Same Projectile, Different Brass, Same CBTO

[CheapBasterd]

Why would different brass with with the same bullet seated to the same CBTO have a different COL?

Peterson Brass
140gr ELD M
CBTO 2.30"
COL 2.840"

Hornady Brass
140gr ELD M
CBTO 2.30"
COL 2.850"

 

[supercorndogs]

Because one bullet is longer from the ogive to the tip of the bullet than the other.

 

[Rio Precision Gunworks]

Is this an average of many rounds or just comparing two rounds total?

 

[CheapBasterd]

Is this an average of many rounds or just comparing two rounds total?

Its an average. I loaded two batches first was with Peterson brass then I did the Hornady brass.


I just grabbed 5 from each batch

Hornady Brass - 140gr ELDM
2.850 / 2.230
2.850 / 2.230
2.849 / 2.231
2.851 / 2.231
2.850 / 2.230

Peterson Brass - 140gr ELDM
2.842 / 2.231
2.840 / 2.229
2.840 / 2.229
2.841 / 2.230
2.839 / 2.229

 

[Aftermath]

Why would different brass with with the same bullet seated to the same CBTO have a different COL?

Bullets are not all same length.
Take a few projectiles and measure their overall length. I bet you will find your variance to be very similar.
As far as that goes, there is also about the same variance in length from the base of the bullet to ogive.
It's a wonder we can hit anything at all.

 

[Rio Precision Gunworks]

Its an average. I loaded two batches first was with Peterson brass then I did the Hornady brass.


I just grabbed 5 from each batch

Hornady Brass - 140gr ELDM
2.850 / 2.230
2.850 / 2.230
2.849 / 2.231
2.851 / 2.231
2.850 / 2.230

Peterson Brass - 140gr ELDM
2.842 / 2.231
2.840 / 2.229
2.840 / 2.229
2.841 / 2.230
2.839 / 2.229

Same lot of bullets?

 

[Rio Precision Gunworks]

Bullets are not all same length.
Take a few projectiles and measure their overall length. I bet you will find your variance to be very similar.
As far as that goes, there is also about the same variance in length from the base of the bullet to ogive.
It's a wonder we can hit anything at all.

If it's the same lot of bullets, he would have had to grabbed 5 of each that happened to be about the same variance. Which is possible, but not incredibly likely.

 

[CheapBasterd]

Bullets are not all same length.
Take a few projectiles and measure their overall length. I bet you will find your variance to be very similar.
As far as that goes, there is also about the same variance in length from the base of the bullet to ogive.
It's a wonder we can hit anything at all.

Same lot of bullets?

Yep. Same lot. Im baffled or im doing something wickedly wrong that I cant figure out. The only thing I did differently was reset the seating die before starting the batch with the Hornady Brass and worked back down to 2.230 CBTO. I wasnt paying attention to OAL until a couple were done, measured, noted it and I kept going.


Grabbed 5 projectiles from the same box. Tight.
Projectile length / B2O
1.374 / 0.768
1.374 / 0.770
1.373 / 0.770
1.374 / 0.769
1.374 / 0.769

 

[Rio Precision Gunworks]

Make sure primers are flush or below flush.

 

[CheapBasterd]

Make sure primers are flush or below flush.

That’s one thing I’ll need to look at closer and it would make sense. I’m using that flat base attachment on my calipers so a proud primer would definitely be suspect. I’ll check tomorrow. I did notice that the pockets in the Hornady brass are more flat than the Peterson brass. I saw this while I was using the primer pocket cleaning tool the Hornady pockets had a flat face and the Peterson brass was more concave and I couldn’t get that last crud out around the flash hole. OCD things…

 

[Rio Precision Gunworks]

That’s one thing I’ll need to look at closer and it would make sense. I’m using that flat base attachment on my calipers so a proud primer would definitely be suspect. I’ll check tomorrow. I did notice that the pockets in the Hornady brass are more flat than the Peterson brass. I saw this while I was using the primer pocket cleaning tool the Hornady pockets had a flat face and the Peterson brass was more concave and I couldn’t get that last crud out around the flash hole. OCD things…

That's only thing I can think of. I'd normally suspect some faulty measurements, but you seem to be measuring everything else properly.

 

[Aftermath]

Did you load the Hornady and the Peterson brass during the same reloading session?

 

[Threadcutter308]

Its an average. I loaded two batches first was with Peterson brass then I did the Hornady brass.


I just grabbed 5 from each batch

Hornady Brass - 140gr ELDM
2.850 / 2.230
2.850 / 2.230
2.849 / 2.231
2.851 / 2.231
2.850 / 2.230

Peterson Brass - 140gr ELDM
2.842 / 2.231
2.840 / 2.229
2.840 / 2.229
2.841 / 2.230
2.839 / 2.229

Your CBTO dimension is VERY consistent. That's what matters.

Why do you even care ? I think you're getting hung up on something that really doesn't matter.

 

[CheapBasterd]

Did you load the Hornady and the Peterson brass during the same reloading session?

Same session one after the other. I processed all this brass in the same batch. Loaded Peterson first. Reset the seating die and then loaded Hornady batch.

 

[Rio Precision Gunworks]

Your CBTO dimension is VERY consistent. That's what matters.

Why do you even care ? I think you're getting hung up on something that really doesn't matter.

If he has proud primers on one batch that aren't seated to the bottom of the pocket, there can be issues.

And at this point, primer is just about the only thing that could give same BTO and different OAL based on the measurements he provided.

 

[Threadcutter308]

If he has proud primers on one batch that aren't seated to the bottom of the pocket, there can be issues.

And at this point, primer is just about the only thing that could give same BTO and different OAL based on the measurements he provided.

I'm making an assumption that that is not the case, based on his comment about not being able to get the primer pockets clean. That means that the pockets are already deeper than what the pocket cleaning tool can reach.

Now yes, if he isn't getting his primers fully seated, then I concur. My point being is that the bullet jump from the ogive to lands is very consistent, which is what matters. In that regard, COAL doesn't matter, unless the rounds are magazine fed And he's running out of room.

I shoot a lot of 168 grain Match Kings and the tips are really ratty. Off the top of my head, I seem to recall bullet length variations of as much as 0.020". I used to clean them up with a pointing tool, but found that it didn't make any difference accuracy wise.

And, the age old question seems like it has yet to be asked;

How do they shoot ?

 

[Rio Precision Gunworks]

I'm making an assumption that that is not the case, based on his comment about not being able to get the primer pockets clean. That means that the pockets are already deeper than what the pocket cleaning tool can reach.

Now yes, if he isn't getting his primers fully seated, then I concur. My point being is that the bullet jump from the ogive to lands is very consistent, which is what matters. In that regard, COAL doesn't matter, unless the rounds are magazine fed And he's running out of room.

I shoot a lot of 168 grain Match Kings and the tips are really ratty. Off the top of my head, I seem to recall bullet length variations of as much as 0.020". I used to clean them up with a pointing tool, but found that it didn't make any difference accuracy wise.

And, the age old question seems like it has yet to be asked;

How do they shoot ?

If you're assuming that's not the case, then how do you explain .010" difference in OAL when the BTO is the same and the bullets are measuring the same?

There's a delta there. You're using other bullets from personal experience as an example of differences in length when he's posted measurements from his bullets that are the same length. Which would mean that he somehow picked 5 bullets for one brass and 5 bullets for the other.....that are inconsistent (while being consistent with each of the 5 in the respective brass), but the 5 that he picked to measure OAL and BTO of the bullet were all within .002.


I'm not going to ask the age old question "how does it shoot" when there's an obvious issue. He's either making an error in his measurements or the primers aren't seated deep enough. Either of those issues should be fixed before you shoot. As one will have ignition issues, and other other will have him getting inconsistent measurements.....so, even if it shoots well, he's going to have issues making repeatable ammo since he has an issue with measurements.


And just in general, it's always good for anyone making their own ammo to understand why we get the measurements we get. So, worst case is, he learns something here.

 

[Rio Precision Gunworks]

Also, it's an error to think that BTO is what really matters......as that's only one piece of seating depth in relation to bullet jump.

You can have inconsistent shoulder bump, so even when the BTO is the same, when the firing pin strikes the primers, it pushes the round forward to the shoulder. Inconsistent bump means the bullet jump is different once the firing pin strikes.

You can have primers sitting proud and can either have ignition issues, or primer seats on the strike which in turn causes similar issues with bullet jump.


BTO is only one measurement of several that need to be consistent for your final bullet jump to remain consistent.

 

[Threadcutter308]

You guys have fun, I'm out. Hope the OP gets his "problem" solved.

 

[Chris1972]

Same session one after the other. I processed all this brass in the same batch. Loaded Peterson first. Reset the seating die and then loaded Hornady batch.

I’m confused, why would you reset the seating die between brass types. How would you change the die and not expect a different result? It’s very possible I’m misunderstanding.

 

[Rio Precision Gunworks]

I’m confused, why would you reset the seating die between brass types. How would you change the die and not expect a different result? It’s very possible I’m misunderstanding.

Some people back their seating die off anytime they change something or start a new batch. Then just work their way down until they get the desired BTO or OAL.

He set the die down until he got the same BTO as the other rounds he loaded. If the bullets are as consistent as his measurements, that means something like a proud primer that would give the same BTO but different OAL.

 

[Aftermath]

Reset the seating die and then loaded Hornady batch.

There ya go

 

[CheapBasterd]

It was not the primers. They were all seated below flush. I have a feeling It is a measurement issue with the calipers and "base" that was being used. Just checked what I think may be the problem. Its the smaller anvil base.

Here it is installed

Here it is if I snug down on the thumb screw just a little more. It puts a slight cant on the anvil even with ample pressure trying to keep the pieces together.

 

[Rio Precision Gunworks]

It was not the primers. They were all seated below flush. I have a feeling It is a measurement issue with the calipers and "base" that was being used. Just checked what I think may be the problem. Its the smaller anvil base.

Here it is installed
View attachment 8347845

Here it is if I snug down on the thumb screw just a little more. It puts a slight cant on the anvil even with ample pressure trying to keep the pieces together.

View attachment 8347849

Has to be a measurement issue then.

If the bullets are consistent, then you should have an OAL similar when the BTO is similar.

So, has to be an issue with the measurement tools or the technique.

 

[Xferbuckeye]

Shoot em. All the above may matter or may not. Proof will always be on paper.

Take this for what you paid for it and hope you’ll post some teeny groups!

 

[Aftermath]

It was not the primers. They were all seated below flush. I have a feeling It is a measurement issue with the calipers and "base" that was being used. Just checked what I think may be the problem. Its the smaller anvil base.

Here it is installed
View attachment 8347845

Here it is if I snug down on the thumb screw just a little more. It puts a slight cant on the anvil even with ample pressure trying to keep the pieces together.

View attachment 8347849

I prefer to use only the piece that holds the comparator and use the caliper jaw at the base of the cartridge. I usually spin the cartridge some to be sure it is real flat on the caliper jaw. Then use consistent tension, as in very little, to measure where the bullet ogive is. My mentor when I started all of this many decades ago had me using sooted bullets to see that I was using consistent tension. If I pressed a little, there would be a little ring. If I pressed harder, I would leave a wider ring. The goal was to leave a very very small ring of disturbed soot.
By not using the other end of the comparator set, I am eliminating a piece that is held in place with a set screw and one source of induced error.

 

[CheapBasterd]

I prefer to use only the piece that holds the comparator and use the caliper jaw at the base of the cartridge. I usually spin the cartridge some to be sure it is real flat on the caliper jaw. Then use consistent tension, as in very little, to measure where the bullet ogive is. My mentor when I started all of this many decades ago had me using sooted bullets to see that I was using consistent tension. If I pressed a little, there would be a little ring. If I pressed harder, I would leave a wider ring. The goal was to leave a very very small ring of disturbed soot.
By not using the other end of the comparator set, I am eliminating a piece that is held in place with a set screw and one source of induced error.

While it was entirely my carelessness not checking the caliper zero as I should have been. This small anvil is going to stay in the toolbox...I just messed with it a little, it has the thumb screw and bottom set screw. Too much room to change the zero on the calipers using either one. Thank you.

 

[axarob44]

I get more consistent measurements without the anvil on the caliper. Just the comparator and the face of the caliper jaw. The anvil can get out of alignment or loosen and get moved around. I found it was more consistent without it.

 

[CheapBasterd]

I feel like im going crazy now lol
Primers are below flush 100%

Peterson Brass CBTO - 2.230"

Hornady Brass 2.230"

Peterson Brass COL: 2.837"

Hornady Brass COL: 2.848"

 

[Chris1972]

Measure the oal without any attachment just using the calipers. Now that I see how your doing it, I believe this is a thing. I don’t even understand the purpose of the piece your using on the base.

 

[abn31c]

Irrelevant

 

[Rio Precision Gunworks]

Measure the oal without any attachment just using the calipers. Now that I see how your doing it, I believe this is a thing. I don’t even understand the purpose of the piece your using on the base.

The piece on the base is a Hornady comparator tool with a bullet insert. He's using it to measure both the BTO and the OAL. He just has the calipers zero'd on that base/comparator.

I agree though, I'd remove it and see how the OAL compares.


Personally, I'd also invest in a better set of calipers such as Mitutoyo.

 

[abn31c]

 

[Rio Precision Gunworks]

View attachment 8350326View attachment 8350327

What are you trying to point out?

If the calipers are zero'd when closed onto that insert, it will measure the same.

 

[abn31c]

What are you trying to point out?

If the calipers are zero'd when closed onto that insert, it will measure the same.

Yes, I edited my post...I didn't read it the whole thread. That's on me.
If he's using them correctly, appears to be a caliper issue. As posted above, when measuring cbto no need to use any attachments.

 

[Chris1972]

The piece on the base is a Hornady comparator tool with a bullet insert. He's using it to measure both the BTO and the OAL. He just has the calipers zero'd on that base/comparator.

I agree though, I'd remove it and see how the OAL compares.


Personally, I'd also invest in a better set of calipers such as Mitutoyo.

Yeah I guess i misspoke. I don’t understand using it in that capacity. I use the exact one to measure the ogive.

 

[Earnhardt]

I have a feeling that somebody's dad didn't beat the OCD out of them when they were a kid...

 

[Aftermath]

I prefer to use the comparator to only measure to the ogive. I also use it so that the bullet is skyward. This prevents the bullet from being pulled into the comparator by gravity as I spin the cartridge base on the caliper jaw to be sure it is not cocked to one side as I gently press the cartridge up with the thumbwheel.

Except for the issue involving a cartridge being too long to feed from the magazine, the COAL doesn't even matter. That being said, again, I prefer to eliminate as many sources of induced error as possible. If I were to care about COAL, I would remove all attachments prior to measuring just to prevent any sort of induced error.

Calipers are not real expensive. I have several sets. Calipers are dedicated to the various comparator sets, a set for 6mm, a set for 7mm, a set for 30 cal, a set for 223 and a set for 338. Another for general measuring of stuff without any attachments. Same reason for having more than one set of micrometers.

 

[Rio Precision Gunworks]

I'd just be looking to see what the error in measurement is. As if it's happening here, it's happening somewhere else.

That's where my OCD would kick in. Because I'd want to make sure I'm getting the important measurements correct.

 

[CheapBasterd]

Well, I ended up putting that COL measurement tucked away in the back of my mind and focused on the consistent 2.230" CBTO. Maybe I'll pony up for some better calipers.
Hornady case with tighter groups.