.505 Gibbs bullet seating offset

Simon Catinski

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So…. I finally got some brass in and loaded up a few rounds of .505 to test when I get my rifle back from the gunsmith, while seating the bullets (Barnes TSX and Woodleigh RN SP) I noticed that I was having a difficult time getting them to seat “square”, I have reloaded other calibers (7.5 swiss, .308, 30-06, .458 win….) and have never had a this problem of getting them seated correctly.
Some have a fair bit of wobble when rolled on a table others aren’t bad.
So questions:
1, any easier way to seat the bullets to have them more or less drop in square?
2, obviously it would affect accuracy to some degree so ideally 0 offset is preferable but how much before accuracy suffers?
3, is there any safety concerns in sending them down range as they are, obviously its not ideal but I did just load 10 for function test to make sure rifle goes bang and cycles some common bullets.
Attached is the most extreme example by far. The others at worst are 1/2 as bad with a few with 0 visible wobble when rolled.

D953CFD1-A286-44D8-AAF5-267ECA98164A.jpeg
B13A62DA-5B37-40CE-BB78-E242E9CA6955.jpeg
 
Last edited by a moderator:
It looks like a crimp has been applied. How was it done? Were the bullets 'square' before crimping?
 
I haven’t reloaded 505 but the concentricity issues could be associated with the bullet shape not fitting the seating plug in the die or the bullet entering the case at an angle. You could try flaring the case mouth slightly as with straight walled cases or use a Lyman M expander if available in 505. Presumably you will be crimping the bullets after seating? Otherwise I have had good luck with inside chamfering with a VLD type chamfer tool like the K&M but I’m not sure if they will cope with a 505.
Accuracy will be affected to some degree but at 505 distances probably not significantly.
 
It looks like a crimp has been applied. How was it done? Were the bullets 'square' before crimping?
They crimp had no effect on the bullets they were “off” before, I could pull them but had a pain of a time getting them as good as I did.
 
I haven’t reloaded 505 but the concentricity issues could be associated with the bullet shape not fitting the seating plug in the die or the bullet entering the case at an angle. You could try flaring the case mouth slightly as with straight walled cases or use a Lyman M expander if available in 505. Presumably you will be crimping the bullets after seating? Otherwise I have had good luck with inside chamfering with a VLD type chamfer tool like the K&M but I’m not sure if they will cope with a 505.
Accuracy will be affected to some degree but at 505 distances probably not significantly.
The cases were expanded using the step expanding plug, I may change my seat plug to the more rounded one and see if that makes a difference, I guess I could always pull the worst ones.
 
You may be causing the problem. Try belling case mouth, as in handgun reloading, and then be aware of how you set the bullet in case mouth before stroking ram into die. The problem may be caused by bullet being on angle as ram is levered into die.
 
You may be causing the problem. Try belling case mouth, as in handgun reloading, and then be aware of how you set the bullet in case mouth before stroking ram into die. The problem may be caused by bullet being on angle as ram is levered into die.
Upon further investigation it seems like the expander plug is expanding it slightly offset, might try belling it out with chamfer tool before expanding.
 
The cases were expanded using the step expanding plug, I may change my seat plug to the more rounded one and see if that makes a difference, I guess I could always pull the worst ones.
Would be worth taking both expander plugs out of the die and comparing against shape of the ogive. One may fit better than others. Also partially seat the bullet, rotate the cartridge in the shellholder, seat a bit more etc. also was the case mouth expanded enough to get the flat base of the bullet fully into the case mouth or did it just ease the entry into the case mouth?
 
The neck expander seems to be causing the issue by expanding one side of the neck more than the other, I ordered a new chamfer tool may be a burr forcing the expander off to one side.
 
Would be worth taking both expander plugs out of the die and comparing against shape of the ogive. One may fit better than others. Also partially seat the bullet, rotate the cartridge in the shellholder, seat a bit more etc. also was the case mouth expanded enough to get the flat base of the bullet fully into the case mouth or did it just ease the entry into the case mouth?
Yes the bullet fit in case mouth, it’s offset when just expanded seems as expander may be entering case mouth off centre, ordered a new chamfer-deburr tool on order hoping that solves the problem.
 
One thing that I do when seating bullets is to start them into the case mouth, them lower the ram and rotate the cartridge 180 degrees and them complete the seating. It seems to promote better concentricity.

You might also investigate a Lee collet neck sizing die. I have them in several calibers and they work very well because they put zero downward or upward pressure on the case, which helps avoid shoulder deformation.
 
One thing that I do when seating bullets is to start them into the case mouth, them lower the ram and rotate the cartridge 180 degrees and them complete the seating. It seems to promote better concentricity.

You might also investigate a Lee collet neck sizing die. I have them in several calibers and they work very well because they put zero downward or upward pressure on the case, which helps avoid shoulder deformation.
I don’t think lee makes one for the .505, CH Tool and die may, I will try new chamfer then go from there.
 
I have a 505 too. TBH I just ram those bullets in and dont look at them too much. After reading this though I may have a look at my loads in the morning
 
I don’t think lee makes one for the .505, CH Tool and die may, I will try new chamfer then go from there.
Lee does custome loading tools for a resonable price. They did special order 404J FCD for me... it is now a standard offering, though. You might inquire - just a phone call...
 
That is almost always caused by buckling the shoulder when seating the bullet. I did not read the whole thread, so bear with me... are you chamfering and deburring the brass? If you feel resistance in the first mm or two of seating the bullet, you should bell the case mouth slightly. Check the bullets for burrs or rough spots and take note of the seating pressure required. Maybe mic the base to shoulder before and after bullet seating and check around the case for concentricity.
 

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