Need help predicting the FPS.
Posted 22 May 2013 - 03:08 PM
Posted 22 May 2013 - 05:00 PM
:edit it's tough to say really, what weight bb do you plan on using for chrono? Are you tuning for outdoors/cqb/max fps for plinking? Most LM4s i've seen shoot in the neighborhood of 380-390fps stock with 0.20g bbs. Throwing in the Dangerwerx valve (mp7 version) should drop you to around 300-320, putting in the tbb will pick it back up to 340-360 fps all with 0.20g ~ 1.13-1.7J Given power creep and moving up to 0.30g bbs, I'd expect you shooting around 300-310fps with 0.3g ~= 330s with 0.25g. However, I haven't taken into account how much a ra-tech full length tbb could raise your fps since i've cut mine down.
:edit2 to increase range and accuracy, look into the evoII/ksc hop up kit, introduced by boobiem4h. You really don't even need to mess with the fps if you're playing outdoors. However the evo kit may take some tweaking if you don't want to use heavier than 0.30g bbs
Edited by thatguyx, 22 May 2013 - 05:36 PM.
Posted 23 May 2013 - 05:04 AM
Posted 23 May 2013 - 05:56 AM
Anyways with less gas the barrel will have less of an increase in FPS as there will be less pressure and gas expanding. So as mentioned a TBB plus a DW MP7 valve will equal about 340fps with .20g bbs. Shaving the valve or buying the LM4 valve will get you around 350-360. You could also install a stronger rocket valve spring or stretch the OEM one to raise it a little more. Though the DW valve with how much it blocks the nozzle opening you can't really get the fps to high.
A good way to tune your FPS would be to cut the rocket valve spring. This will take some trial and error but you'll be able to get the fps down to where you like it if you take your time.
Posted 23 May 2013 - 10:05 AM
Ok I'll install the RA Tech TBB and the KWA lower power mp7 valve. I'll report back what happens.
Posted 28 June 2013 - 09:15 PM
Posted 12 July 2013 - 06:05 PM
Edited by Migwl300, 13 July 2013 - 06:59 AM.
Posted 12 July 2013 - 09:07 PM
is that a chart for GBBR's and your barrel length?
Posted 13 July 2013 - 04:43 AM
We had a discussion a couple of months ago that noted that GBB guns react much differently than AEGs to BB mass and barrel lengths. AEG charts are inaccurate in predicting muzzle velocity with GBBs. AEGs have a limited supply of propellent based on their cylinders while GBBs react much like cartridge guns as the gas expands until the BB clears the muzzle. Your predicion of 320fps with 0.20g BB based on 300fps with a 0.25g BB may be low (but probably well under 350fps).
I use the military/LEO "training bolt group" sold by KWA and on a typical day average 391fps with 0.32g BBs and my hopup settings (it'd be faster with the hopup off). Muzzle energy is 2.28j. CQB energy level limit is 1.0j which works out to 100mps muzzle velocity with a 0.20 BB. The 350fps limit of most CQB venues is just over 328fps (100mps) and the BB's velocity drops quickly. Minimum engagemet ranges assure the BB is under 1.0j at impact. Standardizing testing with 0.20g BBs allows airsoft venues to avoid a bunch of math.
Posted 13 July 2013 - 06:44 AM
Posted 13 July 2013 - 06:57 AM
Posted 13 July 2013 - 12:54 PM
Posted 13 July 2013 - 02:46 PM
Oh, and Niko got 477-480 w/.2 at 78 degrees.
I'm liking this bolt!
Posted 13 July 2013 - 03:59 PM
My gun is otherwise functionally stock although it has a Magpul stock and railed handguard to mimic my "duty" LWRC M6 carbine.
The velocity helps in my opinon although most of my shooting is against scaled targets (9" silhouettes) mixed with full scale targets out to 50 feet or so. Used in training courses mainly for demonstration purposes as well.
I've not taken the bolt carrier apart so have no idea what modifications KWA did to get the muzzle velocity up.
Edited by Chuck S, 13 July 2013 - 03:59 PM.
Posted 20 July 2013 - 08:41 PM
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