View Full Version : Intrusive feed ramps?
02-12-2009, 08:06 PM
I understand that some of the new .40 caliber pistols use what is referred to as an "Intrusive feed ramp". would someone please elaborate on this type of feed ramp. I know the term implies that it protrudes into something, perhaps the magazine well?
02-15-2009, 08:04 PM
I think that this term refers to the fact that some 40 "Short and Weak" pistols were orginally designed as 9mm Para firearms. In order to get the "fatter" cartridge to make the trip from the magazine to the chamber required the feed ramp "intruded" in the chamber. This leaves a small section at the rear of the case "unsupported" in the chamber. The 1911 in 45ACP also has this "type" of chamber, so it isn't something "new". An unsupported case will expand ("bulge") in this area. Depending on how "hot" the load is and if you plan to reload that case this can be a "problem". Most Military and LEO types, just want their gun to go "BANG", get the spent brass "OUT", and the next cartridge "IN".
02-16-2009, 08:04 PM
Thanks for the input. What has me wondering is what you say does pertain to the early conversions and the Glock but the Steyr M40 has a fully supported chamber and is a high pressure cartridge. It still uses the intrusive feed ramp. The 1911 in .45 caliber is a low pressure cartridge and works fine with a partially supported chamber. One of the problems associated with using reloaded cartridges that have been used in a glock in a pistol with a fully supported chamber is that the enlarged section of the case may not allow the round to chamber fully. If the round is chambered several times the bullet can move deeper into the case causing the pressure to rise dangerously. I am still wondering why the Steyr uses the intrusive ramp.
That is what got me wondering to begin with, I'm starting to think that maybe
it needs the extra space to clear the fired round before it comes back far enough to engage the new round to move it into the chamber.
02-21-2009, 08:14 PM
I had to look up on the "web" just what a Steyr M40 is (there is a Steyr M1911). It seems that the Steyr 40 was designed to be a 40 S&W, with a "well supported chamber". I read that as "marketing" (there is a little bit about the Steyr M40 "designer" being a former Glock employee). I don't see how (mechanically) a tilting barrel, rimless cartridge firing auto-loading pistol can have "fully supported chamber" (like a single shot firearm or revolver) and still have "combat/gunfight" reliablity.
If a round won't fully chamber isn't the gun "out of battery", and thus should not fire?
Are you asking about the brass not going "fully" into the die when reloading, resulting in a cartridge with "too long" OAL that is then "forced" into the chamber?
Most "modern" auto-loading pistols are "short recoil", with the barrel moving a relatively small distance, and the spent brass and "slide" continuing rearward, to the ejector, hopefully tossing the spent round "away" and then returning forward to "scrape off" the next round from the magazine.
I don't think I directly answered your question, only took the long way to say that all designs have "faults" that other manufactures will exploit when marketing their product.
02-23-2009, 09:26 PM
Thank You. You have answered my original question very well.
A pistol "out of battery" should not fire but some do and damage the pistol and sometimes the shooter. They refer to them as "Kabooms".
I think you answered the 2nd part also when you refereed to the short length of the .40 round. They need something to bridge the gap better because of the short cartridge length. The barrel is evidently set a little farther forward because of the fact it is a fully supported chamber.
When I look at something I have to fully understand what I'm looking at before I go on. I appreciate your input. Hashing over gives me better understanding.
In the past I understand 'Kabooms" were caused by lead shavings not permitting the round to fully seat and the rounds going off out of battery.
Of course if the overall length is correct "fully sized" and the bullet type is correct and seated properly. All should be well. I am going to take a look at the edge of the chamber and see if it has a slight bevel. I believe it should have.
02-26-2009, 12:26 AM
I TIG welded up an old GLOCK 22 40S&W feed ramp and then re cut the feed ramp and chamber in a way that supported to the web of the case.
I can now shoot more than double loads without blow up the brass or gun.
The recoil is impossible to deal with.
15.5 gr 800X 200 gr is a max load for 44 mag, but shot in the smaller volume of a 40sw it is much hotter.
I have a listing I have made of different pistol cartridge, the thickness of the web, and the intrusion of the feed ramp in the various pistols I have in those cartridges.
The way I measure intrusion is to put a case in the chamber of the barrel [out of the slide] and scribe a line to outline the feed ramp. I scribe with a sewing needle. Then I measure with dial calipers from the base of the case to the forward most point on the scribed line.
To cross section the brass to measure the web thickness grinders are problematic, as the brass smears. Easier is a Dremel waffle cut off wheel.
02-28-2009, 03:58 PM
What you are doing makes the purpose of the ramp very clear. Have you had any feed problems at all? Did you polish the ramp? What type of bullet shape are you using?
03-18-2009, 11:42 PM
No trouble with half the feed ramp.
With all the different bullets too.
email me and I will send pics
03-19-2009, 02:53 PM
I would actually presume that the term "intrusive feed ramp" refers to the sort of feed ramp that relieves away a portion of the chamber as opposed to a "ramped barrel" that has a ramp that is an appendage external to the chamber. There is nothing about a throated and polished barrel that is exclusive to the .40 chambering, or to Glocks or any other brand of gun. While many guns are of the ramped variety, many others are of the throated variety. My 1911 and most all 1911's for decades have used a barrel with some degree of relief cutting (throating) or another. One of the common performance/reliability modifications is to widen this relief to allow feeding of not-so-ideal bullets like HP's and SWC's and to polish this throat for better feeding as well.
One of the troubles with internet chatter is that disinformation gets a life of its own. The "9mm turned into a 40 so they could rush it to market" thing with the Glock is an example of this sort of disinformation. I have heard that particular tidbit of crap repeated a lot. Peter Alan Kassler wrote a book that makes it clear this is not the case. It did happen that Glock got a gun in this chambering out before Smith&Wesson, but that did not mean that corners were cut. This is the first time I ever heard anyone tie that with the other big pice of misunderstood internet chatter and I do not understand how anyone could tie the two together:
The Glocks...especially those in .40S&W get labelled as having an "unsupported chamber". Some gun expert wannabe's web sites includes a picture of the barrel throating as though this throating were somehow different from dozens of other guns...as though that sort of throating only occurred on Glocks chambered for this round and the throating was what accounted for the "unsupported chamber". This makes their lack of knowledge pretty apparent. Nothing could be further from the truth. I have a Glock 23 in .40S&W. I am not even a glock nut...the gun is what it is and I have made mine tolerable, but I hate it when disinformation gets repeated, and the use of the term "unsupported chamber" is an example. One thing that has made the Glock ultra-reliable is a loose chamber fit. It prevents failures to feed at the expense of stretched or "glocked" brass. I can't imagine it helps accuracy either although my 23 is quite accurate. This fit is intentionally loose...but its a totally separate issue from barrel throating and its the loose chamber and not the throating that is the issue.
I bought a third party replacement barrel for my Glock. Chamber fit is nice and it has standard rifling. What the Glock "polygonal" rifled barrels do not do well is shoot non-jacketed lead bullets. The absence of sharp rifling edges makes for some smeary lead fouling. I would like to be able to shoot lead at least occasionally and I also don't want my brass weakend prematurely by being worked heavily. Taking brass that is over-expanded and sizing it back will work harden and then split the brass sooner than you might like.
The third-party (nameless at this point) barrel is another story. It had some rifling damage in the throat. I contacted the mfg. and they asked that I return it so they could see it. They indicated that there was no unusual problem and then *bead blasted* the bore and returned it to me!
I was furious. I spent more time than it was worth shooting some macro photos of this damage in the throat and emailed them back indicating that the problem appeared to be swarf under the reamer pilot or something as the chipping was all on one side of the lands, and only in the area right in front of the chamber. Scratches showed the direction of rotation too. The photos made the problem obvious and the owner called me and apologized indicating that the chipping was from a reamer pilot but that the bore was simply not cut to size properly and that was why the pilot created the damage. He said that he had seen it before and that the barrel never should have made it out. Since he was nice about it, I didn't want to grill him over someone *bead blasting the bore* and returning this barrel to me!!!
I am still waiting on the replacement, but hope to have it soon.
03-22-2009, 04:51 PM
Thank you for your input on the subject. By listening to what others have said I've gained a better overall understanding.
03-23-2009, 11:56 AM
Link to long shpeal I just typed about 40sw feed ramps (http://www.snipershide.net/forum/ubbthreads.php?ubb=showflat&Main=96329&Number=1056645#Post1056645)
9mm will be a .160" web. The feed ramp intrusion should be .180" or less.
40sw will be a .180" web. The feed ramp intrusion at .235" is poor.
10mm will be a .180" web. The feed ramp intrusion at .235" is poor.
45acp will be a .180" web. The feed ramp intrusion at .235" is poor.
03-23-2009, 06:21 PM
I pulled my Glock 23 barrel this weekend and did some looking at it, and some fired cases and it mostly supports what you point out in you article, Clarkmag. I checked several cases with a square and its clearly apparent where the problem occurs, and its ahead of the web area, and not in the area where the glock chamber is cut away.
That barrel very definitely "glocks" the brass, but the bulge area is well in front of the portion of the barrel that is relieved for better feeding. The glock barrel is semi-ramped. It has an external feed ramp, but also has some relief at the throat that extends into the case web area. This throating does not, however extend to the end of the case web area and its this area ahead of the web where the brass is weaker that it actually bulges. The "unsupported chamber" description needs to be clarified by the folks who use it...and the relieved throat does not necessarily make for a chamber with poor support.
Its interesting that you pointed out that the bulge is opposite the extractor which makes the most sense as that's the point at which the brass should have the maximum gap with relation to the chamber. If a magic extractor could hold the brass centered in the loose chamber, likely instead of the guppy belly you mention, you might see an even expansion.
I really think that for the pressure involved in this cartridge, the web could have thinned much more gradually toward the front of the .40 case. Of course that comes at the expense of case capacity and a decent chamber fit should make it a non issue.
Few people seem to understand that the brass itself should not be made to be the pressure vessel. It should be well supported brass in a proper fitting steel chamber.
03-23-2009, 09:56 PM
I TIG welded up the intrusive feed ramp.
I re cut the feed ramp and chamber with support right up to the web of the case.
The pistol can now shoot the 44 mag max load in a 40sw: 15.5 gr 800X, 200 gr, but the recoil is intolerable.
03-24-2009, 02:54 PM
I am really surprised you can get the max 44Magnum load of 800x in that case and still seat a bullet--especially a 200 grain bullet which would cramp some normal 40S&W powder charges. I think that's why most folks relegate the 200 grain bullets in .400 to the 10mm cartridge.
Of course there is the issue of the wisdom of such a move since you will likely stretch your slide and could easily have grenaded the pistol:eek:
There are things you do...and then things that you publicly admit you did and this might not ought to fall in the latter without a giant disclaimer at the end of your post. I know we would all like to believe that the folks who will read from this public forum have the good judgement to know what to do and what not to do, this one is pretty iffy. This is definitely under the "don't try this at home" heading.
04-19-2009, 12:50 AM
It is more than a case full of powder.
The first case full of powder must be compressed, and then more powder added.
To get 15.5 gr 800X to fit in a 40 S&W case, this double compression process must be done more than once.
But 800X has a low bulk modulus, and it will all fit.
For compressing powders in cases, a bullet in a bullet puller collet die is not always the best. The bullet may deform. The best is a pin gauge.
05-11-2009, 09:13 AM
are there moderators on this forum? if so, you really need to remove this 'clarkmag' stuff. totally dangerous, blow your nose off, or some digits....... .40 S&W cases are not that stout, and i really can't belive this so-called data doesn't remove the head of every case very violently, along w/ various pieces of the gun...... i reload alot of .40 for USPSA competition, and it's a twitchy caliber at best. it's a small volume, high pressure round in normal usage. this stuff is totally crazy, and very dangerous! 5 grains of 'titegroup', or some similar medium fast powder is too hot for a 200gr. bullet. i really don't think you can get 15 grs. of anything in that case. one of the problems computer forums is the lack of 'truth in advertising'......this is definitely in the class of "hey bubba, hold my beer, and watch this......." and the reason most ranges have a sign posted that there will be shooters there using 'reloaded ammunition'. just make sure you're about 50 yds. away......the guy is pretty good w/a file though....people posting bogus reload data on the computer is a big pet peeve of mine, and this is easily the worst i have seen!