Ernest barrel straightening

It’s the same principal we used to use straightening aluminum arrows. They had a couple of roller blocks with a lever in the center that had a built in dial indicator. Just roll the arrow/barrel liner around find the high spots and counter bend it in the opposite direction. Think God for CF shafts

Jking

You may or may not have seen this video Michael but If you watch Matt Dubbers video from a couple of years back with his tour of the FX Factory at the 3:25 minute mark it shows the method the factory uses to check and straighten the barrels. It’s just a simple press jig with a dial indicator showing if the barrels straight or not.

You don’t necessarily need to use or buy roller bearings you can simply use V blocks or something that is relatively even and stable on a bench and roll the shaft with your hand while checking the dial indicator.

I have a metal lathe and also a wood lathe and use a dial indicator many times to check things for straightness. I haven’t checked my Stx barrel liner as yet but it would be interesting to see just how straight it is. 

Darren

https://youtu.be/DqTm_XmfQpg

A arrow straightener would work but the dial indicator wouldn't work with the rifling groves on the outside.

That depends on the brand and often the gun. Some makers and some specifics guns that have one type of barrel will have a run of guns with bent barrels. I had more than a few of my Crosman guns with bent barrels but have a mini lathe so it was not hard to straighten them.

I saw the arrow straightener on line. Do you think it would work to straighten a liner? Are they strong enough. You can bet if I bought one I’d find my liners are dead straight!

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DON'T___WATCH OUT!!! Read this before you ruin your barrel!!!!

The straightness of a barrel is related to the BORE straightness or concentricity, meaning that what is important is the difference between the breech (Chamber) and the exit of the barrel (crown)...The purpose of those bearings is related to the straightness of the OUTSIDE of the barrel (one piece barrel system) of the shroud in the case of the FX's....Other purposes (we will get into this), so DO NOT ruin your bore concentricity (bore straightness) in order to have the outside of that barrel LINER straight....

The bearings and/or the arrow straightener are only helpful to make sure the shroud or the barrel (not a liner) is straight to the block (action), you don't want a crooked barrel where the bullet is not leaving as straight to the line of the action/barrel...Finding a barrel that is straight on the outside with perfectly concentric bore (straight) is VERY DIFFICULT and when you find one that has the right measurements of bore, lands and groves (Both: depth and ratio) you have found a GOLD MINE...I have only found 2 of those barrels in my more that 45 years of gun making and fitting barrels to my centerfire, rimfire and airguns...

Then if you are using an FX liner inside a liner housing, the liner housings are NOT ever perfectly straight and those parts are the ones attached to the action (block) of the gun and those shrouds command the straightness of the BORE LINE of the liner that is attached tho them under compression...

Prime barrel makers turn their blanks to perfection and then drill the holes and lastly ream them hoping everything is as straight as possible...Most of the times there is a difference between the outside straightness and the bore line and this is why we use indicators at both ends of the barrel that is attached between the choke and spider of very precise lathes for cutting the threads and chambers straight...The process explained (indicators-lathe-choke-spider) is VERY TIME CONSUMING and no company selling commercial products guns) does it this way and this includes FX but it applies to barrels and NOT liners...You may have a barrel that is not perfectly straight on the outside, but if block (action) and barrel are aligned and the bore is relatively straight, this barrel will shoot OK...

FX liners are NOT drilled nor reamed and the rifling is not cut, button pulled nor hammer forged...It is stamped from the outside using a press/mandrel or equivalent system and the liners might not be straight on the outside but are as straight as you will be able to get them on the inside given the process used...And since the outside of the tubes were not turned in a lathe those are NEVER perfectly straight....So assuming you were able to straighten the barrel with the arrow jig or similar, by the time you see it straight you already damaged the bore straightness/concentricity and there goes your accuracy...The problem will be magnified if the SHROUD/BARREL HOLDER is not straight either...You WILL NOT find a perfectly straight Shroud because those are tubes vs. a steel blank that is machined/drilled to perfection (very expensive process)

Soooooo....DON'T mess with the barrel....TUNE YOUR GUN with reg pressure seeking a certain velocity with hammer strike and then optimize air consumption with the valve opening micrometer (if a FX Impact or equivalent).

Best regards,

AZ

Dumb question but don't the o'rings go over the liner and into the sleeve? I would guess the sleeve should be just as straight as the liner, ideally somehow tensioning the liner seems like it would cure many of these problems. The 27" liner has a ton of harmonics to tame, anyone try loading 8 or more o'rings over it??? 

Dumb question but don't the o'rings go over the liner and into the sleeve? I would guess the sleeve should be just as straight as the liner, ideally somehow tensioning the liner seems like it would cure many of these problems. The 27" liner has a ton of harmonics to tame, anyone try loading 8 or more o'rings over it???

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8 O rings?...Why not 16, 40 or a stack of O rings from the breach to where the sleeve/liner bushing is threaded?....More is not always better.

Crooked sleeve = Non concentric O rings which means uneven pressure on the liner = Liner not straight or unevenly set (different pressures on the sides)...The more O rings you put into a non concentric liner/sleeve set up, the more pressure on the walls of the liner and the worst the precision...If liner/sleeve are straight and concentric, then a few O rings might help. There is nothing as accurate as a straight solid 1 piece barrel (No liners-No O Rings-No Sleeves)...Nevertheless, the system as in in those guns works just fine and is very convenient for changing calibers and barrel profiles...Its advantages are above its disadvantages if you know how to take advantage of them.

Don't be misled by the "Harmonics Game"...Yes, Harmonics exist on any gun and on any barrel after firing it, but the more balanced and well tuned the gun is, the less influence those harmonics have on the precision of your gun...Please re-read this paragraph time and again until you fully understand what I am saying.

Note: The issue about harmonics is to make sure your pellet leaves the gun at the same point on the harmonics curve EVERY TIME, preferably at the lowest point in the amplitude where it will have the minimum effect...Look for the definition of "Node" 

I have a barrel that has 1/2 of a ten thousand (.00005") of an inch in bore dimensions (air gauging) and about .0001" straightness between breach and crown...The outside of this barrel is about as straight as its bore and this is as straight as you will ever get...It is a Shilen Ratchet custom made personally by Ed Shilen some 20-25 years ago, it is .177 cal and is currently installed on a RAW TM-1000. This gun is tuned for HV (20 ft./lb.) shooting 13.4's at 25 Meters and it is my HV 25 Meter USARB Gun; this rifle is probably one of the most accurate 25M guns in existence in the USA or the world for that matter (gun has many records not ever shot anywhere in the world)...As it is, tuned for 13.4's and without touching any adjustments, I can load 8.4's or 10.3's and it will shoot them with the same accuracy...Fact: VERY DIFFERENT HARMONICS but very little impact in its precision....Of course that you will need to readjust your scope but the groups with any of those pellets will be as tight....Scope adjustment is for improving accuracy not precision.

What does this mean?...It means that the gun is a VERY WELL BALANCED, VERY WELL TIMED AND VERY WELL TUNED up to the point where the difference in harmonics between the different pellets and their corresponding different velocities given the current tuning of the gun have VERY LITTLE or NO effect in the precision of this rifle...

Look at your gun as a system that operates depending on the settings of many variables: Mass of gun, mass of barrel, length of barrel, internal bore dimensions and ratios of rifling, , mass of the stock, distribution of mass in the entire gun and materials per-se of the rifle, tuning, etc...TIMING is extremely important but nobody talks about timing, can you tell why??....HARMONICS is just one of those many variables and it is as important as ANY of the rest....If I were given only one option (messing with one and only one variable) for improving the precision of a gun, I would select MASS OF THE BARREL eyes closed...Exaggerating the example: Put a 3-4 inch diameter 22-24 inches long barrel on your gun and you might as well forget about those HARMONICS that nowadays seem to be the thing that everyone is interested in controlling for improving precision... 

So the HARMONICS game is no different that the tuning game, or the timing game, or the mass of any and all individual components game, or total mass of the gun game, or the mass distribution game....etc., etc.

This is my last response to this thread as I don't usually participate in this forum...My best wishes for all of you in finding the best settings for your guns.

Best regards,

AZ 

Very good posts AZ, this one and the one warning about barrel straightening.

AGN, if you don’t know who AZ is, you should. Not only is his gun knowledge encyclopedic, he can shoot, and has won many high level tournaments. I think he won the National 25M BR in 2018, beating all the “big names”. I met him at the Saguaro Classic near Tucson AZ this year and saw his shooting skills. Plus, he’s a very nice person, always willing to talk and share his knowledge...

Dumb question but don't the o'rings go over the liner and into the sleeve? I would guess the sleeve should be just as straight as the liner, ideally somehow tensioning the liner seems like it would cure many of these problems. The 27" liner has a ton of harmonics to tame, anyone try loading 8 or more o'rings over it???

Click to expand...

8 O rings?...Why not 16, 40 or a stack of O rings from the breach to where the sleeve/liner bushing is threaded?....More is not always better.

Crooked sleeve = Non concentric O rings which means uneven pressure on the liner = Liner not straight or unevenly set (different pressures on the sides)...The more O rings you put into a non concentric liner/sleeve set up, the more pressure on the walls of the liner and the worst the precision...If liner/sleeve are straight and concentric, then a few O rings might help. There is nothing as accurate as a straight solid 1 piece barrel (No liners-No O Rings-No Sleeves)...Nevertheless, the system as in in those guns works just fine and is very convenient for changing calibers and barrel profiles..

How many people actually change calibers? Why would anyone spend so much time tuning a gun just to say " ah f*$# it i'm going to change calibers? lol

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the arrow straighter is not strong enough to use on an airgun barrel. the idea is a good one using the proper equipment though.

I have straightened many aluminum arrows and still have the straightener I used to do so; there's no way it would bend the barrel.

a good set of "V" blocks and a good press is in order.

I remember seeing a pistol. I think it was a FWB the barrel twisted all the way around the air cylinder. They claimed it shot accurate. As thin as some of these barrels are, I would think it would be easy to make a kink or add unwanted resistance. I remember kinking a few aluminum arrow shafts.

A friend of mine dropped his TM1000 and put a serious bend in the barrel just forward of the receiver. He sent it to Martin Rutterford who was able to straighten it out perfectly. Martin's website is: www.airguns-usa.com

The liners are straightened at the factory.
It seems azuaro was wrong. Anyway, has anyone tried to do it? I have no guarantee that my liner was really straightened. I also wonder if it influences accuracy.

Bent barrels is a thing? Oh my.

I would say a straight liner is a unicorn.

Yikes just mention a maybe issue and everyone is wondering if they have a problem? I would think your targets would tell you a story better than some contraption that supposedly checks for straightness.
If your gun is shooting well you have nothing to worry about and will only decline in accuracy once you start mucking around with pushing this and that direction on a precision tube.