Compensator Question

[EricW]

Pat,

If I get some time, I may drag out the thermo / fluids books and come up with some rules of thumb and design guidelines for various applications. I've been itching to buy an o-scope and some test equipment, so this may be the impetus to do that. The mistake that I think everyone is making is that they are looking for absolute results. They're not necessary. All we really need are tables in terms of %'s.

As far as comp development, I think the industry has done a good job of controlling muzzle flip. I think the industry has done a poor job of noise management. And yes, I realize the fact that suppressors are controlled items is to blame, but I have to think that there's some way to reduce the noise signature of a comp that we're just not seeing. It would be nice to throw away the rulebook and see what one could come up with for a rifle comp that reduced felt recoil, controlled muzzle flip, and did not produce substantially more noise than an unbraked rifle. Pipe dream? Maybe. Maybe not.

[Radical Precision Designs]

Years ago, while I still had a wife to put up with me, I was having one of my "usual" enlightened dreams, where ai would get in the middle of the night and grab a piece of paper and pen to record the bright idea that just came to me ... She (my wife) was not ever amused about it.

One early, early morning I got up and wrote down something about building/designing a "self feeding pistol, fixed position barrel, with a short gas operated dual direction pistons to activate feeding and ejection by moving the barrel forward and the breech-face rearwards in a mass/distance balanced fashion. Mounted at the front would be a barrel integrated "enclosed" compensator with rear 360 degree discharge ducts... and an electric trigger...

One of these days I will get up in the middle of another dream/(nightmare!) ... maybe I can get the rest of the design.

Edited to ad: I was composing the above post while EricW was sending in his, and had no knowledge of his "pipe dream" mention. Cross my heart!!!

Edited again to ad: That Bob was composing his post as I was posting mine. Therefore nor did EricW, Bob Hostetter or myself had an inkling of what was being posted by the other. Strange Word we live in. Maybe I'll have the rest of that dream tonight?

Edited July 14, 2006 by Radical Precision Designs

[Bob Hostetter]

One of the problems with comps on Open guns is as they become more effective (thru whatever means) they start to effect the slides ability to cycle. So, at least in theory, if you had a comp that completely balanced out the recoil impulse the slide won't have enough energy to fully cycle.

So what about mounting the comp to the frame and letting the barrel and slide function freely? Then you could use slide weight and spring rates to control the felt recoil produced by the slide impacting the frame at both ends of it's travel...........

Edited July 14, 2006 by Bob Hostetter

[shred]

Don't some Bianchi guns already have gas ports on the back of the comp to give the slide a little extra boost?

I talked to somebody about building some experimental comps. His quote "the first three are fun". He had a bucket full of trials..

[Dave Sample]

Here is one I did 15 years ago. It is my design and does not blow gunsmoke up in front of the sight like a Choo Choo Train. These are rocket ports at the correct angle and I used the side ports to take the torque out of the overloaded .38 Super rounds. It shoots like a .22. I did 3 or 4 of these before I quit building IPSC Race Guns.

11 degree crown on the front of the comp. An interesting angle

20 line per inche on the front strap and 30 on the wrap around trigger guard.

20 line on the back end checkered into the lower end.

[Dave Sample]

I ran out of bandwidth so here is a little more of the Red Eye Special.

This one was outdated when I finshed it 14 years ago. That is when the single stacks were put aside for the Hi Caps. It was way ahead of it's time back then but no one cared except me. It is my Steel Gun and fun to shoot. I do not compete any more so I am saving it for my son.

It did have a big brother.

[vincent]

Wow Dave, that is a cool blaster! I especially like the checkering on the slide where it is usually serrated and the custom mag button - very trick.

[Dave Sample]

Thanks! I used to do the mag button in all calibers and I was surprised that no one else did these things. The hand cut checkering on this slide was the fore-runner for other designs along the way and I did not like the idea of a "Cocking Handle" at the time. This gun is very easy to use and comes down with a paperclip for cleaning. It also has S/S thin grip panel shims under the grips to prevent hand damage from overloaded .38 Super-Duper rounds I loaded back then. I knew that I didn't need an expansion chamber in my comp because it would have rendered the rocket ports less effective.

I used the heavy lead bullet loads back then instead of the LW jacketed trend that prevailed. I wanted that Briley Barrel to last longer than a couple of thousand rounds. I loaded 158 .38 Kieth Bullets with AA #7 powder and made Major the easy way. It was 175,000 power factor back then! I still like the Rooster Red Zambini for my bullet lube.

Chip McCormick handled this one at a Shot Show and he liked it a lot.

[ArturoJ]

I just found a comp from Sabre Defense called the "Ultra Efficient Gill-Brake" in the bag of stuff I picked up from the SMM3G prize table. The baffles angle back, kind of like what Erik was talking about. I don't know how well it works.

[tightloop]

Seeing those take me back to the WARS...when it was a monthly thing to change something on the pistol or comp...I had mine EDM'ed thru the slide and cone and bbl ...it ported off the majority of the gases that torque the gun and the comp helped with the recoil...yes, it was trick and shot like a .22, but for all that, it was still a single stack with irons..and fell by the wayside to widebodies with dots...

I miss those kind of pistols..lots of fun to shoot...and yep, they were a great steel gun..

[smokshwn]

Dave,

Will you adopt me?

[MarkCO]

Granted I did not read all of the threads on this post...I'd go blind...But Billski pretty much summed up the problem in his first post. And, since I did not see it yet, and I want someone to be impressed...Pv=nRT also applies.

I am a mecahnical engineer with specialization in fluid dynamics (gases ARE fluids) and while I did not actually see it posted specifically, the problem is one of mass transfer, or momentum. Gas pressure and volume...not really, but kind of.

Related pop quiz...how does a jet engine create propulsion? Actual answer at bottom of post.

If you know the answer, you have a basis for understanding comps/ports design. The Tru-Sight expansion chamber, regardless of what the officials say, IS a compensator. Go find an A1 M-16 compensator, it is the same thing.

The problem CAN be mathematically solved for a given set of variables with a fixed breech and barrel...If I know the clamping force of your grip, the rotational friction of your wrist, the actual pressure curve (area and spikes) of the powder, weight of the ejecta (powder and slug), bearing surface of the slug on the actual bore, actual chamber and bore dimensions, density altitude (for simplicity), ambiant temperature, humidity (mass basis) and the total firearm weight. All of these except the pressure curve can have a static value. But the pressure curve must be expressed in an equation based on time. Oh, and I'll need a way to puncture the case right before the primer ignites to affect mass flow as the powder ignites, of ocurse with some tubes.

IF you want to add in a cycling slide, I'll need an expression for the actual dynamic friction of the slide, an expression for the spring force as a function of slide position, and slide mass. Three simulataneous equations is not too bad, paper and pencil solution, probably about 2300 hours. Computer model, maybe an hour or so of Cray time.

So I do all this and what I come up with is that I need about 250 small fast acting valved ports with evacuation tubes. Hmm, let's see, I bet they could be built for about $10,000/barrel, if you order about 10,000 barrels, email me for the address to send your $10 million to and I'll get started right away.

It certainly can be done, but no-one wants a port in the chamber itself. It becomes an exercise in futility becasue of the cost constraints. A firearms manufacturer asked me if I could design a novel concept he had in mind. Sure, but at $1000/unit, not worth the time to even think about it. But the military has paid for a very similar item.

There are some good comps, some better than others. But the scratch is the constraints. There has to be enough energy to cycle the slide safely and reliably, keep the firearm in battery and deliver the projectile downrange. As the window gets wider, the port/comp gets "less" efficient.

PQ ANSWER: Jet engines produce thrust by mass transfer, using the energy in the fuel to suck in and "throw" the air mass to the rear. The equal and opposite reaction, based on mass transfer equations, thrusts the plane forward.

[tightloop]

And I thought working for the Govt was boring....man, I need an advil just reading that last post...glad there are guys like that who can tell us that stuff, but to do it each day....I don't know...

[Bear1142]

MarkCO,

Thank you for your detailed analysis. I knew that all along, I was just waiting to see if anyone else knew the correct answer.

So, if I understand you quiz, then a comp design with ports having a back angle will not only take advantage of the impact momentum of the gas on the baffles, it will also use the "thrusting" aspect of the gas to help pull the gun forward?

Erik

[.40AET]

I just found a comp from Sabre Defense called the "Ultra Efficient Gill-Brake" in the bag of stuff I picked up from the SMM3G prize table. The baffles angle back, kind of like what Erik was talking about. I don't know how well it works.

I have one. I paid $89. It throws a sh!t load of gas backwards. The guys standing next to me can feel thier hair blowing in the wind from the comp. I thought that it was going to blow the contacts right out of my eyes. That said, it doesn't help the muzzle stay on target. I shot it side by side with a cooley comp and it just doesn't cut it. I bought one of Sabre's 18" barrels and love it....and kinda fell for the hype behind their comp. It's been relegated to the box of stuff that didn't work the way I wanted it too. YMMV

Edited August 2, 2006 by .40AET

[MarkCO]

So, if I understand you quiz, then a comp design with ports having a back angle will not only take advantage of the impact momentum of the gas on the baffles, it will also use the "thrusting" aspect of the gas to help pull the gun forward?

Yes, that is accurate. One thing that must be considered in port design is that since we place the ports at the end of the barrel (or middle to end), some rearward motion has already occured when the ports start to act. An "overcomped" firearm can actually be harder to shoot than a slightly under-comped one. If we have some rearward thrust and then attmept to completely counter that thrust, we would have to move the firearm forward and then we would have to stop that motion. From a shooting perspective, it is better to be slightly undercomped and deal with some recoil.

If you read Dave Sample's post carefully (one of the premier smiths IMHO) you will note that he understood the problem and managed to deal with it using a lower velocity load than was the norm. That takes more skill and precision than using the higher velocity loads. In order to have the most amount of gas mass to deal with (and make the job the easiset) choose the powder with the highest charge weight. All gunpowders, regardless of burn velocity, create a mass of gas equal to the mass of the powder charge since they use no combustion air from the atmosphere.

Edited August 2, 2006 by MarkCO

[Dave Sample]

Mark understands what I did here with this Compensator. I did not want the hot gases going back because I wanted the force to push the muzzle straight down and not affect the scope lens. If you notice, the ports go out at 45 degrees from the top down and the side ports are at 180 degrees for stabilizing the hot gases and helping with the bullet torque common in this caliber. For a very long time I thopught I was the first one to use side ports and then Chip told me about his early comp gun called the Gammon. He was the first and then it became a common part of comp building folks.

I only did about 6 of these and the IPSC Crowd was underwhelmed by my design. They are still doing the same old stuff making comps that blow everything straight up in the air and covering that scope lens with crap everytime they pull the trigger. I have never pushed the stuff I did, because I do it for my own amazement.

They were made from a Clark Blank by Chuck Rogers to my specs. He is the best machinist in our business, bar none. I used to charge $250.00 for this type of comp and that was big bucks back then.

This is my Steel Gun and I did not build it for IPSC Matches. It was obsolete when I gave it birth back then , as was I. It was made from spare parts and just for fun.

With lead bullets, it's a 100,000 round race gun. It has had about 20,000 to 30,000 though it already and the 2lb trigger has never followed. Metaloy refused to obey my instructions and blasted most of the engraving off of it and did the worst job of hard chrome I have ever seen. I wouldn't let them pet my dawg!

[Dave Sample]

These were taken when it was new about 13-14 years ago. It hasn't changed much!

[tightloop]

There were several iterations of the Gammon pistols...the first one used in competition was used by Mickey Fowler, and while the Gammons were built by Charlie Kelsey's bunch, and Chip and Charley were tight, I never saw Chippie shoot one in competition.. the only pre dot comp guns I ever saw Chip shoot were one by J. Michael Plaxco, one by based on John Shaws gun when he won the 80 Natl's and a local (Austin) copy of the Wilson LE comp guns...in no particular order...

I might be mistaken, but I don;t ever remember him flaunting a Gammon anywhere....

[Dave Sample]

That was why I was confused too, Tightloop. I saw it in a magazine a year or so ago and thought to myself, "there is nothing new under the sun" Kelsey was a big player back then and did some very neat stuff! He was surrounded by like forward thinking people that were not afraid to go to new places with 1911's. There are not too many like that now. Maybe there never was.

I know this. Chip McCormick loved my Red Eye Special and we both wished we were still shooting matches with stuff that dreams are made of. I offered to let him take it home and play with it but he turned me down because like me, he didn't have any time for fun anymore. I am going to change that here. I am going to resume shooting, but not matches. I had enough of that a long time ago. I would have 6 of my guns kicking my butt and everyone but me was laughing about that! Except me!

It was fun and I do miss it but I am in no shape to play the games anymore.

[tightloop]

Well, Chip McCormack was one of the fastest shooters these eyes have ever seen...the guy could really go...I think he won the Steel Challenge a couple of times, but never did any great shakes at the Natls or the world shoot..winning neither..he won lots of local and regional stuff, but stopped shooting when Charles Kelsey helped him get his business going and he devoted most of his time to getting that going...but when he was shooting lots...one of the best...can't tell you how many times he dusted me..and everyone else..

Even our host here can probably tell stories about Chip...'cause he was one of the hot rocks when Brian and Rob came on the scene...

There have never been too many "outside the box" guys in the gun world...there have been a few, JM Browning, Sam Colt, and a few more, but not too many...Kelsey was a real forward thinker for that time he was in it..too bad that Charley did not make it big time and even more sad that he was murdered just last year, I think it was...

[Dave Sample]

At the Shot Show a couple of years ago, Chip said he liked me because

I think "out of the box" I grinned at him and said "What box?".

Let us take a look at this whole gun for a minute. The Compensator is just part of it. We lightened the slide by continuing the rocket ports toward the back and did it where there was no stress. Many others did the cuts inside and the slides cracked. I knew that wasn't a good idea. Why do you guys think the muzzle rises when you shoot any 1911 semi automatic pistol? The force should be forward and backward, shouldn't it? The slide travel is horizontal. The bullet is going straight out of the barrel, right?

I think it's two forces. When the slide reaches it's full travel back and hits the frame, it can cause the barrel to rise. Also, the barrel is jerked down and hits the barrel bed when that slide starts back. You lessen that with a ramped barrel and by making the slide lighter, you also cut the muzzle rise. Then you apply the force up front with the escaping gases going at 45 degrees on each side of the comp right behind the bullet exit, which makes a V shaped force and pushes the barrel down to the bottom of the V.

This .38 Super was designed as a scoped steel gun. The slide was slick and there were no grasping grooves or slide serrations. I checkered it by hand and then had Chuck surface gring the sides of the slide to make the checkering stand out. Most of the single stack race guns were fitted with iron sights when the comped scoped fad started and the scopes were mounted on guns desingend for iron sights. I saw many cocking handles on thos old slides. The comp gases didn't hurt a thing back then. You could see the front sight OK. You had a good sight picture BEFORE the gun went off.

I have yet to see a scoped race gun built that considered that it should be a No No to blow all of the smoke right up in front of the scope lens. They all did their best to design new ways to chew up metal with the big mills, but never gave a thought to what I considered to be a "Common Sense" thing that I overcame with a little thought about the way it ought to be. That is where I thought an 11 degree crown on the front of the comp might help make it a tiny bit more accurate. It couldn't hurt and it was "Kewl".

I considered slanting the ports back a little but decided the slight gain (Maybe) was not worth blowing all the crap back in your face.

This gun has been seen a little on the Internet, and at matches in Grand Junction, CO, but very few people have had the pleasure of handling it. It really is the stuff that dreams are made of, but very few people are aware of what it is. They just don't get it and never will. Since I am not in business anymore, I really don't care what they see. I had 120 hours in just the cosmetics so at $75.00 an hour, perhaps you all can understand why it will never be sold. I just got 500 rounds of Starline 3.8 Super brass and we are going to have some fun reloading it and then blasting away again at stuff that don't shoot back!

[tightloop]

The first 11 degree crowns I saw were on bench guns...it did look cool, so I started putting that crown on all my rifles. On my .45 old school race gun, I had the slide lightened inside so not to show all the other guys what was going on...then EDM'ed the ports thru the slide, comp shroud and barrel..added grip weights with very thin grips and wa la, a low rise, low recoiling pistol that allowed me to stay on target with very little downward force form my grip. Inside the barrel were three circular cuts (edm'ed) in the barrel opposite the exhaust ports. The gun really looked very cool when you shot it at night..a Vee of flame about 8 inches tall from each side of the slide at each shot..it kept the smoke and gas away from my face and the sights...it was way before its time and I shot it until the hicap supers drove it into retirement..still a very cool steel gun and for the better part of 82 and 83 it was technically the best singlestack comp gun in the southwest..only three of them were made....wish I still had it..

Chip shot it a few times and tried to buy it from me after he saw it at the 82 Texas Challenge...He was always trying to think outside the box and his natural talent coupled with the changing technology of pistols propelled him to become one of the top IPSC shooters in his era....Now that was really FREESTYLE. Also cut open my California Challenger Davis holster and took out the steel in the holster and cut the front of the holster down to about 1.5 inches from the bottom...fastest real leather holster I have ever seen or used...but time changes and Kydex and race holsters finally replaced even that modified holster...still have that one...

Did a shorter version of that same gun with a commander slide. Also put the first nightsights on both those guns...Self Powered Lighting in New York did the mods there..made three cuts in the blade of the BoMar sight and inlayed Strontium filled rods in there...came with a warning that the half life of the Strontium was 50 yrs, and not to keep it next to your privates for long periods..lol

[titandriver]

Dave Sample (aka "Captain Eagle")!!! You built a comped 40 S&W single stack for me back in 1991. In fact, I still have the letter dated 12 April, '91 and four pictures, one of which is your match gun at the time, a 10mm Centaur. It was marked "not for sale"! The other three were of Bob's Para-Caspian 40 S&W comped gun. As expected, everything was flawless and many is the time I wished I had that gun back!

When I was deciding on a gunsmith before you built that 40 S&W for me, the two page letter I received from you made me realize that your were the man! Your brutal honesty and this line: "I will need your NRA number. If you're not a member I won't do any work for you because you don't deserve to own a gun", told me that you were a man of principle and a man to be trusted!

Great to see you on this forum, thanks again for the great pistol!

Rich Redovian

Melba, Idaho

[Dave Sample]

Woweeee! Rich! I remember you so well. I still have pictures of you here holding that race gun! That was a great project and a fun one because you were a sensible guy to work for. That was an eary .40 that came out pretty good. The old 10mm Centaur was the gun I was hitting an old log out at my ranch over a 300 yard canyon 8 out of 8 that no one believes we did , but my son was with me and he was doing the same thing! That was a swell shooter. I built the R.E.S. right after I did yours and I left Colorado and shut down the Custom Caspians Shop in December of 1992. How great to see you again.

On another matter, my good friend G. Wm. (Gordon) Davis has closed his shop for good due to eye problems brought on by diabetes. It was a heart breaker for me as we were very close for many years. I have a lot of his gun leather here but I will miss those great lunches in Ashfork we had and the projects we did together. He managed to finish the rig for "The High Plains Drifter" 2006 SHOOT! Magazine raffle, and made a wonderful Clint Eastwood rig that was exacttly like the one Clint Eastwood wore in those great cowboy movies back then. I did the sixgun and it fought me all the way, but came out exactly like I wanted it to. Gordon is down in Tuscon with his son and his wife so he is in good hands. He was the King of the holster makers and many a cop had that kind of holster on his hip back then. I do not want to Hi-Jack this thread but here is a couple of pics of that deal.

Gordon gave a lot of himself to us shooters and I wish I was not the Bearer of this bad news. I will try not to change the subject again but I heard his name mentioned and thought some of you might want to know about him.