Airmax Dominator MKII/SPA M16A rifle builds. .177, .22, .25

[AustinBinTX]

I've had my M16A for a while now. I was definitely not impressed by it out of the box. I tinkered a little bit and ended up needing some spare parts. The rifle has great potential in .22, but what about .177 and .25? While exchanging emails with Julie from SPA I asked about full assemblies of the other 2 calibers. While she couldn't ship any assembled parts, she could ship almost any individual part so with the low price of parts, and the high price of shipping, I went ahead and ordered a .177 and a .25 rifle minus the barrels (I can fit my own), the shrouds (same as the barrels), the stocks (I plan on just swapping my stock and checking if Kraale can get two here cheap), and the bottles (I've got a few CF spares).

I'm not expecting amazing results from .25 caliber, but since it's all here I'm gonna go for it.

So far all the parts got here fine, minus a mix up on the drop down block that holds the fill port and regulator. I expect I'll get the two correct parts quickly when they get time. I am a little disenchanted about how well the parts are fitting with each other. So far I've had to break the Dremel out to widen a few areas on the breach, and I've had to drill larger holes for some of the pins. I was hoping everything would be a quick fit and assembly, but right now I'm expecting to have to invest a good amount of time to removing burrs and getting clearances so the parts fit.

Can't attach photos right now, as it broke the previous link.

[WesBob]

It'll be great to hear your results! I bought a bunch of parts as well and was surprised some parts needed some work to fit as well. Looks like they are pretty poor in making the parts and must have guys doing work on them while assembling.

[Wayne52]

I'll follow this thread for sure because I've got the Dominator but it's not the bottled version.

[AustinBinTX]

2 of the 3 breeches are assembled now. One part was so far out that I gave up. They're just going to have to toss a new one in when they ship the tank/regulator blocks.

On a side note, I really hate the little keeper pins. Every hole in all 3 breeches was way undersized for the pins. I ended up having to ream all of them to get anything to fit. I know they should be slightly undersized, but .030 is a little small.

[KnifeMaker]

I have found very little on the Bottle Version. What was your disappointment out of the box? Seems the tube versions have found favor with many so far.

Knife

[AustinBinTX]

Knife,

I was extremely dissatisfied with the regulator performance. After 1500 shots the consistency was still not good. I remedied that by building my own regulator.

Overall, the rifle needed a huge amount of deburring to get smooth operation.

Accuracy was good, but my barrel had a bad tendency to loosen itself from the breech. On my 3  builds I'm making a breech insert that holds the barrels with a set screw as well as using the threading. The 12mm barrel doesn't leave enough for me to trust in .25 caliber, so I'm going to make my inserts take a .500 diameter instead of the 8.8mm turned down portion.

The bottle was heavy walled aluminum to handle the higher fill pressure. It weighed too much for me and didn't hold enough air to justify the weight. CF bottles held 33% more air and weighed 35% less.

At the $650 price point, I wasn't expecting a rifle that didn't need any work. I was expecting one that might need a some massaging though.

I'm ISO barrel blanks right now. Hopefully I can find LW barrels for all 3 calibers instead of paying full price, and just machine them all as a group.

As far as I know there are only 4-5 other bottled Dominators here in the USA, and I'm almost certain my .25 will be the only one.

[AustinBinTX]

Lothar Walther polygonal barrels are on order. Hopefully I can get them in next week and get everything assembled minus the two tank/regulator blocks that were the wrong parts.

[WesBob]

Nice!

[KnifeMaker]

Good luck, and I will be following your post!

Knife

[AustinBinTX]

Bad news:

Barrels from Lothar Walther came today. Opened them up, and they were button rifling. Looks like it'll be next week before they get the correct barrels here. He said they'll ship out once these are back there. That's a little frustrating. He said he'd see what he could do to get them out earlier, so hopefully they'll ship when they get the shipping confirmation on these.

Good news:

The two regulator/tank blocks got here.

[KnifeMaker]

Grrrrr!!! on Barrels, Yeah! on Blocks.

Knife

[AustinBinTX]

Finally finished assembly on all three actions. Talk about a fight. I don't think I had one go together without some sort of drilling or reaming. I had to do significant work on the .22 breech to get it to cycle. A Dremel and needle files have it smoothed out and it's as smooth as the .177 and .25 now. I ended up with 5 magazines for the .177 and .25, and 10 for the .22 caliber. I expect to pressure test when my AV compressor gets here as the Shoebox would take forever to pump up the tanks. There are some real oddball o-rings in the rifle. Odd enough that I can't find them on Theoringstore.com or McMaster. Hopefully I was easy enough on them during the install that they don't leak.

I've contacted SPA again and let them know I'd take the risk of having stocks shipped from China, and I understood shipping would be high. They got me in touch with their Euro office and hopefully I'll hear back from them tomorrow. I have one stock on hand, and will just swap actions for the time being. Worst case scenario I might see if my old man wants a project now that he's retired.

The correct polygonal LW barrels will hopefully be here before I load my lathe up for the move. I'd like to have them machined asap, or else I'm not sure when I'd get the shop time to start work on them.

I'm expecting extended strings with decent power on the .177 caliber.

My stock .22 shot something like 110 shots at 27fpe on its first string. I'm hoping to up the power to 32-35 fpe and get a few less shots.

Not sure on the .25 caliber. I'll set the regulator higher and go for 5 mags at whatever for is highest and most consistent through all of them. There isn't a ton of plenum volume so it'll be interesting.

I'm planning on machining a spacer for the bottles out of 7075 that I can install another pressure gauge on so I can see bottle pressure. Right now all I see is regulated pressure.

I don't believe anyone will care for pressure test results, so the next update will be after the barrels are installed and I get initial numbers.

[AustinBinTX]

Well, I lied. I went ahead and made a pressure tester/ regulator tester.

Machined from1"  7075 round. M18x1.5 threads to a 1/8" not 5000psi gauge. I had started a spacer so I could add a bottle gauge, but changed my mind mid machining. It's got a little more plenum than I want, but it should still cut down the time to test and set the regulator.

Now I won't update until the barrels are in unless something major happens during testing the seals and regulator.

[KnifeMaker]

Looking good so far Austin!

Knife

[AustinBinTX]

Just a quick update.

Barrels finally made it in. All three are machined and ready to roll. I left them all at 23.xx" for now. I have tested the .177 and .25 calibers.

.177 with a 1200psi setpoint is shooting 10.61g at 900fps over the 52 shots I shot (4 mags). I had to turn the rifle down to keep them under 1000fps. The regulator is breaking in still, but it looks very promising. Not sure what my goal is yet with this setup.

.25 with a 1400psi setpoint is slinging 25.4s at 815 over 27 shots I shot (3 mags). I can get them up to 850fps, but that's a lot of hammer spring to do it. At 815 I'm backed off the hammer spring about as far as I can go. The regulator is breaking in as well, but it looks like it will be fine also. This rifle will be my pecan protector at the new house. Max distance will be maybe 30 yards. 37.5fpe should be plenty of power.

There's still plenty of air left in each rifles bottle after testing, I just get bored loading the mags that many times.

I plan on setting up the .22 barrel tonight, and then taking the rifles out for accuracy checks tomorrow or Sunday.

I need to buy two more bottles, and I'll have to make stocks on the duplicator for the two rifles that don't have them. Not sure if I'm going to turn down the 16mm barrels or not yet. I kind of like the weight.

On a side note, I got an Air Venturi compressor while I was waiting. Takes 5 minutes to fill the 490cc CF tank to 3600 psi. That's about 45 minutes faster than my Shoebox F8 will do. I don't fill tanks, just the rifles themselves, so I'm expecting to be able to go extended amounts of time between rebuilds.

I took a photo of the .25 with the polygonal barrel. No use in taking all three as they are identical.

[AustinBinTX]

Took the .177 and .25 rifles out today to test accuracy at 25 yards. The .22 is not right, and I had to get SPA to send a new breech as this one is not machined square. Both rifles were paired with 3-9 UTG Bug Busters. The eye relief is a little short for these rifles, but it's not the worst.

I used 10.61g Stoeger pellets at 900fps in the .177 caliber. Winds were gusting. The polygonal barrel did its job and 13 shot groups (1 magazine) were all 0.250" CTC or less. I managed one group that was almost one hole, but I got way to excited around shot 11 and pulled it.

I used JSB 25.4s for 4 magazines (8-9 shots each, don't remember the exact number) in the .25 caliber. Average speed is 815fps. These spread more than they should have. I believe I had cutting oil in the barrel from machining because after the 2nd mag they tightened up to about 0.300" CTC. I shot 2 magazines of Predator Polymags as well. These were mainly just to see if they fit the mag, and if they would cycle well. They fit, but barely. The 2 magazines cycled perfectly. They grouped the same as the JSBs, but about .500" left and .250" high. I will recrown this barrel tonight. I see some chatter marks from when I crowned and threaded the barrel the other night. Maybe they are affecting accuracy, but I don't like the way it looks.

I have decided not to turn the 16mm barrels down any. I like the weight. I will shroud them though. A Marauder shroud fits nicely and will leave me 3.5" from the muzzle to cap. I'll order those from Crosman tomorrow. I'll machine the caps tonight and do some test fitting with the shroud I have on hand.

I have still not shot the .177 out of air. I'm at maybe 190-200 shots on a 3600 fill. It has a Talon Tunes 490cc bottle on it though.

The .25 is using the stock bottle, I have a TT bottle I bought from a member here that will go on it. I got right at 90 shots on the stock bottle. I'm hoping for a 33% increase with the CF bottle.

I'm still looking for a CF bottle for the .22 caliber. Hopefully parts from China will be here next week and I'll have it up and going.

There is room to up power on the rifles, but I don't like maxing hammer spring tension out. I have a spare transfer port tube for each rifle. I might max the hole size out for each caliber and see how much it ups power. The way these are built, the transfer port tube is the restriction, everything else has excellent flow.

I purchased a stock duplicator today so I can make my two stocks. I'll have that up running as soon as possible.

[AustinBinTX]

No real work done tonight.

Shrouds assemblies have been completed though. Instead of making a complete shroud from scratch, I went ahead and used Marauder shroud tubes. I machined the caps myself though. I've got roughly 4" from muzzle to cap of the shroud to work internals into.

I still need to setup the stock duplicator and make the two stocks I need. After that I plan on doing a wood stock for my Maximus.

I'm hoping I might get to take the .177 out to the next get together down the road from me. I'd like to see how it holds up against some of the high dollar rifles. I say that because as of right now, I have about $260 into each rifle minus scopes.

Here's the .177 scoped, and sporting the new shroud.

[AustinBinTX]

Finally ran strings on all three rifles.

The .177 is at 17fpe for 200+ shots. There is lots of room to increase power if needed. It takes too many pellets to shoot strings, so I probably won't shoot a full string again unless I try to sell the rifle. Its shooting Nickel sized holes at 30 yards right now. I'm sure as the barrel and regulator are broken in it will tighten up.

The .22 is at 130 shots at 27fpe, but I'm still waiting on another carbon fiber bottle. I expect about 160 shots at the current level. There is lots of room to up the power on this rifle as well. It's currently doing nickel sized groups at 30 yards as well. I'm expecting better groups as the barrel and reg break in here too.

The .25 is shooting 80 shots at 39fpe. There is a little room to up the power, but I think there is lots of room to up the efficiency of this one. This one manages dime sized groups at 30 yards. The barrel still needs to be broke in, and the regulator is new still.

Each rifle is using a full diameter polygonal Lothar Walther barrel. They're heavy, but the rifle didn't gain much weight over it's stock form since I'm using carbon fiber bottles. They are also long, but I don't plan on taking these out in brush, so I don't plan on cutting them down unless I sell them and the buyer requests it.

I ended up with a ton of spare parts. Almost enough to build 1 more rifle in each caliber. I might take the transfer port tubes and ream the spare ones out to 80% and see how much power I get.

My stock duplicator is sitting here still. It's up for sale, because I'm a little worried some of my PB stocks won't fit in the work envelope. If it doesn't sell by the time we close on our house, I'm putting it together and making the two stocks I need.

I managed to snap one picture of the three completed actions this morning. The .22 doesn't have a bottle on it since I was hoping my last CF bottle would come today.

[WesBob]

Thanks for the writeup and pics! Sounds like some real shooters and great all around guns. Super shot count!

[Wayne52]

Nice custom trio you've got going there for sure.  It will be interesting to see how much power you get from the bigger exhaust transfer port.