Barrel Heating: Allsop & Toomey & Rheinmetall, oh my!

Last night, musing over a possible technical post for this morning, we opened Allsop and Toomey’s Small Arms: General Design to see how what they wrote on barrel heating compares with our recent translation of the Rheinmetall HandbookAnd there was the same damned diagram.

No, not a close parallel. Or a close copy. The same jeezly thing. Don’y take our word for it. Here’s Allsop & Toomey:


…and here’s Rheinmetall:


That’s not coincidence; the form as well as the facts of the diagram are identical. Which gives rise to the question: who copied whom? Beats us with a stick. Although the Rheinmetall handbook has some primacy (1973 versus 1999, as the yellowed pages of our copy show) it’s quite possible that both derive from an earlier source. We don’t remember seeing this graphic in Balleisen (our copy of which is still adrift somewhere in office or library) or in Chinn (which we ought to check, because we have the e-book, although we just moved 150 GB of ebooks to our RAID array, which promptly ate a disk and needs repair stat — just reminding ourselves here).

One indicator we see that hints that both derive from some earlier source is that both graphs show an approximation of barrel heating, without numbers. It is the numbers, of course, that are most useful to the designer or engineer, although the graph showing how these numbers are arrived at over time is not without its own utility. The suppression of numbers in both the Handbook and Small Arms: General Design suggests that they’re both using a graph from some earlier technical report. Absence of this graph in US design books makes us speculate that the ur-source may have been European.

rheinmetall_heat_pageHere you can see the two graphs in context on their relative pages. (All images, including these thumbnails, embiggen with a click; the square thumbnails expand to show the full page with legible text, although the Rheinmetall is in German, naturally). What’s more interesting is that the two texts handle the same graph quite differently. Rheinmetall (whose text is translated in our earlier post) explains the graph and its meaning at some length.

allsop-toomey_heat_pageConversely, Allsop & Toomey just throw off a sentence telling you that breaks in firing reduce peak internal temperatures without really delaying the rise of external, overall temperatures. But they also include some numbers, despite the suppression of them in the graph, numbers that are quite useful to you. (All the numbers in both works are in SI units). They suggest there’s a difference of as much as 400º to 100º (C, F equivalents are roughly 750ºF and, of course, 212ºF).

The Britons warn that, if 500º C (932ºF) is maintained, “permanent damage will be done to the barrel through accelerated wear and erosion.” And then they go into a number of useful equations. They do not seem to estimate the point of failure of the barrel with all this sheet music; that is all tied up in pressure as well as temperature and there are an awful lot of variables baked into it; today’s engineers, unlike those of 16 years ago (Allsop & Toomey) or 42 years ago (Rheinmetall) would certainly use something like CATIA to do a finite element analysis of the barrel to substantiate the strength of the barrel in its predicted use, and estimate where and when it would let go.

We do note that the temperatures noted in Allsop & Toomey, and the surprisingly sparse cadence that will produce them, are in line with some of our previous material on the carbine failures at COP Kahler in Wanat (see here and here; the Wanat failures happened in part because soldiers are not taught to understand nor a practical way of avoiding overheating, beyond a simplistic “short bursts” drill) and on heat-driven accuracy problems in the ANM2 .50 caliber machine gun in the USAAF.

If readers would like, we can walk through some of the math. We’ll probably need the Blogbrother’s assistance, as he’s rather better at maths that your humble blogger.

A Note to Readers

This sort of technical post would be banned — would, indeed, be a felony — under Secretary of State John Kerry and his minions’ extreme and un-American attempt to suppress free speech about weapons design. Even though this post is based primarily on two textbooks published in two foreign countries, and available to all the world for decades! The Ivy League inbreds at State base their proposal on the contemptible and flimsy excuse that sharing knowledge constitutes international trafficking in arms.

Meanwhile, those same cretins are negotiating all obstacles out of the pathway to nuclear arms for the most terrorist-sponsoring regime in world history, the Islamic Republic of Iran. Got that? Iran/IRGC/Hezbollah/Hamas, getting nukes? No problem. You, understanding barrel heating, whether you are Iranian, Russian, Chinese, Canuckistani, or, like the majority of our readers, American? Problem. The guy should stick to what he knows, whatever that is. Seducing trust funds off of heiresses, perhaps.


If you would like to keep the First Amendment operative in the United States, and thereby disappoint the man who’s a living parody of Thurston Howell III, here’s a three-point plan for you:

  1. Read the background on the issue from the NRA.
  2. Read the actual notice of proposed rule making (.pdf; relevant bit begins in lower right of the first page) in the Federal Register and make sure you understand it.
  3. Make your comments in your own words about how this regulation works to harm you instead of its ostensible goal.
  4. Comments go here at or by email to: with the subject: “ITAR Amendment—Revisions to Definitions; Data Transmission and Storage”. Ceteris paribus, this link should open in your email application with the correct subject header.
  5. As a backup, contact your Congressman and two Senators. The very best way is to call their direct number; Google is your pal on this. Next best is to call the congressional switchboard (202) 225-3121, and ask for each of them in turn (you do know the names of your Senators and Representative, don’t you? If not, Google again). You’ll either get dumped in voicemail or to a junior staffer or intern, unless you’re a big donor. Have an index card with the points you want to make, make them briefly and politely, and end the call. For example, we have been making the point that a State Department that can take on prior restraint of Internet content is a State Department that is heavily overstaffed and overbudgeted, and might very well give up a few hundred millions in personnel expenditures for the Congressman’s pet projects.

D2S2 here, folks. No threats, no bluster. Make real, substantive comments on how this proposed regulation harms you and yet, does not prevent the sort of arms races and weapons proliferation the State Department usually knocks itself out encouraging.

If you have questions, we will try to answer them.

ITAR is no joking matter. It is an all-encompassing and deliberately vague law — it would even apply, on professor avers, to Superman —  and because it is so large and so difficult to comply with, it’s frequently used as a club to beat political opponents with.

For example, this iteration of the .gov has not been shy about really stretching to try to punish gun-culture figures with flimsy, but very costly to defend, ITAR prosecutions. Our ITAR counsel is telling us the blog has to go (archives and all) if this monstrosity of a rule becomes final.

Do not delay. They are already playing games with the availability of the comments website and email addresses to limit opposing comments.

Expect to hear this from us again.


Allsop, DF and Toomey, MA. Small Arms: General Design. London: Brassey’s, 1999. (Note that this out-of-print text is Volume 6 of a series on ballistics and weapons design called “Land Warfare: into the 21st Century” by authors mostly affiliated with the Royal Military College in Shrivenham, England).

Rheinmetall. Waffentechniches Taschenbuch. Düsseldorf, West Germany, 1973.

2 thoughts on “Barrel Heating: Allsop & Toomey & Rheinmetall, oh my!

  1. duchamp

    Is there any data as to what percentage of heat is generated through friction vs. hot gas? If I recall correctly friction is a very low percentage.

  2. Hognose Post author

    Yes, Duchamp, that’s what they say. I think we’ll continue with this discussion of heat, maybe with some of the equations in a downloadable spreadsheet in case anyone wants to try.

Comments are closed.