Kevin. Try seating a bullet normally, measure it's length, and then really crank down on the handle. See if it changes. My cast iron Lee is heavy but still seems to flex. I usually use .002" interference fit in the necks. From just lightly bottoming out the ram to putting 15-20 lbs on the handle, the bullet (only tried one) seated .006" deeper. I don't think the ratio of force to seating position is a linear. Probably more like chattering, as you keep adding pressure nothing moves, then it will break loose and jump to the next position and stop. This is probably happening on a level no one could detect. The steps may be .0001 or less.
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Using The Bob Green Bullet Comparator
- Thread starter kvd
- Start date
ckaberna
Gold $$ Contributor
T-shooter, I have not tried that but will. I just push the ram up with consistent and firm pressure (guessing 2-4 lbs.) and hold it for a second or two once the lever or handle bottoms out. Although I didn't pull the projectiles and measure them, it was like two would be the same then one would be off .007-.009, very random. This is what got me to correlating it to my groups. I loaded about 9 different charges narrowing down my OCW and this issue was the same on every group.
I have thought about trying to modify the Redding sleeve to accept a larger stem Although the die set is for a 6.5 creedmoor, the seating stem measures approximately .206" whereas the Hornady insert I am using measures .245" and on the VLD bullets that is a good bit of difference between contact points. Especially considering the bullet length differences I have identified.
I have thought about trying to modify the Redding sleeve to accept a larger stem Although the die set is for a 6.5 creedmoor, the seating stem measures approximately .206" whereas the Hornady insert I am using measures .245" and on the VLD bullets that is a good bit of difference between contact points. Especially considering the bullet length differences I have identified.
What are you measuring? The stem outside diameter or the contact diameter on the bullet nose?T-shooter, I have not tried that but will. I just push the ram up with consistent and firm pressure (guessing 2-4 lbs.) and hold it for a second or two once the lever or handle bottoms out. Although I didn't pull the projectiles and measure them, it was like two would be the same then one would be off .007-.009, very random. This is what got me to correlating it to my groups. I loaded about 9 different charges narrowing down my OCW and this issue was the same on every group.
I have thought about trying to modify the Redding sleeve to accept a larger stem Although the die set is for a 6.5 creedmoor, the seating stem measures approximately .206" whereas the Hornady insert I am using measures .245" and on the VLD bullets that is a good bit of difference between contact points. Especially considering the bullet length differences I have identified.
It may intuitively seem like seating contact on the nose would be more accurate at/near actual land contact(high on bullet noses). In practice, this would produce horrible results. I don't have to do this to know it, and neither do you.
Just draw a bullet nose on paper, and consider the shallow angle at leade contact, that you would be pushing against with great force during seating. Think about how that contact could wedge up/down the nose with varying forces. A light bulb should come on, and then you should know why seater stems are made to contact where they do(lower on bullet noses).
Just draw a bullet nose on paper, and consider the shallow angle at leade contact, that you would be pushing against with great force during seating. Think about how that contact could wedge up/down the nose with varying forces. A light bulb should come on, and then you should know why seater stems are made to contact where they do(lower on bullet noses).
Those Sierra 142's have to shoot inside 1/2 MOA extreme spread at 200 yards across dozens of 10-shot groups tested during a production run of thousands. They average 1/4 to 3/8 MOA. I doubt they're at fault.
Creedmoore throats advance down the bore .001" every 20 to 30 shots.
As the Creedmoore headspaces on its shoulder, it's that reference to bullet ogive that matters. The case head will be off the bolt face a couple thousandths when the round fires. A couple thousandths spread in case headspace is normal.
Creedmoore throats advance down the bore .001" every 20 to 30 shots.
As the Creedmoore headspaces on its shoulder, it's that reference to bullet ogive that matters. The case head will be off the bolt face a couple thousandths when the round fires. A couple thousandths spread in case headspace is normal.
All the rifle seating dies I have are Lee, Redding, and Forster. All have a tapered hole in the inside. I don't see a straight surface to measure from. Maybe if you colored a bullet with a magic marker and spun it in the step and measure the mark. My Redding measures about .245" on a .308 bulletMeasuring stem I.D. once I took it out.
This came along at a great time. For about a month I have noticed my groups would have 2-3 touching at 100 yrds. then one or two would be out by .5"-.7" very randomly. This has been going on since trying to develop a load for my new creedmoor. I weigh sorted two lots of 142 gr. SMK's trying to solve the issue. Newbie mistake of mixing two lots. Never again.
Yesterday while loading i noticed my seating depth varied by as much as .010" CBTO, again randomly. So then I got to measuring the bullets, these things had three different distinct groups with the ES @ .036" OAL. I remeasured my distance to lands on the rifle using one from the shorter group and one from the longer group. The differences in the two were .017". Wow. I am relatively new to reloading and this has become an obsession (almost OCD). I am using the redding comp. dies/seater and was somewhat frustrated about the different contact points between the stem and the hornady comparator but seems Bob's tool may help with this issue. I did manage to get all sets of loaded ammo to the same CBTO length by adjusting micrometer on the seater but I had to adjust my targeted depth to match the shortest. Not to mention time consuming. Maybe this will help with the grouping issues if it ever stops raining.
I know a lot of you have years experience in this but I am having a hard time understanding how neck tension or "friction" would cause inconsistencies with seating depth. You are pushing two rigid objects (case/bullet) in a press, if the handle goes to the same place every time how can it not push the bullet to the same point every time? I am using a rockchucker single stage with .002 neck tension and do not see how the press could flex which might cause the difference in seating depth.
Thanks,
Kevin
I'm having difficulty understanding this concept as well. I can't visualize any relationship between seating depth and any force that may be required to park the bullet in the neck somewhere. Still pondering it though as mikecr does have much experience.
Glad the thread is of use to you.
Ken
Spin it in the STEM, not STEP. It's hard to type with fat fingers!All the rifle seating dies I have are Lee, Redding, and Forster. All have a tapered hole in the inside. I don't see a straight surface to measure from. Maybe if you colored a bullet with a magic marker and spun it in the step and measure the mark. My Redding measures about .245" on a .308 bullet
So basically the tool is giving you a second point on the ogive to compare and/or comparing the distance from the seating die insert to the (.298" I.D.) comparator. I don't see why it's necessary to achieve consistent seating depths. Seating from the larger diameter of the tool instead of the seating stem diameter should be a better way. You can get consistent seating depths and consistent distances to the lands. I use a cast iron Lee single stage press with a 1-1/4" ram and a Redding Competition micrometer seating die. Still even using graphite in the neck, if I seat until I just detect the ram bottoming out, then press down with maybe 4-5 lbs force, the bullet seats about .003" deeper. I also tried putting 15-20 lbs on the handle and it went in another .003". The press uses quick change inserts but they are always screwed in tight, not to where they just index against the locating pin. I seat with the bullet usually .002"-.003" from where I want it and then apply a bit more pressure and remeasure. Normally once does it unless I get a bullet too far out of specs. Occasionally I'll get one that goes to the desired setting with very light pressure. Sometimes one may stop .010" out instead of the .003" and even with heavy force, I can't reach the correct depth, so those are used for other purposes. What I'm getting at, it all my rounds are within .001" when measured from the comparator I.D. (0.298") to the lands. I know this adds an extra step or two and will not work in a turret press without doing a final resizing later. I measured both .308 seating dies (stems) I have and they contact the bullet about .100" different in distance.
T-shooter,
Sounds like you have developed a way to "finesse" your press to get the desired results with verifying measurements. Nothing in the world wrong with this and I applaud your ingenuity. For my own efforts, I can't really do this because I primarily use Wilson seating dies and an arbor press. Once the seating stem assembly contacts the top of the die - I have no more room to move. Your post quoted above makes me think that nowhere is the cleverness of mankind on more full display than among handloaders. Thank you for sharing this.
Ken
With a Wilson seater, seat all your bullets long. Then take measure them and group them in batches of .001 then seat to your final depth whenever your ready to shoot. All your lengths will then be consistent.
Their bullet's jump distance to the rifling will not be consistent. It'll vary directly with the distance from case shoulder to bullet ogive diameter reference. All cases don't have the same dimension from head to shoulder reference; 2 to 3 thousandths is common.Then take measure them and group them in batches of .001 then seat to your final depth whenever your ready to shoot. All your lengths will then be consistent.
Cases are driven full forward in the chamber when fired; case heads are not against the bolt face when that happens.
Ned Ludd
Silver $$ Contributor
IMO, 2-3 thousandths variance in CBTO would be unacceptable; it should be one of the most consistent dimensional measurements reloaders can produce. Without any special effort or tools, I can typically select 10 resized cases at random and more often than not, obtain zero length variance among all 10, which is within the limit of accuracy of the measurement of about .001" with a quality set of calipers. If resized cases are showing .002" to .003" variance in CBTO, I'd say the resizing process needs to be examined. Even if you accept .002" to .003" CBTO variance, loaded rounds should still all fall within a single .003" seating depth test increment if sorted properly with Bob's tool. If the seating depth of a particular load is sensitive to seating depth variance of .002" to .003" or less, I would estimate the seating depth wasn't properly optimized to begin with. That would be a very narrow optimal range for most reloading applications. The OP was referring to the use of Bob's tool as a means to improve seating depth consistency when ogive variance might otherwise produce as much as 6-8 thousandths variance in seating depth. Bob's tool will certainly improve that when properly used.
ckaberna
Gold $$ Contributor
I have measured the base to shoulder and all case were within.001 or I bumped them back to where they were before loading. As I mentioned I am developing a load using what was new Lapua brass. The issue was only noticed when I was reloading these. The first time I didn't bother to measure every CBTO, I assumed once the seater was set all would be the same. Now I know to not "assume".Their bullet's jump distance to the rifling will not be consistent. It'll vary directly with the distance from case shoulder to bullet ogive diameter reference. All cases don't have the same dimension from head to shoulder reference; 2 to 3 thousandths is common.
Cases are driven full forward in the chamber when fired; case heads are not against the bolt face when that happens.
Case headspace spread of .001" is at the top few percent of all of them. That's excellent.
I've not seen any accuracy issues with a .003" spread in case headspace. That means firing pins have to move a couple thousandths more forward before they start firing primers.
Head clearance can also vary with a given round depending on how it's indexed in the chamber when the bolt face is out of square with chamber axis. That causes 1/4 to 1/2 MOA increase in average group diameters. Both previous fired cases in that rifle have out of square case heads mating with out of square bolt faces; a big no-no for accuracy afficianados.
I've not seen any accuracy issues with a .003" spread in case headspace. That means firing pins have to move a couple thousandths more forward before they start firing primers.
Head clearance can also vary with a given round depending on how it's indexed in the chamber when the bolt face is out of square with chamber axis. That causes 1/4 to 1/2 MOA increase in average group diameters. Both previous fired cases in that rifle have out of square case heads mating with out of square bolt faces; a big no-no for accuracy afficianados.
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ckaberna
Gold $$ Contributor
Yes, mine is tapered as well. I was measuring the very widest, at the edge. I did stick a bullet in it and spun to develop a ring and I forget the measurement but it was very close to what I got measuring the stem itself. And way up the nose from my o-give tool.All the rifle seating dies I have are Lee, Redding, and Forster. All have a tapered hole in the inside. I don't see a straight surface to measure from. Maybe if you colored a bullet with a magic marker and spun it in the step and measure the mark. My Redding measures about .245" on a .308 bullet
I could use the smallerhornady insert and match the seater and I am sure the measurements would be consistent, I am confused though as to what good that would do if that part of the bullet is not near the land contact point of the bullet.
I still have the bullet and will try and post a picture and remeasure. I may even take a "long" bullet as well as a "short" one and create both rings (seater and hornady bushing) to measure the difference.
ckaberna
Gold $$ Contributor
Case headspace spread of .001" is at the top few percent of all of them. That's excellent.
I've not seen any accuracy issues with a .003" spread in case headspace. That means firing pins have to move a couple thousandths more forward before they start firing primers.
Head clearance can also vary with a given round depending on how it's indexed in the chamber when the bolt face is out of square with chamber axis. That causes 1/4 to 1/2 MOA increase in average group diameters. Both previous fired cases in that rifle have out of square case heads mating with out of square bolt faces; a big no-no for accuracy afficianados.
So I am guessing the way around this is to have a smith "blueprint" it and square everything up?
This is the ruger RPR but I know it is still mass produced and can not be anywhere near a custom rifle. But still I want it as good as it can be. Is their an easy way to check squareness? This is getting deeper than I have been yet, but I want to learn.
Thanks for your input.
kevin
Yes, mine is tapered as well. I was measuring the very widest, at the edge. I did stick a bullet in it and spun to develop a ring and I forget the measurement but it was very close to what I got measuring the stem itself. And way up the nose from my o-give tool.
I could use the smaller hornady insert and match the seater and I am sure the measurements would be consistent, I am confused though as to what good that would do if that part of the bullet is not near the land contact point of the bullet.
I still have the bullet and will try and post a picture and remeasure. I may even take a "long" bullet as well as a "short" one and create both rings (seater and hornady bushing) to measure the difference.
I only have 2 Hornady bullet inserts. Both of mine are .010" smaller than the bullet O.D. If that holds true, you may be able to find one very close. As far as I'm concerned, the measurement point near the ogive junction is the only important one. That's the one to set your seating depth to and determines the jump distance. The other measurement would be closer to your seating stem and only matter if you set your seater at one spot and leave it there. I don't and measure each round and apply a bit more pressure with the press to fine tune them if necessary. I guess having both measurements and knowing the distance between them would give you an idea of the ogive curvature is the same when sorting bullets. I've never checked this but may try. Who knows, I may even learn something. I usually separate bullets by weight as any lot will have variations in length to the tip and that may be because how the individual tip was formed vs the ogive profile.
We all want to learn more and no one knows everything. Here is a good article on ammo testing in a .308 that probably would apply to other calibers as well. 2 different rifles, one a high end rifle, and tested with 16 different factory loads. Besides shooter skills, ammo matched to the rifle is the most important thing to consider. Tuning ammo is like tuning a race car. Everything you try will do one of three things, make it better, make it worse, or no detectable change. And never change more than one thing at a time. It's too easy to get lost.So I am guessing the way around this is to have a smith "blueprint" it and square everything up?
This is the ruger RPR but I know it is still mass produced and can not be anywhere near a custom rifle. But still I want it as good as it can be. Is their an easy way to check squareness? This is getting deeper than I have been yet, but I want to learn.
Thanks for your input.
kevin
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