**WHY do my seating depths vary so much???

[hogan]

Can't really see the spring tension or oal being a factor.

The spring in either a Forster bendhrest or competition seater controls the ascent of the die body within the sleeve. The seating stem is threaded into the thimble head and stopped with a bolt. Seating depth on the benchrest tool is controllec by moving stem in/out. Depth on the competition/mic-head die is controlled by the upper threaded thimble's movement on the micrometer index.

Without a bullet comparator how do you know what oal you're getting at the ogive?
I guess a heavy spring rate and overly long dimension would impede your efforts, but adjusting the seating stem to give the correct overall length is still going to determine your results.

Might find that the seater plug profile contacts different bullets at different points back from the tip. That is a function of the ID of the seater plug and different bullet designs. Curious to know how you rigged your torque wrench and why you decided to use it as a press-handle. Maybe you meant you used a cheater-bar???

Forster is very excellent to deal with. Glad you got it all worked out...

 

[gunner69]

This video solves this seating depth problem for vld bullets like bergers

http://www.youtube.com/watch?v=etgIVSSl8L8

 

[Bradley Walker]

I am convinced that the seater deforms the tip of the bullet when the seating pressure is excessive. Resulting in varying seating depth.

 

[Bradley Walker]

That video is really good. He is asking the same question I have been sling myself. Why aren't seating stems made to contact the bullet at the tangent?

I other words the point where the bullet reaches the large diameter.

 

[jdb]

If the stem were to contact the bullet at its largest point, wouldn't its walls have to be so thin it would (with any reasonable amount of neck tension) be forced to flair out against the inside walls of the die, and start hanging up?
Just a thought!

 

[Bradley Walker]

If the stem were to contact the bullet at its largest point, wouldn't its walls have to be so thin it would (with any reasonable amount of neck tension) be forced to flair out against the inside walls of the die, and start hanging up?
Just a thought!

Well then just before.

I think seating from the nose is less than ideal.

 

[jdb]

Bob Green @ (greensrifles.com)makes a bullet comparator designed to sort bullets to deal with this very issue. Possibly he could make a stem to index at the point you're wanting or explain why it is or isn't practical. It would definitely be nice not to have to sort bullets into sub lots!

 

[Erik Cortina]

Bob Green @ (greensrifles.com)makes a bullet comparator designed to sort bullets to deal with this very issue. Possibly he could make a stem to index at the point you're wanting or explain why it is or isn't practical. It would definitely be nice not to have to sort bullets into sub lots!

It would not work, since the bullet tip would be so far into the stem that it would make contact, so a very long stem would need to be used. Also, the bullet would "jam" into the stem like it jams into the rifling. Sorting bullets is the only option.

 

[gunner69]

This video on a bullet sorting technique will solve the seating depth issue

http://m.youtube.com/#/watch?v=etgIVSSl8L8

 

[boogershooter]

JDB's post is what I was thinking. After talking to Mr. Green last week I now understand what is going on with seating depths. What I don't understand is why someone doesn't make a seater that seats from the rifling contact point, or there abouts.

 

[Bradley Walker]

JDB's post is what I was thinking. After talking to Mr. Green last week I now understand what is going on with seating depths. What I don't understand is why someone doesn't make a seater that seats from the rifling contact point, or there abouts.

You need a seater die made with something like the modified lands tool from the video as the seater.

 

[jlow]

That video showed some very good ideas but one thing I am not sure have been mentioned is that I think the VLD bullets are likely to be more prone to problems with getting seating depths that are less consistent compared to regular bullets.

This is not a slam against any of the VLD bullet manufacturers but if you assume that they can make bullets with the exact precision and accuracy as regular bullets, by virtue of the fact that their ogive have a shallower angle (because they are VLDs), it would seem that any inaccuracies should translates to a longer distance in terms of seating depths error. Does that make sense?

 

[ThunderDownUnder]

This discussion about using seater stems that contact the ogive much lower down than normal VLD stems bothers me and I find it hard to understand. The reason for my difficulty in accepting this is simply that if the bullets vary dimensionally enough to make a difference to accuracy then its a major manufacturing QA problem.

If the ogive changes dimensionally from bullet to bullet why do you think only the first 1/2 to 2/3 of the ogive would be effected? If the ogive can change bullet to bullet then the ogive at a lower point to be measured could also change bullet to bullet. Just because the comparator is opened up to be representational of the lands doesnt mean the bullet measured at that point will be more consistent. Manufacturing dimensional variances are not just limited to the front 2/3 of the ogive.

If you are after perfection than measuring and adjusting each bullet's seating depth individually is the answer. The suggestion of sorting bullets into matched lots is also a solution. It seems to me if you use quality projectiles then the variance at the ogive is very little and like I have said before, using Redding Match Seater dies and Wilson seating dies with VLD seater stems I get 0.0" to 0.003" variance in my OAL measured at the ogive using a Hornady comparator and a lab quality digital caliper. All my comments relate to using target bullets and mostly the 4 big brands of Lapua, Berger, Hornady, Sierra and Aussie HBC projectiles.

Interesting thread!

Ian

 

[BoydAllen]

Some years back, while shooting a short range benchrest match, I came to the conclusion that my load was out of tune, and made the mistake of changing my seating depth by increasing amount that the bullet was into the rifling by .003. It turned out that I had made two mistakes, making that change, and not bringing rounds loaded both ways to the line with me to test on the sighter, before shooting my record target. IMO .003 variance is significant.