I'm trying to practice my consistency on powder measure and overall cartridge length. I set my seating die to my desired length 2.680 for my .243 70gr speer tnt. I locked it down the first four were perfect then they started seating shorter between 2.672 -2.678. I know this is going to sound newbie as all hell would trim case length and or variances in overall projectile length affect this.
Overall cartridge length
- Thread starter Fng65
- Start date
Case length in itself doesn't matter here, but seating force variances do.
Bullet overall lengths mean nothing without understanding of where the lengths are on the bullets.
Bullet nose shape(ogive radius) variances can affect seater stem datum (the push point).
Often, bullet noses vary in lengths as they run to differing tip (meplat) diameters. This can definitely affect COAL.
Add a few of these together and you'll fight to get any consistency.
I could tell you how to get em all the same, but it'll cost you to do so. It ain't free.
Bullet overall lengths mean nothing without understanding of where the lengths are on the bullets.
Bullet nose shape(ogive radius) variances can affect seater stem datum (the push point).
Often, bullet noses vary in lengths as they run to differing tip (meplat) diameters. This can definitely affect COAL.
Add a few of these together and you'll fight to get any consistency.
I could tell you how to get em all the same, but it'll cost you to do so. It ain't free.
Dusty Stevens
Shiner
You got one of 2 issues goin on. Either compressing powder or sucky bullets. You need a comparator set to measure right- or at least better than what oal does
No Powder compression and I'm using Speer bullets
and what would that cost me
Dusty Stevens
Shiner
You can use the comparator on speer bullets
D-4297
Gold $$ Contributor
Fng65 ; if you were seating your bullets by pushing down on the tip of the bullet , you'd get very close , if not identical seating for OAL . You are not . The seating die most generally seats the bullet by pushing against the ogive , or radius of the bullet . The measurement on quality bullets is consistent from the base to the Ogive . If you measure ten bullets at random for over-all length , you may get eight different measurements . Bullets vary in OAL . That is why precision shooters use a bullet comparator mounted to a dial / electronic caliper . To measure from the base of the Case , to the ogive of the bullet . Base to ogive is consistent . Base to point ( meplat ) isn't . And for the record ; the only stupid FNG question is the one not ask . Sometimes ; Super-mega , Big-gun Super Stars forget they were "Newbies" once upon a time , too .
Like mentioned, you need a hornady comparator....
You can buy the comparator body for $ 15 and the caliber specific insert for around $ 4 ? or you can get the kit that comes with either 5 caliber inserts ( 22, 243, 256, 277, 284 & 30 cal ) for about $ 30.
I got the Headspace comparator kit (for measuring how much far you're moving/sizing the brass shoulders when resizing the brass ). And then you get the caliber specific OAL inserts for measuring cartridge base to bullet ogive.
And in the future you can get the OAL lands finding gauge ( I got the bent one so I can use it for bolt guns and gas guns ) so you can find the spot where the bullet touches the lands.
Just foogle or bootube Hornady comparator.
At the end, we want the cartridge base to bullet ogive to be consistent, cause the overall length to tip is never going to be perfect because bullet tips are not identical to the thousands of an inch.
You can buy the comparator body for $ 15 and the caliber specific insert for around $ 4 ? or you can get the kit that comes with either 5 caliber inserts ( 22, 243, 256, 277, 284 & 30 cal ) for about $ 30.
I got the Headspace comparator kit (for measuring how much far you're moving/sizing the brass shoulders when resizing the brass ). And then you get the caliber specific OAL inserts for measuring cartridge base to bullet ogive.
And in the future you can get the OAL lands finding gauge ( I got the bent one so I can use it for bolt guns and gas guns ) so you can find the spot where the bullet touches the lands.
Just foogle or bootube Hornady comparator.
At the end, we want the cartridge base to bullet ogive to be consistent, cause the overall length to tip is never going to be perfect because bullet tips are not identical to the thousands of an inch.
everything I've produce so far as in the safe range so for now I'm happy with that. At this point in time I'm mostly trying just getting the steps down to produce safe rounds and have fun with it. So far I've made 40 rounds and shot about 12 funny part is just firing those 12 I have figured out that my rifle likes longer overall ammunition. I never realized how much a few thousands of an inch can make that much of a difference in a rifle
Ned Ludd
Silver $$ Contributor
In my experience, a typical Lot of 1000 Berger or Sierra bullets might vary in OAL from about .010" to .015". Some might be slightly better, some might be slightly worse. Regardless, some part of the OAL length variance can exist any of the different regions of the bullet (boattail, bearing surface, nose). Presumably due to the manufacturing process, I typically find the largest portion of OAL length variance resides in the bullet nose region. Because nose length varies in unsorted bullets, you could easily observe cartridge overall length (COAL) measurements that varied .005" to .010" even though the cartridge base-to-ogive (CBTO) measurements as taken with a caliper insert tool were essentially identical.
Measuring the CBTO of loaded rounds using a caliper insert tool (rather than COAL) is generally the much better way to go as has been mentioned above. However, just be aware for future reference that even CBTO measurements are not perfect. The nose region with its inherent length variance contains the contact points where your seating die stem pushes the bullet into the case (farther out toward the meplat), and where your caliper insert tool seats (just above the top of the bearing surface). Length variance in the nose region between these two points of contact (i.e. bullet length variance between where the seating stem pushes the bullet in, and where your caliper insert actually seats on the ogive) can also cause variance in CBTO measurements, although it's rarely as large as the variance in COAL measurements. The picture below illustrates much better what I'm describing ("critical distance", green box). The most common ways to deal with CBTO variance include length-sorting bullets or having to occasionally tweak the seating die micrometer setting. Sometimes, a heavy stroke versus a very light stroke with the press handle can even be worth an extra .0005" to .001" in CBTO, if that's all you need.
As you load more rounds and ask more questions, I have no doubt you will become more familiar than you ever wanted to be with all the subtle sources of variance in the dimensions of loaded rounds
. Don't hesitate or be afraid to ask questions here if you're not sure, there are plenty of folks with the expertise to help you. Best of luck with it!
Measuring the CBTO of loaded rounds using a caliper insert tool (rather than COAL) is generally the much better way to go as has been mentioned above. However, just be aware for future reference that even CBTO measurements are not perfect. The nose region with its inherent length variance contains the contact points where your seating die stem pushes the bullet into the case (farther out toward the meplat), and where your caliper insert tool seats (just above the top of the bearing surface). Length variance in the nose region between these two points of contact (i.e. bullet length variance between where the seating stem pushes the bullet in, and where your caliper insert actually seats on the ogive) can also cause variance in CBTO measurements, although it's rarely as large as the variance in COAL measurements. The picture below illustrates much better what I'm describing ("critical distance", green box). The most common ways to deal with CBTO variance include length-sorting bullets or having to occasionally tweak the seating die micrometer setting. Sometimes, a heavy stroke versus a very light stroke with the press handle can even be worth an extra .0005" to .001" in CBTO, if that's all you need.
As you load more rounds and ask more questions, I have no doubt you will become more familiar than you ever wanted to be with all the subtle sources of variance in the dimensions of loaded rounds
. Don't hesitate or be afraid to ask questions here if you're not sure, there are plenty of folks with the expertise to help you. Best of luck with it!Kurz
Silver $$ Contributor
Learning is a marvelous thing to behold!
Those Ah Ha! moments are priceless and you'll never forget them.Do a quick search for the folks showing targets and asking questions about ladder testing. You get a very clear picture of what the tiny changes can do to your group size and placement.
Enjoy the process!
Variance in bullet Length is what is always come down to for me I sort all my bullets by weight then check them for length obviously a longer bullet will be heavier sorting by weight gets rid of most of this it all depends just how picky you want to be but since I started sorting for weight and length I set my die once run 30 rounds they will all be within .001 or less.Also i used to use rcbs gold-medal match dies they are very inconsistent I have since gone to Redding dies a major improvement
dogdude
Egan O'Brien
I've recently spoke with a very respected custom bullet maker..mentioned all the sorting tools I have, he said ''that's nice'', but the first and most important part of sorting is OAL!
As ''338 dude'' mentioned..the longer ones will be heavier, on a 6mm that .0005-.001 is not much weight, but a variable, so measure OAL in separate piles and be done with it.
As ''338 dude'' mentioned..the longer ones will be heavier, on a 6mm that .0005-.001 is not much weight, but a variable, so measure OAL in separate piles and be done with it.
I don't think a bottleneck case head should be the rear reference to some place on the bullet. Case heads are rarely, if at all, against the bolt face when the round fires.
The case shoulder is hard against the chamber shoulder, sometimes set back a thousandth or two, when the round fires. A 2 to 3 ounce firing pin pushed 15 to 20 fps by a 25 pound spring force pushes it there before the primer's dented and fires. There's a bit of head clearance to the bolt face at this time. Somehow measure from shoulder to bullet ogive diameter that first touches the rifling in the throat. That's about a couple thousandths less than bullet diameter.
That's also good diameter for the seating stem point to touch bullet for best consistency. A seater that used the case shoulder as the reference would help.
The case shoulder is hard against the chamber shoulder, sometimes set back a thousandth or two, when the round fires. A 2 to 3 ounce firing pin pushed 15 to 20 fps by a 25 pound spring force pushes it there before the primer's dented and fires. There's a bit of head clearance to the bolt face at this time. Somehow measure from shoulder to bullet ogive diameter that first touches the rifling in the throat. That's about a couple thousandths less than bullet diameter.
That's also good diameter for the seating stem point to touch bullet for best consistency. A seater that used the case shoulder as the reference would help.
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These are 250 grain Berger elite Hunter bullets after I Molly coated them I sorted them for weight I will next check the length but as with most burgers 96 out of 100 bullets are within 3/10 of a grain only four are 5/10
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After I sorted the 96 that were within 3/10 of a grain in weight I shorted them by length and separated them by 1000th of an inch and this is what I ended up with another reason why I shoot burger very consistent I don’t think 1000th of an inch in length is a big deal but when I load these and shoot them I will shoot them in the groups according to their lengt
D-4297
Gold $$ Contributor
As I was in the learning process ; and still am , I wondered about all the comments in other threads , and sites regarding the seating stem , so I pulled several of my dies apart to inspect them . What I found , I could not believe . Gouges , ridges , out of round , and just plain rough surfaces with little to no thoughts to a "finished" smooth surface . By my standards , it was like someone carved them out with a rough mill-bastard file , and finished them with a rock . SOoooo...Fire up the Hardinge , and go to work . After several hours , I had three very nice polished , radiused stems that had deeper meplat clearances that made truer , straighter , more consistent ammo . And low and behold .....My scores jumped ten to twelve points overnight . The dies are from three different well regarded mfg.'s so that says everybody's Q.C. could stand some improvement . Might want to check your "stems" , folks . The problem could be hiding up in there , too .
Get a Hornady "Overall Length gauge". This will give you the length of your round with a particular bullet set against the lands. You can then start loading with different overall lengths to determine what works best in your rifle. I usually start with .020" off of the lands, except for Barnes bullets. Barnes recommends .050" for their bullets.
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