK</div><div class="ubbcode-body">Your at 41.3 grns, but have been as high as 48 grns? Is that a typo?

Either way, moving the bullet out should reduce pressure, until you hit the lands, then it can spike up again,
How much this will affect the velocity depends on powder burn rate blah blah blah.. Shoot it and see.

As long as your confident you know your .020" OFF the lands it will be fine, if your getting to within .010" then move slowly, to allow for a little 'fudge factor' on your lands readings

</div></div>

Moving a bullet closer to the lands will increase pressure. When you get to .010 to the lands the pressure increase gets big.

Actually, what you said may be correct but, the way it's stated seems like the opposite of what a reloader should be watching. You have to watch carefully for pressure increases, which will happen when reloading close to the lands. When moving out, you EXPECT a pressure increase.

So, I'm not trying to bust your balls.....

Imagine rolling over a speed bump after you are going 5mph then try to do it from a dead stop.... This is the way it works and, I'm very surprised that nobody has chimed in on this sooner here of all places.

My own accuracy load for my big bolt gun likes to be jammed .010 into the lands but, If I did a ladder test at SAMMI specs then jammed the bullet .040 forward on the high accuracy node, I'd have an explosion in my face.

PLEASE BE CAREFUL WHEN GIVING ADVICE TO FOLKS SEEKING IT!!!

Actually... from this post's content, the shooter in the OP should be ok going to .020 but, it appeared that there were two posts saying that moving the bullet out reduced pressure.... well, it may reduce pressure a tiny bit before it will SPIKE going out further.

Sorry if I over reacted... LOL