Let's talk Air Strippers

[Pete Wass]

I have long been a doubter of the efficacy of air strippers, with regard to adding to accuracy of firearms. I noticed in a thread on another forum here pictures of bullets after they had passed the muzzle, showing the ring of gasses and how the bullet very quickly is propelled out of the ring of gas. It again made me wonder exactly how a ported device could aid, in any way, the accuracy process.

Now, I realize, quick as a flash, someone is going to say there is a big difference but, is there really? I guess until I saw some photos of a pellet escaping the air cloud behind it could I see any meaningful difference between the two.

Question: are there any pictures illustrating proof of benefit from air strippers to accuracy that can be shown on here for me and others to see?

Thanks,

Pete

 

[Tone]

Hi Pete, there is not a lot of detailed research that I know of that deals with air strippers for air rifles.

I tend to look at the 'muzzle break' comparison's that you see on Youtube using full bore rifles, these basic experiments show that their is a definite effect on the movement of the riffle when certain muzzle breaks are used.

With a PCP air rifle you can get a lot of muzzle flip and the addition of a muzzle break/stripper can really calm it down.

However, in terms of aiding the pellet after it exits the barrel, I think at the moment it comes down to individual trial and error and gut feel until someone is able to get some slow mo cameras and time to do the analysis?

Tony

 

[Dave Shattuck]

Pete,

You have to think of an Air Stripper as a barrel tuner. By adding the extra weight out at the end of the barrel helps to calm the flip/vibration, then to "fine tune" the stripper you reposition the adjustable cone within the stripper by either moving it in or out, just like with what we do when tuning a Harrel's tuner. It takes a while to find the sweet spot, but once you do you can definitely see a difference.

Case in point: On my Dan Brown Poly barrel, when I first put it onto my Theoben I was shooting not too impressive groups to start before the stripper, but once I mounted it and played with it a little the groups dropped to less than half of what they had been. Now that barrel is definitely a killer barrel. Of course, Paul B has the same barrel on his Thomas, doesn't use a stripper, and look what his gun does.

Another example is the AA S400 MPR I just sold. Straight out of the box that gun was shooting in the mid 230's with the occasional 240. I bought a stripper from a fellow over in the UK and had him set it up to where he had set others, then I immediately started seeing mostly high 240's or 250's. I told its new owner he'd be smart to not touch a think.

Let the debate go on.

Dave

 

[blades]

Used one on a co2 match pistol calmed down the flip, since that time most of the high end Match air pistols incorporate an air stripper as well as relief ports machined into the barrel/ shroud assembly- so there must be something to it. My FWB 40 has this. Firing the pistol in a match and it is dead still throughout the firing sequence, no evidence of barrel movement due to pellet/ air clearing the muzzle. Now if I could just get the rest of the equation to co-operate ( me ) life would be grand.

 

[AZUARO]

Pete:

I agree to what has been said...The mass of a stripper at the end of the barrel will act as a "Tuner" mitigating some of those detrimental barrel harmonics...Nevertheless, I am going to discuss two critical issues about devices that either strip air or minimize rapport like silencers...

These devices CAN and WILL improve accuracy, but there are some conditions that need to be met: The internals (cones, baffles, etc) need to be TUNED and CONCENTRIC, otherwise the pellet/bullet will receive a disruption while passing though the device, and I am not talking about bullet/baffle clipping which will then kill any existing accuracy, I am talking about the GAS STRIPPING VARIABLE that is created when: The bullet/pellet is stripped from the air pushing it, the air that the projectile is pushing forward, and to some extent the rotational turbulence natural in a spinning pellet....

So, any "disruption" while stripping air interacting with a bullet is as said, detrimental to accuracy...See it as a similar effect of a crown that is not perpendicular to the bore...
The second issue (Tuning) is about locating the mass of said stripper and its internal components at the optimal point in front of that barrel...

We did one particular test at a lab with a gun shot from a vise...We were testing the impact of the first cone of certain brand stripper set right vs. slightly setting it in a non concentric position, but without having any pellet-baffle clipping...The first test was shooting with the bare stripper attached to the barrel (without cones) to corroborate if the sole mass of the stripper would act as a tuning device and improve accuracy...It did, but there were points where accuracy decreased because of the mass of this stripper not being located right for best harmonics attenuation.

We then added one cone that was set perfectly concentric...The accuracy improved vs. stripper with no cones located at optimum position as discussed above but we did not test if the improvement was a result of the added mass of the cone.
The THIRD test was moving back and forth this cone for best accuracy...We found the optimal point and accuracy improved...
We then set this cone slightly non concentric to the bore, but kept it located at the same optimal location mentioned above...The accuracy DECREASED to being about the same or less that the barrel without no stripper...
We came back and re-positioned the cone as in the third test above...The accuracy returned to this optimal point...
We finally did the same experiments to a second cone while keeping the first cone in its optimal position (third experiment)...The results of adding this second cone were similar in general terms, but much less critical given the fact that most of the air was already stripped with the first cone, nevertheless, the setting of the second cone indeed affected accuracy to some point..

So yes, there is something to be gained with air strippers and silencers, but I believe that such devices need to be set right and TUNED to the specific gun-barrel combination, there is no out of the box perfectly tuned stripper...

My experience has also been that there are instances where some barrels don't react to tuners/strippers/silencers...I have 2 of those gun/barrel combinations that are excellent shooters but that don't like anything hanging, my explanation to this is that these barrels are already pretty much TUNED without anything attached, and from there on, anything that you "hang" will not only not improve but will deteriorate accuracy...

Best regards,

AZ

 

[Pete Wass]

Thanks Everyone

As I have suspected, the main benefit appears to be tuner weight and I will open my mind up to believe there can be a benefit derived from exactly positioning a stripper in addition.

I have tried, in the past, some ported tubing that slid inside another tube which was affixed to the barrel by set screws. My conclusion was that it was simply the extending of the weight of the ported tube that made any difference. It was also very finicky as to it's position.

I subsequently went to a mid barrel ring of weight, copied from someone else and seems to work better than the muzzle mounted "Stripper". The ring is positioned roughly 3/4 of the distance from the muzzle to the breech. It appears to be a lot less finicky as to how precisely it is positioned.

Thinking back a bit, my first custom rimfire rifle came to me with a Fudd adjustable tuner on it. In experimenting with that tuner, I found the tuner worked equally well if the entire mass was mounted behind the muzzle. I use to keep it there so I didn't have to clean the inside of it.

So, I have had a number of conclusions reached over time. I do wonder why a mid barrel mass seems to tune barrels though. I have never read or heard any discussion about that subject but I am certain enough it works. My E V 2 seems to be somewhat comparative, wearing it's mid barrel weight, considering the rest of the rifle remains stock out of the box, barrel and all. Not a full blown Benchrest rig, by today's standards but pretty good, considering.

Good stuff to beat around this winter as long as folks are willing to keep talking.

Thanks again,

Pete

 

[AZUARO]

Hi Again Pete:

" I do wonder why a mid barrel mass seems to tune barrels though. I have never read or heard any discussion about that subject but I am certain enough it works..."

Man, with these kinds of interesting topics and my long discussions we are going to end writhing a book!

Locating MASS closer to the pivoting point (s) is optimal for dealing with harmonics...If the same Mass is located at the tip of the barrel the tuning becomes peaky and there is a TOO MUCH and a TOO LITTLE variable...
If by contrast, you put too much mass close to the breech area, there isn't a TOO MUCH variable, but there is a point where adding more mass doesn't make any difference..

There has been much experimenting regarding mass, barrel contours, tapering, reverse tapering, etc...all trying to cope with harmonics and accuracy and all with mixed results...In general terms, the larger the barrel contour the more mass and better accuracy potential; But then we have that vibrations can be attenuated (tuned) by other means besides adding mass...

Stepping out of the topic of this thread, but interesting information about these tuning devices, we have done some experimenting with active and passive VIBRATION ISOLATORS set/tuned exactly as you set those mid barrel mass pieces and have found that they also work very well...Using fluids from water to viscous fluids to semi-solids like mercury to Silicon and Sorbothane kind of materials in contact with the vibrating surface can provide the very same or better results than adding mass...We have done it mainly for the aerospace industry but the same can be done with a gun barrel...The simplest experiment for anyone reading this post will be to sleeve a barrel along its longitudinal axis a little larger that the outer surface of said barrel and fill it with any of these materials...
An active isolator is more complex and requires and external generating apparatus generating the same frequencies in opposing direction(s) and I will not touch this topic here...

Steyr with its LG-100, later upgraded to the current LG-110, Anschutz with their 8002 and 9003 lately 9015, and Walther with the 400 and a previous model, all use an opposing recoil/vibrations principle using a mechanical MASS device....There is a bar that has a spring for pushing it backwards in opposing direction to the pellet as soon as the gun is fired...It has a sear mechanism that is triggered by a fulcrum/spring and a bearing acting as a pushing valve as soon as the pressure rises inside the bolt...This simple mechanism reduces recoil/vibrations and works pretty well but understand that such a device is not MANDATORY in all guns...RAW is leading the BR accuracy standards without one.

For attenuating (tuning) vibrations one thing to keep in mind is that the straighter and the more concentric the barrel is, the better you can make it shoot with little effort...Sometimes the addition and proper tuning of peripherals helps and sometimes it will shoot its best without anything attached.

Let me give you an example for 2 of my barrels:
Barrel number one is a Shilen that my friend Ed custom made me for me for doing some testing about 2 decades ago...This barrel has no more than .0001" (one ten thousand or less) bore straightness and it is perfectly concentric to its outer surface, it is a 6 groove ratchet 22+ inches long with no choke...The second barrel is a LW 12 groove that has .0015 to .002" (one and one half to two thousands) bore straightness and its outer surface is as concentric as it can be had with this bore difference and has a choke....Both barrels were air gauged to .0001".

Barrel one (Shilen) shots anything you throw at it with outstanding accuracy and this is one of those barrels that don't like anything hanging I talked about in my previous post...Anything I add at any location will either have no gains or will deteriorate its accuracy...This barrel is pretty much "Naturally Tuned".
Barrel two is also a very good shooter that becomes alive and close to barrel one when tuned right...Nevertheless, this barrel is VERY PEAKY as to where you locate the tuning pieces....If for example I use a mid barrel mass and find a good point, but slightly rotate this piece, the accuracy varies...
Why? Because of the unbalance in between bore and outer surface make it impossible to add mass equally around said barrel and because the mass piece is not perfectly homogeneous and balanced...Tuning it I am dealing with the sum of two or more inequalities...

Gong back to air strippers...You mention that you are inclined to believe they work mostly because the added mass at a critical point...I agree with this statement...
Then you mention: " I will open my mind up to believe there can be a benefit derived from exactly positioning a stripper in addition"...In this respect I will only add that the function of an air stripper is to remove the air from the pellet as discussed in my previous post: From the skirt, frontal area and turbulence around it...If the pellet is not perfect, then the sooner the air projecting the pellet stops interacting with the projectile's surfaces, the less destabilizing forces and the more accurately that pellet will shoot...If the pellet is perfect and flying straight coming out of the crown and the barrel is straight and concentric, the air stripper will pretty much do nothing but add weight as you mention.

If you ask me, I don't use the air stripper that came with my Steyr LG-110...It worked very well with the factory's original barrel which is a slightly less than 1/4" barrel at 50 yards, but not good enough for competitive BR...The stripper didn't helped nor worked on the Shilen barrel discussed above unless the pellets shot were from a bad batch, otherwise it worked negatively deteriorating accuracy...
In the LW 12 groove I used it for some time, but then cleaning the barrel after each target required much attention to those thin threads that detach from the cleaning patches and stick around the edges of the stripping cones, cleaning solvent also around the these cones, etc. and I decided to retire it for good.

Regards,

AZ

 

[Tone]

If you ask me, I don't use the air stripper that came with my Steyr LG-110...It worked very well with the factory's original barrel which is a slightly less than 1/4" barrel at 50 yards, but not good enough for competitive BR...The stripper didn't helped nor worked on the Shilen barrel discussed above unless the pellets shot were from a bad batch, otherwise it worked negatively deteriorating accuracy...

Regards,

AZ

Hi Pete & AZ

Agreed a stripper can be beneficial as a muzzle weight to tune the harmonics, but if it wasn't for a PCP's noticeable muzzle flip when it has no additional moderator or stripper I wouldn't use one just as a tuner, as I have found that some days its on, some days it is off (thats air rifles for you!), and just having an exposed barrel eliminates the question mark.

AZ, assuming you are talking about the Steyr double cone stripper, have you tried it with just the one cone closest to the barrel crown, taking the outer one off.

I found that it shoots better with just the one cone.

Cheers

Tony

 

[AZUARO]

Hi Tony,

You ask me: "AZ, assuming you are talking about the Steyr double cone stripper, have you tried it with just the one cone closest to the barrel crown, taking the outer one off."

Yes, we did some extensive testing with this particular Air Stripper in very good, good and regular shooting barrels...In our testing adding the second cone slightly improved accuracy (if set right) in all but the outstanding barrel, and it did nothing in other positions that were too far or too close to the first cone...Maybe it was the mass of the cone and not the air stripping of this second cone what was making the slight improvement as Pete states, but we did not test replacing the second cone for something with similar mass but without stripping qualities to see if the results were the same because we were analyzing vibrations and the accuracy results I obtained were a bonus to the testing.

One fact of the testing is that this stripper provides different accuracy results depending on the barrel...The better the barrel (bore concentricity and bore to outer surface concentricity) the less effective the air stripper

I mentioned some of this on my post from 12-14:
"We finally did the same experiments to a second cone while keeping the first cone in its optimal position (third experiment)...The results of adding this second cone were similar in general terms, but much less critical given the fact that most of the air was already stripped with the first cone, nevertheless, the setting of the second cone indeed affected accuracy to some point.."

Thank you so much for participating and adding valuable info to the thread Tony...

Best regards,

AZ

 

[AZUARO]

Tony,

I forgot to mention that if you are after controlling MUZZLE JUMP or recoil on your PCP, you may want to use a staged muzzle brake where the air pressure is reduced in a more controlled manner than with an Air Stripper...If you have a scrap barrel to test it on, drill some holes or slots around the last 3 inches of the barrel and then use a piloted reamer as close as possible in dimensions to the pellet head/skirt diameter after exiting that particular barrel...

A staged muzzle break tames the somewhat abrupt gas release of air strippers as we have been discussing...If this works well for you, then you can emulate this 3" section as an extension to the barrel you are using and maybe even use it in other barrels...

Regards,

AZ.

 

[Pete Wass]

It seems to get back to Barrels, Barrels, Barrels - - -

Makes one wonder why we bother with all the ornaments. How difficult is it to measure a barrel to know for sure it is absolutely straight and concentric? What device will tell one if a bore is dead straight? I understand concentricity and how to measure that.. How many barrels come off the machine dead straight?

Az, have you tried to straighten barrels to make them shoot better and if so, what have your results been?

Thank,

Pete

P.S.

Has every straight barrel you have tested been a great shooter?

Thanks

 

[AZUARO]

Hi Pete:

Measuring barrels?
There are bore lasers and other instruments that are very precise, we have some of those at the lab but I rather do it the old fashion way for simplicity at home...I have piloted range rods from 4.40 mm to 4.60 mm in .005 mm increments that go together with a couple of .0001" indicators...I mount the barrel in between the choke (4 jaw) and the spider on the head stock. I also use roller bearing V blocks. At the lab we have air gauging probes for measuring anything and I have used them for bore dimensions, chokes, etc...My experience has been that good barrel manufacturers are drilling-boring barrel blanks much better than 10-20 years ago, I don't really see any need for spending the big $$$ in air gauging equipment if you are dealing with good barrel/gun suppliers.

I don't know about air gun barrels, but mostly all of the good powder burning barrels are air gauged at the factories and some of those carry .0001" warranties.

How many barrels come out straight?
Most of the MATCH quality barrels are straight to less than .0005 to a max of .001" which is plenty for good accuracy...I wish we had availability of hammer forged barrels produced with current technologies...

Hanging Ornaments?
Yes and no...Top barrels don't need them, next step down they may need them to maybe shoot as top barrels do...Some more steps down, no matter what you hang, those barrels will never be shooters!...
Check what the cream of the crop BR shooters are using....Look at Anschutz 9015's, Feinwerkbau 800's, Walther, RAW's BM and TM series, etc....None of these shooters nor manufacturers hang ornaments because that is another variable to deal with ALL THE TIME and they rather spend resources in technology for producing top components...Manufacturers want their brands shooting well without having to depend on the consumer's knowledge for adjusting ornaments.

Straightening Barrels?
I don't usually do it because I believe you are much better off spending your $$$ and time in finding the best available barrel on the market. Nevertheless, I have straightened some powder burners bent in hunting trips (falls) and experimented with one air gun barrel for a friend...Some tuner indexed the barrel and glued it to the action with Acraglass. The gun was shooting OK but not up to BR standards.
This was a good opportunity for experimenting and I had the time...You can read this in more detail in a previous thread, please go to the very last post: http://benchrest.com/showthread.php?98176-Barrel-length-question

Best regards,

AZ

 

[Pete Wass]

During my years

of Benchrest shooting I have seen a few exceptional barrels, most of them on Centerfire rifles. I have seen some Rimfire barrels that seem to be every bit as good but have yet to own one. I haven't spent a lot of time with Air Rifles but know of a few Air Rifle barrels that shoot fantastically, the ones that one can shoot competitively right out of the tin, without any gauging or rolling of pellets. I don't think there are many of those barrels out there however.

Thinking through what AZ said, one would be better to keep fitting barrels and hope to eventually find the one (s) that didn't need any help. I will say I don't know of any maker who guarantees straightness to .0001" or have never heard of one. I think a number of people would pay a pretty big premium to be able to purchase dead straight barrels. I would,at least. I think most people simply buy barrels and hope for success.

Many years ago there was an article in PS magazine that featured Tony Boyer @ Dwight Scott's shop having 20 barrels chambered, hoping to get a couple good enough to be competitive at the level he was at at that time, On Top. Now, that was a long time ago. Some of the best CF barrels I remember came from lots of barrel orders which were group purchases. Not all of them were great. I don't know what that says, exactly, but may say the great two or three were dead straight and the others not so much.

Still mulling this over but should great barrels be as rare as they seem to be?

Pete

 

[AZUARO]

Pete:

You stated: " I will say I don't know of any maker who guarantees straightness to .0001" or have never heard of one."

When I mentioned the .0001" I was talking about bore DIMENSIONS along its entire length...Shilen, Lilja, and some others will warranty having air gauged their premium barrels to within this number...

Bore straightness and bore concentricity are two other variables on top of bore dimensions...We all tend relate button cut barrels with the most accuracy because this is what the industry is supplying us with, but don't discard hammer forged barrels...If made with current technologies these barrels have very close tolerances and are very, very precise and comparable to any of the best of the best.

In a PCP, timing and regulator consistency (spreads no larger than about .5 to 1% of shooting velocity) are very important, and when not right, people tend to confuse these issues with a bad barrel...
Testing a barrel in a similar gun that shoots extremely well is a very good way testing what we suspect is not a good barrel ...Accurizing a PCP's is probably harder than doing the same in rimfires or centerfires.

At one time we used Walther and Anschutz actions for testing parameters that required the out most precision...Nowadays a RAW or one of its many clones are probably the best alternative given the reliability and tank built construction...

Regards,

AZ

 

[Pete Wass]

So, how does one

Pete:

You stated: " I will say I don't know of any maker who guarantees straightness to .0001" or have never heard of one."

When I mentioned the .0001" I was talking about bore DIMENSIONS along its entire length...Shilen, Lilja, and some others will warranty having air gauged their premium barrels to within this number...

Bore straightness and bore concentricity are two other variables on top of bore dimensions...We all tend relate button cut barrels with the most accuracy because this is what the industry is supplying us with, but don't discard hammer forged barrels...If made with current technologies these barrels have very close tolerances and are very, very precise and comparable to any of the best of the best.

In a PCP, timing and regulator consistency (spreads no larger than about .5 to 1% of shooting velocity) are very important, and when not right, people tend to confuse these issues with a bad barrel...
Testing a barrel in a similar gun that shoots extremely well is a very good way testing what we suspect is not a good barrel ...Accurizing a PCP's is probably harder than doing the same in rimfires or centerfires.

At one time we used Walther and Anschutz actions for testing parameters that required the out most precision...Nowadays a RAW or one of its many clones are probably the best alternative given the reliability and tank built construction...

Regards,

AZ

avail them self of a truly straight barrel?

Pete