A Note re: Ramp/Chamber Radius

[sheepherder]

This mainly concerns aftermarket barrels for Lugers among other pistol makes. I had been getting failure-to-chamber with FMJ-RN ammunition for my 1911 clone, using the 'kits' from Sarco. After inspecting the frame ramp and the barrel ramp in the Sarco kit, I thought something was off. The barrels had a sharp 'chisel edge' rather than the ramp-to-chamber radius called for in the gov't print. IOW, they had not been fully machined, and the listing on the online page does not mention 'additional fitting required'. Ouch.

In any event, I have the capability to radius the barrel ramps myself with minimum difficulty, despite being unable to accurately measure my actual radius. ('Tennessee Windage', I believe it's called.)

This got me to wondering about the Luger barrels Sarco also sells. I have one here, new/never installed, and sure enough, it also has the 'chisel edge'. The Luger print clearly calls for a .5mm [.0196"] radius on the barrel ramp (same radiusas on the 1911 print). [Yellow circle on print].

If members are having difficulty with chambering 9mm cartridges in their Luger with an aftermarket barrel installed, it may be because of this 'chisel edge'. Instead of smoothly riding into the chamber, the cartridge may be dragging on the chisel edge enough to impede chambering.

I also found, while checking to see if my reloaded cartridges were too long/too short, that the SAAMI specs are different for commercial ammunition vs military ammunition. Not a great deal different, but enough to warrant comment.

The barrel ramp/chamber radius (or lack thereof) may not be the end-all 'fix' for Luger fail-to-feeds, but it may well be a contributing factor.

I've attached pics to illustrate my findings.

As always, YMMV...

[sheepherder]

Here's a pic of the barrel...

That sharp edge should not be there...

[DonVoigt]

Rich,
you may want to try the pictures in post # 2 again.

I have always "broken" the edge of the ramp on any pistol or barrel I had the need to "mess" with.
Sharp edges are just not conducive to smooth chambering. Sometimes with some well crimped ammo it is a non issue, but most/many .45 acp and 9mm P have a sharp edge to the cartridge mouth- necessary for headspacing. That edge can sure catch on a sharp chamber edge.

D

[sheepherder]

Originally Posted by DonVoigt

Rich,
you may want to try the pictures in post # 2 again.

Eh? It's not sharp enough???

I'll try outside...

There's another factor - That sharp turn makes it harder for the cartridge to make a smooth 'glide' into the chamber. It tries to 'pivot' instead of sliding...

[DonVoigt]

Rich,
there was no picts there when I looked first.

I believe the luger barrel you show was "ramped" by running a ball end mill into the edge of the chamber/bbl.

The drawing shows a curved flat with the radius to break the sharp edge -not a circular sector cut. The end on view shows it pretty well, if you feel like adding that view.

I believe the maker of that barrel just took a short cut that looked easy and that works some of the time. Maybe peculiar to that maker, I have not seen the same type of cut on the few aftermarket barrels I've handled.