MilSimEmpire.com Default Font Increase Font Increase Font


All times are UTC - 5 hours  




Post new topic Reply to topic  [ 6 posts ]  Share Topic:
Author Message
 Post subject: Walther/RAP4/APS RAM 68 velocity: differences betw. 7.5/16J
PostPosted: Fri Sep 25, 2015 8:09 am 
Offline

Joined: Fri Sep 25, 2015 5:27 am
Posts: 3
Hi guys,

I just recently aquired a RAM68 in Germany, which is distributed by Umaxrex there (labeled as Walther SG 68) and has some minor modifications compared to the 16 Joule RAM68 in order to keep it below 7.5 Joules as it is required by (nonsense) German law. I measured the shotty's energy output and it is way below 7.5 Joules. That's why I bought replacement parts in order to be able to increase its muzzle velocity.

So far, I identified three parts that are different, but I am not sure if that's all and I hope you guys can help me here. I own the newer version (Mk2) with ball holder and without pressure indicator. Here's the blueprint for it: http://www.realaction.de/ftp/manu/expl/ ... 410%29.jpg
Here's the blueprint for the older model: http://www.rap4.com/images/diagrams/RAM ... m_1000.jpg

So far, I bought three parts (windpipe, valve spring and hammer spring):

1) Steel Windpipe L242H: The 16J windpipe has larger holes and is 1mm longer, with half a millimeter accounting to the lengths of the brass tube and steel ring, respectively. In the 'valve open' configuration, the valve cover nicely opens the way for the compressed CO2 gas through the smaller holes (D) but obstructs the larger ones a bit (C). On the side where the windpipe's steel ring is located, there is a recess milled into the brazen valve cover. Can someone please check if this is the same for your 16J shotties? The length of my valve cover is 11.6mm. The depth of the recess is 2mm.

Image

Image

2) Springs L429 and L417: The 7.5J valve spring is 30mm shorter and a bit thicker than the original 16J spring. It is also not connected to the velocity adjustment screw, but sits inside the launching compartment housing, thus cannot be adjusted. Suprisingly, the 7.5J hammer spring is 10mm longer. Both have the same diameter and thickness.

Image

Image

3) Launching Compartment L432A: My core unit unit has non-concentric holes leading to an offset where they meet (see pictures A to D). Measured from the front, this offset is at 30mm depth. From the back it is 81mm. The 7.5J shortened valve spring was sitting inside the housing at this point with its larger diameter, inserted from the front. However, the larger 16J spring has the same large diameter, so I can only insert it from the back. I think the fricting between spring and housing could be to big at this narrow offset position, also the offset could prevent the spring from moving freely. The space seems that narrow to me, that I think the offsets could jam the spring during operation. Can someone please check his launching compartment and give me feedback on how it looks?

Image

Image

Summarizing, I think I got all parts that are different (windpipe and springs). However, I am not sure about the launching compartment because of its design with the holes being non-concentric, which seems awkward to me. The valve cover might also be a bit different in order to fully open the holes. It would be great if you guys could check these things with your shotty and give me a short feedback. :)

tags: RAP4, APS, RAM 68, steel windpipe, valve spring, L424H, L417, L429, 16J, 7.5J, velocity adjustment

_________________
Image


Last edited by sebah on Wed Oct 21, 2015 10:03 am, edited 2 times in total.

Top
 Profile  
Reply with quote  
 Post subject: Re: RAP4/APS RAM 68 velocity: differences between 7.5/16J
PostPosted: Tue Oct 20, 2015 12:37 am 
Offline
E-2  PFC
User avatar

Joined: Sun Jan 13, 2013 4:04 pm
Posts: 39
Location: Russia, Saint-Petersburg
hmm, looks interesting and I agree on most of those parts, internals looks same as one, that I have
I think, I'll check possibility to mod my ram68 soon :mrgreen:


Top
 Profile  
Reply with quote  
 Post subject: Re: RAP4/APS RAM 68 velocity: differences between 7.5/16J
PostPosted: Wed Oct 21, 2015 9:57 am 
Offline

Joined: Fri Sep 25, 2015 5:27 am
Posts: 3
I would like to follow up on my previous post and present the mods I did on my Walther SG68 / RAP4 APS RAM 68 for increasing its velocity and energy output. Due to the windpipe holes being obstructed by the valve cover (L425), I tried to find a (shorter) replacement part on rap4uk (http://www.rap4uk.com/Paintball-RAP68-S ... -s/362.htm). Unfortunately, the valve assembly is currently out of stock and the customer service told me that there is no specificied ETA for that item. The valve cover cannot be purchased on its own anywhere else on the internet. :(

However, the springs, and the windpipe can still be ordered there, seperately. The windpipe can also be ordered here: http://www.paintball-atlantic.com/Piece ... /RAM-Glocq. If you don't want to spend that much money, a small dremel with a drill does the job as well. As listed in the table, the 16J variant has 3mm holes, whereas the 7,5J version holes amount to 2mm diameter. Paintball-Atlantic also lists a 25J version, without a picture though. I guess this one will have around 4mm large holes (I don't know whether custom made or delivered like that by APS). Maybee I'll drill open my 7.5J windpipe and try to upgrade it to 25J this way. I'll report on that.

Following the purchase of the valve spring, bolt spring and 16J windpipe, here's my first mod to my original 7.5J Walther SG68:

Mod 1: Shorten valve cover (L425/L425H) to allow full air flow

As outlined above and as depicted in the first picture in the previous post, my valve cover suits just fine for the smaller 2mm holes, but doesn't fully open the way for the 3mm holes of the 16J windpipe. I thought about deepening the recess where the windpipe ring goes into, however, I came to the conclusion that this would not be a good idea as there is currently only 1mm of material left holding together the hexagonal screw head with the rest of the screw itself (E). I didn't want to risk it breaking off. So I decided to shorten the screw by lathing off 2mm. Here it's important that the original planar ring shape that goes into the plastic valve material remains unchainged in order to avoid leakage. That's why there are several working steps required (see pics below): First, I lathed of 2mm from the front (B), then another 2mm at 10.5mm diameter (C), which is subsequently formed into a cone with a 45deg tool (D), yielding the nice planar ring shape with roughly 1mm width at the front to go airtight into the plastic valve material. It's also important to give it small chamfers towards the inner hole and the thread in order to avoid sharp edges. Et voilà! I just got mylself a nice shortened valve cover with about ten minutes of work (F, G) that perfectly fits the 16J steel windpipe.

Image

Mod 2: Flatten out non-concentric holes in launching compartment to allow free valve spring (L429) movement and adjustability

As presented in my first post (point 3), the holes in my launching compartment (L431A) are non-concentric with the shortened 7.5J valve spring sitting on the edge (see pic B), inserted from the front. Hence, although there is a spring tuning screw, turning it would not change anything. With the given design of the housing, the purchased, longer, and thus tuneable spring did not really fit nicely through that thight space between the front and back hole. It was blocked a lot and did not contract over its full length, but only until the tight spot where it was jammed. In order to allow a free movement of the valve spring and to give full tuning capability with the tuning screw, I used a dremel with a milling tool to flatten out the sharp transition between the two holes. I milled them both from the front (30mm depth), as this process would not have been possible from the back (80mm depth). Thats also why the top one (see pic A) looks a bit nicer that the bottom one (pic C). I simply couldn't see it during milling and had to check regularily from the other side. I found it to be best to use a flashlight from the back through the hole and angle it at the opposite side of the spot to be milled.

With this being done, the longer spring can also be inserted from the front, move absolutely freely without any jam, and I can turn the adjustement screw all the way in and out with the spring following its adjusted position - yeah!

Image

Mod 3: Remove bolt-forward mechanism and close barrel opening to increase air efficiency

The marker core has a bolt-forward blocking mechanism. If there is no ball loaded, the blocking plate blocks the bolt from fully moving forward and thus does not allow the hammer hook to be released. If there is a ball loaded, it moves the blocking plate upwards, the bolt can now move all the way to the front and the hammer hook can be released with the trigger plate. Although this mechanism can be deactivated with the bolt-forward switch, it is a really bad design, as it leaves open a significant gap in the barrel behind the ball and in front of the bolt. During shooting, a lot of air will get lost through this gap, lowering the effective air pressure behind the ball and thus also lowering the realizable speed and energy of the paintball or whatever else was loaded into the shotty.

I removed that senseless blocking plate and closed the hole with metallic two-component epoxy glue. First I drilled open the front hole for the pin to go throuh and be able to hold the epoxy (pic A) at the front in addition to the back. As there was only one pin for the blocking plate, I made an additional one from a nail. The pins are there to support the epoxy "plug" and prevent it from being pushed out by the internal air pressure. Before glueing the hole, I used Gaffer tape on the inside to yield a convex roundish mold for the glue. I prepared it in a way that the tape surface closing the opening was not sticky towards the glue. Thus, I could remove the tape before the epoxy was fully hardened and used a thick pen (e.g. an Edding) inside the barrel to make sure it does not stick out and reform it if necessary. The neat thing about metallic epoxy is that it can be processed easily when fully hardened, e.g. be sanded, poslished or whatever.

Now the air pressure coming through the bolt will be used for accelerating the ammunition only instead of dissipating somewhere in the marker housing - awesome!

Image


Mod 4: Shorten trigger plate to allow auto-tigger and increase hammer momentum

In its original version, the trigger plate is very long and the back side lever of the hammer release moves it backwards, both with the trigger being released (see C) and fully pulled down (see D). This results in the trigger plate not being able to actuate the trigger once a shot was fired and the trigger is kept pulled down. For shooting another ball, the manual trigger first has to be released, a new pump action executed, and finally pulled down again to shoot the ball. This design is quite disadvantageous, as it is not possible to shoot fastly. In addition, the spring-actuated trigger plate removes kinetic energy from the incoming hammer that is subsequently missing for opening the valve.

I shortened the trigger plate (see A) to allow the hammer to move freely above it once the trigger is pulled. If the trigger is kept pulled, moving the pump bar to the front (see B) will automatically fire the ball. Thus it is possible to move the pump bar backwards and forwards with every pump action loading and shooting a new ball, respectively. In addition, the hammer will have a higher momentum when it hits the valve, allowing more air to flow through it. I gave the top of the trigger plate a roundish form and polished it toroughly. I did the same to the outstanding lever of the hammer catch/release mechanism. Thus, after releasing the trigger, the trigger plate reengages in a position being the hammer release lever where it can keep the hammer from moving further backwards during loading. Mod 7 will elaborate more on this topic.

Image

Mod 5: Adapt cocking handle bar to allow ammunition double feed

The SG 68 has a mechanism that will prevent it from loading another ball once the hammer has been cocked. However, this can be an important feature, e.g. if a rollout occurs. It's quire simple to get rid of this senseless feature: just increase the length of the inclination of the cocking handle bar, as can be seen in the sequence below. This will swiftly move the lever below the bar. Done.

Alternatively, it is of course possible to simply remove or cut of this nasty arm. Due to the fact that when cocking it, the arm will move below the bar and thus automatically pull the trigger a bit while also lowering the trigger plate for a millimeter or so, I finally decided to get rid of it and dismantled it. I decided for that, because I do not want the trigger plate with its rounded tip to be lowered as this would change the contact angle with the hammer catch lever (see Mod 7 pic B). If the contact angle becomes too flat, the hammer catch lever would slide over the tip too early, not allowing the trigger plate anymore to block the hammer movement, see mod 7 for more details.

Image

Mod 6: Mold out and polish bolt to achieve swifter hammer catch

Although I shortened the trigger plate, I still wanted it to be long enough to stop the hammer from moving backwards to much during loading in order to prevent the valve from opening while cocking. The next mod will present more on this issue which actually only becomes an issue if the valve spring is adjusted to be very loose in comparison with the hammer spring. During cocking, the hammer catch will move downwards at its bolt-oriented side (see A). On the opposite side, the lever will have to move upwards during cocking, however there will also be a significant amount of friction as the lever is also pressed against the trigger plate. This might jam the cocking process. In order to make cocking as swift as possible and to minimize the distance the lever has to travel upwards, I milled out the bolt at the spot where the hammer catch is located. I gave it a nice inclination and lowered the hight to be bridged, both by milling off a bit from the top of the catch and the bolt. Finally I gave it a nice polish to minimize friction. With this mod, the lever only has to move upwards at the very end, right before the hammer catches the bolt and thus, neutralized the sping-induced force on the trigger plate.

Image

Mod 7: Achieve blockable and adjustable trigger plate movement to allow full spring adjustability and maximal shooting energy

As can be seen in figure A below, cocking the weapon by moving the bolt to the back, compresses the (newly bought and shorter) hammer spring and thus increases the force acting on the hammer in direction to the valve. Even if the (newly bought) valve spring is adjusted to its maximum position with the spring adjustment screw inside the housing, its tension is not great enough to hinder the valve from opening during the cocking process (without added air pressure). As a result, the bolt cannot catch the hammer, because the hammer and valve are pushed away by the compressed hammer spring force which is greater than the valve spring force.

That's why I added a custom blocking arm that connects the trigger plate with the bolt that keeps together the marker core with the trigger unit (see pic B). Applying this arm (see pics E-G for close-ups), the trigger plate is blocked in its backward motion, the hammer is stopped from moving further towards the valve by holding against its outstanding lever. Subsequently, the valve won't open even though the valve spring can be adjusted to be much softer than the hammer spring. I built the blocking arm with a dremel from the removed bolt-forward mechanism lever. As it is hard to exactly get the positioning right when working on this part, I also added a small adjustment screw here. Turning it further in will move the maximum allowed trigger plate position to the front.

When pulling the trigger, the trigger plate is also pulled down, below the hammer lever such that the hammer can move freely and hit the valve with its full momentum. Even after firing when the valve is closed again and the bolt located in its forward position, the hammer spring will always press the hammer against the steel ring of the wind pipe/valve. When releasing the trigger, the rounded form of the trigger plate tip allows it to slide back upwards into place. Note that the motion of the trigger plate is not linear but curved (down and forward, up and backward). Milling this roundish tip was an iterative process, I had to check several times if the form fits for both, stopping the backwads motion and allowing it to slide back into place. For achieving this, I also rounded the tip of the hammer lever a bit.

Image

After making and dry-testing this fancy mechanism, I wanted to also give it a shot with compressed CO2. The pressure behind the valve will give it an additional force in addition to the valve spring, and I am curious what will happen. I made a short video of this test (see below). In the video, I show that dry cocking does only work with the blocking arm. When pulling down the trigger and executing a back and forward pump action, the bolt does not catch the hammer anymore, because the hammer and valve are pushed backwards in the direction of the marker housing (launching compartment) by the compressed hammer spring. A bit - but not totally suprinsingly, when I added the CO2, the auto-trigger pump action worked as well. It seems that the pressurized CO2 added enought additional force that the force of the compressed hammer spring during cocking was not sufficient to open the valve - which is good news after all. However, I do not think this result renders the blocking arm disfunctional or unnecessary. I think it will be useful for adjusting the valve spring, i.e. making it softer, or even for using the adjustable valve spring together with the longer 7.5J hammer spring for gaining an even higher bullet velocity and energy. But see for yourself:

Walther SG 68 Cocking Test Video:
Image

Mod 8: Remodel hand guard openings for tighter fit around magazine tube

To be added.

tags: RAP4, APS, RAM 68, Walther SG 68, steel windpipe, L424H, 16J, 7.5J, velocity adjustment, home defense, Tuning, Geschossenergie erhöhen, Heimverteidigung

_________________
Image


Last edited by sebah on Mon Oct 26, 2015 12:16 pm, edited 11 times in total.

Top
 Profile  
Reply with quote  
 Post subject: Re: RAP4/APS RAM 68 velocity: differences between 7.5/16J
PostPosted: Wed Oct 21, 2015 9:59 am 
Offline

Joined: Fri Sep 25, 2015 5:27 am
Posts: 3
Placeholder for energy measurements of multiple types of ammunition (rubber balls, powder balls / pepper balls, steal balls).

_________________
Image


Top
 Profile  
Reply with quote  
 Post subject: Re: Walther/RAP4/APS RAM 68 velocity: differences betw. 7.5/
PostPosted: Mon Nov 23, 2015 10:25 pm 
Offline
E-1 Private

Joined: Tue Sep 08, 2015 11:05 pm
Posts: 10
also the offset could prevent the spring from moving freely.
sbobet444


Top
 Profile  
Reply with quote  
 Post subject: Re: Walther/RAP4/APS RAM 68 velocity: differences betw. 7.5/
PostPosted: Sun Jan 21, 2018 2:22 am 
Offline
E-1 Private

Joined: Fri Dec 08, 2017 5:19 am
Posts: 15
It's a shame.













m8bet


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 6 posts ] 

All times are UTC - 5 hours  


Who is online

Users browsing this forum: No registered users and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum


Search for:
Jump to:  

Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
For any questions, comments or concerns please feel free to contact the Admins at MilSim Empire Admins