I noticed in another thread (in the old forum) that someone was asking for FS Dimensions. I remembered that I put together some fairly extensive measurements taken with a digital caliper / micrometer and, I figured that this sub-forum would be a good place to post it.
First off, these measurements were taken some time ago (approaching ten years now), and I cannot vouch for whether or not there have been changes (intentional or accidental) to the rounds since. In 2015, Scott Quarles of First Strike published some metrics on their rounds. It's worth checking out here.
So, with all that being said, below is what I have.
First up, length. Using the caliper, and measuring from the very tip of the fill nipple, to the tail, a round measured to .6805" and I didn't notice any significant differences between rounds (i.e. everything was around .680"). I'll document this more thoroughly in the future.
When it comes to diameter, this is where things got tricky. I had to resort to three measurements here. The Equator, and the Skirt in two axii.
The Equator (where the skirt is attached to the payload section) was straightforward. They measured out to be effectively circular at .6850" What made this challenging was consistently measuring on the seam as it is fairly narrow.
As for the skirt, I took two measurements- at the widest and the narrowest points, I will refer to them as the Y and X axii respectively. I did my best to measure from two opposing fin tips. And the pictures show this well in one image but, not so well in the other.
So, simply put, the skirt is somewhat lopsided and, the equator is the widest point of the rounds at .681"
I purchased an ammunition reloading scale. These are more accurate than the vast majority of scales you will find in other consumer stores. I measured two sets of 20 rounds, one from a box that was one month old, and the other from a box that was five months old. Before measuring I let the scale warm up and, I calibrated it with the included calibrtion weight (as per the manufacturers instructions).
I switched the units to grains (for finer resolution) and I found the following:
Data posted here.
At one point, I fired several rounds into my bathtub (full of water) to evaluate if the fins or shell were getting wear marks from the LAPCO/Tiberius rifled barrel. I found no noticable wear but, I recovered a complete shell, rinsed out the paint and found it to weigh 9.9grains.
Finally, in all the drawings and even the oversized 3D printed model that showed up on Facebook, the fins are depicted as having a squared cross section. In reality, the fins have a curved cross section, and you can see this if you look closely at the pics or, if you pick up your own rounds. I suspect it's within the limits of the manufacturing process (i.e. maybe they designed for squared but, they come out rounded).
First off, these measurements were taken some time ago (approaching ten years now), and I cannot vouch for whether or not there have been changes (intentional or accidental) to the rounds since. In 2015, Scott Quarles of First Strike published some metrics on their rounds. It's worth checking out here.
So, with all that being said, below is what I have.
First up, length. Using the caliper, and measuring from the very tip of the fill nipple, to the tail, a round measured to .6805" and I didn't notice any significant differences between rounds (i.e. everything was around .680"). I'll document this more thoroughly in the future.
When it comes to diameter, this is where things got tricky. I had to resort to three measurements here. The Equator, and the Skirt in two axii.
The Equator (where the skirt is attached to the payload section) was straightforward. They measured out to be effectively circular at .6850" What made this challenging was consistently measuring on the seam as it is fairly narrow.
As for the skirt, I took two measurements- at the widest and the narrowest points, I will refer to them as the Y and X axii respectively. I did my best to measure from two opposing fin tips. And the pictures show this well in one image but, not so well in the other.
- The X-Axis (narrowest) came in at .6595"
- The Y-Axis (Widest) came in at .6755"
So, simply put, the skirt is somewhat lopsided and, the equator is the widest point of the rounds at .681"
I purchased an ammunition reloading scale. These are more accurate than the vast majority of scales you will find in other consumer stores. I measured two sets of 20 rounds, one from a box that was one month old, and the other from a box that was five months old. Before measuring I let the scale warm up and, I calibrated it with the included calibrtion weight (as per the manufacturers instructions).
I switched the units to grains (for finer resolution) and I found the following:
- 1mo old box:
- Avg Weight: 47.94grains
- 95% +/- .7875grains
- 5mo old box:
- Avg Weight: 48.03grains
- 95% +/- 1.4321grains
Data posted here.
At one point, I fired several rounds into my bathtub (full of water) to evaluate if the fins or shell were getting wear marks from the LAPCO/Tiberius rifled barrel. I found no noticable wear but, I recovered a complete shell, rinsed out the paint and found it to weigh 9.9grains.
Finally, in all the drawings and even the oversized 3D printed model that showed up on Facebook, the fins are depicted as having a squared cross section. In reality, the fins have a curved cross section, and you can see this if you look closely at the pics or, if you pick up your own rounds. I suspect it's within the limits of the manufacturing process (i.e. maybe they designed for squared but, they come out rounded).
and they consistently measure 0.683" on the seam and from 2.99 to 3.00g on an Ohaus Scout II scale. Average diameter of the tail is about 0.679. I didn't spend much time on the tails because 1.) they are a out of circularity by ~0.008+ and 2.) they're very thin and IMO probably expand against the barrel on firing.
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