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PGM ultima ratio intervention / PGM 338


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Hi Guys,


my first post in this forum and i hope you will enjoy what i'm going to present as much as i did and still do while carrying out the project.


So what is it all about: for years i have been wanting to build custom airsoft guns but only recently i was able to start on one of all the projects i had already thought trough in the last years.


My entry for this years ACBC is going to be a replica of a PGM ultima ratio intervention mixed with a PGM 338, basically the same gun with some altered dimensions and features.


Just in case not everyone knows what it looks like, here is a picture of what I am aiming at:




My version will be different from the one in the picture regarding the furniture which will be made out of wood.


Internally it will be driven by a gas system, but a really special one: it will have asahi M40A1 style hpa air catridges. Inspiration for this comes, of course, from the well known video by scaar on the M40A1



With some help from wolfgeorge and scaar himself, thanks again guys, and some asahi M40A1 manuals I tried to re-engineered the shells and got started on the lathe. Here are some pictures from the manufacturing process:








And finally, a picture of two disassembled cartridges with all components on display:




The cartridge is modeled after a .338 lapua magnum in respect to the external dimensions. some of the parts you can see are still from the prototype stage, the homemade springs for example. these are being replaced by some from the hardware store.


Until now I was able to finish one shell in a way that it is able to contain about 116 psi of high pressure air, the two others are still having some sealing problems.


More pictures to come this week, I already started machining the aluminum body last week.





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Update on the gun-body:


Last week I started to work on the stock of the PGM with cutting grooves and drilling holes in the main rod where everything else is bolted on to






Continued to work until it looked like this:




Next up was the adjustable butt plate with rough cutting and the smooth finish:






on the following picture: countersinking the holes for the screws of the rear guide of the cheek rest




rounding off the edges on the hinge between the stock and the main body rod:




And finally, to conclude this post, a picture af the stock connected to the main body rod via the hinge:







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weekly status update:


nearly finished the stock, catches on both sides for holding the stock in the extended and folded position are in place and the attachment for the grip is finished. on top of the main body rod the guiding bar for the bolt is installed:
















and at last a sneak peek at the work for the next week and weekend. Anyone who wants to guess which part of the gun this is going to become?



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I've got a problem, and I'm counting on the community in order to solve it, I may even hand out some cookies for suitable solutions :D :


in order to continue with the gun I need to drill a hole with a diameter of about 30mm (differing a bit at the barrel end of the block) in an aluminium block which is about 265 mm thick. I ordered a drill tonight with adiameter of 12mm and 295mm in length to pre-drill it. 


So, the question is, how do I widen the hole to 30 - 35mm ? I was thinking about a boring head, but I'd have to buy one and they are not really cheap and I'm not shure if it can take a hole of about 135 mm ( half the block) without producing too much vibration. Any other suggestions? I have a rotary table with a 4 jaw chuck. but that is difficult to center correctly as it has 4 independent chucks and I'm not shure if there are 


not so really shure how to solve it, I hope it doesn'T stop the project from happening. Until now I was somehow waiting for a solution to pop up, but I'm at the point know where it already should have done that!


Any kind of advice is very much appreciated!





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Back when Candyman still made guns, his approach was to drill many small holes round and round then manually smoothen it out with a dremel or sandpaper on a round stick. Or have your block of metal in two halfves, mill semi circles on both of them then weld them back together.

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The Problem I see with drilling many holes and manually make it into a big one or making two halves out of it is that this block will house the bolt and barrel which will have to be aligned as perfectly as possible and also round enough to cycle properly. Also I do not have any other possibility than gluing the halves back together which I think will not produce an adequately round shape of the hole at the end. Atm I think about going with the boring head solution. I found a relatively cheap supplier. Still have to calculate if a set or separate boring head and bars is more cost-efficient.


Anyway, thanks for the advice so far all of them are much appreciated.



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Hmmm. Your mill is really not going to be capable of handling that kind of work. It's not rigid enough, doesnt have enough Z axis travel and clearance, and 270mm odd of unsupported boring bar sticking out of the boring head is a recipe for an extremely innaccurately dimensioned hole - the same problems you get on all small mills, sadly.


Your only real option to do it with any degree of accuracy (or even being able to do it at all!) is by boring between centres on the lathe.


Hemingway do some between-centres boring kits for a very reasonable price (you finish the machining on them yourself) that might do the job. Sadly, finished between-centres boring bars tend to be beaucoup money....


Example of between centres boring (not my pic):



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You can buy a milling attachment to fit on mini lathes. They're generally pretty gash for use as intended, but coupled with some 1,2,3 blocks, shim stock and some clamps and you should be able to find some way of mounting your ally block on the cross slide. It ain't ideal, but I can't see any other way to do it.

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  • 2 months later...



no update in a very, very long time! just a small one today to show that I'm still working on this.


Picture of the soon to be cut trigger as part of the trigger mechanism:




more pictures of the current status are following this week. I only got this week left to more or less complete the project, as I will continue studying on the first of october

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my last week is over now, I am leaving tomorrow and will not have access to my workshop for the months to come so this is the status of the project as part of the ACBC.

As soon as possible I will finish the gun, still some things missing to work as intended, but I will explain what is missing when I get there with my pics.


First of, the adjustable cheek rest. made from american walnut.



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and the hole thing attached to the already known stock





top shot of the main body with a view on the trigger box




the other end of the main body where the bipod is attached




mag catch underneath the trigger guard




two pics of the still WIP grip. It is beeing modeled after a HK Battlegrip known from their M416/17 rifles.






picture of the bolt housing with the bolt handle slot




three pics of the forward upper handguard (kind of ;), not shure what else to call it)








except for the two bolted on accessory rails on the side, the whole thing was milled from a solid block of aluminum.


next up we have some pics of the wooden handguard, again american walnut.






and the bolt, fully assembled and partly disassembled











one pic of the magazine, also still a WIP




the top rail, as a whole shot and with pics of small details








the barrel, fully assembled (consists of 5 tubular pieces) pictured as a whole and again in details














continuing in the next post with pictures of the gun fully assembled.

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And now a bunch of pictures of the gun assembled


the only parts i bought are the g&p bipod and the king arms scope with rings.























I hope you like my build and maybe even give me your vote in the competition ;) I am pretty confident with it so far, considering that it is my first time ever using a lathe / milling machine.


there is still quite some stuff to do , unfortunately I did not get as far as intended. the inner barrel / hopup / chamber still has to be bored, magazine finished and ejection port milled. safety and bolt guide / retainer are missing and some cosmetic milling on the cheek rest etc. has to be done. I hope I will be able to finish it around christmas / new year.


thanks for your interest in my project :)

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