1911 Ramp/Throating

[schmeky]

I know there is a sticky on this, but I have not been able to find what I am looking for. This pertains to a 1911/.40 project, specifically a match barrel install.

The new Kart barrel I purchased was throated for FMJ style bullets and had a very narrow throat. The angle was also quite steep. The edge of the ramp was approximately even with the frame's ramp after the barrel was fitted; the barrel locks up very well.

I feel my ramp angle is to steep and have more 3 point jams (with no extractor) than I would like. The rounds do not chamber as smoothly as I would like, emitting that "ka-chunk" sound most of the tme. I am using a Colt factory .40 mag.

The ramp angle is approximately 15 degrees. I cannot find any info in Kuhnhausens manuals on an approximate ramp angle. I have checked my other 1911 ramp angles and they are around 22 degrees.

I have approximately .075" of the case exposed presently. I fear if I increase the angle 6-7 more degrees, I will expose more unsupported case as well, potentially leaving about .090-.100 exposed.

What is the optimal ramp angle in degrees? Will I have an unsafe barrel if I wind up with .100" of the case unsupported? The .40 operates at a higher pressure than the .45, but I "assume" the webbing of the .40 is thicker, thus having a greater saftey margin.

 

[Bailey Boat]

You would be well served to PM "1911 Tuner" as he is one of the best with this platform.... I would undertake the challenge but I haven't stayed at a Holiday Inn Express for months.....

 

[rcmodel]

I would not change the ramp angle at all on a .40 S&W barrel.

They need all the case support you can get, and then some.
Witness the Glock KaBoom's in the past.

You might be able to address the three-point issue in a 1911 by seating longer. Or try blunter bullets shapes that would contact the top of the chamber sooner.

Plenty of room in the 1911 magazine for longer then standard length loads.
You might play around with that and see if it helps.

rc

 

[rbernie]

Me being me (i.e. relatively ignorant and cheap), I would probably buy another magazine and modify it to taper the feed lips to get the base of the round higher earlier. It's certainly cheaper to play with the magaazine than the barrel.

 

[olyeller]

Your 40 Kart is probably not finish reamed. Ive used more than a few kart 40's.
Have you a finish reamer?

 

[schmeky]

I had contemplated modifying the mag lips to acheive an earlier release, but have not. I am using a 170 gn LSWC as a test round.

I tried the barrel with the original as supplied feed ramp, which was very steep, it had virtually no ramp, maybe 10 degrees at the most; I could never get the first round to chamber. The nose of the bullet would stop at the feedramp everytime.

I have carefully worked the ramp slowly and now have the pistol chambering, but it is not smooth. I'll try lengthening the rounds, then the mag feed lips.

The chamber will need to be finish reamed. The barrel seems to me as though some machining process may have been omitted. The barrel was described as "throated for SWC bullets", but it most assuredly was not.