Seating into the lands , Pressures & velocities

[hounddawg]

No idea how some get such radical differences in measured base to ogive measurements. I measured 15 seated bullets (Berger 105 hybrids) and all base to ogive measurements were exactly the same. Lee press and Forster seating die with Berger 105 hybrids

[Metal god]

I don’t know either . I’ll measure the ones I just loaded and see what the differences are . FWIW I use a Hornady classic press and Redding comp seater

[Bart B.]

If the seater die touch point diameter on the bullet ojive is only a couple thousandths under bullet diameter, a few thousandths spread in X to ojive dimension is normal.

The closer to the bullet's tip that touch point is, the X to ojive spread from case head will be less.

This ain't the best way. Case shoulder to seater touch point on bullet is best because this is what happens in the chamber when the firing pin fires the primer. Assuming the case shoulder ain't set back too much in the process.

[Metal god]

Top line is where my seater contacts

Middle line is the Hornady insert = ES .001 , 30 measured

Bottom line is the Sinclair insert = ES .002 , same 30 measured

This ain't the best way. Case shoulder to seater touch point on bullet is best because this is what happens in the chamber when the firing pin fires the primer. Assuming the case shoulder ain't set back too much in the process.

Agreed if you mean throat touch , I can't do that or at least I don't know how with the tools I have . This is why I intend to seat them long enough to be jammed no matter what .

[Unclenick]

That's what I've found, too. The Sinclair insert holes are close to actual throat dimensions, so they come very close to stopping on the real throat contact location. The Sinclair nut tool is, I understand, finished with actual throating reamers and these inserts look quite similar. I think it is possible because they are made of stainless steel, where the Hornady LNL inserts are aluminum and aren't tough enough to maintain such dimensions against the force of wedging against the bullet at shallow angles.

Here's what I found measuring 30 150-grain .308 MatchKings some time ago. Mind you, this is just measuring the bullets themselves and not seated in cases. The seating die will fix its contact point on the bullet as the reference point, so I have often thought what you really want is to measure the difference from the seater stem ram's contact point to the land contact point, and from there to the shoulder datum. That will tell you more about how consistently you can position the bullets off the lands.

[Bart B.]

Agreed if you mean throat touch , I can't do that or at least I don't know how with the tools I have . This is why I intend to seat them long enough to be jammed no matter what .

Soft seat a blackened bullet barely in a resized case neck then push the case full into the chamber. The case shoulder will be against the chamber shoulder and the bullet will be pressed against the chamber throat as it seats in the case neck.

Pull the bulleted case out and note where the throat marked the bullet. That bulleted case now has its bullet position where it will be when the round fires as the bullet is touching the throat.,

[Bart B.]

Unclenick, when did you get those Sierra 150 HPMK 2190 bullets? Their dimensional spreads are huge which sometimes happened in their California plant.

[Unclenick]

I think I must have got those in the mid-'90s. I remember I got them specifically to replace M2 ball bullets in pseudo Mexican Match style for 100-yard local reduced range matches.

[Bart B.]

Originally Posted by Unclenick

I think I must have got those in the mid-'90s. I remember I got them specifically to replace M2 ball bullets in pseudo Mexican Match style for 100-yard local reduced range matches.

I asked because Sierra often didn't change bullet lot numbers and packaging after minor adjustments to bullet making dies in their California plants a few years before moving to Missouri. Accuracy was barely acceptable but some bullet dimensions weren't always 100% up to snuff.

Mid Tompkins went to Missouri and convinced Sierra Bullets owner Bob Hayden and plant manager to change lot numbers when any change in the bullet making machine was made.

[hounddawg]

with a comparator it really does not make a darn if the hole is throat size or not, just as long as it is smaller than the diameter of the bullets bearing surface. I did not have a 6mm insert for my Hornady when I first played with the 6 CM so I used the .22 cal insert. I loaded my rounds that way for a few weeks until I remembered to add a .243 insert to another order from Midway. My base to ogive measurement for the rounds changed but the base to meplat measurement did not

[Bart B.]

Originally Posted by hounddawg

with a comparator it really does not make a darn if the hole is throat size or not, just as long as it is smaller than the diameter of the bullets bearing surface.

It does if you want to be exact when you use the proper rear reference, the case shoulder.

Close only matters in 4H activities; hydrogen bombs, hand grenades, harassing fire and halitosis.

[hounddawg]

It does if you want to be exact.

Close only matters in 4H activities; hydrogen bombs, hand grenades, harassing fire and halitosis.

that is pure BS Bart

exact to what? A throat that erodes as it wears? Might want to look down a borescope sometime

[Bart B.]

The bullet's bearing surface is any place bore diameter or larger.

[hounddawg]

and your point is?

[Bart B.]

Bearing surface is that portion of a bullet’s outer surface that comes into direct contact with the interior surface of the barrel bore when moving through the barrel. Includes lands and grooves.

Exact measurement is from case shoulder to where ever the bullet touches the throat.

[hounddawg]

stil have no idea what point you are attempting to make here, I think everyone here knows bullet nomenclature 101

[Bart B.]

Bullet nomenclature is listed in SAAMI 's glossary.

[hounddawg]

Ok you pass bullet nomenclature 101, now define comparator and give and example of how it works

[Bart B.]

Originally Posted by hounddawg

Ok you pass bullet nomenclature 101, now define comparator and give and example of how it works

A comparator shows the difference of a property of one thing to a property of another. Size, shape, weight, color, whatever matters for its objectives.

Optical comparators compare shapes.

[Unclenick]

Originally Posted by houddawg

with a comparator it really does not make a darn if the hole is throat size or not, just as long as it is smaller than the diameter of the bullets bearing surface

If you go back to my post #30, you'll notice the Hornady insert produced a larger bullet base to ogive standard deviation than the Sinclair did. What caused that is that even though bullets have a nominal ogive radius, the ogive radius is often imperfectly uniform on them. As a result, when the caliper insert hole is smaller than an actual barrel throat, it will rest on these varying ogive radii at different distances from the bullet shoulder (where the bearing surface ends and the ogive begins—the part that contacts the throat). Your Sinclair inserts avoid that added variation by being throat-size, so they measure the bullet where the throat will actually make contact with it. But this doesn't fix the fact the seating dies contact the shoulder a way up. What it does do is give you the opportunity to select an insert that contacts the ogive where the seating die does and to sort them by the difference in the dimension from the shoulder to that point.

I've found about 0.002" variation fairly common, but occasionally up to 0.005" on non-match bullets. You also get some lots where there is essentially no practical variation.

It's another in the long list of things to check when rolling super-match loads. If you find the variation, it is something you can separate into two or three identifiable groups pretty easily. You can adjust your seater to make them all the same, though I doubt the few thousandths difference in bullet jump itself makes a detectable precision difference. But if you look at that variation as a clue there is something different about the bullets themselves that made that difference occur, then sorting can, with some lots, break them into a more and less accurate groups.

[hounddawg]

well Nick if the ogives are inconsistent then they will be inconsistent whether the comparator hole is .025 smaller than the throat or .010 or .001. It's the consistency of the assembled round that counts.

As far as bullet jump distance I have found that as little as .003 difference in jump can make a difference. Using my old Hornady comparators I am now getting groups down into the .3's and .2's (MOA) out to 300 yards and sub .5's out to 800. Not benchrest accuracy but not bad for garage built rifles and a old fart shooting them that took up precision shooting about 10 years ago

[Bart B.]

Originally Posted by hounddawg

As far as bullet jump distance I have found that as little as .003 difference in jump can make a difference. Using my old Hornady comparators I am now getting groups down into the .3's and .2's (MOA) out to 300 yards and sub .5's out to 800.

What's the size of the biggest groups with the same ammo that shot in the 2s, 3s and 5s at their respective ranges?

[hounddawg]

depends on how well I am reading the wind that day Bart. The more I shoot the more I have found that that the equipment means far less than the person using it.

[Metal god]

I found it interesting that my Sinclair insert gave me a .001 larger ES closer to the bullet diameter then my Hornady insert did a little bit further up the ogive . Can they both be right ? I was thinking that one must be measuring incorrectly but the more I think about it they both could actually be giving correct measurements .

[hounddawg]

Metal both are right. You are comparing, not measuring.

example - my Hornady inserts measuring a loaded 105 grain Hornady in a 6BR case

.20 insert = 1.979
.22 insert = 1.891
.24 insert = 1.873

as long as I use the same insert for both the initial distance to lands using the OAL and setting my seating depth the rounds will all be the same distance to the lands allowing for whatever ogive discrepancies that are present in the manufacture of the bullets

You could have 2 comparator inserts from the same manufacturer but different lot numbers that would be slightly different if the tooling was changed. Your distance to the lands also constantly changes as throat erosion causes changes in the throats diameter and rifling gets as metal gets ate away with every round fired