seventh round modification

[cgroc09]

I thought ya'll might enjoy a few pics. Here's a few pics of a reciever with and without the seventh round modification.





Enjoy, Bubba

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[RCS]

The small extra rib found on the left side is normally found on revision 2 receivers but I do have some data on a revision 1 receiver with low guide ribs and an extra narrow rib. This receiver is in the 49 thousand serial range. It is kind of rare to find too.

A few collectors are always tracking the extra wide rib, most have had the correction and all to date are revision 1 receivers. They fall into the late 30,000 to early 40,000 serial number range

[Calif-Steve]

Was the modification only done at Springfield? Did they ever produce a Modification Work Order (MWO)?

[RCS]

There are some Winchester receivers with low guide ribs around, never seen one that had the correction.

[Rick B]

In the Winchesters, I had 100185 and it was welded up. I also had 101660 and it had no 7th round mod. I had 100434 and it was build with the 7th round mod. Conclusion from seeing many of the other Educational WRA's is that they started making the factory mod around 100200 and 101660 must have been on a desk and put back on the line later and serial numbered after it was handled.. It was an early receiver within the 1st 200 built.
So to answer your question.....

Yes WRA had some early receivers built without the 7th round rib
Yes, some WRA's were welded up for modification but very few and rare.

The 7th round cut was all caused by the cutting bit for the threads. They later tapered or shortened the stroke inwards as to not chop off these ribs. If you look through the thread holes in the front of the receiver you will see the rounded angle is perfectly in line with the threads. Rick B

---------- Post added at 09:19 AM ---------- Previous post was at 09:15 AM ----------

Here is 100185 and as you can se it was welded and then that was removed. I am clueless if it was done outside of the factory or not as it made no sense why someone would remove it. Rick B





---------- Post added at 09:23 AM ---------- Previous post was at 09:19 AM ----------

Here is 101660 built without the ribs. Rick B

[ABPOS]

I'm totally lost. Can someone school me on this?

[Bill Hollinger]

Here you go. Karl nailed it. 7th Round Modification ?

[Bob Seijas]

Model Shop rifles had the sheared rib and did not experience the stoppage. Art Tuttle always said the whole brouhaha was WAY overblown and the rib wasn't the problem, it was a stack-up in the tolerances of the follower. I did a lot of pondering on the issue and I am satisfied that it was a combination of both: a rifle with a high or repaired rib could handle a barely acceptable follower, but a rifle with low rib could jam if mated with such a follower. A rifle with a sheared rib worked just fine if the follower was to spec.

[ABPOS]

Thank you!

[RCS]

What is the serial number range of the receiver in the first photo with the extra narrow rib ?