Is there a link to the GB listing?

Odds are that the "W" standard for "Weatherby" and that it's a rechambered 300 H&H Magnum.  The 300 Winchester Magnum was not released until 1963.  A photo of the top of the action would tell if it's an H&H action or not.  If it's not an H&H action, then it may have been a standard action converted to short magnum.  But those were usually done either by rechambering a 30-06 barrel (that was marked "30-06 SPFLD") or by putting a 1963 barrel in 300 WIN MAGNUM on a converted standard action.

This barrel "300 XXX MAGNUM" was once marked "300 H&H MAGNUM" in style 3C.  Too long a cartridge to convert to 300 Winchester Magnum.  

Best,

Lou

 That being said I have purchased three M70s over time that were originally 300 H&H that had been rechambered to 300 WBY.

 Other may correct me here but to get it to 300 WIN MAG would require shortening the chamber and then reaming to 300 WM.

 A quick test would be to chamber a 300HH cartridge, If it chambers it is likely HH if it doesent ....??

The script of the "W" looks somewhat Weatherby ish.

 Doug

BRP

I've seen a few Jennings rifles over the years but never had a clue about the inner workings of the action.  I found it fascinating.

Thanks for posting Mark!

I'm also in agreement with the others on such a great video, and you sharing some very interesting information with us.

As mentioned above, that rack and pinion did remind me of the Bullard, that you kindly shared a while ago.I never knew that the Jennings had that mechanism inside of them, and you're explanation is second to none! IMHO! I've had thoughts of one, (Bullard), ever since!

Tony

Maverick said
Once you get that spring fixed, come back and let us know how well she groups. I want to see some red jugs flying!
Maverick
  

All kidding aside one of the displays at this year's Cody Show featured a recreation of the rocket ball ammo. I think the same creative process could be applied but I'm quite sure our friends at the CFM would not endorse this project. With the low velocity of this round I suspect the results on Mark's favorite targets would be less than spectacular. I like the way you think, though!

Mike

Maverick

Sincerely,

Maverick

Mark Douglas said

Jeremy P said
Mark, wasn't there another contemporary "mainstream" rifle that used a super-smooth rack and pinion? I seem to vaguely remember one...
  

That's right.  The modern Browning BLR's use a type of gear system.  However it's a completely different design than the Jennings and Bullard rifles utilized.  Mark
  

Ah, the Bullard is what I was thinking of I think, probably from a former video of yours I recall. I'm behind on this new one, will watch soon!

Jeremy P said
Mark, wasn't there another contemporary "mainstream" rifle that used a super-smooth rack and pinion? I seem to vaguely remember one...
  

That's right.  The modern Browning BLR's use a type of gear system.  However it's a completely different design than the Jennings and Bullard rifles utilized.  Mark

MidwestCrisis said
Great video Mark.  
  

Roger Adam said
What an interesting and educational video.  I would have had no idea what the interworkings of that action were.  Thanks for sharing and educating the rest of us in the Winchester community.
  

Jim F in CT said
Mark . . . .
I just watched your video of the Jennings rifle, and . . . .
As usual, you “hit it out of the park!”
If I ever needed someone to work on any of my firearms, I’d look for someone of Mark Douglas’ “aptitude and attitude”!
I just disassembled an original Remington “New Model Army” from 1864, and, likewise to the Jennings, it’s’ mainspring looks to have “come from a TRUCK!”
Keep up the good work, Mark! . . . . I enjoy the “fruits of your labor!”
  

Thanks a bunch, guys!  We really enjoy our work on both the firearms and the videos.  The relationship we have with the folks at the museum is really a treasure and having an opportunity to work on a firearm from the collection that likely passed through Oliver Winchester's hands has been a real treat.  

If it had only been anything but the mainspring.  A mainspring like this one makes a gunsmith question his career choices. The geometry and placement in that recessed housing are making this one particularly interesting.  Almost done with it, then comes heat treat, tempering and lots of prayers that it doesn't snap the first time we test it.  Mark

I just watched your video of the Jennings rifle, and . . . .

As usual, you “hit it out of the park!”

If I ever needed someone to work on any of my firearms, I’d look for someone of Mark Douglas’ “aptitude and attitude”!

I just disassembled an original Remington “New Model Army” from 1864, and, likewise to the Jennings, it’s’ mainspring looks to have “come from a TRUCK!”

Keep up the good work, Mark! . . . . I enjoy the “fruits of your labor!”

Mark Douglas said

TXGunNut said
Neat stuff, Mark! Mainspring reminds me of something from a Sharps rifle except for that little leg that goes off from the short side. Sharps also had a primer magazine, I'm wondering if there might be another branch to this family tree. 
 
Mike
  

Mike,
Even though it differs quite a bit from the Lawrence pellet priming system used by Sharps, I believe RS Lawrence had a hand in the Jennings Rifle as well.  Mark
  

That certainly makes sense, Mark. The Jennings is a clever little design but probably not very reliable by today's standards. I haven't been able to closely examine the priming system on a Sharps, most are incomplete. I know where one is, maybe the owner will let me take a closer look at it someday. I'll make sure he sees your video, he'll certainly enjoy it!

Mike