Electro Chemical Machined rifling

[Bob Wright]

I used to work at an ECM shop back in college. All of those parts back then were sheet metal. Very precise tolerances For sure. That said, you'd have to have to bore already drilled, then find a way to get the rifling impression printed inside the bore, then use the photochemical etching process. Doable for sure, just don't know how viable financially it would be.

No, it's actually a graphite machined negative of the bore and rifling. The barrel does need to be gun drilled/reamed prior to machining and straight. The ECM tool will follow the undersized bore and process everything including bore and land diameter in one pass. It's some tool engineering to get it right, but once it's developed, multiple graphite tools can be made and kept in inventory. Other metals can be used for tooling, but we stayed with graphite as it didn't become consumed much.

 

[epoletna]

I'm guessing if you could etch the rifling you could also etch the chamber. I'm wondering if you would end up with greater dimensional precision and concentricity that way, and not have machining marks? Sounds like it could be a winner. I'd like to hear more.

 

[Bruce Treloar]

Back in the 70's and 80's we machined a variety of gas turbine blisks, compressor blisks and related parts using this ECM process. Since we had a lot of heavy metal sludge like cobalt, we abandoned the process due to environmental issues.
Surprising to see a new barrel company in England utilizing this old specialized technology.
'Pendragon Precision' (on Facebook).
Apparently the barrel bore and rifling is carefully choked all the way to the muzzle.
The process is essentially de-plating to make a form, in this case, rifling. Using graphite form tools and pumping electrolyte thru the barrel and around the electrically charged metal and the process ends up being a non-contact machining process, similar to EDM. No imparted stress to rifle the barrel.
Just need plenty of amps and some good engineering.

Looks great technology, like to see more. Would help my quest to build 8- 1/2lb hunting rifles that shoot !/4" MOA all day and don't change point of impact.

 

[esorensen]

No, it's actually a graphite machined negative of the bore and rifling. The barrel does need to be gun drilled/reamed prior to machining and straight. The ECM tool will follow the undersized bore and process everything including bore and land diameter in one pass. It's some tool engineering to get it right, but once it's developed, multiple graphite tools can be made and kept in inventory. Other metals can be used for tooling, but we stayed with graphite as it didn't become consumed much.

I misunderstood the process. I was thinking photochemical, and NOT electrochemical…although photochemical might be possible.

 

[Bob Wright]

I misunderstood the process. I was thinking photochemical, and NOT electrochemical…although photochemical might be possible.

We used photo chemical for thin sheet metal that were stacked and brazed into hydraulic valves. They were impressive as to how these stacks were used.