Home Forums Hunting & Shooting Air Guns Umarex Hammer 50 caliber

I purchased one. Funny thing is that I'm not a hunter. I just like to lob lead of all sizes downrange and shoot for tiny groups. I mostly bought this because I want to do something different and have been designing my own PCP in my head that I'm also going to make a 50 bore. I already started on the valve and have it mostly done which included a way to make it effectively seal and not have to fight the pressure of the plenum to open. The one thing I was struggling with was the math to figure out the plenum volume to get the desired fps that im after which is 1000 with 325 grain slugs. Apparently the Hammer uses 8 cubic inches. I also ordered and recieved a high pressure bottle rated at 5000psi and a regulator with a 4350 inlet and 3000 outlet pressure and a 500/510 bore barrel blank from green mountain. Anyhow, I have a compressor that I bought to fill my Air Venturi Avenger so I wanted to fire off the hammer out in the backyard range and got it filled and loaded with 2 rounds of whatever bullets that came with the rifle. I touched that thing off and holy schitt is it loud! It sounded like firing off a 308 back there and the thing has the recoil of a blackpowder gun. It's definitely fun but it needs a moderator and I'm terrified to purchase one since I own powder burners and heard about the Donny guy getting a visit from the alphabet people. Either way if someone is wondering if you can really take large game with this thing, I'd say absolutely so. If anyone has any interest I'll also post updates on the PCP build.

This sounds like a cool project, please keep us updated!

I'm also looking forward to more on this air cannon....grin! What a monster of an air rifle.

Just s little update. I started on what's going to be the receiver today. I have to drill and then ream a .500 hole 8.5 inches through the aluminum block. The transfer port will go from the air valve into the reciever and through the closed bolt/probe and directly behind the bullet in the barrel which will all seal when closed.
Receiver

Air valve


Barrel, valve and tank with regulator.

A little more progress. The first valve that I made had to be abandoned. I wasn't aware of valve lock so this time I made a proper balance valve. It works so well that you can open it just by using your fingers against the poppet stem and it dumps the air fast.





The pics just show the internals of the valve. Any idea how I can post a video here without using YouTube?

I've gotten quite a bit further on this build. I wish I knew how to post a short video clip without doing a YouTube video.

I have it set up in my vise for test firing. The tank is rated for 4500psi and the regulator is at 3000. I discovered that plenum volume is very important in this ordeal. I only have about 3.5 cubic inches of plenum volume that pushed a 250 grain slug at 665fps at 2500psi. Meh.

So today I took out the regulator and made an adapter, making the tank, plenum and valve all one big plenum volume, about 32 cubic inches and set it back up, pumped up to only 2500 psi and pushed a 388 grain slug at 725fps! Much better but still not good enough.

I have a different idea to gain quite a bit more velocity and I'm gonna give it a try, maybe tomorrow. I'm hoping to push the 250 grainers at 1100 or more when it's all said and done.

The pressure and volume of air required to push a 50 cal at speed, WOW!

One shot and a full refill?

If ya keep goin up in volume/psi, you're probably going to hafta adjust/increase the hammer spring, so ya get the full volume each shot.

At the moment it is, without the regulator but I'm going to try to find the sweet spot with the regulator that will allow as many shots as possible without velocity suffering from it.

I actually painstakingly made the valve so that it's easy to open. It's a balance valve design and so far it opens with little effort with very little pressure or max pressure in it. Being a balance valve it should in theory be impossible to suffer valve lock. I didn't want to have to have a beefy hammer and spring to make it open and it's taken some time to get it to work right.

You obviously know more about that than me.

But, you'll also need ta keep the valve open a long time, pushin a mass like that.