Airsoft Canada - View Single Post - A new HPA system for the KJW M700

MadMax · January 8th, 2007, 14:52

Truth is that the KJW M700 can already exceed most field and even minimum firearms limits:

http://www.airsoftcanada.com/showthr...&highlight=kjw

A consistent regulated HPA setup could go far in improving shot to shot consistency (reducing cooldown related varation), but the stock M700 is already capable of becoming too powerful to field if one cranks up the adjustable bolt. I did not mess with my bolt before doing my FPS measurements. Tests were done on a factory built gun.

Unfortunately the M700 does not have a particularly consistent hop up design. For all of it's capacity for power, it does not translate into surprising accuracy. It also has a design flaw in the magazine design. The metal retention fingers at the top of the magazine often scratches the pellets as they are pushed into the breech by the bolt. This can result in bizzarre flyers. I have attempted to circumvent this issue by hand loading pellets into the breech so they don't get cut by the mag fingers. While the very crazy flyers are prevented, the net accuracy still isn't very impressive. I suspect that there may be an inconsistency in the way the hammer pin opens the magazine valve. It's also possible that the outlet port on the magazine does not provide a consistent seal against the bolt contributing to muzzle velocity variation.

WARNING: Do not exceed 160psi outlet pressure on your HPA rig. Even at 120psi, the KJW M700 can exceed minimum firearms limits (500fps AND 5.7J) with heavy rounds. However, it is doubtful that the cast metal magazines are carefully engineered to proof pressure standards. The metals used in airsoft often fail in brittle modes and are not particularly well suited to high pressure applications. If you insist on very high pressure use, you should proof test your system with your magazine and lines filled with incompressible liquid such as silicone oil or water. This is called hydrostatic testing. Proof your system to at least 3 times expected operating pressure. Do not proof test with gas filling your suspected pressure vessel as a ruptured vessel filled with high pressure gas fails VERY energetically. A vessel failing with an incompressible liquid fails rather benignly as the contents do not have a very high potential energy (like freezing water bursting a pipe), but expanding gas can propel shrapnel. If you are not directly experienced in hydrostatic testing you may not understand the hazards of it. Take your setup to a scuba shop which offers hydrostatic testing. They are used to testing very high energy pressure vessels.

January 8th, 2007, 14:52	#2
MadMax Delierious Designer of Dastardly Detonations Trader rating Join Date: Dec 2001 Location: in the dark recesses of some metal chip filled machine shop	Truth is that the KJW M700 can already exceed most field and even minimum firearms limits: http://www.airsoftcanada.com/showthr...&highlight=kjw A consistent regulated HPA setup could go far in improving shot to shot consistency (reducing cooldown related varation), but the stock M700 is already capable of becoming too powerful to field if one cranks up the adjustable bolt. I did not mess with my bolt before doing my FPS measurements. Tests were done on a factory built gun. Unfortunately the M700 does not have a particularly consistent hop up design. For all of it's capacity for power, it does not translate into surprising accuracy. It also has a design flaw in the magazine design. The metal retention fingers at the top of the magazine often scratches the pellets as they are pushed into the breech by the bolt. This can result in bizzarre flyers. I have attempted to circumvent this issue by hand loading pellets into the breech so they don't get cut by the mag fingers. While the very crazy flyers are prevented, the net accuracy still isn't very impressive. I suspect that there may be an inconsistency in the way the hammer pin opens the magazine valve. It's also possible that the outlet port on the magazine does not provide a consistent seal against the bolt contributing to muzzle velocity variation. WARNING: Do not exceed 160psi outlet pressure on your HPA rig. Even at 120psi, the KJW M700 can exceed minimum firearms limits (500fps AND 5.7J) with heavy rounds. However, it is doubtful that the cast metal magazines are carefully engineered to proof pressure standards. The metals used in airsoft often fail in brittle modes and are not particularly well suited to high pressure applications. If you insist on very high pressure use, you should proof test your system with your magazine and lines filled with incompressible liquid such as silicone oil or water. This is called hydrostatic testing. Proof your system to at least 3 times expected operating pressure. Do not proof test with gas filling your suspected pressure vessel as a ruptured vessel filled with high pressure gas fails VERY energetically. A vessel failing with an incompressible liquid fails rather benignly as the contents do not have a very high potential energy (like freezing water bursting a pipe), but expanding gas can propel shrapnel. If you are not directly experienced in hydrostatic testing you may not understand the hazards of it. Take your setup to a scuba shop which offers hydrostatic testing. They are used to testing very high energy pressure vessels. __________________ Want nearly free GBB gas? Last edited by MadMax; January 8th, 2007 at 15:03..