Another 7.62 x 51 Mystery


#1

Hi All,
Actually the bullet measures 7.62 x 52 which is really confusing to me. The round appears to have a plastic yellow-brown (almost see through) case. The head head attracts a magnet but is brass colored. The bullet also attracts a magnet and is copper colored. There is no headstamp. The primer has a ring crimp with red annulus. Upon closer inspection of the case just bellow the shoulder there are 4 evenly spaced holes about 1/8 th. in dia. Any ideas? Thanks in advance, joe


#2

Based on your description, I believe that this composite cartridge was made by Remington in the 70’s using brass plated steel for the case head and shoulder/neck. I have two variations - I will post pictures of these and a possible box once I have access to my collection. I’m pretty sure that the round has been discussed previously on the forum. My internet access is limited at present so I haven’t been able to search for you.

NATO Dave


#3

Joe

I have the same cartridge. As Dave said, I think it was discussed on the Forum some time ago. This may be it:

viewtopic.php?f=1&t=2695&hilit=+Remington+composite+case+

Somewhere, I have a short report on it. I will look for it as soon as I find my glasses and car keys.

Ray


#4

Here are two of the Remington composite 7.62x51mm cartridges - note the differences in extractor groove between the two - I don’t know if they are from Lot A and lot B (see below) or there is another variation I’ve yet to find. Almost all the rounds I’ve seen have the wide extractor groove.

A box that may be associated with the cartridges is labeled lot A but the insert indicates lots A and B exist, and that the cartridges date from 1974 or earlier.




NATO Dave

Edited for clarity


.308 SAKO Experimental Plastic-Case -about 25years old-
#5

For what it’s worth, I have one with the wide extractor groove and my notes indicate it is from lot B.


#6

There is a DTIC report (ADA307469, dtic.mil/dtic/tr/fulltext/u2/a307469.pdf ) entitled FEASIBILITY STUDY OF THE MANUFACTURE OF 7.62 mm CARTRIDGE CASES FROM PLASTIC MATERIALS, by the Franklin Institute, Philadelphia, PA, 1959 -1960. In the study they tried various plastics, epoxies and nylon/fiberglass for making cartridge cases composed of two parts, the head (“plastic butt” as they called it) and the plastic “cylindrical wall”. These two parts were fit together via a lap joint which proved to be problematic in that it was often a point of case failure and the plastic head was prone to extraction problems. They finally ended up using brass cartridge heads (“brass butts”) to help overcome extraction problems. The sectional diagram of these brass head / plastic “cylindrical wall” cartridges are very similar in appearance to the Remington experimental cartridges shown above which appear to have a lap joint between the metal cartridge head and the plastic tube of the cartridge. I wonder if the work by Remington was a continuation / advancement of the Franklin Institute work?

Below are 2 case head diagrams (plastic/plastic and plastic/brass), representing a portion of the designs tried in the tests.

Brian


#7

Brian

That’s the report I mentioned in my first post. I really did mean to look for it but now I won’t have to. Thanks.

Ray


#8

BD, did you mean Franklin Institute or Frankford Arsenal?


#9

jonnyc

I’m not Brian. but he did mean Franklin Institute. It was prepared for Frankford Arsenal.


#10

As those rounds are Remington products, I wonder if the drawings wouldn’t be more representative of some of these rounds?


Paul


#11

Ray, that’s funny, as now the Franklin Institute is known as a fun science/technology museum that you take kids to! Now I wonder if they still do any real science there.


#12

Paul,

Interesting casings. They appear to be another step (next step?) in trying to develop a composite case by having the brass case head bored (?) through. So when the plastic portion of the case is formed the result in something more than a lap joint between the case wall and the case head. It would appear from the casing you show that when plastic was injected into a cartridge case mold /form, the brass head was in the mold and the void in the brass head was filled with the same plastic used to form the case walls. The resulting plastic “plug” was drilled or formed in someway to make a primer pocket.
Which (for me at least) raises the question concerning the above picture of the Remington cartridge case head, provided by towaz, is that a battery type primer or is the case wall plastic used to form the primer pocket? Or is it something else all together?

Brian


#13

I just pulled out the cartridge I showed above for a closer look. The material around the primer appears to be metal in a battery-cup configuration, not plastic.


#14

If you read the Franklin Institute report you’ll see that one of the problems they did not overcome was the expansion of the primer resulting in the fracture of the base. They recommended a ring insert to contain the primer and reinforce the head. That is what Remington did, not only on this case but on others, such as the aluminum Light Rifle cases and the FAT49E4 years earlier.

Ray


#15

Ray,

I missed the recommendation of the ring insert for the primer.

Thanks,

Brian


#16

Ray,
Sorry, forgive me if I’m missing the obvious…but whatever is the FAT49E4?


#17

Disregard my last Ray, a Google search brought up your previous posts regarding this and has answered my question.
Jim