Home Blog  
DIY Reloading firearm cartridges: Part 5

Reloading firearm cartridges: Part 5

by Tom Gaylord
Writing as B.B. Pelletier

Part 1
Part 2
Part 3
Part 4

This report covers:

  • Reloading rimfire cartridges
  • Top speed for lead bullets
  • Strip out?
  • Case preparation
  • CUP?
  • Transducers
  • So what?
  • Brass flow
  • 5.56 mm brass
  • Trimming cases
  • Summary

There is a lot of interest in this series. I’m stretching it out over time because it deals with firearms, but it’s useful for all of us to understand in order to better understand airguns.

Reloading rimfire cartridges

Reader Yogi asked about reloading rimfire cartridges. And he was justified in doing so, for the first firearm cartridges in any caliber were either rimfire or needlefire — a type of ignition I don’t want to get into in this series. Centerfire cartridges — the kind we reload today — came a little later in the world of self-contained cartridges.

Actually, Yogi, you not only can reload rimfire cartridges — there are actual kits to help you do it! Since I had no idea any of this was possible, I’m not going to pretend I know what I’m talking about. Here is an excellent article on reloading rimfire cartridges. And here is the place where the supplies and tools are sold.

That said, would you WANT to reload rimfires? It takes a LOT of time to do everything that has to be done to reload a rimfire cartridge. Unless you are huddled in the ruins of a post-apocalyptic shelter and fending for your life I’m going to guess most of you have better things to do. Read the article and you decide.

Top speed for lead bullets

Reader 1st Blue asked me what the top speed for a lead bullet might be. Now a copper gas check can be put on the base of a lead bullet and it changes everything, so what I’m talking about here is an all-lead bullet.

bullet gas check
A copper gas check has been swaged onto the base of the .308 bullet on the left. The .308 bullet on the right is just lead.

I have shot soft lead rifle bullets up over 1,300 f.p.s. with some success. I don’t like going that fast, though, because staying around 1,200 f.p.s. or less is almost always more accurate. But he asked and that is my experience.

Some reloaders believe that bullets have to be cast very hard to go their top velocity. They speak of Brinell hardnesses of 28-30 for their bullets and some go higher than that. My cast bullets are soft — in the Brinell 8-12 range. I do know that the harder the bullet the more lead it will deposit in the barrel. Soft bullets shoot much cleaner — but their top velocity is probably in the 1,300s, where some hard bullet shooters are claiming up to 2,000 f.p.s. Put a gas check on the base and the top speed goes up over 2,300 f.p.s.

Strip out?

Many shooters including 1st Blue are concerned that lead bullets will “strip out” of the rifling at high speed. I have never seen that or even heard of it happening. As long as the bullet is one-thousandth of an inch over groove diameter, it should do well at any speed up to its max. I said bore diameter in an earlier report and somebody brought my attention to it. I’m talking about measuring the diameter of the bore across the rifling grooves.

I have heard that glass-hard bullets (Brinells of over 30) will sometimes shatter from the force of the gunpowder exploding behind them. I have never seen that but again, I don’t harden bullets that hard. I do know that soft lead bullets don’t do that.

Case preparation

Some cartridges are low maintenance and require little beyond cleaning and possibly resizing before reloading. Straight-wall cases are among those that are easy. You can just reload a .38 Special case or a .45 ACP case for a long time before they begin to fail. So the shape of the case is one big part of whether it will last a long time or not.

Pressure is the other big reason for case failure, and it is even more influential than the shape of the case. Load a .38 Special up to +P+ pressures (over 22,500 copper units of pressure — CUP) and the necks will start cracking after a few reloads. Discard the case when you notice that. If you load the .38 Special at or below 15,000 CUP you may get 20 reloads from it. I have a .32-40 rifle case that’s been reloaded about one hundred times and is still going strong, but I doubt my loads for that cartridge ever went above 10,000 CUP. In fact they are so low that the lead unit of pressure or LUP would be used to express them.

Build a Custom Airgun


When we get into the pressure ranges of firearm cartridges we generally don’t refer to pressure as pounds per square inch — even though it still is. We refer to copper units of pressure — which is the pressure that crushes a copper crusher gauge that is held in a test fixture when the cartridge is fired. It isn’t incorrect to express pressure as psi, but CUP and LUP are the more common means of expression when talking about internal ballistics. When the pressure is below 15,000 psi, the LUP is used.


Today electronic transducers are used instead of copper or lead crusher gauges. They are faster and cheaper to use and cause fewer mistakes because careful measurement of the crusher gauge is no longer required.

So what?

Here is so what. Shoot that .44 Magnum with loads that develop about 20,000 CUP and get 10-12 reloads per case. Bump the pressure up to 36,000 CUP and the case longevity drops to 3-4 reloads. Drop it back to 15,000 CUP and get 25-30 reloads from each case.

Okay, all of that discussion was about straight-walled cases — except for the .32-40. What about bottleneck cartridges? Let’s start with a common one — the .223 Remington that is shot in the AR-15. It typically generates around 55,000 CUP/psi if you load it with standard hunting loads. You can go a little higher, but not too much.

Brass flow

At this pressure level the brass the case is made from will move forward under pressure. It’s called flow because that is what happens. At the high pressure the brass will flatten against the walls of the chamber and actually flow (move) forward. The length of the case will grow the more times the cartridge is fired. To offset that growth, we must trim the case back to a standard length before reloading it again. So we measure the length of each fired case and then trim all cases to one standard length before reloading begins. In my experience, the .223 Remington case needs trimming after every three reloads. Trim it two times and then throw it away, because the place it flowed from is getting too thin.

5.56 mm brass

The military version  of the .223 Remington cartridge is called the 5.56 mm cartridge. It is the same size on the outside, but it’s made of thicker brass. It can be loaded into and fired from many rifles that are chambered for the .223 Rem. BUT — the 5.56 mm generates higher pressure than the .223 Rem. It generates 58,000 CUP which doesn’t sound like a lot more — BUT the 5.56 mm cartridge chamber is 0.125-inches longer than a .223 Rem. chamber. Shoot a 5.56 mm cartridge in a .223 Rem. chamber and it generates 65,000 CUP, which is closing in on the proof pressure for the .223 Rem.! Case length and chamber length matters!

Can you reload 5.56mm cartridges and shoot them in a rifle chambered for the .223 Rem.? Yes — as long as you keep in mind that the thicker brass of the 5.56 case will hold LESS powder than the .223 Remington case when the bullet is seated to the same depth. That’s not a bad thing because that thicker 5.56 mm case will generate more pressure with less powder. My advice if you want to hit what you shoot at is do not mix .223 Remington and 5.56 mm cases together, and NEVER load them with the same amount of gunpowder!

I keep my cases separated (the headstamp tells you what’s what) and I develop loads for each type of case, keeping a sharp eye out for any signs of excessive pressure. They would be:

  • flattened primers
  • primers that flow back into the firing pin hole
  • primer pockets that become loose (evidenced by soot around them after firing)
  • cases that are bulged at their base (also a sign of excessive headspace)
  • cases that are split at their base
  • cases that are difficult to extract
  • cases whose heads are deformed (often they flow into the extractor cutout)

If you see ANY of these signs, stop shooting immediately and do not fire the remainder of those reloads.

Some cases REALLY stretch!

Of all the centerfire cartridge cases I have reloaded, the 6.5X55 Swedish Mauser case stretches the most. I had to trim them back after every firing and they started splitting at the base after as few as three reloads. To prolong case life I reduced my loads until they generated around 20,000 CUP. You have to read the reloading manuals and interpolate to figure out things like that. When they were loaded to that level I could get 5 or 6 reloadings before the danger signs appeared, and they stopped needing trimming after each firing.

The 6.5 Swede was such a chore to monitor that I stopped shooting them altogether. Someone asked whether this stretching was due to excessive headspace, but it happened on all 6 Swedes that I owned at one time or another. It was just too much to keep up with.

Trimming cases

I trim cartridges to length with an L.E. Wilson case trimmer. This tool dates back at least 80 years and still does wonderful work. Lee Precision also makes a much less expensive case trimmer that I use for a couple calibers. Where the Wilson relies on a bushing into which the case fits, the Lee has a central rod that limits the depth the cutting head can travel. The Wilson is universally adjustable for length, the Lee only trims to one standard length.

case trimmer
The Wilson case trimmer adjusts to a wide range of cartridge case lengths. Once adjusted, each case that’s inserted into the bushing will be trimmed to the same length.


That’s about as far as I want to go with reloading, unless there are specific things some of you want to discuss. Reloading starts out simple and gradually becomes quite complex as you learn more and more. As I said in the beginning, those who reload can be shooting while others lament the lack of commercial ammunition. Plus, it’s fun!

32 thoughts on “Reloading firearm cartridges: Part 5”

  1. Reloading for all my myriad calibers WAS fun! I had progressive presses for my 3 shotgun gauges (12. 20 & .410, which I used extensively for Skeet, trap & sporting clays), plus a great press I don’t now remember the name of for my 7mm AHIMSA bbl for my Contender. For other calibers I didn’t shoot as much, like my .264 WMC, I used inexpensive Lee Loaders. And then there were my black powder guns, which I eventually stopped using because they were a pain to clean, even with so-called cleaner powder. All these guns are gone now, replaced by airguns.

    • JoeB,

      Seems that there is quite a bit of interest in swaging custom slugs for airguns – especially for the larger calibers. You might want to look into that if the ” reloading ” itch is still there. 🙂


      • Hank
        I was going to try swaging small bore at one time.

        I offered to make BB a swaging tool even for a blog he did but he declined.

        I just kind of left it behind after that.

        I guess I should come up with something to make pellets. I do have some lead to start with.

  2. BB,

    All quite fascinating and a potential rabbit hole, like many hobbies can be.

    “copper gas check”? Ok,… but on what principal does it work? It expands? Or, it causes the lead bullet to expand? (either way sealing in gas/pressure better?)


  3. BB,

    Reloading was indeed fun. It was almost zen.

    Our reloading was never to a level that would approach maximum. We would work “up” loads for accuracy with particular rifles. We would never work “down” to an accuracy load.

    Our cases usually lasted for quite some time. We would have occasional neck splits with the .25-06, but they were usually with cases that had been resized from .30-06. Military .30-06 was awesome, but was difficult to resize initially.

    At the time, there was almost no military surplus 5.56 NATO, so we used strictly .223 for our rifle. We never had any problems with it.

    Thanks for finding the information on reloading .22LR. It sounds like a job for real nasty Winter days.

      • WIKI has a pretty good article on the different pressure measuring systems. This is a part of the conclusion that, to me, seems logical.

        “One outcome from this transition to using measurement transducers is, for example, that a Speer reloading manual from 1987 lists all SAAMI pressures in CUP, while current references list nearly all pressures in PSI. Another outcome is that design margins are now better determined, which has the effect of increasing the long-term safety of firing multiple thousands of rounds in a gun. With estimates based on crusher guns, actual safety margins could never be accurately assessed, short of actually firing tens of thousands of rounds in a sample gun”

        • We never had all of that fancy stuff. We always started a little low and worked our way up to a good accuracy load for that rifle.

          1/3 MOA at 300 yards ain’t half bad.

  4. Regarding 5.56×45 versus .223 Remington – there is a bit of overlap in cartridge case weight across the various manufacturers- i.e., some .223 cases weigh more (are thicker) than some 5.56 cases. What can be generalized is that the 5.56 case head area will be heavier to stand up to the greater extraction forces of automatic weapons.

  5. BB

    This series is the cat’s meow for anybody getting into reloading. Lots to learn here even for someone like me who has almost 40 years doing it. I did not know about the Swede 6.5×55 tendency to stretch. I rarely reload my Swedish Mauser even though I’ve had it many years. It may be my most accurate Mauser. It was so easy to work up an accuracy load I stopped trying to make it better and moved on to another project.


      • BB

        Yes, I picked up a K31 back in the 70’s and yes it is more accurate. However I don’t count it or Krags as being Mausers. My Krag is amazing too. I reload both.


          • BB

            None of my kids and grans reload yet but they will eventually get my tools that can reload everything I own. Many of my old guns have been given them as Christmas presents. They all know gun safety. This is my way of assuring future generations know the joy and importance of our 2nd Amendment. I have enough powder, primers, brass and bullets to assure they can still shoot hard to get or obsolete ammo.

            Hey readers, this is another reason to start reloading.


  6. In my teenage years during the 60″s the .220 Swift was the hottest factory cartridge around, maybe 4000 fps ‘ish but never did reload them. P’dogs at 300 yds. just exploded. Can you even buy ammo for that gun now? I should qualify that to “before the virus induced shortage” could you find it?

    • BBB,

      The .220 Swift isn’t as popular as it once was. Several other newer .22 cartridges have topped the 4,000 f.p.s. mark and seem to be more consistent. The Swift is stilkl being made, though and rifles are still being chambered for it.


      • It’s always fascinated me that while airgun manufacturers were at the beginning of their velocity wars so were firearm manufacturers and wildcatters (think 1960’s-1970’s).

        1,000 fps mark for airguns and The 4000 fps mark for firearms. I remember all the hype in all the magazines at the time for ackley’s .22 Eargesplitten Loudenboomer and weatherby’s 30/378.

      • Had a custom 220 Swift for a while,30 some odd years ago. 98 Mauser action ,Shilen heavy barrel, Timney trigger and thumb hole stock. Weighed over 12 lbs. without a scope. Boy would it shoot. Had some 40 grainers that would blue streak all the way to the target. P dogs at 500 yds with 55-60 grainers were in trouble as long as there was a little wind. Never did like shooting when it was dead calm. I think my ex-brother-in-law still has it.

  7. BB, thanks for clearing up the idea that a bullet can ride over its lands, and about the speed limit for lead. So the 6.5 Swede’s reputation as one of the best long range rounds is tempered by the CUP it generates from such a narrow neck, and as a result, it can stretch allot with full power loads . The bullet itself has a very low coeffcient of drag compared to bigger calibers, making it less susceptible to wind drift. I can see why there is allot of time and energy being spent on getting an airrifle to shoot a full size lead bullet at or near the trans sonic region. To fly 300 yards, a lead air gun bullet is going to need to be more like a corvette than a freightliner, I think 1,300 fps is at the limit right now. My Prod is maxed out at 860 fps with .22 FTT’s. To go faster the energy needed goes up quickly. To ride 33 miles per hour on a bike takes nearly twice the energy it does at 30 mph, so the same is true for bullets. I ran out of plenumn. I may even go so far as to weld up a small vessel for the gauge port, just to find out if that is the bottle neck keeping the gun from shooting heavies at 950 fps or so. Then, we just decide to get a bigger, nicer gun, if I want to! Maybe there will be some new ones to choose from by xmas. I will read about the reloading .22’s, but sounds like AG’s are here to stay!
    Thanks for sharing,

  8. Tom and Edith got me in reloading many years ago as a hobby. I shoot on Friday’s after lunch and reload as a relaxing hobby over the weekend. I have a portable setup that I put in front of the TV and watch football or a movie as I process the brass. It becomes an addiction as I save my brass and pick up whatever others have left at the range. My amount of ammunition increases each weekend. I gravitated to 300 Blackout last year and ammunition was either unavailable or expensive. With all the “free” .223 brass left at the range, I was able to convert the brass to 300 Blackout easily.

    Here is my portable workbench:

  9. B.B.,

    Thanks for another great Blog on reloading! I think i will stick with Big Bore Airguns to cover the rimfire+ range. I figure by the time i run out of .22 rimfire ammo i can go dig up the stockpiled ammo, paper towels and toilet paper of the Prepers that didn’t ever bother to do any actual Survival Training. Especially the Wilderness/Remote Medical training.


  10. “I figure by the time i run out of .22 rimfire ammo i can go dig up the stockpiled ammo, paper towels and toilet paper of the Prepers that didn’t ever bother to do any actual Survival Training.”
    Thanks, Shootski, I needed a good laugh today, and I cracked up when I read that! =)~

Leave a Comment

Buy With Confidence

  • Free Shipping

    Get FREE shipping on qualifying orders! Any order $150+ with a shipping address in the contiguous US will receive the option for free ground shipping on items sold & shipped by Pyramyd AIR during checkout. Certain restrictions apply.

    Free shipping may not be combined with a coupon unless stated otherwise.

    View Shipping Info

  • Shipping Time Frame

    We work hard to get all orders placed by 12 pm EST out the door within 24 hours on weekdays because we know how excited you are to receive your order. Weekends and holiday shipping times will vary.

    During busy holidays, we step our efforts to ship all orders as fast as possible, but you may experience an additional 1-2 day delay before your order ships. This may also happen if you change your order during processing.

    View Shipping Times

  • Shipping Restrictions

    It's important to know that due to state and local laws, there are certain restrictions for various products. It's up to you to research and comply with the laws in your state, county, and city. If you live in a state or city where air guns are treated as firearms you may be able to take advantage of our FFL special program.

    U.S. federal law requires that all airsoft guns are sold with a 1/4-inch blaze orange muzzle or an orange flash hider to avoid the guns being mistaken for firearms.

    View Shipping Restrictions

  • Expert Service and Repair

    We have a team of expert technicians and a complete repair shop that are able to service a large variety of brands/models of airguns. Additionally, we are a factory-authorized repair/warranty station for popular brands such as Air Arms, Air Venturi, Crosman, Diana, Seneca, and Weihrauch airguns.

    Our experts also offer exclusive 10-for-$10 Test and 20-for-$20 Service, which evaluates your air gun prior to leaving our warehouse. You'll be able to add these services as you place your order.

    View Service Info

  • Warranty Info

    Shop and purchase with confidence knowing that all of our air guns (except airsoft) are protected by a minimum 1-year manufacturer's warranty from the date of purchase unless otherwise noted on the product page.

    A warranty is provided by each manufacturer to ensure that your product is free of defect in both materials and workmanship.

    View Warranty Details

  • Exchanges / Refunds

    Didn't get what you wanted or have a problem? We understand that sometimes things aren't right and our team is serious about resolving these issues quickly. We can often help you fix small to medium issues over the phone or email.

    If you need to return an item please read our return policy.

    Learn About Returns

Get FREE shipping on qualifying orders! Any order $150+ with a shipping address in the contiguous US will receive the option for free ground shipping on items sold & shipped by Pyramyd AIR during checkout. Certain restrictions apply.

Free shipping may not be combined with a coupon unless stated otherwise.

View Shipping Info

Text JOIN to 91256 and get $10 OFF Your Next $50+ Order!

* By providing your number above, you agree to receive recurring autodialed marketing text msgs (e.g. cart reminders) to the mobile number used at opt-in from Pyramyd AIR on 91256. Reply with birthday MM/DD/YYYY to verify legal age of 18+ in order to receive texts. Consent is not a condition of purchase. Msg frequency may vary. Msg & data rates may apply. Reply HELP for help and STOP to cancel. See Terms and Conditions & Privacy Policy.