bullet alignment issues?

[jimsbriar]

Hi all,

I have been reloading for my sako 6.5x55 and things have been going pretty well, but more and more I am starting to get some inconsistent groups. I began noticing that when I chamber a round from the magazine or gently place the round into the chamber with my finger tip, when I close the bolt, I get a little resistance. Many times this is normal because I typically neck size and just assume that I have a snug fit.

but, when my groups started to get a little bigger, I started examining the cartridges that fit snug by extracting them from the chamber rather than shooting them. what I noticed was a shiny abrasion right at the ogive on just one side of the bullet (see pic). What is causing this?

some of my reloading info:

Neck size lapua brass, RCBS dies, 3rd firing of this brass, berger 130 gr. vld, bullets are seated well off the rifling (.072). This is the minimum seating depth that would allow me to get a one diameter width of contact in the neck. Also, sakos have REALLY long throats to accommodate the bigger 160 gr. round nose bullets which is why the seating depth appears so far.

I am struggling for reasons why this is happening....bullet seating alignment? chamber burrs?

 

[Mikecr]

Given minimal sizing I doubt your loaded runout is so bad that it would create an issue. I don't know what's causing the marking.
Roll the cases and make sure the case heads are square.

What was the 72thou seating depth based on?
Your cases are gaining in capacity with fire forming until stable in dimension. Maybe as you get to the 3rd firing, capacity change has affected your load.

 

[Pdvdh]

Chamber could be cut crooked to the bore? That would cant the bullet into one side of the throat/lands. If the shiny mark is always on the same side of the bullet relative to the casing position in the chamber, then that's one cause for the seated bullet to impact the lands/throat in the bore at the same location, over and over again.

 

[drbill]

Chamber could be cut crooked to the bore? That would cant the bullet into one side of the throat/lands. If the shiny mark is always on the same side of the bullet relative to the casing position in the chamber, then that's one cause for the seated bullet to impact the lands/throat in the bore at the same location, over and over again.

Look at the chamber and lands with a borescope and see if the lands are cut right.

 

[jimsbriar]

thanks guys, I will follow each of your advice. I also plan to just buy some factory loads and chamber them to see if this does that with them.... I will mark the factory and reloads to see if the mark appears at the same location each time.

as for the seating depth, it was the only seating depth that gave me one diameter of bullet contact in the neck.. I was concerned that if I seated the bullet .005 off the lands, that it only had 0.12 of bearing surface in the neck. did not want the bullet to fall out

I am not sure I am skilled enough to look through a bore scope and be able to determine if there was a problem.

If you have any more suggestions they would be greatly appreciated.

thanks.

 

[Pdvdh]

If I was looking with a bore scope, I'd look to see if the rifling lands/grooves looked any larger/deeper on one side than the other at the end of the lead area and in the throat area where the chamber neck transitions into the rifling. If the chamber is canted, this is where it might be most obvious to the human eye while looking at it with a bore scope. If a gunsmith pulled the barrel, he should be able to determine if the chamber is crooked to the bore also.

I think if the shiny mark on the bullet is always at the same location in the chamber that there will be something cattywompus with the alignment of the chamber to the bore. This is a factory Sako rifle, correct?

 

[jimsbriar]

yup, this is a factory finnlight 85, just got it in may. I only have about 200 rounds through it and I have been working up loads slowly using either re-19 or imr 4350.

Whats got me so confused is that my velocity spreads are under 10 fps on most days regardless of the charge. But, I get some weird fliers on the target where my groups go from 1/2" to 1.5" that got me looking for answers and that is when I started to notice the mark on the bullet.

so, when you guys seat your bullets, do you seat half way and then spin the cartridge 90 degrees and finish seating??

also, should I full length resize vs. neck size?

 

[Lefty7mmstw]

Likely a bit out of round chamber; if the problem is at the back near the web of the case it may take a couple of firings for the brass to fill there.
FL sizing will likely let you shoot anyway as it'll get the brass sized down so the out of round spot on the case isn't wandering in the chamber as it is when you just neck size.
Another fix is to index your brass with a marker or file; you'll get them in the chamber at the same alignment every time then. Much to anal-retentive for me though; I'd just fl size and forget it.