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Old February 3, 2013, 12:11 AM   #1
UncleGrumpy
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Advice on Bullet Jump vs Powder Used in Theory

Hi,

I am playing with a newly got .222 Rem. I am investigating a hunting and paper target loads using berger 52grn varmint bullets and H4895 powder.

For hunting, the loaded round needs to fit the magazine so the oal needs to be 2.130" or 1.740" measured with comparator. To sit the same bullet on the lands the comparator measurement is 1.850" This leaves a 0.110" difference.

These changes in the bullets depth into the case by half a neck length approx.

So I am wondering if a slower powder for the cartridge like H4895 is to be used on the hunting round to help with the longer jump and a quicker powder for the target which will be closer to the lands?

cheers
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Old February 3, 2013, 12:23 PM   #2
Ifishsum
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I don't see how powder speed would make much difference in that case, it might be worth a try - but first off do the longer seated bullets actually shoot much more accurately in that rifle? I have the same circumstance with a couple of Savage rifles - one of them in particular (a .204 Ruger) has a very long throat. I have done some pretty extensive testing of different powders, seating depths, etc and I never actually saw any better accuracy with the longer seated bullets. Kind of surprised me, but that rifle just does not seem to care what the seating depth is. Sure simplifies things as I was also planning to load 2 different depths for that rifle. I have another Savage in 7mm-08 that actually shoots better groups with the bullet seated at mag length than it does .020 off the lands.

It probably has more to do with physical properties of the chamber/throat and bullet ogive than propellant speed, but I might be wrong.
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Old February 3, 2013, 03:14 PM   #3
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Second on that. Also, the advantage to being close to the throat is to help center the bullet. If you do a short, 0.001" bump back of the case shoulder, you'll find the cartridge self-centers well in the chamber. If it then also has a straight neck and the bullet is seated straight, the alignment is pretty well accomplished and the dependency on seating depth should be less. You can often tune the seating depth, as you see for VLD bullets, here. You just have to find where it's best in your chamber. There's no magic universal number.

I've shot lots and lots of cloverleafs out of a Plain Jane Remington 600 in .222 Rem just using a Lee Loader and IMR4198. 4198 was recommended as the best accuracy powder in an old NRA publication, and my rifle seemed to agree. 4895 is slow enough that it is more commonly used in .223 with heavier bullets with a faster twist barrel than the .222 normally has. Not that it can't work, but you end up using almost 20% more powder weight for no better or even inferior results. Something inbetween that may serve you well is Reloader 10X.

I also recommend the Sierra 53 grain MatchKing, specifically in this chambering. The flat base bullets are almost always easier to get shooting accurately at 200 yards or under, and often do better up to 500 yards, depending on the chambering.

Also, the .222 was always sensitive about primers for me. It liked them mild. Federal 205 or 205M or the TulAmmo KVB223 or the Wolf NCSR primers would be specific choices to consider.
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Old February 3, 2013, 09:52 PM   #4
UncleGrumpy
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Thanks,

I see it appears all trial and error but I am also trying to see if there is any basic logic to choosing components. (Mainly because i am not very rich)

With this .222 I first looked at nosler 50 b/tip but at magazine length the jump was even worse, there was no .224 outside the neck. Looking at earlier design projectiles like the speer hp the ogive is longer in length so it should be starting closer to the lands. So are there bullet designs better suited to long throats?

My current belief in making a load is to try to get a bullet as close to the lands as possible, use the powder than gives a compressed load and try to be as consistent with the assembly.

Cheers
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Old February 3, 2013, 11:37 PM   #5
Bart B.
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Your .222 Rem cases will perfectly center in the chamber when fired regardless of how much their shoulder's set back from full length sizing them. The firing pin's impact drives the case shoulder hard and well centered into the chamber shoulder a split second before the primer fires. As long as the case neck's well centered on the case shoulder and the bullet runout's no more than 2 thousandths, excellent accuracy is at hand. But I'd not set 'em back more than 2 thousandths for long case life.

If the barrel's a standard factory sporter one, you may get better accuracy with flat based bullets. Sierra Bullets noticed this years ago testing their boattail and flat base bullets in all sorts of rifle barrels. In best quality match barrels, the boattailed ones shot more accurate. But shoot at least 20 shots per test group to be sure.

Sierra Bullet's ogive curve has typically shot best with contact with the lands when chambered. In contrast, many of Berger's bullets' different shaped ogives need a few to several thousandths jump to the rifling to shoot best.
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Old February 4, 2013, 12:15 AM   #6
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It really is a lot of trial and error, because every rifle has it's own quirks. I start with a bullet weight that should work well with the barrel's twist rate, choose a powder that matches the velocity range I'm going for and offers good load density - and then see what I can do with that. I usually do all initial load development with the bullet seated to mag length or about .020 away from the lands (whichever is shorter). If I'm not satisfied I usually try a different bullet before trying a different powder. I don't tend to think much about bullet jump until I have already chosen a bullet, and trying to further tune a good load.
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Old February 4, 2013, 07:42 AM   #7
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If one looks at the results of one lot of ammo being used in all sorts of chamber dimensions and a wide spread of how far the bullet jumps into the lands, maybe they'll not be all that concerned. At the National Matches when a single lot of Lake City arsenal match ammo was issued, it would shoot under 6 inches all day long in good service rifles rebuilt with match grade barrels. To do that, the ammo has to shoot under 1/3 inch at 100 yards.
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Old February 4, 2013, 08:45 AM   #8
Nathan
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There are lots of variables, but guessing can work pretty well.

For best accuracy, I pick:

A flat base match type bullet which is light for the twist rate.

Cases of one make which have been fired out of this rifle. I FL size to bump the shoulder back about .001". I could probably do slightly better with a shoulder bump and bushing neck die.

A powder like Benchmark, Varget, or other which is known to have good accuracy and fills my case to a compressed charge or almost compressed charge.

Primers of one type bought by the 1000 or more so I have 1 lot to develop with. I do buy match primers when I expect to shoot under 1" at 100 yards.

That is how I guess components. I may have really accurate guns, or that is a pretty good method. If your loads are way off, change the bullet.

Tuning:
Basically, I start with lands - 0.030". Then I find a best powder charge for accuracy. At that charge, I will adjust from +0.010 to -0.060 in 0.010" increments. When going long, it might be advisable to back off the powder charge slightly and increase slightly, but this changes 2 variables at once, so I never do that. Then after finding an OAL, I retune the powder charges.

All this said, I tune to a goal, not to "best". Best costs exponentially more than my good enough goal.

Goals like: (5 shot@100 yds)
.5"-.75" for my 300 WSM
2" for my AR
1.5" for 375 JDJ pistol
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Old February 4, 2013, 10:32 PM   #9
Unclenick
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Quote:
Originally Posted by UncleGrumpy
My current belief in making a load is to try to get a bullet as close to the lands as possible
That may or may not work. Writing in the Precision Shooting Reloading Guide in 1995, Dan Hackett tells how one day in switching bullets for his 220 Swift, he turned the micrometer adjustment on his seating die the wrong way and wound up loading 20 round with the bullets seated 0.050" off the lands instead of 0.020" off the lands as he'd intended and had apparently simply been assuming, based on word of mouth, was best. To his astonishment, the rifle, which had never previously shot 5-shot groups under 3/8" at 100 yards, gave him two 1/4" groups and two bugholes in the low ones (0.1xx") with this "bad" ammo.

So you don't know until you try.

Also, a lot of folks report finding two seating depth sweet spots. One is usually out nearer the lands or touching them, while the second is often when the bullet bearing surface (the .224" portion in your case) is about one caliber into the neck. That's not a universal truth, but it's reported reasonably often.

Read item 3 on this old page.
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