View Single Post
Old 04-01-2014, 07:44 PM   #8 (permalink)
Whiskey Hammer
Shaped Ammo Advocate
 
Whiskey Hammer's Avatar
 
Join Date: Nov 2013
Location: Jacksonville, FL (and a lot of the time, Tampa)

Our velocity standard deviation averaged around 3. Sometimes as good as the mid 2s and sometimes as bad as the high 4s. Were shooting at 75ft, the same as the Punkworks test.

Its certainly possible that the paint was somehow different. But it seems unlikey considering that we have evidence suggesting an improvement in manufacturing consistency.

In so far as the markers, I do think that there might be some difference between platforms (for the moment ignoring my concerns about the smoothbore presection). When I had the high FPS camera I did some slow-mo of the barrel in the MR5 during firing. I did it because FS are so accurate/long range that barrel harmonics might actually start to matter as a contributing factor to accuracy and I wanted to see if the barrel experienced any flex during firing. It definitly showed some flex. Not exactly like an AK but still noticable.

I tested it in my first and second round of shooting, but didnt find anything to conclusivly support the idea. Whatever is throwing off my groups could also be masking the effects of the harmonics (if they matter at all). If they do end up mattering then it stands to reason that the characteristics of the markers operation will alos matter. You might expect long slow impulses to be less disturbing than hard fast ones. Or inline internals to disturb the shot less than the assymetric forces of stacked tube blowbacks.

For now, Ill put together a rough cut of the data. I dont think it matters a whole lot, but it's been asked for a couple of times. I gotta properly describe and qualify everything, so I'll get that up tomorrow afternoonish.

I'll PM you tonight or tomorrow afternoon, scott. I gotta get back on the road to Jax.

Also here's some relevent info from another disucssion. And a link to my argument in favor of the x-component.

Quote:
In terms of the platform, it's an unmodifed spyder MR5. I've rigged it to run on a palmers stab (as you can see in the "behind the scense" pics). The MR5 uses a method of barrel attachment simialr to the T8x/T9x series of markers and hammerhead doesnt stock a back for it. The MR5 did however come with an early run of a standard threaded barrel adapter, so I'm using it with that. That's where my concern for the smoothbore presection comes from. In addition to that I'm firing the marker upside down, and clamped to mobile contruction table/clamp setup. It's stable and super conveinent for firing - I cut the bottom off of the mag, and feed the rounds in hopper-style now. It's way faster to run the tests and I dont have the shifting POA problem.

In the first round of tests we measured in CMs out to roughly 0.1 resolution. That took way too long however, so I went out and bought one of those vinyl DND battle mats. It's a premade 30x40 inch grid that makes assesing the rounds (and cleaning up afterward) super easy and fast. This we measured out a rough 0.1 resoultion. I ran the numbers though, and the extra resolution doesnt add anything to the final SD calculation, so next time well just go for a resolution of 1 or 0.5 inches.

I did look over my first round of data today though and there was one outlier. When I shot my first baseline group with the first round of testing, I got an x-component SD of 2.48, which when accounting for the mathematical centering actually beats the Punkworks value. At the time, I thought the value was kinda crazy so I ran it again to be sure - I wasnt able to reproduce it. Thinking about it, I explicitly recall grabbing only rounds that were nose down at the top of the bulk box. It was easier to extract the rounds by just clamping the skirts with my fingertips. It's possible that I grabbed a bunch of rounds that were naturally settled nose down for that one test. I think it's even more likely considering that punkworks shot thier rounds from the old stacked tubes.

Last edited by Whiskey Hammer; 04-01-2014 at 07:49 PM.
Whiskey Hammer is offline   Reply With Quote