How much does bullet jump affect accuracy...is this too much

C

czscotia

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Hi all,
I was going to reload 338 WM and crimp at the recess on the bullets but (if I did this right) when I check to see where the
bullet hits the rifleing I find it's quite far beyond the groove.
wondering if A. if I measured this correctly and B. if this will affect accuracy and how much do you think?
I put a 250gr bullet in a fired case and squeezed the case a bit to make th bullet drage, then chambered it.
SDC13030_zpsa0855418.jpg
 
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Having the bullet seated far enough out almost touch the lands is usually considered the best way to go about loading accurate ammo. However, this might be tricky for hunting ammo for example, since magazine length may prevent this. Further, they tighter you make things, the less tolerant the gun/ammo will be of any foreign entities, like dust or whatnot.
 
There's no problem crimping it off the cannelure. The cannelure doesn't always sit where you'd want to crimp the bullet.

But by the description of how you came to your measurement, it sounds like the bullet will be jammed into the rifling. Most guys will seat the bullet .02" away from the rifling, work up a load, then later on start tweaking the seating depth closer to the rifling if needed. Also, when you use the rifle to seat the bullet to find your measurent, I repeat that process a bunch of times to make sure of the measurement. I also make dummy rounds for each bullet type/weight and crimp them so that I can then set the seating die using the dummy round. A bullet comparator is handy tool to have for all this.
 
I like to hit the lands and back it off. My rifles like to be backed off about 5 thou. if you like your seat your all good broski
 
I asked Hornady that very question about jamming or spacing off the lands. Their suggestion is to make your load, if chamberable at .015 off the lands to give the bullet a good jump. I would imagine, one would try that measurement and then try several loads going both ways to see what happens. I test all my rifles with every different bullet to work out a .015 jump and record all the different COLs. Load rounds at several COLs to see what the rifle likes. Lots of my rounds are well out of the cannelure and they all work well.
 
buy bullets with no cannelure and you won't have to loose any sleep about it being so far forward of the neck...........

I bet if you load to the oal given in the reloading manual it will work out perfect........now if only every chamber reamer was cut to the specs in the reloading manuals life would be peachy......try your estimated oal in the mag....if it will not fit then you have to decide on shooting a accurate single shot rifle with a magazine that is useless or shoot the best accurate load that you can make that fits in the magazine.........

Maybe if we knew what rifle you were loading for, and your intended purpose for it was we could steer you in the direction you need to be going...

Both powder load and oal have an effect on groups size, it is also possible that a lower powder charge with a shorter oal will shoot comparable to a larger powder charge and a longer oal....just remember that when you go shorter pressure will raise at a lower powder charge then when your seated out longer as the bullet will either add or take away from case volume........
 
Thanks everyone for the info. Yodave the rifle is winchester alaskan .338wm.
the best group I can get so far is 1-1/2 off sandbags with Remington 225gr.
Now admittedly I'm new at shooting a caliber this snappy, and neeed more practice, but since
I will be reloading anyway I'd like to get it better.
Only tried Hornady and Remington blue box so far.
 
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