Could using a near max charge of a too slow powber be the reason for severe vertical stringing; because not all the powder burns completely inside the bore, causing different speed from bullet to bullet?

Not typically. Full cases of very slow powder may yield less-than-optimum velocities, but their velocity consistency is usually better than faster powders.

Vertical stringing is usually a result of a barrel bedding problem, most typically from excessive "up" pressure in the forearm. It can also result from placing your rest too far forward on the forearm. Most rifles perform best if the sandbag centers about six inches in front of the guard screw.

What is the rifle, cartridge, bullet, powder combination?

quote:

Originally posted by reindeer:
Could using a near max charge of a too slow powber be the reason for severe vertical stringing; because not all the powder burns completely inside the bore, causing different speed from bullet to bullet?

Vertical stringing is normally related to bedding and heating the barrel.

I'd be very surprised if there was any relationship with the powder used!

I'm with Stonecreek on this!

Stonecreek:

Rifle: Blaser B95 combination gun 12/70 and 30-06.
Free floating barrel; no soldered rib between barrels, but a rubber one.

Bullet: Hornady 180gr. SP. over 56,5 gr. of Vith N160, Norma brass, CCI 200 primers. Bullets seated a little off the lands.

Are you talking about IMR7828? Anyway, what might be causing this is poor ignition. I had this troube with IMR7828 even while using Winchester Magnum primers and I've never heard of hotter primers. I haven't found a place in my reloading for the slowest powders as I get better velocity and more consistancy with powders a little faster, though I always read about others who use H1000 and Retumbo, ect., etc in calibers that I wouldn't consider candidates for these powders.

quote:

Originally posted by Luckyducker:
Are you talking about IMR7828? Anyway, what might be causing this is poor ignition. I had this troube with IMR7828 even while using Winchester Magnum primers and I've never heard of hotter primers. I haven't found a place in my reloading for the slowest powders as I get better velocity and more consistancy with powders a little faster, though I always read about others who use H1000 and Retumbo, ect., etc in calibers that I wouldn't consider candidates for these powders.

Not to hijack the thread but my experience using slower pwoders is exactly the opp. of lucky's. Often the highest vel. & best accuracy comes from compressed loads of slower powders in carts. like the .260, .280 & 30-06, especially w/ heavier bullets, ignition has never been a problem. IMR7828 is my go to powder in the .280 & for heavy bullets in the .260 & 30-06.
AS to vert. stringing, I'm betting it's the relationship of the two bbl. w/ the rubber spacer. If it's moveable, try diff. loactions along the bbls.