Accuracy of Cartridge Length

[Groot]

Hello all,

I've been reloading for a few years now but i just recently bought a hornady comparator set to try to improve my reloading and get a better idea of how long my reloads need to be batch to batch.

I measured 6 of my remaining rounds for my 223 Rem with a 53 grain VMax over 26.6 grain of CFE223 (safe in my rifle maybe not yours, slightly over recommended max) These rounds may have been loaded into the mag box with or without rounds being fired, they may have been cycled though the action to unload the gun as well if that matters at all.

1 - 1.8585"
2 - 1.8605"
3 - 1.8595"
4 - 1.8595"
5 - 1.8590"
6 - 1.8595"

So my question is how much error is okay? Is the variation in the above measurements something to be real concerned with?

 

[L.Sherm]

Depends on your intended purpose.
#1 is the only one I think possibly matter and that my be only at longer than100 yards.
#2 -6 I dont think you will see any difference and the only way to keep that consistency over a bigger lot of ammo is sort the bullets from base to ogive.

 

[Mikecr]

What does your measure represent?
Cartridge base to ogive (CBTO)?
Cartridge overall length (COAL)?
What is your tested best CBTO?

 

[Groot]

What does your measure represent?
Cartridge base to ogive (CBTO)?
Cartridge overall length (COAL)?
What is your tested best CBTO?

base to ogive, and I found my best accuracy at about 10k off the lands. But I haven't tested any jumps larger than 30k. I threw the load together and was getting 3/4 inch groups and just went with it since I was running out of time. Groups opened up when seated without any jump as well.

 

[Groot]

Depends on your intended purpose.
#1 is the only one I think possibly matter and that my be only at longer than100 yards.
#2 -6 I dont think you will see any difference and the only way to keep that consistency over a bigger lot of ammo is sort the bullets from base to ogive.

I use this rifle exclusively for groundhogs anywhere between 50 and 500 yards. With the majority right around 300 and under.

 

[Canhunter35]

I'd start with checking a bunch of 53gr Vmax bullets and see how consistent they are if ur wanting perfect measurements

 

[Groot]

I'd start with checking a bunch of 53gr Vmax bullets and see how consistent they are if ur wanting perfect measurements

I don't know that I'm after PERFECT measurements just because theres always some finite amount of error somewhere in the process but thats a good point, the next box I get I'll measure a bunch. I think I may try 55 blitzkings again and see how they compare as well.

thanks!

 

[Bart B]

Why use the .223 Rem case head as the rear reference? It's not against the bolt face when the round fires. The case shoulder is hard against the chamber shoulder when fired; driven there by bolt face ejector or spring loaded firing pin before firing. Case head clearance to bolt face spread is equal to the case head to case shoulder (case headspace?) spread.

 

[Runandgun]

Your goal for consistency is moving you in the right direction.

A couple of questions though:

1. What type of rifle is this? And how much have you experimented with finding a really accurate load other than going with 10 thousandths off the lands?
2. Did you use the Hornady threaded case to measure bullet jump? Their case is not going to be an exact fit to your chamber, so there's a small error introduced.

I personally woudn't be worried about the variation you list unless this is a benchrest level rifle, though knowing the bullet jump and loading to it consistently is worth doing.

 

[Groot]

Why use the .223 Rem case head as the rear reference? It's not against the bolt face when the round fires. The case shoulder is hard against the chamber shoulder when fired; driven there by bolt face ejector or spring loaded firing pin before firing. Case head clearance to bolt face spread is equal to the case head to case shoulder (case headspace?) spread.

I measured from head to ogive because I was using comparator and digital caliper, can you elaborate on your way of measuring? Are you saying measure from shoulder to ogive?

 

[Groot]

Your goal for consistency is moving you in the right direction.

A couple of questions though:

1. What type of rifle is this? And how much have you experimented with finding a really accurate load other than going with 10 thousandths off the lands?
2. Did you use the Hornady threaded case to measure bullet jump? Their case is not going to be an exact fit to your chamber, so there's a small error introduced.

I personally woudn't be worried about the variation you list unless this is a benchrest level rifle, though knowing the bullet jump and loading to it consistently is worth doing.

The rifle is a Marlin X7 (bolt gun) definitely not a bench gun lol, I've tried loading into the lands, and gave me about a 2 inch group at just about every powder level, and then I tried 10k and 30k at 4 powder charges in .2 grain increments, and found my best group just under 3/4 with 10k and 28.6 grain of cfe 223. Id say I've spent around 50-75 rounds tinkering at 100 yards and at distance. I did the same load up twice once in bitter cold weather snd once in temps between 80-90

I did not use the hornady overall length gauge. Ive found the lands by feel by seating little by little and closing the bolt

thanks

 

[rsmithsr]

the 50 vmax/zmax are great bullets out of the box for the money.

unless you TEST with .001 and .002 variations you will not know how close you have to be.
don't let that guy confuse you. if you are sizing close to chamber size, it is .001/.002 and the ejector is keeping them all in the same place.

 

[Bart B]

I measured from head to ogive because I was using comparator and digital caliper, can you elaborate on your way of measuring? Are you saying measure from shoulder to ogive?

Yes, because that's the controlling factor. And the ogive reference diameter that touches the lands in the throat is about .002" bigger than barrel bore diameter.

If the gauge reference diameter is smaller than bore diameter, its not going to touch the ogive where the lands do.

As you're working tolerances seen to be 1 to 2 thousandths, I'm pointing out things that effect that. And assuming there's no case shoulder setback from firing pin impact.

 

[Groot]

H

Yes, because that's the controlling factor. And the ogive reference diameter that touches the lands in the throat is about .002" bigger than barrel bore diameter.

If the gauge reference diameter is smaller than bore diameter, its not going to touch the ogive where the lands do.

hmm, i see what youre saying..

I know the length that I measured isn't the actual measurement to the lands, im just using that measurement to measure the consistency of the reloaded rounds. The comparator diameter will stay consistent and as long as the bullets are consistent the way I measured them should be accurate... I found the oal by seating the bullet little by little and by feel closing the bolt, I took that measurement by doing an average of 5. Later I cut a case and measured by letting the bullet seat itself and found my average measurement was almost right on.