Tuning Crosman DPMS SBR build

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I must admit that I am primarily a gunpowder gun shooter, easily 80% of my time and while I have numerous "Air Guns" of various types and models, not one of them is a PCP or HPA. To really be into it, you have to invest into a really really good compressor, and those babies can run into $1k. I'd rather spend a $k on another SIG Sauer or CZ combat match pistol in 9mm or 40ACP than a compressor. I've been shooting Air Rifle and 10meter Air Rifle National Match since a kid and even at 72 I still do in the "Senior Class" and am still using my 32 year old German Feinwerkbau 300 series which uses 2 CO2's, high-tech for its day. It's on its 11 replacement barrel, that is a LOT of pellet shooting to "shoot out" that many barrels. I think all the current 10 m match rifles are PCP these days.

Most of our practice shooting using the replica Crosman's or others, you have to change magazines after 25/26 shots, just as you would with a real firearm, so an HPA conversion is completely impractical. Actually, most of the time we only (with the Crosman's) only use 1- CO2 in the mag and we still get 60 to 80 shots for a single CO2. Each of us has at least 4 to 6 magazines.

Good luck on your HPA conversion. There are a couple Crosman HPA Conversion threads running irregularly over on the "GTA" Forum. You might want to look for those.
 
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There is no real brand of converter. You have to use a c02 to hap adapter but the ones on ebay are not there any more. Below is a link to get one.

https://www.ebay.com/itm/372836684074

Then you will need a remote bottle and line. I hooked a small bottle to the stock on mine. And used a small braided stainless steel line. Also for the 2 stage hammer system, this is something I built. I did this to keep pressure on the valve so it does not bounce because I am running 1800psi. If you are going to stay lower then just a spacer will work behind the hammer spring t give it more tension. You will have to try different spacers depending on psi but the goal is to get the valve to fully open. You will know right away if it doesn't it will seem like it lost power and is not as loud as well as maybe not cycling correctly. You can go up to 2k with the adapter above but I would stay around 1800 max to make sure everything works good for an extended period of time. A crony is really best to test this as you will see an increase in psi as the hammer opens more for a specified psi.

Anyhow if you need more info let me know but unfortunately nobody make theses kits so you have to build your own. But its not to hard once you get in there and get comfortable with it.
 
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There is no real brand of converter. You have to use a c02 to hap adapter but the ones on ebay are not there any more. Below is a link to get one.

https://www.ebay.com/itm/372836684074

Then you will need a remote bottle and line. I hooked a small bottle to the stock on mine. And used a small braided stainless steel line. Also for the 2 stage hammer system, this is something I built. I did this to keep pressure on the valve so it does not bounce because I am running 1800psi. If you are going to stay lower then just a spacer will work behind the hammer spring t give it more tension. You will have to try different spacers depending on psi but the goal is to get the valve to fully open. You will know right away if it doesn't it will seem like it lost power and is not as loud as well as maybe not cycling correctly. You can go up to 2k with the adapter above but I would stay around 1800 max to make sure everything works good for an extended period of time. A crony is really best to test this as you will see an increase in psi as the hammer opens more for a specified psi.

Anyhow if you need more info let me know but unfortunately nobody make theses kits so you have to build your own. But its not to hard once you get in there and get comfortable with it.
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I would also like to add that your posts are what motivated me to do this conversion as well. Thank you for sharing your experience and knowledge with us. Best regards!
 
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I just bought my 1st DPMS SBR, actually it's my 1st air gun. Noticed this post so I signed up. I bought mine used. Has a Browning Buck Mark Reflex Sight already co-existed with factory sights. Paid 100.00 for the package. Im interested in the build. This is basically a fun piece, atm. However, if this proves itself, I am interested in the upgrades to make this a much different system. 

Is the 300 rd mag really worth it? I've read mostly bad reviews. Is it difficult to build? How expensive is the build, ball park figure will do? 

Like I said, if this proves itself, I will build. If not, I'll keep the Buck Mark sight and just sell the gun. Any help would be appreciated. 
 
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If you go hpa it's a must for the 300 quick reload clip. The air goes through the mag so having the quick reload you just pull the tab down and up and it's ready to go. Otherwise you would have to put hpa adapters in multiple clips and un plug the air every time you changed a clip and reply in the new clip. I have the 300 rounder and it works great. Also it's super easy to reload the resovoir so I never take the clip out. It's by far the best way to hpa this type of gun. 
 
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re. the "300 round magazine" -

You do realize that you can still only shoot 25ish BB's with that magazine at one time?? You have to pull out the "300" magazine, turn it upside down, pull the reload spring (just as you would a 25 shot mag), shake a few times to get all the 25 BB's to move from the reservoir fully into the BB "tube" and reinsert the mag back into the Crosman. Can't hardly see how that is a "must" for HPA powered converted Crosman since the Mag now has to be "Tethered" physically to the SBR or R1, means you have to shake the whole, now weighing 15 to 20 lbs, rifle.
 
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I have had the gun for over a year and shoot 1000s of bbs. So yeah I do relize how it works. Do you have the gun and mag set up with hpa? Or are you just saying what you think? 20lbs? Come on its much lighter then that. Try multiple clips with hpa. Have fun with that.
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Well, I'll call a big BS on all of that. I've had my DPMS SBR for 2 years now, a CFAR1X for a year and a Bushmaster MPW when it came out 4 years ago. My CFAR1Xis the most modded and "accessorized" 10 simulate my real Colt M4A2 and the CFAR1X weighs in at 7lbs 12oz with a Green Laser and CREE light, steel flip-up MilSpec Iron Sights and a Multi-Reticle Red/Green Hologram sight, 1 CO2 and 25 BB's. You can't tell me that all those HPA covert rigs on this thread with hoses, multiple fittings, pressure gauges, heavy tanks, and all the gadget accessories weigh in less than 18 lbs, TWICE the weight of my "lite-weight" M4 replica?? And if you use that new 300 BB new magazine n a HPA rig, easily 20 lbs!

To me these HPA setups remind me of those carnival BB rifle arcade games to win a Teddy Bear. Love to see anyone lug one around for a 5 mile Run n Gun match. Totally unrealistic for battlefield replica use. But, .... to each his own. enjoy



CFAR1X right 8-21- B1.1631665747.jpg

 
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Like I said, this was a steal at the price point for a benjiman. I am always curious about upgrades and improving the accuracy and function of my guns. This build, if it becomes one, will be for play. I have my practice weapon and the Browning Buck Mark Reflex Sight was the seller ( 55.00-80.00 retail). I didn't get hurt. 

Air guns are a new item for me and my research tells me this, expensive. But that in itself is of the beholder. Depends on what your intentions for the weapon are. Something of this nature, not so expensive. Hunting, targeting, competition, etc, deep pockets required. Airguns are built with different quality metals and parts and that equals higher prices. Plus they require many neccessties to maximize their potential and fun.

All the builds, shown in photos, are worth it to each individual. I was simply asking for experienced knowledge to save me time and money. Thanks to everyone for their input. Every weapon I've ever shoot or built has never been perfect, something somewhere will give you a pain. It is simply a matter of the weapons intentions and use and how you deal with it to make it better. 


 
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Keep us posted on that build. Interested how it turns out. I'm set up now to fully test this gun in its factory setting. I'm hoping for good results. If so then I start building this into an HPA, to increase the fun. Please send pics. Good luck!

I believe building this is still cheaper then making a thousand dollar purchase upfront. At least it gives you insight into an unfamiliar interest. Which makes perfect sense if think about it.
 
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I don't know if you're still doing build outs... But I am about to order my first one ... But just curious, have you seen or considered building a picatinny M203 grenade launcher that is actually an air tank for your hpa?

If you've seen anything like this let me know as I think that would be ultra cool looking...

I'm still trying to figure out how you and others have done the HPA conversion.
 
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