OK, see what you think of this. After comparing a photo of the breech block of another R51 (sent to me by another owner), it appear the projection at the bottom of the breech face  of my pistol was shortened noticeably. His is definitely longer and more pointed than mine (I know, that sounds weird, but stick with me). The malfunctions I was experiencing only happened on the first round from a full magazine when there was already a round loaded in the chamber. Upon firing, that longer projection might drag across the rim of the top round in the magazine. Under full magazine spring tension, the pressure exerted against the rim of the case as the slide/breech block was moving rearward, might have caused the front of the cartridge (i.e. the bullet) to cock slightly upward in the magazine. As the slide came forward, the breech face would strike the base of the cartridge that was now at too steep an angle to move up the feed ramp as it normally would. Instead, the bullet would move forward and jam against the top of the barrel. In some instances, the drag/snag against the cartridge rim was so strong that the entire cartridge was pulled/flipped out of the magazine. In those instances, the cartridge was either captured by the slide and wedged against the barrel, or it exited the ejection port with the spent casing. Those were exactly the malfunctions I was experiencing, that that longer projection on the breech block COULD have caused them in that manner.

(Does this all sound a little mentally ill?)

Howard

Your evaluation makes sense to me. If the lip tips the cartridge nose up, I wonder if the lip was added to help prevent nosedive jams. Has any of your ammo tried to nosedive?  On the other hand, mine will experience nosedive jams when using flat point or hollow points, so I suppose maybe the lip was not for preventing nosedives.

Out of 400+ rounds,  have experienced precisely 1 nose-dive, and that was with an FMJ round. I suspect that was an anomaly. Possibly just a bad round of ammunition.

HRF

Howard,
Thanks !  I'm going to check both of my 51's for that lip you mentioned.  Both of mine cycle well.  However, I will say, I load the seven without one in the pipe.  I also insert the mag with slide back as mentioned months ago on this site.  I think Blackie called it military style. One shortened follower mag and 3 untouched.
Rog

I trimmed the bottom of the breach block like yours.   There are no 7+1 issues. 

To be fair, my magazines have been hacked and modified so many times its hard to say.   

I'm glad it's running well for you! For the life of me, I don't know why it has taken so much time and experimentation to get these pistols running properly. I would expect that the engineers and gunsmiths employed by Remington would have figured all this out long ago. I think the R51 is a nice little carry pistol, but Holy Smokes! they've got to make them run reliably without every purchaser having to troubleshoot the things after they get them home.

Howard

Yep Howard, that's their job. You think after the first debacle, they would have gotten things straightened out. Nope.  I think the team assigned to the R51s are a bunch of dopie oakies. They should have revived John Pedersen for this job. He would have gotten it right the first time. Anyways, I am glad the 1911s they are turning out are better quality and consistency than these pistols.