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Compensator Gas


cb60130

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Being new to open, I'm actively sponging as much wisdom as I can from the folks who have been doing it longer than me. I'm hoping someone can shed some light about gunpowder and how it relates to the way a compensated pistol shoots. From what one can easily gather, the general opinion is slow powder + light bullet = magic. Full disclosure here, I'm shooting a Tanfo Gold Team in 40S&W so that changes the dynamic somewhat on the specifics of load recipe but the concept remains the same.. Make major + Shoot flat = Happy shooter!

I have about 1500 rounds out the snout of my gun, a whole bunch of which are over the top of a chrono with different powders and bullet weights in search of "THE ONE". Since I am shooting a "40 in OPEN" and it's "NOT a 2011" my approach is clearly unorthodox, but I'm having fun learning and I like to tinker.

Without getting overly specific I want to share my impressions and maybe some of you wily veterans can help me make light of my observations. I've tried loads with 6 different powders in varying weights and 3 different bullet weights.

In spite of conventional wisdom I have found that with the lighter bullets and slower powders I do not like the recoil impulse and I find the loads obnoxiously loud.

Heavier bullets with faster powder (my go to load for my non comped gun) shoot almost like my limited gun.

But heavier bullets with a powder that falls somewhere in between (WSF to be exact) seem to be my happy place.

 

All that said... On to the question(s)

 

Let's take 2 loads right from Hodgdon's load data and compare:

 

135g bullet, 8.0g Winchester AutoComp lists 26,600cup pressure

165g bullet, 6.1g Winchester WSF lists 27,600cup pressure

 

Both loads just barely squeak in to major PF to the best of my recollection. I'd have to look at my spread sheet again to verify. When shooting these loads, The Autocomp load was obnoxiously loud and the recoil was much more stout. Muzzle flip feels about the same with the WSF load but I didn't video and watch in slow motion (yet) to verify my suspicions. The WSF load is much kinder to both my hands and ears. The general consensus of opinion says Autocomp would make "more gas to run the comp" but according to the specs it makes less pressure. All things being equal (same barrel length and diameter) isn't the comp essentially just redirecting the gas pressure in a different direction to obtain the desired result of less felt recoil and muzzle rise?

Is there a point of diminishing return with the slower powder? In other words, am I just needlessly using more powder to get the same pressure gas to exit the comp?

Does that obnoxious noise come from the slower powder still burning as it is being vented out the comp?

Am I the only guy in the world who lays in bed at night wondering these things?

 

Thanks for reading through my rambling thoughts and any insight would be appreciated.

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It's not the slower powders that does it, it's the higher charge weight you use. The gas being made is directly proportional to the charge weight of the powder you have loaded the case to. The slower powders are just more dense, and therefore weigh more than the same volume of a less dense powder. 

 

Open guns are loud. There is no such thing as a quiet open gun.

 

Take your WSF load with the 165 bullet...drop that to a 135 grain bullet and what is the CUP pressure? At the same charge weight, it will be substantially lower. You are comparing apples to oranges...

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They make a frangable 115g .40 bullet. I wanted to get some to try for .40 open
115 under accurate 9 or h110 something really slow. May have to go 3n38 or N105 to get major. May be worth playing with

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1 hour ago, GrumpyOne said:

It's not the slower powders that does it, it's the higher charge weight you use. The gas being made is directly proportional to the charge weight of the powder you have loaded the case to. The slower powders are just more dense, and therefore weigh more than the same volume of a less dense powder. 

 

Open guns are loud. There is no such thing as a quiet open gun.

 

Take your WSF load with the 165 bullet...drop that to a 135 grain bullet and what is the CUP pressure? At the same charge weight, it will be substantially lower. You are comparing apples to oranges...

I see what you're saying with the same charge and two different bullet weights...

 

I guess what path I'm going down is thinking same powder and different weights to make major... for instance with WSF. I can get major PF in a 165g bullet with 6.1g of powder. If I go down to a 135g bullet I'm going to be running something like 7.5-7.6g of powder. I am finding the recoil impulse much more pronounced with little perceived difference in muzzle rise. Not to mention the accompanying shock wave that follows. That's where I question the point of diminishing return.

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That's because wsf is a fast powder. It's not generating enough gas to work the comp. It's the opposite of loading soft for non comped guns. No comp, heavy bullet, fast powder. Clays, wsf n so on. With the comp you need a light bullet and sloooow powder. I loaded 10++ Vv N105 under a 115g bullet for supercomp. 8.4g VV 3n38 for 9mm. Both are pretty slow powders and full cases. It's going to be very loud (double plug) and you will have to work up a load that works for your gun.

Get some slow powder and try it with the lightest bullet you have. Do a load ladder. You will find the more powder the less rise in the barrel. It's reverse logic. The cup pressure is just pressure acting on the bullet not gas pushing on the comp

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My 1st open gun was a Glock. I put a comp on it and ran to the range to try it. I got a box of winchester white box and was sooo disappointed. I thought my comp sucked. I started loading my own ammo and it was a night and day difference.

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6 minutes ago, Open1215 said:

That's because wsf is a fast powder. It's not generating enough gas to work the comp. It's the opposite of loading soft for non comped guns. No comp, heavy bullet, fast powder. Clays, wsf n so on. With the comp you need a light bullet and sloooow powder. I loaded 10++ Vv N105 under a 115g bullet for supercomp. 8.4g VV 3n38 for 9mm. Both are pretty slow powders and full cases. It's going to be very loud (double plug) and you will have to work up a load that works for your gun.

Get some slow powder and try it with the lightest bullet you have. Do a load ladder. You will find the more powder the less rise in the barrel. It's reverse logic. The cup pressure is just pressure acting on the bullet not gas pushing on the comp

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I tried WSF because the Tanfo has all those ports in the barrel. The logic is to go a little faster to get the bullet moving before I hit the ports and start bleeding pressure. I'm not sure I'd put in the same group as Clays? Clays is #9 on my burn rate chart and WSF comes in at 37. Autocomp is 43, 3N38 is 48.

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No no you need more gas because of the holes. They will bleed off gas but that's why they are there. They vent to keep the barrel down.

Hopefully kneelingatlas will chime in soon. He has a ton of open tanfo exp.
This is mine. Only 2 holes and a bigger comp but it shoots flat because of the slow powder.
Check out the open gun picture gallery. Many diff open gun set ups. Look at the load data for 9/38 anything mentiong major will be for an open gun. All the data will be with slow powder. Looking on .40 reload page will primarily be for limited .40 major. No comp. 5dc3f9ae71440d6c56901438107f2f2b.jpg

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I would say that by using .40 for open you are outside the bounds of "conventional wisdom" and discussions regarding open reloading in general.  Key factors that contribute to this is the fact that the majority of open guns are built in .38 or 9mm based on the fact that .40 is at a disadvantage of mag capacity size limitations that WILL cost a person time over the course of a match.  Maybe not every stage or even that much time but there will be opportunities that someone can exploit or have less risk in a stage that will impact their match score.  This fact pushes people to .38/9 variants.  If there was a 20rnd mag limit in open, I think you'd see a lot more .40 shooters but since there isn't a mag limit we get forced into .38/9mm

 

So now we have to work within the .38/9mm case limitations and the requirements of making power factor and keeping loads within length limits that fit magazines.  .38 has far less limitations from a reloading stand point as the larger case capacity is easier to work withing the pressure limitations of the case.  However, 9mm is a much smaller case and to achieve PF you have to deliver a smaller bullet within a totally different velocity range than a typical .40 heavier bullet would require.

 

So then you get into how to do this within the pressure limits of the case.  Reducing the volume, increases increases the pressure (think balloon) if everything else remains constant.  Bigger bullets decrease case capacity which increases pressure developed from a specific weight load.  Increasing pressure will increase velocity up and to the point that the pressure is too great for the case to handle the spike as the powder burns.  If the spike is too fast this increase in pressure overcomes the strength limits of the case quicker than the time it takes to relieve the pressure spike of ignition.  The pressure spike is reduced back to zero by increasing the volume of the case which happens as the bullet leaves the case and continues to decrease as the bullet leaves the barrel.

 

So to the way to push smaller bullets to higher velocities, we have to overcome and decrease the initial pressure spike from ignition to be within safe limits.  To do that, you have to slow the burn rate down so it burns and develops pressure slower and continues to develop pressure for a longer period of time than a fast powder would.  As the bullet starts moving, volume is increasing as the powder is still developing pressure which allows for a higher amount of total developed energy while still working within a more confined starting point.

 

What this really means is that the majority of open shooters are forced into a very small range of possible options that meet all required criteria of playing the game.  With .40, you are at a huge advantage of options and choices for what you can try and find works best for you.  More gas works the comp better but comp design efficiency is also a big part of that equation.  

 

I'd say you're a pioneer and there hasn't been nearly the focused effort on determing the ideal setup in .40 like there has in .38/9mm so do whatever feels best to you.  The other thing is people saying fast powders won't work the comp just isn't true.  The comp is used to focus the release of energy in a way that offsets a force so you get the most benefit from all the energy developed.  Most comps are designed to maximize the use of larger volumes of gas because that larger volume of gas is developed by the requirement of getting the velocity needed to make major.  What this really means is that most open comps won't work on less gas because they were never intended to do so.  Looking at comp designs that were developed for different pressure requirements, there are comps that will work, we just don't use them because they don't work with the crap ton of gas we develop as a byproduct of making major velocities. 

 

I think WST would be awesome recoil feel with 180's if you can find a comp to maximize the use of the small volume of gas being developed

 

 

 

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26 minutes ago, drewbeck said:

I would say that by using .40 for open you are outside the bounds of "conventional wisdom" and discussions regarding open reloading in general.  Key factors that contribute to this is the fact that the majority of open guns are built in .38 or 9mm based on the fact that .40 is at a disadvantage of mag capacity size limitations that WILL cost a person time over the course of a match.  Maybe not every stage or even that much time but there will be opportunities that someone can exploit or have less risk in a stage that will impact their match score.  This fact pushes people to .38/9 variants.  If there was a 20rnd mag limit in open, I think you'd see a lot more .40 shooters but since there isn't a mag limit we get forced into .38/9mm

 

So now we have to work within the .38/9mm case limitations and the requirements of making power factor and keeping loads within length limits that fit magazines.  .38 has far less limitations from a reloading stand point as the larger case capacity is easier to work withing the pressure limitations of the case.  However, 9mm is a much smaller case and to achieve PF you have to deliver a smaller bullet within a totally different velocity range than a typical .40 heavier bullet would require.

 

So then you get into how to do this within the pressure limits of the case.  Reducing the volume, increases increases the pressure (think balloon) if everything else remains constant.  Bigger bullets decrease case capacity which increases pressure developed from a specific weight load.  Increasing pressure will increase velocity up and to the point that the pressure is too great for the case to handle the spike as the powder burns.  If the spike is too fast this increase in pressure overcomes the strength limits of the case quicker than the time it takes to relieve the pressure spike of ignition.  The pressure spike is reduced back to zero by increasing the volume of the case which happens as the bullet leaves the case and continues to decrease as the bullet leaves the barrel.

 

So to the way to push smaller bullets to higher velocities, we have to overcome and decrease the initial pressure spike from ignition to be within safe limits.  To do that, you have to slow the burn rate down so it burns and develops pressure slower and continues to develop pressure for a longer period of time than a fast powder would.  As the bullet starts moving, volume is increasing as the powder is still developing pressure which allows for a higher amount of total developed energy while still working within a more confined starting point.

 

What this really means is that the majority of open shooters are forced into a very small range of possible options that meet all required criteria of playing the game.  With .40, you are at a huge advantage of options and choices for what you can try and find works best for you.  More gas works the comp better but comp design efficiency is also a big part of that equation.  

 

I'd say you're a pioneer and there hasn't been nearly the focused effort on determing the ideal setup in .40 like there has in .38/9mm so do whatever feels best to you.  The other thing is people saying fast powders won't work the comp just isn't true.  The comp is used to focus the release of energy in a way that offsets a force so you get the most benefit from all the energy developed.  Most comps are designed to maximize the use of larger volumes of gas because that larger volume of gas is developed by the requirement of getting the velocity needed to make major.  What this really means is that most open comps won't work on less gas because they were never intended to do so.  Looking at comp designs that were developed for different pressure requirements, there are comps that will work, we just don't use them because they don't work with the crap ton of gas we develop as a byproduct of making major velocities. 

 

I think WST would be awesome recoil feel with 180's if you can find a comp to maximize the use of the small volume of gas being developed

 

 

 

Thanks for the inspiration on the Pioneer front. You may be on to something about conventional wisdom not applying to my journey. There is not nearly the treasure trove of information available for loading open 40 that there is for 38/9. It also seems that there's a lot of tinkerers who spend a lot of time and effort creating a perfect compensator to work with the load they want to shoot. My approach has been to find the load that works for the comp I have. And...the journey continues.

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13 minutes ago, js1130146 said:

 

And he's got a Tanfo Gold Team V12 which is the loudest and most obnoxious open gun you can get

I'm not sure, I think I read somewhere that Tanfoglio is Italian for "we hear you"

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8 hours ago, cb60130 said:

Is there a point of diminishing return with the slower powder? In other words, am I just needlessly using more powder to get the same pressure gas to exit the comp?

Does that obnoxious noise come from the slower powder still burning as it is being vented out the comp?

Am I the only guy in the world who lays in bed at night wondering these things?

 

Yes, there is a point of diminishing returns.

 

A book load listing more pressure does not necessarily produce more down force with the comp (the pressure drops faster with faster burning powders as the volume behind the bullet increases).

 

Yes, the noise comes from burning powder exiting the barrel.

 

No, you're not the only one :cheers:

 

Like you said, your setup is unconventional in a number of ways, so  you won't see the same results as others shooting Open guns with:

-smaller bores

-fewer holes

-better comps

 

There's no nice was to say it: the comp on the V12 Gold Team is terrible.  Comps serve two functions:  to divert gasses upward, reducing the "muzzle flip", and to provide a bearing surface to catch gasses and pull the gun forward, reducing the "slap in the hand".  The two tiny ports in the V12 comp don't do a very good job of either, made worse by drilling 0.420" holes in the baffles.  The majority of the down force comes from the 12 ports in the barrel which do very little to mitigate that "slap in the hand".

 

Given all that you may find a different balance between muzzle flip, noise, and violence than someone shooting a 9mm or 38 super with a better comp and fewer holes.

 

If I were in your situation my focus would be on predictable dot movement, I suspect your fastest times will come not from your flattest load, but the one which allows you to watch the dot lift and gets it back on target fastest.  Hint: springs and firing pin stop angle will do as much to that end as will the powder or bullet weight.

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1 hour ago, kneelingatlas said:

 

Yes, there is a point of diminishing returns.

 

A book load listing more pressure does not necessarily produce more down force with the comp (the pressure drops faster with faster burning powders as the volume behind the bullet increases).

 

Yes, the noise comes from burning powder exiting the barrel.

 

No, you're not the only one :cheers:

 

Like you said, your setup is unconventional in a number of ways, so  you won't see the same results as others shooting Open guns with:

-smaller bores

-fewer holes

-better comps

 

There's no nice was to say it: the comp on the V12 Gold Team is terrible.  Comps serve two functions:  to divert gasses upward, reducing the "muzzle flip", and to provide a bearing surface to catch gasses and pull the gun forward, reducing the "slap in the hand".  The two tiny ports in the V12 comp don't do a very good job of either, made worse by drilling 0.420" holes in the baffles.  The majority of the down force comes from the 12 ports in the barrel which do very little to mitigate that "slap in the hand".

 

Given all that you may find a different balance between muzzle flip, noise, and violence than someone shooting a 9mm or 38 super with a better comp and fewer holes.

 

If I were in your situation my focus would be on predictable dot movement, I suspect your fastest times will come not from your flattest load, but the one which allows you to watch the dot lift and gets it back on target fastest.  Hint: springs and firing pin stop angle will do as much to that end as will the powder or bullet weight.

 

Thanks for your insight. Kinda reinforces what I've been finding through my experimentation, especially after really looking at other comps and noting that they are mostly WAY different than the Gold Team comp. I feel like I'm getting real close to where I want it to be but it's just so far from conventional.  But taking in to account the fact that my set up is like a special unicorn, it's starting to make sense.

 

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cb, I've done just what you are doing, except with a different Tanfo comp.  I also have a 2011 Open 40, and another on the way.  Here is what my experimentation tells me.

 

Your comp is not going to be very effective, for two reasons.  First, it is too small with too few ports.  If you actually make enough gas to get it to "work", the effect will still be minimal.  Second, your plethora of barrel ports bleeds off pressure and gas so quickly, there isn't any left to work the comp, unless you go very slow.  You already know what that will sound like.

 

In your situation, going with a 135gr is a mistake.  165 is too heavy, so try the 155.  I love them.  Next you have to decide what it most important to you.  You are not going to get any effective recoil reduction from the comp, so your choices are softer on the hand or less dot movement.

 

Softer on the hand means less of a faster powder.  That will still work some of the barrel ports to reduce flip.  The more of the ports you work, the less flip.  WAC and Silhouette are the slowest powders to use.  They are going to be loud.  Stay with the 155.  Go with progressively faster powders until you get the combination of recoil pulse and dot movement you are looking for, or are willing to settle for.  It will most likely be the latter.  

 

I'd follow ka"s advice and look for the most predictable dot movement. 

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4 hours ago, Hi-Power Jack said:

Just curious   .....     WHY a .40 Major?

I enjoy shooting my local outlaw matches on Thursday nights. At this time I really have no aspirations more serious than that. Most stages can be run without consequence of reduced capacity since the match director seems fond of throwing mandatory reloads in to stage design. I wanted to tinker with an open gun. Regardless of how many people do it, I wasn't real comfortable loading 9 to make major. I have everything I needed to load 40. I didn't want to have the added expense of setting up to load 38 super. I have a Tanfo in 9mm that I have grown quite find of so I am comfortable with the platform. I race motorcycles too which takes up my weekend time and money budget. I suppose if I decide to thin my current herd of 3 motorcycles in the garage I may end up with a 38 super and aspirations of big matches.

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4 hours ago, Hi-Power Jack said:

Just curious   .....     WHY a .40 Major?

I enjoy shooting my local outlaw matches on Thursday nights. At this time I really have no aspirations more serious than that. Most stages can be run without consequence of reduced capacity since the match director seems fond of throwing mandatory reloads in to stage design. I wanted to tinker with an open gun. Regardless of how many people do it, I wasn't real comfortable loading 9 to make major. I have everything I needed to load 40. I didn't want to have the added expense of setting up to load 38 super. I have a Tanfo in 9mm that I have grown quite find of so I am comfortable with the platform. I race motorcycles too which takes up my weekend time and money budget

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zzt... You're spot on. Of the 18 combinations I've chrono'd and shot my favorite few have been 155 and 165 with moderately quicker burning powders. They seem to produce the favorable dot movement.

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Jack, I started in 40 for Limited.  When my eyes got bad enough that I had trouble sighting (even with an insert) I decided to go Open.  I first bought a 40 Open upper for my CZ TS from kneelingatlas.  It worked, but not as well as I hoped.  I spent a couple hundred getting it setup and then shot it.  It was just like shooting Limited, but with optics.  A while later I ran across a reasonable deal on a 2011 Open gun.  I bought it, and preferred it over the CZ Open.

 

I fixed the 2011 up, bought mags for it and ran it for the bulk of two seasons.  Here is what I discovered.  There is no real disadvantage to shooting 40 Open.  26 vs. 29 round mag capacity and weight of the ammo are the only two I can think of.  40 is easier to reload, makes Major at way under SAAMI max if you want, and uses straight walled cases..  A Lee FCCD solves the "glocked" brass problem 100%.  40 costs me no more to reload than 9mm, at least with the components I use.

 

My comp is starting to loosen.  I came across another reasonably priced, semi-custom gun with a lot of accessories and supplies I decided I wanted.  When it arrives, I'll check it out, replace what needs replacing and use it as my backup gun.

 

Now before everyone jumps in with how important 29 in a mag is, let me stop you.  It may well be that where you shoot, it is.  It isn't where I shoot.  The course designers go way out of their way to make sure Open shooters cannot stand in one spot and hose half the course, then take a step or two and hose the rest.  They make darn sure you have to cover the same ground as everyone else, and there is a lot of it to cover.  There is always a spot or two to reload without costing any time, and reloads are always needed.  That's fine by me, because I think all courses should be 30-32 rounds long.  I like to shoot.

 

Now, all that said, I am in the process of building two Open guns.  One will be a 1911 dedicated to Steel Challenge.  The other will be a 2011.  I haven't decided whether it will be Minor or Major yet, but either way, I'll be able to directly compare it to the 40.  Same for SC.  I shoot 40 Minor in SC right now.

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