Bullet penetration myth busted

Yesterday I had a need to test fire just a few rounds from my carbine after some repair. So, not wanting to go all the way to the range for this minor event, I decided to do it at home. My home owners assoc has restrictions for firearms in the neighborhood, so I could not fire outdoors, but I thought inside the garage would be OK where the sound would be dampened.

But, what sort of contraption could I create to be sure and capture the FMJs from a few test fires? Like many others of you, I had heard the stories about how the lowly .30 carbine had trouble penetrating the heavy Korean Chicom winter jackets (which I have now, unfortunately, discovered is BS). So, considering that, and after a short spell of mental engineering, I concocted the following test bed to catch just the few rounds I needed.



A three foot tube (concrete form) stuffed with 'something' that would stop the bullets. I also place three 1/2 inch thick boards at the other end of the tube just in case I miscalculated and a round snuck thru the 'something'.

Well, the 'something' turned out to be folded heavy fabric blankets like the ones used in baby nurseries, and which are coated with an additional thick waterproof layer.



I figured that if I folded, maybe 4 of these, and stuffed them into the tube, I'd have no problem. After all, how many layers could a Chicom jacket have?

I folded each blanket lengthwise 4 times, and then folded it over itself 5 times. This created a 'wad' that was 20 layers thick.







Actually, only 2 of the 4 blankets were folded into 20 layers. Two of them were folded only into 16 layers. So, in all, I had 72 layers of thick blanket folded for stuffing into the tube, which I did.




These 72 layers crammed tightly into the tube amounted to 16 inches of material which, surely, would deter any errant FMJ from the interior of my garage.



Now, all set up, I fired the first round. Seemed to work fine. I looked at the boards at the end of the tube and did not see any holes. So far, so good. I fired the second round and checked the boards again and....uh, oh! There is a hole.



I had missed the hole from the first firing due to a shadow on the board.

Checking further, I noticed 2 holes thru the sheetrock of my garage wall. Fortunately, no penetration thru the brick exterior wall.



Had to beef it up some. So I placed a 3 inch thick landscape timber between the end of the tube and the boards. Now, she's good to go.



"BAM BAM". Couldn't believe my eyes!



And the BACKSIDE?



They did not penetrate all the boards however. But before continuing, I filled a bag with 6 inches of sand, and sandwiched it between several of the folded blanket 'wads' in the tube. That finally did the trick.
There are two morals here (to me anyway):

1. As they say on Myth Busters, do not try this at home. Was a dumb idea on several levels.
2. The lowly .30 carbine will hurt you severely, even if you are layered up out on a frigid adventure. Seventy two layers of folded blanket, three 1/2 inch boards and drywall (throw in a landscape timber as well).

I now have a much greater respect for my little rifle, and really do wonder about that Chicom jacket claim.

A 30 cal barrel with sand usually does the trick. 50 gal better.
The flaw in your test is you are firing at point blank range. You can kill someone with a 22 at that range. For a true test you would have to have Target at a range that the bullet has had time to stabilize.

Incidentally, the carbine made an excellent urban police rifle. Due to lack of penetration of buildings. When cities went to AR platform they found a bullet could penetrate building and cause unintentional casualty.

Ah, the repairs.....Rifle a new acquisition. On the range last Wednesday, rifle would fire and eject normally, but not pick up and feed a new round from mag. It didn't jam, just the bolt closed on empty chamber as if pickup was never attempted. Most frustrating is that it would cycle perfectly manually. Would empty a whole mag manually without hesitation.
Changed many things (in turn) at the range. including 5 mags, main spring, trigger housing complete, and bolt. Stretched mag spring some for more tension. Spread mag feed lips (?) slightly. More lube. Same result for 2 hours. Brought home.
At home serious eval (3 hours). One thing at a time. New trig house complete. Had to dremmel the lug to allow fit. Tested. No fire. Light primer strike 3 times.
Changed bolt (complete). Tested. It fired but no feed. Back to orig malfunction.
Changed slide but did not test with it. Rifle didn't like it. Showed some binding (manually) as it approached the rear end of the bolt cycle.
Changed slide (another). Tested. It fired and tried to feed (Yea), but bullet jammed entering throat. More dremmel work smoothing and polishing feed ramp area.
Reassembled. fired. WORKED (4 rounds, different mags) with both FMJ and soft point.
Now, I have a $450 PMC instead of a $250 PMC. I suspect someone might be asking what the rifle make is. So there you have it.
PS: The PMC had an original night scope mounting bar on it, type II if I remember. Got the package for a good deal (scope bar alone was worth it). Couldn't resist. My first commercial carbine. Won't make a habit of it.

Colreed, great details, appreciate you sharing them. I was making reference to the date time stamp of your pictures of 2018. Just kidding of course, no offense intended.

I've never had a PMC, nor have I seen one in person. Had a 60's Cadmus style folding stock with GI parts in it. Sold the innards. A true bubba fit job though. Still can't get the recoil plate out of the remaining folding stock. Some kind of large bolt down the center of the pistol grip.

Paging Dr. PMC.

Charles,Thanks for the tip. I forgot to mention that I pipecleanered the gas chamber and piston with solvent and pressure air. Was pretty clean to start with but who knows. Again, appreciate the input.Reed

Reed, no worries. My sense of humor can be a little dry.

Will there be USGI repairs made to the dry wall?

ColReed,

Hi. I'm the crazy guy who has bought and sold many of the commercial carbines you see on M1CarbinesInc.com. One of my goals has been to examine, document, test fire and trouble shoot each one. More than one or two from each company. While I've moved on to other carbine projects I still pick up a commercial carbine now and then if it's the latest new version or a variation I haven't worked with yet.

Plainfield made carbines from 1962-1977. What they made early on was a bit different than what they ended with and passed on to Iver Johnson. Trouble shooting a Plainfield carbine, it helps to know the serial number and markings it has which helps date it to a given time period. What they did during that time period helps to focus on known issues. Bottom line is a carbine is a carbine if built close to GI design and dimensions but some of the commercial ones can have idiosyncrasies.

One thing as a word of caution. Polishing or altering the feed ramp needs to stay clear of the chamber. Check your spent casings for bulging on the side at the rear to make sure the feed ramp work didn't affect the specs of the chamber.

Cartridges hanging up on the feed ramp is not an uncommon issue for both commercial or GI carbines. Reads like you've done all the right things with trouble shooting. I'll add a few variations that may be of help to others. Then I'll address the failure of the bolt to pick up a new cartridge during it's return forward.

#1 cause of feeding problems with carbines is usually magazine related. Magazines were a weak link in the orchestra right from the beginning and Ordnance knew it. They were made in the quantities they were made as they were disposable. You tried different mags, which is a good start. If those mags were all GI mags or well used mags you might like to have a quality new mag handy to also check with. Which you may have done.

There are two issues with the mag, besides the spring, that can affect the ability of the round to chamber but can also cause the bolt to pass over the cartridge it's supposed to chamber. One is the bend of the lips at the top of each magazine which are easily damaged by dropping the mags occasionally. You did good checking this one. Another is the magazine nubs that sit on top of the mag catch to hold the magazine in place. If they're bent or damaged the magazine can sit lower than it should.

For awhile in the late 60's and into the 70's Plainfield used aluminum trigger housings. While okay for the short run it's now many years later and aluminum doesn't have the lifespan of steel. Same applies to the aluminum trigger housing used by Universal. The wear that causes the mag to sit lower isn't always clearly visible. Again, you done right by swapping trigger housings. Another suggestion would be to push up on the magazine as you are firing and see if it makes a difference. Push up on the rear, then the center, then the front. If something works and something doesn't it narrows the suspects.

The majority of Plainfields, but not all, have a barrel skirt to route the incoming cartridge into the chamber. Make sure yours has the barrel skirt on the rear of the barrel chamber that extends into the 6 o'clock to 10 o'clock chamber area. No barrel skirt isn't a fail, but may contribute to problems.

The bolt passing over the cartridge and fully rotating and locking closed. #1 culprit is the magazine is sitting too low. Helps to know if there are scratch marks across the top of the cartridge the bolt passed over. Also helps to know if the bolt encountered any resistance as it moved over the cartridge it didn't pick up.

The #2 most common issue with carbines not feeding is they need to be cleaned. Especially the gas chamber and gas piston. Soldiers had the luxury of using only 1 type of ammo and instructions to turn the carbine over to an armorer for cleaning the inside of gas piston cylinder. Some people have taken this to mean never clean it but they forget the part about the armorer is now their job. Looks like you had this covered too.

If the recoil spring or hammer spring are too short or worn out usually the bolt will stop when it engages the rear of the cartridge or shortly thereafter. This can appear to be a problem related to something else when the nose of the bullet stops against the feed ramp. GI springs are tuff babies, not so all commercial springs. Check the number of coils on the hammer spring and the diameter of the wire. Early GI springs were 22 coils, late ones were 26 1/2 and the ones more reliable. Both had the same diameter of the spring wire. A number of commercial springs are made from thinner wire and wear out easily.

That your bolt fully closed, rotated and locked without picking up the cartridge points to the magazine position being too low being the problem. Have a look at the animations at http://www.uscarbinecal30.com/operation.html. Check the setting of your video player to make them go slow motion. Watch the front of the bolt as it moves forward and engages the next cartridge. You can see the shape of the magazine lips can get in the way but the bolt completely passing over the cartridge and closing you can also see the position of the rear of the magazine is critical.

I just checked the animations and once again something in the world of the internet has changed. If they aren't working for you give it a few hours. When I'm done here I'll be trouble shooting the animations.

Back up a bit, I've found pushing up on the bottom of the magazine as described above will usually ID the problem if the magazine isn't sitting high enough or isn't sitting as it should to allow the rounds to feed.

Also check the mag catch as some commercial ones are slightly too small or the opening they sit in is slightly too large.

Hope this helps someone.

Jim

Any penetration test(s) with any firearm should have a fail safe backstop that's impenetrable just in case the bullet breaks through the objects used to measure penetration.

Sand, dirt, tarred railroad ties in multiples are good alternatives. Just make sure the trajectory of the bullet isn't at an angle to the backstop to avoid ricochets. A large bucket of sand with a vented plastic lid to keep the sand inside and not blow the bucket apart works well for handgun rounds. A larger bucket and more sand is needed for powerful centerfire cartridges. A sandpit size bucket works well.

Wide month steel pipes filled with plenty of sand are stronger than plastic buckets and often used by police departments as bullet traps for chambering or unchambering rounds.

Jim

Dan,

Yes, I think to be completely fair to the original "myth," this test should be performed at distances beyond 100 yards. I don't think the bullets will bounce off a jacket at 200 yards, but I think the result will be quite different than this point blank test.

David Albert
dalbert@sturmgewehr.com