Designing a gun to shoot steel case ammo

[dakota.potts]

Hopefully this is a good forum for this thread.

I hear all the time that it's OK to shoot steel cased ammo in Russian or Eastern European guns because they're "designed" to shoot steel cases.

So, debates about steel-cased ammo being good or bad in American guns aside, if you were wanting to manufacture a gun in America that was designed to run a steady diet of steel cased ammo without voiding the warranty or leading to irregular service life, how would you do it? What are the design features that make a gun "designed" to shoot steel cased ammo?

My thoughts:
Dual extractors to increase reliability of primary extraction and take the stress/wear off of a single extractor unit.
Hardening and possibly coating (nitride, titanium, or other) extractors and ejector
Hardened, heavy firing pin spring for reliable ignition
Fluted chamber to help aid in extracting sticky cases and avoid issues regarding buildup in the chamber.
Chrome lining or nitride treating the barrel to combat advanced barrel wear.

If, theoretically, the issue is with guns being designed or not designed to fire steel cased ammunition, it seems like this list of changes would be a good place to start with designing a gun to reliably take this type of ammo.

Thoughts?

[Jim Watson]

Do we get to design the ammo, too?
Sov Bloc ammo uses a lot of steel cases and they are generally more tapered than USGI for easier extraction.

[Scorch]

The biggest issue with steel cased ammo is on extraction. Why do AKs digest steel cased ammo and ARs choke on it? Simple. Brass is very elastic, steel not so much. When you fire brass-cased ammo, the case expands, then rebounds a little bit allowing clearance between the case and chamber walls, steel expands and stays pretty much that size.
* Look at the cartridges side by side. The X39 case has a lot of taper, 5.56X45 and 7.62X51 have very little taper. When extracting a fired case, you barely have to move the X39 case to get clearance around the case, but you essentially have to pull the 5.56 case out about 1/2 the case length before you get any clearance around the case.
* An AR has a relatively fast, light bolt with a smallish extractor, AKs have a slow, heavy bolt with a large extractor. An AR does not like extracting a case that drags and slows down the bolt, the AK has a bigger, heavier bolt that handles the more tapered case just fine.
* Other guns have similar issues with steel-cased ammo because the case does not rebound as much after firing, so it drags on the inside of the chamber and slows down the bolt or allows the extractor to pop off of the rim.
* Obviously, the ComBloc nations had similar issues with their military ammo, because they copper-washed or lacquered the cases (later poly coated them) so they would slip out of the chamber easier.

So, it's not that steel cased ammo is "bad", or that it will ruin your rifle, the issue is that there are problems encountered when firing steel-cased ammo. You can deal with them. I deal with them all the time. People bring me their jammed ARs and I charge them to remove a stuck case from the chamber.

So fluting the chamber might help, chrome plating might help, but really, if you want to design a firearm to run steel ammo, use a cartridge with a lot of taper.

[James K]

I think the copper washing or lacquer is more to prevent cases from rusting in storage than to aid in extraction. The original lacquer gave the Germans a lot of trouble, mainly in melting and building up in hot chambers, and the copper is intended to replace the lacquer while still providing a rust free case.

Jim

[dakota.potts]

The taper is one aspect I hadn't thought of. So, let's say you wanted a gun to run reliably with commonly available calibers in steel, not just the Combloc ones. After all, there are AKs running 5.56 and 9mm, and a number of battle rifles firing .308 winchester steel case without a problem (or sometimes with a preference, as in the G3/FAL).

With 9mm and .45 you could use a straight blowback system. Others would need some type of delay or locking system. I wonder how steel cases would fare in a long recoil system where the barrel pulls itself off the bolt (and the fired round) rather than in reverse.

The idea is not so much to determine if it's good to fire steel case ammo in common guns, but to pose the question: if you were to design a gun that could be (honestly) marketed to consumers as "designed to fire steel cased ammunition" would the changes made to the gun be noteworthy and effective? What would they be?

It seems that, barrel taper aside, one prevailing feature is "beefiness". Beefy bolts with a lot of mass, beefy extractors with a lot of surface area to hook the rim, etc.

[JohnKSa]

Instead of fluting the chamber, you could go with some kind of chamber coating/finish that is slick and extremely durable. Chrome is springs to mind, but I suppose something like a good melonite/nitrocarburizing treatment would be good as well.

I'm not convinced a double extractor is necessary. After all, the AK uses a single extractor and it's made to work with steel ammo. It just needs to be a sturdy extractor.

[kozak6]

Consider how the Soviets built their guns.

One large extractor, a sturdy ejector (probably fixed), and a chromed bore/chamber (and maybe parts of the gas system), and a large heavy bolt gets you off to a good start.

Steel cased ammo tends to have harder primers, so it will also need a beefy mainspring to set them off.

Long recoil uses leftover spring pressure for extraction. It can be ridiculously reliable, like with the M2HB, but it makes for a complicated and expensive gun. Consider that the only guns left that use it are the M2HB and maybe a single Franchi shotgun.

A fluted chamber is a pain to cut. It's an expensive band-aid for extraction issues. The SVT-38 and SVT-40 had fluted chambers, but fluted chambers were abandoned in Soviet firearms from then on. The only other guns that use it are delayed blowback firearms, although they tend to work well with steel cased ammo.

[4V50 Gary]

Steel doesn't contract like brass will, leading to extraction problems. I'd polish the chamber mirror bright.

[T. O'Heir]

"...and ARs choke on it..." AR's are delicate little things shooting a varmint cartridge. They were never designed to be a battle rifle at all. Or to be issued to illiterate conscripts who wouldn't look after 'em.
"...they're "designed" to shoot steel cases..." Nope. Designed to be issued to illiterate conscripts. Who could be taught to use 'em as fast as possible and would work reliably in all weather conditions. They're not designed to win matches or shoot MOA groups either.
"...how would you do it..." Looser tolerances. Stronger parts. Said parts do not have to be machined either.
In any case, why bother going to the expense in time and money to fiddle with crappy ammo you can't reload?

[MarkCO]

Hardened extractor, melonite barrel. In most pistols that are delayed by whatever method, not a big deal.

In overgassed, straight walls, rough chambers...those are the issues.

[JohnKSa]

AR's are delicate little things shooting a varmint cartridge. They were never designed to be a battle rifle at all.

The original AR was chambered in .308 and was most certainly designed to be a battle rifle. It was scaled down for the 5.56 chambering, but that didn't change the basic design.

"...they're "designed" to shoot steel cases..." Nope.

Yup. Russian ammo is steel-cased and therefore Russian small arms are designed to shoot steel cases.

In any case, why bother going to the expense in time and money to fiddle with crappy ammo you can't reload?

Ok, let's ignore the fact that steel cases can be reloaded if you really want to go to the effort to do so. And let's ignore the fact that steel cased ammo isn't automatically crappy.

Why go to the bother? Ask any of the nations who still load primarily steel-cased ammo for their militaries. Ask any of the people who choose to shoot steel-cased ammo in their firearms.

[dakota.potts]

In any case, why bother going to the expense in time and money to fiddle with crappy ammo you can't reload?

Academic exercise.

If we want to take it further than that, look at the market for steel ammo. Not only are there cheep steel imports in many calibers which are commonly used, but major American ammo companies like Winchester are now producing them.

Some people refuse to shoot anything but steel because they don't believe in any of the negative effects and because it's cheaper. A large majority of these people, I would say, don't reload.

So, if somebody created a simple, reliable, low cost gun that they could point to and say "these are the changes we made for this gun to handle your steel-cased ammo better than that gun made by the other guy," it seems there would be a market for that.

[Mobuck]

The Ruskies have been doing this for about a century, what's new?

[5whiskey]

If we are talking about converting an existing design, such as the AR15, then any modifications will add to the final expense of the firearm. The AR platform is mature, and we are at the point you can build your own of decent quality for around 400-450 bucks if you shop sales. Or you can buy something like an M&P Sport for the 550ish range. Making an AR rifle more reliable with steel ammo would be targeting the budget shooter market (the ones who use steel ammo), but by definition you can't compete with the lowest cost budget rifles because of the added work. Cutting bolts to add larger extractors, fluting or chrome-lining chambers, and other modifications are not cheap and easy to do. Nickel finish is quite slick and used to reduce friction, but I am not aware of whether it is easier and less expensive than Chrome or not. I'm not sure that melanite type finish reduces friction or not.

A new design? Maybe. Plus the world needs more gun designs!

[Hdonly]

Just thought I would share this:

youtu.be/qBAh_8usXBI