Blow Holes?

[blackdragon]

Eric G,

Is using our 124gr FMJ now. Back in the day I was running real close to 12grs of HS-7 to make major with a 115gr Hornady XTP. The noise was just too much. ( 181 PF)

[Radical Precision Designs]

"Flat", in many ways, depends on your grip and stance, and not on how much comp or how many ports you have on the gun. Also, the whole equation depends quite a bit on your powder choice - you need more gas to work those ports.

As long as the hole in the slide is slightly larger than the hole, you should be fine. There's plenty of slow motion video out there that clearly demonstrates that the gas is gone by the time the slide begins to move - here's an example of what I'm talking about: http://www.brianenos.com/forums/index.php?...pe=post&id=2944

Note, too, that in this case, the port is "jetted" (ie, an angle cutter was used to create a nozzle) - you can't do this with a slot.... No, it won't cause slide erosion, yes it works fine.

Hi, Dave-

It is to an extent true that most of the gases are indeed gone by the time the slide moves back. But take into consideration the innate workings of the design. 1911's accomplish their cycling by "residual/leftover" energy to do their 'auto-loading' and ejection, which is provided by rearward motion energy, some of which is stored from the "peak" burst of energy, but which is mainly carried out by 'sufficient ' left-over still combusting powder. Normally when you do not have enough of this you will get malfunctions like feeding and ejection (stove-pipes and that kind of stuff). Evidence of a "well" working semi-auto is the fouling and deposited burned/unburned powder in the chamber and ejection port area, which after a while you must 'kind of' clean. While the peak combustion gas pressures accomplish the bullet propulsion and activation of the comp works, it is the delayed lock of the slide that stops the case from rupturing etc, "untill" that pressure stops peaking and it is safe for the "residual" pressures to carry on (still burning, still hot even at a lower level). So there indeed exist a substantial amount of gases and burning powder when the slide chamber opens (remember the ejection port area?). The barrel (surrounding) area where the "blow holes" are cut normally will require some lubrication. Should the gases (peak or residual) mingle in that area under the slide you will "enjoy" premature/accelerated wear, and some malfunctions due to "extra" friction. When you design one of this "Open-thingies" you must plan ahead for the expected performance and its weak points that will hinder performance by competittors that "hate" to clean/maintain their guns. Most of the problems will be caused by fouling from residual burning powder rather than prospective erosion from peak pressure burning powders. They say: "an ounce of prevention is worth ... "

[spook]

Anyone know what the reasoning behind the porting of this new Eric's Model could be? My thought is that the extra lenght of the barrel provides a little more velocity...

[Radical Precision Designs]

Anyone know what the reasoning behind the porting of this new Eric's Model could be? My thought is that the extra lenght of the barrel provides a little more velocity...

Eric Grauffel has a website at the IPSC.ORG "Global Village" with some forums. You could ask him directly, rather than have someone here give you "their" interpretation, which could be only their perceptions of their likes/dislikes.

[XRe]

Venry - I'm afraid I have to respectfully disagree with parts of this - I'll try to elucidate...

but which is mainly carried out by 'sufficient ' left-over still combusting powder.

Once the barrel's been uncorked, that gas has a very easy exit point (ie, pressure drops off dramatically, and there's nothing to "push" the gun against). The recoil energy required to operate the action in large part results from the acceleration and movement of the bullet and the bulk of the gas created while the bullet is in the barrel. Here's a simple (mental) demonstration - if free burning powder and gasses in the barrel were enough to cycle the action (ie, "mainly carried out"), you could load up a blank (ie, no bullet, but a cardboard card and wad) with your same powder load and it would cycle exactly the same as your normal load. Think that'd work??? Nope.

It's Newton's third law, for starters. In the size, burn rate, and energy content of the propellants we're dealing with, there's no where near enough rocket effect created by burning them in the open to create enough energy to cycle the slide - unless you do something extreme and dangerous.

Evidence of a "well" working semi-auto is the fouling and deposited burned/unburned powder in the chamber and ejection port area, which after a while you must 'kind of' clean.

How come, then, we can create loads that cycle the gun w/ vigor, yet leave cases bright and shiny and leave almost no residue around the chamber, throat, etc, and we can also create loads that leave all sorts of crap all over the place inside the gun, and completely fail to function??? If stuff left over was inidicative of powder burning after the unlock, and that was desirable to cycle the gun, wouldn't it be the other way around?

While the peak combustion gas pressures accomplish the bullet propulsion and activation of the comp works, it is the delayed lock of the slide that stops the case from rupturing etc,

This is true.

"untill" that pressure stops peaking and it is safe for the "residual" pressures to carry on (still burning, still hot even at a lower level). So there indeed exist a substantial amount of gases and burning powder when the slide chamber opens (remember the ejection port area?).

You've no doubt burned powder in the open and seen the bright yellow orange flame it burns with, right? This is a result, in part, of burning the powder in the open, outside of the pressures created inside the barrel. This is also partially responsible for the fireballs some guns seem to generate (in theory, anyhow). If the powder were still burning after the gun has unlocked and started cycling, it would be common to see that same fireball leaving the ejection port, and there would soot evidence of gas blow by on the cases (similar to what you get with a squib w/ no powder).

Remember, the unlock delay is also required to allow the case to unseal from the chamber walls - this is not an instantaneous effect, and requires chamber pressure to drop off dramatically. Without this sealing action caused early in the burning process, you'd also get fireballs all over the place (much like blowing a case).

No, things would be much different if we were shooting guns that still had powder burning when the gun unlocked and cycled...

The barrel (surrounding) area where the "blow holes" are cut normally will require some lubrication.

I agree - at the least, these holes generally appear in high sliding friction areas of the barrel/slide interface.

Should the gases (peak or residual) mingle in that area under the slide you will "enjoy" premature/accelerated wear, and some malfunctions due to "extra" friction.

I disagree - if you had peak pressures venting under the slide, you would definitely encounter issues, I'm with you there. Residual pressure that's still there when the slide unlocks (very minimal) and any residue that results (there's definitely some) would appear, in my experience, to have no effect on wear in those areas - assuming the gun is well cared for and lubricated in those spots as appropriate. I've put 40-ishK rounds on a gun with this setup, most of them at 182PF, know several other folks who've done the same or more on this same setup - and there are folks on this forum with the same setup I have who've put quite a few rounds downrange in their's. Ask them if they have erosions on their slides or barrels, or accelerated wear (witnessed as loose barrel to slide fit) as a result?

Most of the problems will be caused by fouling from residual burning powder rather than prospective erosion from peak pressure burning powders.

I would agree here, too - the problem is that those who do not care for their guns are also likely doing other things - overheating it, leaving it relatively unlubed, etc. The biggest key seems to be a periodic cleaning to remove any accumulated fouling (dependant upon how clean the gun is), sufficient lubrication (applied as require by the type of lube), and allowing the gun to cool off periodically. Bare metal friction is a killer. Most powder residue towards the muzzle end of the gun is graphite/carbon in composition, and if held in suspension in a lube will be relatively harmless. The gunk at the chamber end (including unburned powder) can be more abrasive, but usually gets pushed out of the way of the high friction areas by the action of cycling the gun.

It strikes me that the gunsmith's best friend in dealing with those who won't clean their guns is hardchrome

[Skywalker]

I was getting ready to squeeze a round off and I quote Leo "Oh yea, one more thing; you may want to keep your mouth closed, it's kinda hard on the teeth". My first thought was Awe Sh*t, what have I got myself into this time.

[Radical Precision Designs]

There is light at the end of the tunnel ... I like watching "big boomers" shooting at night time... There are flashes of light coming out of the gun everywhere. Must be some kind of "gun perspiration"...

[gans]

I believe that most of the energy generated to cycle the slide takes place within about the first 1/8" of the slide cycling. About 20 years ago, I was doing repair work for a S&W Distributor. It seems that S&W was plating the feed ramps of their barrels and got some in the chamber that left a jagged edge. The fired round would get stuck and only make it out of the chamber about 1/16"-1/8". There was enough of pressure exerted by the casing in that short of distance for the extractor to rip part of the rim off and to cycle the slide fully and pick up a round.

[38supPat]

I've had pistols with holes in the slide and slots in the slide...it made no difference. Both work flawlessly.