renegadecow Posted June 19, 2013 Report Share Posted June 19, 2013 Kinda bummed. I wanted a teeny tiny bit more power out of my XP-100. As it was, it was doing 1.5J around 328fps using .30g bbs with the stock JG spring and spring guide. From what I read the JG spring is about the equivalent of an M115 and I wanted maybe 30-40fps more. Instead of going for a spring guide spacer I went and bought a King Arms M130 which was rated to about 380-420fps. When I put it in it did a mere 1.3J; 308fps using .30g bbs about as much as an M110! My air seal is great with only barrel length being on the short side and the pull weight on the bolt really was significantly lighter than the stock JG spring so there's something amiss with King Arms. Frustrated from that, I made an aluminum spring spacer about 3/4" long and got me to the desired 1.8J. Link to post Share on other sites
Hessel Posted June 21, 2013 Report Share Posted June 21, 2013 On the subject of tightbore barrels: I know there is not much difference in accuracy between a 303 and a 343 mm barrel, but what about the noise? The 303 barrel will take full advantage of the suppressor, but the 343 will have more room for the gas to expand, but will not use the full suppressor (?)...... Anybody has experiences with this? I really love how quiet the G-spec is and want to keep it this way! Link to post Share on other sites
Rogue Posted July 6, 2013 Report Share Posted July 6, 2013 Just completed renegadecow's internal TDC modifcation. Hop has improved tremendously, and the flight path is much MUCH more consistent than before. Thanks a heap!! http://www.youtube.com/watch?v=kNgSOgVG0SU Link to post Share on other sites
Hatchet Posted July 6, 2013 Report Share Posted July 6, 2013 Weirdly I saw this video/thread somewhere else as I was looking at that whole barrel/cylinder volume matching thing (for about 3 hours...).I had a look but there were a couple of things that weren't immediately obvious to me. First, do you need a tapping set for this install? Second, what's preventing the movement of the hop arm? Edited to add - Ah right, hop arm movement limited by outer barrel - position of screw stays the same relative to the OB, but due to the threading on the hop arm different hop is achieved? Link to post Share on other sites
renegadecow Posted July 6, 2013 Report Share Posted July 6, 2013 Yes. Keep in mind the adjustment will be reversed from conventional thought. Turning the screw CW (assuming it's a CW screw) will have the hop arm move up therefore apply less hop. You don't necessarily need a tap as the abs plastic of the stock hop arm is soft enough to force thread. Maybe if you use a metal arm or use a harder material instead of a chunk of abs to fill the gap in between would you need a tap. Link to post Share on other sites
Hatchet Posted July 6, 2013 Report Share Posted July 6, 2013 Right. Thanks for that. I'm uncertain if I'm going to mod it at the moment, because I'm using one of the Eagle6 hop bars which doesn't seem to suffer from the hook shot, and is pretty tight so I think it's less susceptible to movement, but I may tackle it in the future. Link to post Share on other sites
Rogue Posted July 7, 2013 Report Share Posted July 7, 2013 I had a dangerwerx hop arm in beforehand (same as an eagle hop arm really) and i must say that my consistency shot per shot has NOTICEABLY increased, especially at 70m. We simply screwed a small hole into the hop arm (a little smaller than the screw) and then forced the screw in. The plastic gives way before the screw does, and it's tight enough to not let the screw move at all. Link to post Share on other sites
renegadecow Posted July 7, 2013 Report Share Posted July 7, 2013 I hadn't thought of it before, since Dangerwerx is already making hop arms as it is, making a pre-installed TDC version would probably sell a lot assuming he isn't making them already. I'll hit him a PM. Link to post Share on other sites
Hatchet Posted July 7, 2013 Report Share Posted July 7, 2013 Cheers Rogue. I'll have to give that some thought. The only downside is every time I mod the gun I usually make things worse somehow... Anyway, game day today, time to see how the latest round of tweaks have affected it. Link to post Share on other sites
Hatchet Posted July 11, 2013 Report Share Posted July 11, 2013 As I've been failing so far to find a thin wall (0.02mm) tube to make blow-by ring/shroud out of (any suggestions gratefully received) I decided to mess about with compression related stuff instead. Specifically, I thought I'd take a look at the piston o-ring and see if any improvements could be made. Currently I use a BS115 as it seems to work ok, but there's always a chance to do better. Thus at great expense (who knew o-rings cost so much!) I bought a selection of different rings to try out. The test rig was my vsr gspec. 430mm 6.01 PDI barrelPSS2 cylinder/cylinder head/pistonMarui improved (black) hop unit with Firefly hop, Eagle 6 hop arm. No teflon mods, etc, just standard.PSS10 150 spring Chrono'd on a Combro, each o-ring was greased with Systema cylinder grease before use. Excel 0.2g ammo. Hop was on, low setting and stayed the same for each shot. O ring Inner Diameter (mm) Cross Section (mm) Outer Diameter (mm) Shot 1 Shot 2 Shot 3 Shot 4 Shot 5 Shot 6 Shot 7 Shot 8 Shot 9 Shot 10 Average DifferenceRing A 16.6 2.4 21.4 FAIL FAIL FAIL FAIL FAIL FAIL FAIL FAIL FAIL FAIL N/A N/ARing C 17 2.5 22 300 262 FAIL FAIL FAIL FAIL FAIL FAIL FAIL FAIL N/A N/ARing B 17.5 2.4 22.3 430 433 435 435 436 432 429 428 430 430 431.8 8 BS115 17.2 2.62 22.36 442 445 445 446 444 448 445 439 445 441 444 9 Ring D 17.6 2.4 22.4 439 440 438 443 440 438 434 434 439 438 438.3 9 BS810 17.46 2.62 22.7 411 409 406 414 408 413 414 408 411 414 410.8 8 BS617 17.86 2.62 23.1 401 402 404 397 402 405 404 405 410 407 403.7 13 Sorry if the formatting's a bit off, haven't quite mastered that yet. So, the result of all that was... I've just wasted about £30 (yes, really). I've sorted this by outer diameter to make the results more obvious. There is a ring I haven't tried that has OD of 22.33, but my guess is this would average about 435/440. The first two rings were failures due to no compression at all. Clearly, for this particular setup, the BS115 is the best option. That said, if you're using a different combo, or you actually want to drop a few fps without cutting springs to get power under your site chrono then it might be worth trying one of the near diameter rings. My guess is that the slightly smaller allows more air to escape and thus loses fps and the slightly larger increases friction to the same effect. In which case you'd be better off choosing the smaller of the two (the larger might wear down over time otherwise). In conclusion - BS115 for the win. If you're in the South East and go to Combat South/Battle Lakes/Thunder Ranch and need one, let me know. I have about 30 spare... Link to post Share on other sites
Hatchet Posted July 23, 2013 Report Share Posted July 23, 2013 Some more messing about today, this time looking at cylinder/barrel compression matching.Firstly, a few calculations: Mod AB Mod UnmodifiedCylinder head 5.5 5.5 5.5Airbrake 12.5 0 0Compression Zone 91.5 91.5 98.79True Compression zone. 73.5 86 93.29This shows the inner dimensions of my unmodified laylax teflon cylinder, the modified version (vent underneath extended a bit) and the modified version with the airbrake fitted.The info I read suggested if you have an airbrake you just subtract that length, which I have done (more on that later)Using this, we can then work out the various volumes, as I'm sure you all remember it's pi r2 by length. Diameter Pi Length Volumecylinder volume 22.3 3.141592654 86 33589.07613cylinder volume - AB 22.3 3.141592654 73.5 28706.94297303mm 6.08 Barrel 6.08 3.141592654 303 8797.102828430mm 6.08 Barrel 6.08 3.141592654 430 12484.33735500mm 6.08 Barrel 6.08 3.141592654 500 14516.67133430mm 6.01 Barrel 6.01 3.141592654 430 12198.52389Then, dividing one by the other, we get the compression ratios as follows:Barrel Length 303(6.08) 430(6.08) 500(6.08) 430 (6.01)Compression ratio 3.818197512 2.690497316 2.313827692 2.75353612Compression ratio - AB 3.263226943 2.29943666 1.977515528 2.353312847Note quite a difference in ratio between different barrel lengths, but not nearly as much between tighter barrels of the same length. Also note that, in theory, the 500mm barrel without airbrake has roughly the same ratio as the 430mm barrel with airbrake, so you'd expect to see similar numbers on the chrono.Let's have a look at those numbers (all with a 0.2gbb)Barrel 303mm 430mm 500mm 303mm 430mm 500mmSpring Size SPR-150 SPR-150 SPR-150 SPR-170 SPR-170 SPR-170Without airbrake 400 425 425 500 552 550With airbrake 400 415 400 400 400 380 And also with .4s to check for any differences there. 303mm 6.08 barrel, 170 spring, .4g - 381430mm 6.08 barrel, 170 spring, .4g - 395500mm 6.08 barrel, 170 spring, .4g - 395 So no, this tallies up with the max numbers for .2s From experience I'd say add approx 20fps on for the 6.01 barrel.Not necessarily what you'd expect from the ratios on their own. On the 150 spring the airbrake gives a relatively small fps reduction, but as we scale up to the 170 spring, this increases to a massive reduction in fps, between 100 and 170 fps lost. It's possible on an unmodified cylinder we'd see even bigger numbers. Certainly I'd expect the 500mm barrel to give us a higher fps, maybe up in the 580 range with a 170.It's been suggested that 2.4:1 is a good ratio, but as we can see that's not the only factor at play.It would seem to suggest that there's a bit more reduction that can be done on the cylinder to optimise it for a 303 barrel. That said it needs to be optimised bearing in mind the bore, spring and weight of ammo being used. And if you do modify it you won't be able to get the full power out with a longer barrel. I may modify it aiming for 425 on the 303mm and then rechrono with the longer barrels to see if their numbers have dropped. Link to post Share on other sites
creepingfear Posted July 23, 2013 Report Share Posted July 23, 2013 I remember first reading your Tea and Medals back in '06. You must be getting on a bit now, surely? Link to post Share on other sites
renegadecow Posted July 24, 2013 Report Share Posted July 24, 2013 I used a section off .40S&W PMC brass. Many use 9x19mm, but I find it too tight. The way I made it is it's shaped into a "C", has a space to accommodate the tab on the hop rubber so I don't have to cut it. Link to post Share on other sites
Hatchet Posted July 24, 2013 Report Share Posted July 24, 2013 I remember first reading your Tea and Medals back in '06. You must be getting on a bit now, surely? Not so you'd notice. I put this down to refusing to grow up. That and having a really old looking portrait in the attic... I used a section off .40S&W PMC brass. Many use 9x19mm, but I find it too tight. The way I made it is it's shaped into a "C", has a space to accommodate the tab on the hop rubber so I don't have to cut it. Yes, I picked up some .40 S&W too. Took a bit of filing to get it just right. I still have yet to chrono with it installed. Might give that a try today. I cut about a third of the tab on the hop rubber because I felt that cutting the brass into a C might allow flexing and defeat the point of putting it there in the first place. I may be wrong of course. Link to post Share on other sites
renegadecow Posted July 24, 2013 Report Share Posted July 24, 2013 I don't think it does or at least it doesn't show with mine. The way I see it is it's necessary to have an uninterrupted ring if the hop rubber were unsupported like how they show it on Youtube vids (out of the hop chamber, showing the rings) but with the hop chamber on the ring doesn't really have any place to flex out of and retains a good tight seal. Link to post Share on other sites
scorch Posted July 24, 2013 Report Share Posted July 24, 2013 Do these rings do the same thing as whipping the hop rubber? Because I've already done that, and it has been sealed to the barrel with clear nail varnish too. Link to post Share on other sites
renegadecow Posted July 24, 2013 Report Share Posted July 24, 2013 Yes, but it's more for the seal between the hop rubber and the loading nozzle. edit: Link to post Share on other sites
scorch Posted July 24, 2013 Report Share Posted July 24, 2013 My nozzle is already bulked out with heat shrink to make it a nice tight fit. It's also very slightly overlapped on the end without interfering with the path of the air so that there is no metal-to-BB contact. Might look into this next time my hop rubber needs replacing. (It's working like a dream right now so I'm not gonna rock the boat) Link to post Share on other sites
ltolstoy Posted July 26, 2013 Report Share Posted July 26, 2013 anybody know how i could attach my g spec to my back? some type of shotgun scabbard maybe? as when im over run id like to mount it on my back and use both my mk23s Link to post Share on other sites
ltolstoy Posted July 27, 2013 Report Share Posted July 27, 2013 anybody know how i could attach my g spec to my back? some type of shotgun scabbard maybe? as when im over run id like to mount it on my back and use both my mk23s (dont have mk23s yet but definitely be purchasing one this year!! Link to post Share on other sites
renegadecow Posted July 27, 2013 Report Share Posted July 27, 2013 Backpack sling: http://www.cabelas.com/product/GrovTec-Backpack-Sling/1317825.uts Link to post Share on other sites
Hatchet Posted July 27, 2013 Report Share Posted July 27, 2013 Or a normal sling. The issue with backpack (or biathalon) slings is that they work an awful lot better on rifles with side sling points like the L96. This is because the rifle sits flat against your back. With them on the bottom, like a vsr, it sits uncomfortably and swings left and right. Here's an old picture to illustrate (sling is in black, the green is a chest rig) Link to post Share on other sites
ltolstoy Posted July 27, 2013 Report Share Posted July 27, 2013 Or a normal sling. The issue with backpack (or biathalon) slings is that they work an awful lot better on rifles with side sling points like the L96. This is because the rifle sits flat against your back. With them on the bottom, like a vsr, it sits uncomfortably and swings left and right. Here's an old picture to illustrate (sling is in black, the green is a chest rig) auscam.jpg I understand what your saying. What else do you suggest? Link to post Share on other sites
ltolstoy Posted July 27, 2013 Report Share Posted July 27, 2013 Backpack sling: http://www.cabelas.com/product/GrovTec-Backpack-Sling/1317825.uts probably being asked this a few times before but what would you guys recommend brand and type upgrade wise with a £4-500 budget for upgrades? 1) Z trigger is a must but which brand? taking into account the cyclinder sets as you would have to stick with same brand (pdi/laylax/aspuk?) 2) Stay with original TM hop unit or can you achieve more with the PDI or laylax equivalent? 3) Original Gspec inner or swap to a pdi 6.01 430mm? sorry for the questions but i want to upgrade once as i cannot afford to test out different hop units and 90 triggers hehe (barrels fair enough) rubbers ect not taken into account as i can find that out with testing at the moment my g spec is stock and i plan to upgrade before winter sets in Link to post Share on other sites
scorch Posted July 28, 2013 Report Share Posted July 28, 2013 Stick with the original hop unit, anything else is a downgrade in my opinion. Link to post Share on other sites
Recommended Posts
Archived
This topic is now archived and is closed to further replies.