H/L Inner airsoft barrel question

[Mad Fox]

to be honest I wouldnt know where to start or what to do if I was messing around with the airsoft unit.

I dunno if I need to upgrade the tank to an IR system to join in the tank meets for the battles, and if so Im thinking to make room for the IR system I might end up loosing the airsoft bit,

[Tankie]

I read somewhere that the hole was a function of the hop up - the air being sucked into the hole as the BB goes past causes the BB to spin, and a spinning ball has more range.  Not being a physicist means I can't defend this statement but it sounded plausible to me.

[NigelDerEnglander]

Hi folks,

Well, I got a physics degree 20+ years ago and haven't really used it since and have forgotten everything....However, back almost 4 years ago and knowing nothing about airsoft units I tried to up the power of the HL units. I had a load of reject HL Tigers/Pantigers to repair and they varied from 'plop out the end' to 'hurters'. This is when you put your hand in front of the cannon, fire, and go "bl00dy hell, that hurts".

I assumed the hole must be the hop-up or a power limiting feature so blocked it up. The pellets just 'plopped out'. As Crispy says, the piston cant fill the HL barrel and so sucks the pellet back, slowing it down. The angular position of the barrel varied quite a lot, so either the hole is not a hop-up, or the China girls haven't been told the correct way to put it in. ( Let me show you, dear.....)

I got a drilled out aluminium tube from a German PanzerKetten member and tried various lengths. Only the short ones (~130mm if I remember rightly) worked satisfactorily.

The best I have had so far was the PzIII. With its short, aluminium barrel it shot as a "hurter" from the start. No air hole.

I've since tuned-up a few guns and most of mine are now "hurters". The very best go beyond this and are "not doing that again-ers". This is when it _really_ hurts leaving a tender palm for many minutes.

My mods (from experience and a few things read on RCU) are:

1. Fill both halves of airsoft unit around the breech section with two-part epoxy putty to hold the breech rigid.
2. Use metal shim so that the airsoft barrel is _just_ a tight fit in the breech. Be very careful as the breech is brittle and the slightest interference fit will split it. Hence the epoxy of part 1.
3. The rubber gasket varies according to HL production availability. After I had taken several units apart I found a thinner- and a thicker-walled gasket. Only by having a few to compare can you tell which you have. The thicker one gives better results and jams less as it resists being pulled and distorted into the barrel more than the thinner one.
4. With the shim the barrel should butt cleanly up against the slight ridge inside the breech. It is best to ensure it is as (machined) flat as possible. Not having machining facilities this is not easy. But when it is flat, the rubber gasket will sit flat against it and resist distorting and jamming the unit.
5. I drill out the breech-loader pipe of the air cylinder a bit to reduce throttling of the air-flow. 0.5 to 1mm diameter seems safe. I have gone further but then the breech loader and the chamfered air-seal works less well.
6. I take the spring out and stretch it a little. But only a little. Any more and it seems to lose its cylindricality which would lead to bulging at the sides under compression and possible binding on the walls.
7. From a washer set I put a few washers in the piston barrel end that the spring presses against. This is to increase the momentum of the piston once on the move (I hope!)
8. I shorten the small spring that pushes the breech-loader cylinder back against the BB. This is to ensure the breech has come to a stop against the breech end before the piston begins its compression stroke.

Well, that's it.

I have no real evidence as to how much this improves things, but just a week ago I modded a pathetic airsoft gun that an air-gun shooting friend had. The mechanism was slightly different, but I could carry out points 5/6/7/8. This gun had a proper hop-up too.

As an experiment on a windless day I pointed the gun up vertically and fired a pellet up and then compared it against my PzIII and Pershing, both "not doing that again-ers".

The experiment was to fire the pellet and count how long it took to hit the ground again.
Without hop-up, the pellet from the gun took 6s to return to earth.
With hop-up the pellet from the gun took 5s to return to earth.
Both PzIII and Pershing pellets took just over 4s to return to earth.

My friend had a velocity measuring device so when I saw him we measured the gun's muzzle velocity. It was a shade over 100fps. I had no tanks with me so I couldn't test them.

The device he had fitted on the end of a barrel and he claimed it cost ~£40. It had an LCD display and could also be connected to a PC for logging purposes. I must say I was tempted to get one as another 'gadget' in the armoury.


Regards,

Nige

[afv]

I thought about putting jb weld around the breach, it might stop what happened in the photo but the airsoft unit would never be able to come apart again if needed

regards  Jack.

[NigelDerEnglander]

Hi Jack,

Some of mine have been in that state.
Perhaps I didn't clarify what I wrote earlier.

Superglue the broken breech together. Or better still, use an undamaged one to perform the following procedure, but use the broken-superglued one at the end.

Put some of that two part plumbers putty-style epoxy _in each half separately one at a time_ using the breech as an impression mould.
As it begins to harden add/trim away the epoxy so the breech lies perfectly in the one half of the airsoft case. As you put it in and out you will find the impression becomes less tacky and eventually it hardens to the shape of the breech. Make sure you don't glue the breech in! After/during hardening, trim off any excess so there is no projection from the mould.

Do the same on the other half.

You should now have two halves with epoxy putty fully supporting the breech.

Test-fit the breech and the two airsoft case halves. Trim off any excess or fill up any gaps.

Ta-da.

The breech now has nowhere else to 'break into' and as long as you are fairly gentle putting your airsoft barrel in, it will survive to fight another day!

Using a soldering iron to 'weld' the breech bits together on the outside is also possible once the superglue is holding it in the correct shape.

As earlier, skill and patience are required. But it is do-able.

Nige

[afv]

Thanks Nige, i think i've got it, i call the breach the bit thats smashed so i need to pack out between that and the casing

regards  Jack.

[Saxondog]

Creeping Death has a spec.sheet on the TAMIYA TIGER BARREL,I just received it Saturday.I requested this information and they provided it.I will post after machine work so I know it is accurate.Just give me a week or so,if needed sooner contact CREEPING DEATH.

[afv]

Thanks to Nigelderenglander for the tip, i think i've managed it

repaired the breach
greased it and the inside of the gun casing with silicone grease
used milliput to make the mould, just waiting for it to go off now and see if it pops out of the casing

regards  Jack.

[NigelDerEnglander]

Hi Jack,

Don't thank me yet! You haven't used it successfully yet!!
:-\
Sorry, I had intended taking some pictures similar to yours, but hadn't got round to it as my 'box room workshop' is still not back in action after taking everything out to put a laminate floor down.

Anyway, you've done pretty well exactly as specified, other than that I carry on the epoxy back to the end of the breech. Just to be sure.

Hope it works.

Oh, I recommend following the cracks in the breech on the outside with the tip of a soldering iron (careful!) then doing lines perpendicular to the cracks with the soldering iron to increase the area of contact of the heat-weld. Then use the side of the tip to flatten off the ridges this creates.

Sounds difficult, but once you're into the swing it's a pleasurable few minutes only to do it.


Nige