Tuning Crosman DPMS SBR build

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Hatsan123

Member
Sep 20, 2018
62
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CO, United States
crosman.1603896870.jpg


Just wanted to reach out to everyone and let you know I just finished doing a build on a Crosman DPMS SBR. I wanted to post this because I have not found any other info on this gun anywhere online. This also motived me to do this build. I did a sevral mods on it, including - 

  1. Two stage hammer spring system
  2. Conversion to HPA regulated at 1100 psi
  3. REAL silencer made from mock suppressor
  4. Polished hammer bolt
  5. Rubber upper and lower support bushings
  6. Red dot sight
  7. Real iron alternate sights with quick use
  8. Many other cosmetic items
    [/LIST=1]

    If any body has any questions on this gun I know it inside and out. I would be happy to help anyone else who might be doing mods on this gun. I ran it over a chrony and I am just about at 1000fps. It hits pretty damn hard in full auto. Now if I could just figure out how to build a 100 round clip. :)





 
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Ok - First off thank your for the post. I have put a ton of time into this so I do appreciate when people notice. Secondly - I have changed this gun a bit since I posted it. I have mounted the HPA tank to the stock with a remote line and cover. Also I have polished the inner barrel and added the 300rd clip. I went with a different HPA adapter that allows me to run the gun regulated at 1400psi. Its a beast! Below are links for the items you would need. I used the xxxl wire ties from Walmart to mount the bottle to the stock with some padding between them and then hid the ends of the wire ties. It looks super nice. I cant take pictures now but I will post some later. 

HPA tank

Remote line ( W bleed valve. Its a must! ) 

Remote line cover

HPA adapter from co2 that can handle up to 2k psi

Mock supressor

Supressor cover

300rd clip ( 25 round quick reload ) 



For the gun to be able to handle over 850psi and still open the valve fully, You have to add tension / weight to the hammer spring assembly. Let me know if you want details on this. For the supressor, using the mock as a base it is pretty easy to make this into a functioning silencer. Let me know if you want details on that as well. 



Let me know if you have any questions 


 
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I assume you got the ant adapter for like $60. The gasket blows out at 1000psi. The one I showed you has no rubber gasket and can holt alot more pressure. It's just a better design. I have 3 of those ant adapters that i dont use. Thry suck. I use a hand pump to fill the hpa tank. It takes like 5min. I can send you a link for it if you need. I will get some updated pictures asap. Probably this weekend. 
 
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As mentioned, some videos of it in action, would be fun to watch. :)

Thx to the pointer to the dummy cartridge's. Ordered one. :) I think I have most of the other components to test with HPA. Bottles, regs, top hat with bleed, hoses, etc.

I'll probably mod the original mag first, vs the QR. Do you have a picture of the mag with mod? And how the dummy cartridge is tensioned with the fill nipple extended?



I don't think I'll be going over the 850-900psi, but wouldn't mind understanding how, just in case ;)



PS: I found parts list on crosman. Do you know if there is a schematic?




 
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Hello,

Sorry on the videos. I will try to get some together. I don't do much digital. I'm more into mechanical. :) 

As for the adapter, there is a bottom and side port. The adapter comes with a plug to plug one or the othere. I plugged the bottom port and I drilled the mag on the side to give access to the nipple. Then it just installs like a normal c02. This is nice because you can always switch in a c02 if need be. My gun is packed up but I will dig it out if you need a pic. 

I don't have a schematic for it but I am sure there is one. Honestly it comes apart so easy and there is not to many parts. 
 
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OK, understand what you did with side port. I was going off the 1st pic in the thread.

Yes, I'd want to be able to switch between HPA and CO2, preferably with 2 cartrages.

The QR mag would have port out the back of the mag, which might work well. .

Coming out the side of the standard mag, might be awkward with the hose attached.

Mod'ing the plastic covers would be easy, and can test without the covers.

Will have to do some mock-ups.



PS: Understand, I struggle trying to do videos, myself. Its just that a SBR running over twice the oem velocity, would make one of those "cool" dicing fruit videos. :)


 
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Quick question on your first build. Was that with the ANT adapter? With the new adapter from ebay, do you have it come out the bottom of your mag or the side?

I bought the adapter from ebay, but I am also thinking of moding a full-auto Beretta 92a1 pistol in addition to the crosman rifle. That requires the adapter to come out the bottom, which the ebay adapter supports, but I am not sure about the connection coming out the bottom, which would also have to hold it in place.
 
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My first build was with the ant adapter. But it is only good to 1000psi. The one from ebay is good to over 2k but 1400 was plenty for me. However I had to run the port out the side and drill a hole in the plastic part of the magazine. As for the Beretta, its a very cool gun but that adapter wouldn't work out the bottom with out some serious custom work. Also on those full autos the clip is the valve. So you can only shoot off that clip and then have to reload not able to put a new clip in. On the SBR, I got a 300rd quick reload to fix this. 

If you want to do up a pistol, I recommend getting the Beretta APX or the Glock 19 non blow back. I have both. The clip in these is not the valve so it stops the constant reload problem. And extra clips are dirt cheap! Being a double action you can really build that hammer spring setup easily. Like really easily. There is not a whole lot going on in there. Both of mine are running 1400psi with no issues at all just like the SBR. The trigger is a little hard because the trigger cocks back the valve and releases in one movement. But it hits that valve hard and never has a jamming problem.

If I was going to do that full auto ( which would be so damn cool if they just didn't put the valve in the clip ) I would get 3 clips and make all three HPA. Then I would use a purge valve on my HPA line. Then you could cycle clips and just have to unplug air and re attach to change out the clip. Or if you could fasion a custom 100rd clip. That would probably be ok.




 
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I'm still on the fence if I'm going to try it on the P1-full auto. The only mod looks like opening the hole of the bottom plug to get the nipple thru. Would need a pin spanner wrench to close/seal it. If crosman sells spare plugs, I'll probably just go ahead and try it.

It is the valve in mag style, and would be a pain to reload I think it could be done without taking it off the tether. Also, if using a check valve, would just bleed the connection to separate.



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I'm not sure if this will work for the Crosman P1, but ANT has a version of their adapter that may work for the Beretta 92a1. I'm checking with them if they threads match their adapter.

http://www.advancednoveltytech.com/fire

However, the limitations are that you are limited to 1000 psi and you have to get multiple ones if you want to run multiple clips. At $60 an adapter plus $50 per clip, I'm not sure it will be worth it with the amount of reloading you would have to do and it won't work for those running 1100 psi, which is standard for those using an Air Venturi 13ci tank.

I'll probably stick to modding the DPMS/R1 for now. I'll probably limit myself to 1100 psi, since I am mainly shooting in my garage.
 
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To me, it looks like the ANT would require the same mod to the plug on the P-1. P-1 mags are $30. Crosman doesn't spare the plugs on the DPMS, so suspect they don't on the P-1, as well. I haven't called to verify, yet. I have a spare mag and ebay cart, so might try it if I can convince myself that I'll have a way to keep using it for CO2.

FWIW: The AV can get in the 900 psi range, just by removing the shims.
 
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