I have wondered why no one has built a 9mm “Chipmunk/Crickett” rifle. The 9mm Luger cartridge (also known as the 9mm parabellum or 9x19mm) is the center fire equivalent of the .22LR cartridge. It is very cheap, plentiful and accurate. It is cheaper to buy than the .25ACP, the .32ACP and the .380ACP. Yes it does cost more than a .22LR but has the advantage that it can be reloaded. Building a very lightweight carbine would seem like a good prospect for the market. I also believe it could be a superior “survival” rifle with the ability to take down small game, same as the .22LR, and larger game that would be trouble with the .22LR.
I think I should add here that there are a couple of 9mm bolt action rifles available. The most seen is the Spanish DESTROYER carbine in 9mm Largo (9×23). These were used as police rifles. There are also the ARMALON Pistol Carbine (Armalon PC) that is chambered in a number of pistol calibers and is based off of the SMLE No.4 action.
There are a number of semi-automatic pistol caliber carbines that chamber the 9mm Luger cartridge.
I think this would be a good transition rifle for older children. It may be a good rifle to start a younger person into reloading. This could be a good back pack rifle for adults. If a barrel extension is used in the design then it can be built as a takedown rifle.
I think I will start with some physical comparisons of the two cartridges and their compared performance
avr. bullet weight 40gr. 115gr.
Bullet diameter. .223 .355
avr velocity 16″ barrel 1250fps* 1300fps**
avr. foot pounds energy 139 FPE 432 FPE
max. pressure (PSI) 24,000 psi 35,000 psi (NATO 41,000PSI)
overall cartridge length .985″ (1″ in some) 1.169″
rim diameter .278″ .392″
Case length .613 .754
Rifling twist 1″ in 16″ 1″ in 10″
common bullet weights 30,32,36,38,40*** 90,115,124,147***
* High velocity .22LR loadings, not hyper velocity loads. 16″ barrel!
** Standard velocity non +p loadings in 16″ barrel.
***Bullet weights compared were 40gr in .22LR and 115gr in 9mm. Common listed bullet weights is for information purposes only.
NOTE: Velocities were averaged from those posted at ballisticbytheinch.com. Ammunition compared is name brands such as Federal, Remington, Winchester Western etc.. No specialty ammunitions were added to these averages.
Though there are major size differences between the two cartridges, none of them are so far off, that they could not be built on a common action. The 9mm is going to need locking lugs to safely contain its higher pressure. The .22LR usually uses the bolt handle as its locking lug. The ejection port would have to be longer. The action may have to be slightly longer, though a chipmunk rifle has a very generous loading port. But overall both cartridges can be made to work in the same size action.
Ballistics wise the 9mm is slightly (very slightly) flatter shooting than the .22LR, just barely. Energy wise it is far superior. The ballistic curve is so similar that someone who is very good with a .22LR is going to be just as good with the 9mm. Accuracy should also be very similar with the 9mm getting the edge. Bullet performance will be better in the 9mm considering it uses jacketed bullets.
Someone who is a good shot with a .22LR is going to be able to shoot a 9mm rifle just as well. The recoil from a 9mm in an under 3 pound carbine is not going to be significant. Since the ballistics are very similar, so bullet drop is similar, the shooter is not going to have to relearn to shoot the 9mm carbine effectively.
The Chipmunk and Crickett’s in .22LR are about 2.5 pounds in weight. A 9mm version should be able to be brought in under 3 pounds. The 9mm Barrel is going to be slightly heavier even with an aggressive taper. Since I plan on using a barrel extension, rather than a barrel pinned directly into the action, an Aluminum Receiver could be used to save weight. With an aluminum receiver I would be tempted to use a Stainless steel sleeve inside of it just for better wear.
Some features that really need to be added to the 9mm rifle are;
- Self cocking striker.
- Manual safety.
- Magazine feed.
A self cocking striker will not be that hard to add. With a self cocking system you need to add a safety. The Idea is to provide a “Step Up” Rifle. A rifle that is next in line to the Crickett. The Chipmunk brand was bought out by Crickett and is no longer produced.
To keep the rifle small I would use either a single column removable magazine, or an internal magazine and a stripper clip feed system. for a removable magazine I think the Ruger LC-9 magazine would work well. As to strippers, 5.56 NATO strippers clips will work. The 9mm Luger/Parabellum/NATO and the .223/5.56 have the same head diameter. I would probably cut the strippers down to 5 rounds capacity. The internal magazine may be a better option here in California. It will definitely be 10 rounds or less in capacity.
Personal Note: I think an En Bloc “clip” might be a good choice for this rifle. In the Garand rifle it is hard to do a tactical reload as you have to hold the action open to put cartridges into the partially spent clip. In a bolt action it would be easy to top up the En Bloc clip with loose ammo. Something of 6 to 10 rounds capacity.
I would like to have some better sights than what are on the Chipmunk and Crickett rifles. Though serviceable and robust I would like to see a peep that has settings out to 100 yards. A forward mounted scope rail (mounted to the Barrel) would also be an excellent option.
The Chipmunk/Crickett rifle action uses the bolt handle as its locking lug. The .22WMR (.22 Magnum) version uses the same as a locking lug. The magnum is a longer action, the magnum cartridge has the same pressure specs as the .22LR. The 9mm, being a higher pressure cartridge, needs a little more safety margin than a .22LR needs. At 35,000 psi (SAAMI specs, NATO spec is 41,000PSI) it would be better to have two locking lugs up front of the bolt. I have a seen a design, in Home Gunsmith Forums, where the bolt handle goes through the bolt and has two locking lugs. This would be more than strong enough for the 9mm. I think that design would cause a longer action than I want though. Adding the front locking lugs is going to lengthen the action some either way.
Ejection will be handle by a spring loaded plunger. Extraction will be by a spring loaded claw. The sheet metal extractor used by the Chipmunk has been known to break. I could cheat and use the firing pin as an ejector also. The drawback to that is you can have an issue when ejecting live ammo, though It does simplify the design.
The simplest design would be to used a pinned barrel in the receiver. Then the locking lugs are machined into the receiver itself. A more versatile design is to thread a Barrel extension on. The locking lugs are machined in the extension. With an extension all of the firing forces are held by the bolt head, barrel and the extension. In a Receiver mount the strength has to be built into the receiver and the bolt. The barrel extension is likely the route to take if you really want to lighten a rifle up!
For the stock I think a Laminate is the way to go. They are very stable when used in wet or dry climates. They are also easier to manufacture, at least for the home gunsmith.
Furniture would likely be aluminum for lighter weight. Sights would be steel. I believe a flash hider/muzzle brake might be a good addition to the design.
I thought I should give some information about the next most popular “survival” caliber, the .22 magnum.
.22 Winchester Magnum Rimfire.
Avg. bullet weight. 40gr
Bullet diameter. .224
Avg. velocity 16″ barrel. 1900
Avg. foot pounds energy. 350
Max pressure (PSI). 24,000 PSI
Overall cartridge length. 1.350″
Rim diameter. .294
Case length. 1.055″
Rifling twist. 1-16″
Common bullet weights. 32,36,40,45
As you can see the .22 Magnum closes the gap on the 9mm Luger pretty well. It shoots flatter due to higher velocity. It’s price is near the same as 9mm factory loads. It does not need to expand well to work efficiently. The 9mm does not need to expand much to transfer energy efficiently.
to be continued! The .22 magnum has good penetration. I give the advantage to the .22 magnum for ranged use on small game.
Possible Further design elements
The ultimate design for a 9mm bolt action would be a “Straight Pull” design. A Straight Pull design is where the bolt is pulled directly rearward without be lifted. as the bolt is pulled rearward it causes an unlocking action to take place.
If you have ever watched a Biathlon event, you can see how fast and efficient, the straight pull rifle can be. Whether a 9mm version could be “tuned” to that level of speed and smoothness would be the question. The larger case is going to require more extraction force. This could be accomplished by the fact that there is going to be more bolt head twist (unlocking action) for the locking lugs needed on the 9mm.
To be continued