Airsoft Sniper Forum banner
1 - 20 of 29 Posts

·
Registered
Joined
·
1,045 Posts
Discussion Starter · #1 ·
Ok the mission brief is a 2 day game in some open woodland. The field FPS limit is 350 with .20s for absolutely everything
. Now I don't own a gun that is this low in FPS, even here in England where 328 +/- 10% is absolute max for an AEG. All my rifles are between 400 and 500FPS semi auto and bolty. So I had to buy :'( or make
one ;).

I had this floating round the garage and only ever used it twice because it kept locking up on semi only


Original spec Dboys SPR Mk12 Mod0 (400fps) Locked to semi only so as it was usable in this country

I wanted this rifle to be reasonably quiet when fired as I am expecting to be alot closer to the enemy than I'm used to and also my experience of sites that limit their FPS to 328/350 have a large amount of players that wont accept a hit unless it happens more than once or they see where it came from, pretty bloody useless if your a sniper using a bolt action ;), so a quick follow on shot had to be there as well :).

To achieve this I striped and cleaned the gearbox, Incidental I changed the gearbox shell for a TM one I had floating about as the Dboys 1 had cracked badly at the front.

I then made an Air braked piston head





The last pic shows version 1 but was found to be to short version 2 is now about an 1" long and covered in heat shrink tube to better fill the nozzle tube and be more effective. The foam on the back of the cylinder head is not really necessary but dampens the noise even further and also helps with the Angle Of Engagement on the piston (AOE)
The AOE was adjusted by adding spacers/washers between the piston and piston head so as the primary teeth of the sector gear and the piston are maximized at first contact, this normally means the removal of the second and about half the third teeth though so that you don't get pre-engagement.
Heres a pic to better describe whats going on


Bare in mind that in the photo the piston is sitting hard against the cylinder head and the sector gear is in the actual position it will be in on first engagement, the tooth to tooth surface area has been maximized thus reducing the chance of a stripped piston to virtually nil

Note also the sector gear has 2 teeth removed to shorten the overall stroke thus reducing windup time and therefore noise of the motor, there is a down side to this in that it deduces the FPS of the weapon due to not giving the piston its full stroke.
Next was to eliminate spring rattle. This was done on the spring so that just inside the end of the piston the spring is retained with no space to allow it to rattle when the compression is released and on the spring guide for the same reason. All I did was wrap Insulation tape round the spring so it is an interference fit in the piston and smear it in grease and the same on the spring guide.


After shimming and greasing everything I reassembled the gearbox and then set about covering all the holes in it that weren't used with self adhesive foil tape. This helps to eliminate sound transference and whistling of fast moving air and reduce the 'echo box' effect by containing the sound to one area


With the gearbox done it was time to do the barrel and hop. For this part of the build I wanted to experiment with some stuff and try out a couple of theories I had heard about :-/. I have read that all you need for good accuracy is a good stable hop and a stable straight and highly polished barrel, not necessarily a tight bore either ;) For this project I used a 509mm 6.08 brass barrel out of a TM M16. and I cleaned it and then polished the life out of it :) Heres a pic of the products I used, some guys in the US use real steel cleaning and polishing compounds, but here in the UK we are gun free so make do and mend is the way forward ;)


Next the hop unit. An all metal TM unit was used in conjunction with a standard TM hop rubber, if this turns out to be poop I will try a Guarder Black. The biggest difference here is in the nub. Technically it hasn't got one. I have been thinking about getting one of these H nub doohickeys having read up on the whys and wherefores fore and against them, and the theory is to limit the amount of pressurized contact on the BB to 2 main points and to stabilize the flight path. Now I was thinking 'what if' and came up with this



Poor photos I know but you may just get the idea ;) It basically halves the H into more of an I. Care needs to be taken when sticking the piece of plastic to the arm, I used a section of sprue from a model kit, to make sure it is absolutely perfectly centre. The theory, if the only pressurized contact with the BB is directly on the top in the middle the is only one way it can go and it will be the same everytime, all the time, where as with the H nub there is two points, twice as likely for it to put uneven amounts of spin, remote I know, but still possible ;) I then shimmed either side of the arm in the hop unit to prevent it leaning from side to side when in use then fitted the barrel with the usual Teflon tape, sheep shit and good will


The gun was then re-assembled and the flash hider changed to 1 off my mates M4 so I could fit a QD suppressor to the end. As luck would have it we are not restricted here and are able to have functioning suppressors so its full of foam and baffles to deaden muzzle pop even further

A Crane Stock was also fitted to eliminate the boxy noise that a solid stock gives when the weapon is fired, I know I could of stuffed the space round the battery full of foam but I also use this weapon with a different top reciever as my FIBUA/FISH weapon and it just looks better that way :)
The scope was chosen because its a) Mil dot and not 30/30 like my spare scope b) small, and c) its x2 to x6 with a good Field of view, so I thought ideal if the enemy are going to be all up close and personal


The finished article minus gun rag, just need to touch up the paint on the scope and barrel now ::)




Initial test indicate that the motor whine is the loudest noise, but I have yet to fiddle with the motor height so that can be reduced a little. Gearbox noise and muzzle pop are near inaudible under the motor whine but is still there as a dull thump now rather than a loud crack. The other major advantage to the air brake mod is that it will virtually eliminate the problem of the gearbox shell ever cracking at the front again because of the cushioning effect it gives
The power of it is 340 average over a 10 shot string using .20s.

I'm quite happy over all with this project and think I have achieved what I set out to do, ie. make a quiet weapon. The true test will come when I get to skirmish it and test to see if the hop mod actually works or is just destined for the scrap heap....


VA
 

·
Registered
Joined
·
1,011 Posts
Vindicare.. I don't know how you get so good with these weapons of destruction.. But if you ever wanted to go in the business of selling your works of art, I'm but a PM away.

Onto the topic at hand, from the artistic point of view, I give this rifle a 9/10, simply because that paintjob is amazing, and makes the rifle look like you seriously threw some time into it, however... Me being the 3D man that I am, would like to see some elastic bands thrown onto the outer barrel and scope, simply to allow for addition of natural vegation, however I trust that you already do this when you go in the field, judging by your last few pictures I've seen.

About the gearbox work, I'm not really much of a guru in that aspect, more or less I give my rifle to a friend on my team that makes a small income out of doing it, and have him throw the bits and pieces together, perhaps I'll show him this and see what we can't do with my rifle to help make it better. But with you being within FPS regs with that sucker, I'd love to see what sort of damage you can do on the field. In my opinion you should make a Youtube video of you shooting the thing, with the camera at several distances, so we can hear exactly how much of an improvement it's made.

-Mosin
 

·
Registered
Joined
·
1,045 Posts
Discussion Starter · #3 ·
Cheers mate, should I sell any of my creations a PM will be sent ;)

Re rubber bands, if you look reeeeeeal close at the suppresor you'll see 1 at either end, they're black bands made from bicycle inner tube


Youtube video? I might be a bit of a wizz with Airsoft weapons and I can just manage to post pics in an internet forum but that as far as my tech knowlege goes :-[ but I'll see if I can work something out ;)
 

·
Registered
Joined
·
100 Posts
Thanks for the guide! I'm rebuilding my TM M4 right now. I'm definitely modding my piston as you did. I have a quick question though, I have been timing my gears as they do in the MB.com videos, I was wondering if you need to time it like you did in the picture since the over all length of the piston is larger? And what would happen if I cut the piston to the normal length of a V2 piston? I'm assuming it would do the same thing as short stroking it?

Great guide/gun! I to want to hear the noise report of the gun, maybe like a side by side of another gun without the mods.

sticks
 

·
Registered
Joined
·
1,045 Posts
Discussion Starter · #5 ·
Don't what ever you do cut the piston, the AOE is important as it brings the largest amount of surface area together. If you just follow the instructions/pics you should be fine ;) To shrort stroke it all you do is remove teeth off the sector gear and piston, the sector gear in the pic abouve is short stroked by 2 teeth IIRC. As for timing, just set the gears, reassemble the gear box and fir it, the gearbox will self time itself :) without getting to technical its all to do with being mechanical not electrical.
For more tips have a look in 2echo's post about quietening his AR I've put extra info in there regarding this subject ;)
 

·
Registered
Joined
·
66 Posts
this is my spr!
i've broke my stock, and there is a G36c spring in it

but im going to use this baby, only on private skirms, because im going to get a 550fps upgrade set for this baby!
( with .25 )
love the VERY long range babys! ;)
** I KNOW ITS TO HARD, BUT READ AGAIN, ONLY PRIVATE SKIRMS! **



 

·
Registered
Joined
·
1,045 Posts
Discussion Starter · #9 ·
Hate to say it mate but the front end of your gearbox case isn't going to last long at that fps :-/ Mine was cracked after only about 600 rounds at 400fps, so your planed upgrade will be lucky to see 450/500 before the same happens :(
 

·
Registered
Joined
·
1,045 Posts
Discussion Starter · #11 ·
No chance! my mate fitted a 1Joule one to his M4 last night, did his chrono test this morning, went to set his hop, fired approximatly a dozen shots, and wizzzzzzz...... The entire back end of the piston from tooth 2 up to the side runners had snapped off
Over rated sh1te if you ask me ;)
 

·
Premium Member
Joined
·
802 Posts
patriot, this is your first warning due to continous grammar mistakes in your posts. Please refer to our forum rules and clean up your posting. =) Rules are present for everybodys gain not to restrict.
 

·
Premium Member
Joined
·
716 Posts
Aside from the crap red Systema polycarb pistons, their complete gearboxes are very nice.

vindicareassassin said:
No chance! my mate fitted a 1Joule one to his M4 last night, did his chrono test this morning, went to set his hop, fired approximatly a dozen shots, and wizzzzzzz...... The entire back end of the piston from tooth 2 up to the side runners had snapped off
Over rated sh1te if you ask me ;)
 

·
Premium Member
Joined
·
716 Posts
Very true, but I can also say I've had one of the red pistons strip out in fewer rounds. It's been a known problem for quite some time with that particular piston. Have him get a G&P, Madbull, Prometheus piston, and he should be good for quite some time.

vindicareassassin said:
[quote="Dutton":57qp0gko]Aside from the crap red Systema polycarb pistons, their complete gearboxes are very nice.
You would still expect it to last longer than 30/35 rounds though, especialy considering he forked out
 

·
Registered
Joined
·
1,045 Posts
Discussion Starter · #18 ·
Do you actualy do any airsoft snipeing :-/ I can only say that trying to hold the rifle in a steady firing position, for anywhere from 20 minutes to about a 1.5 hours with out the aid of a bi-pod is bloody knackering, I know, because I never had 1 on my VSR or M14 until very recently, that was when I was younger and more eager (read stupid) and use to use bits of twigg/branchs etc. etc. Now I'm old and wise and dont do anything I dont have to, so a bi-pod I now own ;)
 

·
Registered
Joined
·
100 Posts
m24dave said:
IMO lose the bipod, bipods are made to shoot 400 meters, airsoft.....400 meters....hmmm... well anywho still a very nice gun i dont run a harris on my ptw dmr.
No offense but you cannot equate airsoft to real steel. It just doesn't work that way. Besides if you are only supposed to use a Bi-Pod at 400M then why do you see alot of bi-pods on Remy 10-22's? Because the whole purpose of a Bi-Pod is to make a more stable firing platform.

Plus after a long day at an OP a Bi-Pod really helps your arms out :).

sticks
 

·
Registered
Joined
·
1,045 Posts
Discussion Starter · #20 ·
Right, for those of you that give a toss..... I thoroughly recommend this mod to your hop arm, forget all your H, U, V hop doohickeys this is as accurate, if not better, and doesn't cost a bean ;)





Combined with a hard hop rubber, this was over hopping .25s with the hop completely off, .28s are just lovely with a little bit of hop added and straight as a die


Next thing I have to work on is getting the consistency to a more tolerable 5 fps variance :-/
 
1 - 20 of 29 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top