Reloading accuracy-bullet seating depth

[spitballer]

no vertical stringing on the paper, only horizontal point of impact movement...

My shooting is limited to 22 caliber target so it might be less applicable, but I've found that my rounds tend to roll left and right when I'm at a transition point, just below the point where the group tightens into a round configuration. However, in my case adding a bit more propellant only increased muzzle upset! So I assumed I had to just settle for the least vertical spread and let it go at that. Really had me stumped until I found a powder/bullet combination that gave me solid pressure right out to the end of the barrel. This wasn't easy to do with a 30" barrel and I had to do a lot of experimenting, but now I'm convinced that moving peak pressure as far forward as possible is the key to getting those bullets to spit out in a tight burst rather than being lobbed out with a lot of blow-by. I haven't fired anything as big as a .30 cal since leaving the service but it seems to me a .30 bore has a lot more volume and would be a much bigger challenge than a 22 to get right, so I hope you're able to find some helpful precedent from other .30/06 gunners with longer barrels who've solved this problem, safely. Good luck to you.

 

[Metal God]

Spitballer : am I to assume what you really just said was you are using a pretty slow powder for the caliber something like 4320 or 4350 ?

 

[spitballer]

I hesitate to be specific about what I use because it's a custom powder charge that's not supported by published load data. Nevertheless, when I recall the struggle I had finding what works in a longer barrel I'm compelled to share information if it saves time and effort for others who are struggling with this same issue.

I responded to this thread because the issue of lateral rolling from side to side is one that I've dealt with. I agree with many others that minimizing vertical spread is more important than minimizing horizontal spread, but I'm convinced that even horizontal spread can be dealt with effectively by moving peak pressure forward enough to keep the bullets tight at the muzzle.

But I'll be the first to admit I'm not an expert and I've been criticized constructively and proven wrong before. That's why these public forums are a good learning tool IMO. Sorry if I've mislead anyone.

 

[murf]

morrey,

you pulled the bullets and then seated them shallower. you changed the neck tension on the bullets when you did this. i wouldn't waste my time worrying about this until you get a chance to load up the longer ones from scratch (with a consistent neck tension) so you can compare apples-to-apples. unless, of course, you resized the cases before you reseated the bullets.

less neck tension will probably give you better sd numbers, but will also give you a different barrel time for the bullet. let us know the results of your next shoot.

murf

 

[Lr_athlete32]

I agree with murf, load up some from scratch to compare, we all know what they say about consistency...

For what it's worth, I'm struggling with the same thing the OP has described and am getting ready to test the difference between max magazine length and 0.01 shorter seating depth. Will post again with results.