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Whiskey Hammer 03-31-2014 03:22 PM

Accuracy, Never Enough to Go Around
 
We've completed not one but two rounds of accuracy testing and we've hit a bit of an obstacle. Initially, I wanted to have the data out in a "one or two week" timeline from the posting date but, for reasons we'll get into below, I'm not comfortable releasing it yet.

The problem in my accuracy tests, is accuracy. I'm not getting as much as I should be getting. Take a look at the below comparison of X-component deviation* in the baseline groups from Punkworks and our first shooting session. Punkworks is getting a final result that is more than twice as accurate.
  • Punkworks: 1.725 inches
  • First Round: 3.6 inches
Obviously I was missing something... I came across the FS Centrifuge post here on M. Carter Brown and I thought that it was a very likely explanation for my accuracy problem. The paint in bulk boxes doesn't sit uniformly so the asymmetric mass distribution of odd settled paint throws off the accuracy. Seems legit right? I grabbed a round and forcefully tapped it against a level surface to settle the paint against the nose of the round. Along the same lines of how you would force a bottle of ketchup to settle at the spout. I visually inspected the round and the paint seemed to be pretty uniformly settled in the nose. To be safe I allowed the rounds to sit nose down overnight before the next round of testing and re-tapped them before firing. The comparison between Punkworks, the first round, and the second round is below.
  • Punkworks: 1.725 inches
  • First Round: 3.6 inches
  • Second Round: 3.55 inches
No statistically important difference. I racked my brain trying to explain the difference, and while looking at the 8 shot group distinctions in the Punkworks data set, I remembered that their methodology artificially centered each magazine's group. It follows then that the normalizing might also have a damping effect on the natural randomness of the rounds. The most likely way they did this was to average each groups X and Y values, and then subtract that average from the actual values. This results in three groups whose average values (i.e. centers) are all at the same (0,0) point.

Edit: Ha, I knew I remeber seeing a video about this: Tiberius First Strike Test Thoughts by cockerpunk. It touches on the damping effect that correcting the groups has.

I applied (ostensibly) (confirmed) the same mathematical methodology to my groups and it made a difference. We got about an inch off the group, which is pretty significant. Definitely closing the gap but certainly not all the way there.
  • Punkworks: 1.725 inches
  • First/Second Rounds: approx. 2.6 inches
Now we just need to shore up that last inch.

Thinking about it some more, it could be the barrel setup. There is a short stretch of smoothbore before the rifling in my MR5 setup that could be throwing off the accuracy. We know that smoothbores don't do much to the spin of the round; in some cases it can even rotate in the wrong direction. It's possible that the smoothbore presection is allowing some rounds to get a counterproductive spin before they hit the rifling and that those rounds aren't being stabilized as well as they otherwise would be.

It could also just be that my paint settling methodology didn't work as well as long-term nose down or centrifugally settled paint. I might have just grabbed and visually inspected a couple of rounds that were naturally settled right.

Another possibility is that I'm botching something about the mathematical theory here.

So basically I need to shoot a group that has been centrifugally settled, shoot a group from a system that doesn't have the smoothbore presection, and mess with the numbers more/shoot a larger group size/get confirmation on the Punkworks math.

Once I figure out what's going on with my accuracy I'll feel batter tackling my 121 accuracy/drag data.

The issue going forward is money. It's a finite resource for most of us, and I definitely include myself in that number. It would be a serious kick in the dick to shell out money for the only tested rifled barrel that works natively with the MR5. That would of course be the Hammer 7 threaded Tiberius/Lapco barrel. The other less dick kickish option is to buy the threaded Hammerhead back for Ion/Impulse threads and do a test group on my Ion. There are a couple of concerns there but it's a decent solution from a trouble shooting standpoint. Anybody have the Lapco barrel or a Hammerhead back in Ion/Impulse they'd be willing to loan out? I'd of course be willing to put up collateral through a third-party for the full replacement value. I can float the money easy as pie, but I'd rather avoid sinking it when I need to restock my paint. Other than that, I'm gonna move some gear on craigslist and buy paint as sales allow.

Oh and the studio/warehouse owner shot some behind the scenes stuff when we did our first shooting session. Bro did it gratis and I think it turned out pretty cool. Check it out here.

*I prefer to compare accuracy using just the X-component rather than the vector. I'll get into the specifc reasoning in another this post, but for now bear with me.

Crimson Death 03-31-2014 05:32 PM

What's the consistency over the chrono for you gun? and how far are you shooting?

Cyco-Dude 04-01-2014 01:08 AM

to be honest, i wouldn't even bother comparing your results to other peoples results. the gun is not the same, the paint is not the same, etc. just get the data for YOUR tests, and let the results speak for themselves.

at least, that is how i look at paintball accuracy tests. i view each one as unique, and only compare data in one test (ie, i don't compare punkworks results to rntlee's results, etc).

scottallen1986 04-01-2014 04:16 AM

Honestly, I would say scrap the MR5.

I own and have used with FSR:

BT Tracer
Hammer 7
MR5
Milsig Paradigm Pro
468
T9
TPX

And used on an outdoor gun range a buddy's DAM against all of these. The 468 after I put a reg on it, is pretty accurate, but the best, shot-shot velocity consistency, and total accuracy, is my BT Tracer by FAR. I made up a little side mounting sten like mag for it. It takes cocker threads, is closed bolt, and would be easy enough to put a reg onto for further velocity improvement.

I lowered my MR5's spring strength, adjusted the pressure with a plamer reg, have a barrel/breach adapter for it so I can use other spyder threaded barrels, but it still kicks quite a bit when shooting and has lots of moving parts and the rounds don't sit in a breach. It's just not that great of a platform to be using for such a precise set of tests, in my opinion.

If you want, I can mail you out my Trracer. The mag system can be a bit tricky at first but its nothing an engineer can't figure out. You can also have it right side up too and remove the variable of the round not being fired/seated properly each time due to the open bolt aspect of the MR5. I'm not using it much anymore so if you want, and think it will help as I do, I can send it your way.

Also you'll need to get the centrifuge thing going too. I don't think the tapping is cutting it. I've got a game in a few weeks in Houston I'll be going to, but after that I can send the centrifuge out too if you want. You'll just need a cordless drill to spin it.

uv_halo 04-01-2014 11:04 AM

Quote:

Originally Posted by Cyco-Dude (Post 2930668)
to be honest, i wouldn't even bother comparing your results to other peoples results. the gun is not the same, the paint is not the same, etc. just get the data for YOUR tests, and let the results speak for themselves.

at least, that is how i look at paintball accuracy tests. i view each one as unique, and only compare data in one test (ie, i don't compare punkworks results to rntlee's results, etc).

Actually, with regular paint, I fully agree, storage means to storage means, batch to batch, brand to brand, year to year will introduce different characteristics that can and will affect the paint. However to be clear, rntlee never did tests that contradicted punkworks' data. He actually tested ideas as to what about paintballs makes them perform so poorly, and what kind of things could be done to improve their performance.

As for First Strike Rounds, From box to box, year to year, there has been very little change in the first strike rounds. The weights and sizes have largely remained the same. The most significant thing I've observed would be an improvement to the injection point on the nose (the last couple years have been improved over the first couple years).

Quote:

Originally Posted by scottallen1986 (Post 2930711)
Honestly, I would say scrap the MR5.

I own and have used with FSR:

BT Tracer
Hammer 7
MR5
Milsig Paradigm Pro
468
T9
TPX

And used on an outdoor gun range a buddy's DAM against all of these. The 468 after I put a reg on it, is pretty accurate, but the best, shot-shot velocity consistency, and total accuracy, is my BT Tracer by FAR. I made up a little side mounting sten like mag for it. It takes cocker threads, is closed bolt, and would be easy enough to put a reg onto for further velocity improvement.

I lowered my MR5's spring strength, adjusted the pressure with a plamer reg, have a barrel/breach adapter for it so I can use other spyder threaded barrels, but it still kicks quite a bit when shooting and has lots of moving parts and the rounds don't sit in a breach. It's just not that great of a platform to be using for such a precise set of tests, in my opinion.

If you want, I can mail you out my Trracer. The mag system can be a bit tricky at first but its nothing an engineer can't figure out. You can also have it right side up too and remove the variable of the round not being fired/seated properly each time due to the open bolt aspect of the MR5. I'm not using it much anymore so if you want, and think it will help as I do, I can send it your way.

Also you'll need to get the centrifuge thing going too. I don't think the tapping is cutting it. I've got a game in a few weeks in Houston I'll be going to, but after that I can send the centrifuge out too if you want. You'll just need a cordless drill to spin it.

I think the difference between markers in general (i.e. open bolt vs closed bolt vs pump, etc) would come down to how the markers are mounted, and velocity consistency.

lordkyleofearth 04-01-2014 02:43 PM

IMHO, I'd just post your data and test methods, maybe make a note that your data and the punkworks data do not align. Let the community peer review it. Hell, maybe your data is correct and theirs was flawed. In either case, I'm sure your data (even if flawed) has value to the community.

Cyco-Dude 04-01-2014 03:39 PM

Quote:

Originally Posted by uv_halo (Post 2930823)
However to be clear, rntlee never did tests that contradicted punkworks' data.

sure he did, in his bore vs accuracy testing. he showed a marked improvement using an overbore (he was using a flasc kit) whereas punkworks never saw anything conclusive, even with the flasc kit.

but i'd go along with lordkyleofearth and just get your tests wrapped up and posted. if you really think there is an error, hit up bryce and cockerpunk to go over your data and testing methods. i'm sure they wouldn't mind.

Whiskey Hammer 04-01-2014 06:44 PM

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.

240SX 04-07-2014 12:16 PM

Quote:

I own and have used with FSR:

BT Tracer
Hammer 7
MR5
Milsig Paradigm Pro
468
T9
TPX
How was the performance of the Hammer 7?

Whiskey Hammer 04-07-2014 05:49 PM

And... heres the rough cut of the data. Be sure to look at the below before you dive in.

In the first round, my process with the variables was to create a baseline using a speculative "most accurate" combination of factors and then test each factor one at a time, while the others remain constant with the baseline. In the second round, I wanted the test to be more "apples to apples" with the Punkworks test so that the two sets could be readily compared or used together. Hence the difference in variable schema between the first and second round.

The chrono in the first few groupings of the second test was malfunctioning due to a dying battery. Those cells have been highlighted in a darker orange. The battery was replaced, and the reading became more reasonable and consistent with previous testing.

The rigid variable test group in the second test suffered from a shifting POA every four shots due to operator error. The groups are seperated by dashed lines. I might artificaily center them later (or let someone with excel skills take care of it). Edit: I ran the numbers and unsurprisingly the more groups you break a population into, the more exaggerated the corrective effect of the mathematical centering.

Some quick notes on the variable terminology:
  • Rigid vs Free-Float: whether or not the barrel was braced against the edge of the firing bench/clamp to pretension the barrel and prevent flexing.
  • Unsorted/Ratioed vs Sorted: whether or not the ammo lot was sorted to size. If the ammo was unsorted it was still made to reflect the size ratios found in the Manufacturing Consistency phase of the test.
  • Untapped vs Tapped: whether or not an attempt was made to settle the paint into the nose of the round by a forcefull tapping.
  • Tipless vs Tip: whether or not the barrel had the factory tip during firing.


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