AusVarmint

Anyone using barrel blocks, thinking of barrel blocking my next build with a delrin sleeve on a alloy stock, any thoughts, for and against, will probably be a 6 BR or BRX.

Matt P

I think Shehane's method of 'O' rings and glueing of the barrel to the block is the way to go. Stress free and the block can then be glued or screwed to the stock. I have done a couple of barrel blocked rifles and they shot well. But none of them shot as well as a stretcher tube. Shehane doesn't say, but my money would be that the centre of the block is the balance point of the barreled action to create a sweet spot. The glue he uses is not an epoxy either. It is the same crap that they use to float the Millenium actions on. Sort of a pliable resin to absorb shock. His results are outstanding so it is hard to argue with.
His other blocks are worth a look at too. They are a long base block with two caps very similar to camshaft style caps spread a fair distance apart to minimize barrel warpage when clamped tight. I doubt this method would be ideal for a big banger, but for 308 0r 223 that you will be using Matt it should be more than enough.
If you believe in the shock wave theory of barrel harmonics as i do, i truly believe a clamped block will alter regular known nodes. What you may take for granted as say a 46.5 grains of 2208 as a go to recipe for the 308 and 155 whatever, the block may alter the shock waves from what we know now to something completely different. Experience reminds me of the 284 i did years ago where the known working load had to be increased by one full grain to get things to work as they should so as to get the bullet clear of the incoming shock wave.

Tony Z.

I was a little rushed in answering in the first post Matt. To expand this further, and i am not exactly certain of exactly how you wish to do this blocked rifle, but the very mention of Delrin, or as it is now more commonly known, Acetal, is a certain road to failure IMO. There is no room in rifles for things that shift or do not have a complete purchase on what they are meant to hold on to. Delrin is like so many of the commercial polymers that change with temperature and humidity. Once upon a time i used Delrin to make inline seater dies with which resulted in failure because of its constant growth or shrinkage during the four seasons. Cases were tight one day and a cock in a coat sleeve the next. Acetal and many of the other industrial plastics and polymers are part of the every day line of work i do and not one of them has come up to the claims i have been promised. There will be no difference if used in some sort of bushing to clamp in a block. No two matches will have the same clamping force and thus group aggregating ability. Explain a little more of how the Delrin is to be used as i am only guessing at this point.

That Flexane that the Mellenium actions used to float about on has the jury still out deliberating. But there is no doubt that a dead harmonic that does not transfer vibrations to a stock is a plus. The barreled action can then do what it wishes and if done right can be very repeatable, as Shehane has found. But unlike the Millenium, a recoil lug does not enter into the equation to disrupt the theory. As a marketing exercise, this is all brilliant.

Matt, at the end of the day, what wins matches over the course of a full season, apart from the barrel and bullets, is a rifles ability to aggregate. There is only one way we have found to extend a rifles window of accuracy and that has been with the tubes. This may sound obscure, but a window of accuracy that is extended by only an extra half a grain from the node, is worth owning if you travel to all parts of the country. The BR guys with their PPCs have no issue with this as they just get there a day early and tune with a powder measure and seating depth. The eager Fly shooters do the same in Cantberra. You do not have this luxury. So a screamer rifle in Bendigo turns to shit in Brisbane and vise versa and you go home wondering why or what went wrong. As i have said to you many times already, the tube is the only reliable method of extending the WOA to make it usable in all parts of the world. This is why Tooley is doing just that with his version of a snipers rifle for the US military, so it can be shot from one side of the planet to the other without having POI or accuracy issues.

If and when you build your blocked gun, the thing will shoot, no doubt, but the nodes will be different and the WOA will be similar or even smaller or more fussy than that of a conventionally set up rifle. The only real gain a block does and will deliver, is a larger and more consistent holding and bedding area. That in itself may be enough, and with the likes of the 6BR which you know inside out, accuracy combined with a reliable POI that a block will give you, conventional block that is, may be enough to give you the edge you are searching for. But i guarantee you, that same barrel could be removed, re-profiled, stretched with an alloy tube and deliver the same potential accuracy, usually better, an overall better aggregate during the course of a full year, and extend the WOA so far that plus or minus a grain will make little if any difference other than POI at the longer ranges. My own LG that i still own and have yet to sell has a WOA beyond 7 grains of powder and all it needs now is a shooter that gives a shit. There is no possibility that i could ever say that the load has gone off because it simply just does not shoot a poor group. The shooter does!!

One man who can tell you a lot about his findings on tubes is the Fudge down there in Melbourne. Greg Fuge. He shot all sorts of blocked guns and is now a full convert to tubes. He took known non performing or fussy barrels and got them to drill holes. It only took him a few hours to see what we had been trying to drum into him for the last ten years.

It is at the end of the day your choice, but you did ask for opinions. Best of luck mate.

Tony Z.

Thanks Tony
I have a new barrel on order that I'm thinking maybe a bit heavy for the action so that's the main reason for the block, so the action doesn't have to hold the weight of the barrel. The barrel is at least 3 months away so I've time to think about which way to jump, weight isn't to much of an issue, it will weigh 10kg using a Leupold BR scope so plenty to play with.

Matt

Tony, the change in nodes you mentioned is something I was thinking about. I have come to know the nodes for 27-30" barrels and since I dont get much of a chance to shoot targets, I get a lot of tuning done shooting a few shots over a crony in the bush and getting it close. When my blocked 308 is finished, I wont be able to load it to the usual known node. I was thinking the tuned length wont be able to be calculated by either the total length of the barrel, or the barrel hanging out of the block, is there any sort of rule of thumb on this?
I can imigine the flat earth society spluttering about a big barrel tube on an F std rifle, if they complain enough about "Benchrest barrels" as is. HHMMM, I might go a barrel tube instead.

Rod, i haven't done enough blocked rifles to be as confident about them as i am with the tubes. But of what i have seen, the "nodes" are different and are narrower. With two ends of the barreled action to vibrate now, and if you believe in conventional vibration theories, the nodes have to be different in both position and duration. This is why i reckon the placement of the block has a lot to say about the final outcome. For example, if you have a long flexible section of bar stock in a rack and get it to oscillate about, there is one place where it can be grabbed hold of that does not try to transmit the energy into your arm. That spot is completely neutral and does not shake you about. But grab hold of it at a peak or trough and the thing will let you know that you have got hold of it and with thick bar stock like that of what a barrels dimensions are, this energy transfer can feel quite uncomfortable or even painful. This observation has me convinced that block placement and the overall size of the block is crucial to how such a rifle should be built.

Just getting a little sideways to this block thing. Tooley asked myself and JR a question about one very different aspect of his tube rifle design. I won't say what that was, but at the time i questioned him as to why he would deviate from known successful tube builds. After looking at his idea again, partly because of this thread, and then taking the theory of shock waves in barrels into account, Tooley has done something either on purpose or by accident that can explain why the three barrels in JRs rifle, all with very subtle but evident changes in tube arrangement, have given three distinct barrel performances. Each progressively lesser than the previous. The shock wave theory can explain why barrels of varying profile configurations can and will shoot similar loads. For example a 222 that doesn't shoot 20 grains of 2207 or there abouts is not worth owning, a 308 that will always respond to 46.5 grains of 2208 and a 155 grain something, a 6 PPC and 29.x grains of BM2 etc. There are known working loads that will work in almost any barrel profile and shock wave theory can explain that clearly. But sine wave or vibration theories cannot do the same as the amplitude and frequency is different for every barrel steel, different for every barrel profile and different for every attachment on that barrel and in that stock. There is no way with the frequency of a vibrating barrel of 7 to 10,000 hertz that two shots will ever leave at exactly the same frequency count because of so many factors. The major one being velocity deviation.
So, if an attachment is placed on a barrel, and forget vibration theory for the moment, the shock wave traveling up and down that barrel at 4 to 5 cycles (7000 hertz) compared to the one time span of milliseconds of the bullet inside it, hits and meets an attachment, shoulder etc, that causes it to change direction and timing ever so slightly. A tuner really fucks this up and remains inconsistent in a centerfire, but the tube i believe redirects the pulse through itself backwards toward the chamber or forward to the muzzle, depending on what cycle it is in, and keeps it away from the muzzle so as to prevent the damaging bore distortion. This widens the accuracy window because the pulse that does reach the muzzle is diminished in intensity and does not alter the bore dimensionally while the structural advantage the tube offers retains barrel position. A plus plus. The tuner fucks this up where the every day changes to load deviation and bullet exit timing crash together and give the all too familiar story of worked great one day, and went to shit the next. Put simply, the window of accuracy or shock wave timing avoidance is still very narrow and the very slight adjustment of the two rings alters the shock wave timing just enough to allow the muzzle to snap back to its proper dimensional shape. We are now at the point of timing things by splitting thousandths of a second and the BR guys like Schmidt have it worked out and adjust their two ring tuners on the line to compensate for this crash. But for my mind this is just a bandaid that a tube would fix permanently and this two ring system has nothing to do with tuning in the true sense, but is a shock wave timer that splits the hair twice. This shock wave has a narrow window of avoidance where it requires you pick up the next lull or drop back to the previous one if you are to use another node(lull). The problem with this is that the next lull is just about always beyond the reach of the brass and the previous one is way too slow velocity wise.

The point of all this diatribe is that there is a reason why the two ring tuners work behind the muzzle while the naysayers, like me, said it can only work with the weight cantilevered forward of the muzzle (vibration node theory) and why a stretcher tube does what it does. The tube i believe redirects the shock wave and minimizes its effect on the muzzle. In effect the tube may after all be nothing more than a simplistic shock absorber with enough structural strength to control things. If vibration theories came into it, a tube would never work as the dissimilar expansion rates would alter tension and then one would assume accuracy potential. This does not happen. Somewhere and somehow, the tube has done something to the shock wave that enhances barrel accuracy potential over a very broad band or node if you wish. With some of these guns, there is nowhere where a bad group can be found. So i can only assume that the damaging aspects that the shock wave has is altered to a point where there is little if any effect to the muzzle and thus accuracy. The same can be said of Shehanes' Flexane filled blocks where they may be just a very unintentional(???) shock (wave) absorber. This can all explain why a tube fitted to a rimfire has zero benefit as there is just not enough ummph in a rimfire to create a shock wave for a tube to absorb it. Every trial i have done with a tube fitted to a rimfire has had no direct improvement and in one case was detrimental. Rimfires are to centerfires what Hustler magazine is to Bob Brown.

So getting back to Tooley and his snipers rifle, there is something in his design, not the compression system he uses with his tubes, but the lock up arrangement that may have a seriously positive effect on accuracy. Something he said to me that will facilitate a suppressor and then something that i wrongly replied back to him that was based on some vibration theory that i should have known had no place in a tube gun. I don't want to sound like Calfee and play in riddles but i won't say what it is, and i won't know for sure until i see it perform downrange, but i do want a donor barrel from JR fitted to his rifle to test what i think will take the tube to the next level.

Tony Z.

Hi All , OK ,my take on all of this is i would never use a barrel block on a light gun.. The minimum barrel dia would be 1.450 ins,which dictates a H/G..I would probably not go to one anyhow from what level of accuracy i have been able to get out of a L/G with a conventionally bedded action fitted with a normal full floating barrel .. After seeing Tony's experiments with the early tension Tubes and how well those simple fit ups worked on paper ,it was a no brainer for me to go to this on my current heavy gun .. Tony has taken the early success of my light weight tube set up and reduced it further to get a gun that will get down to 17lbs ..This works so well that it is the only way i would head.. What we have seen on target is that a gun with a 20 fps spread in MV should have about 6 ins of vertical in it at 1K ,now in a properly set gun we have been able to get that to 2.5 to 3.0ins .. The maths say it can't happen ,yet it does , so in some way there is a compensation effect coming from the barrel ,ie the muzzle is not in the same spot as the bullet leaves the barrel ,allowing the difference in bullet speed to be compensated for by the position of the muzzle ( fast bullet = low barrel position etc).. Now i do believe that my heavy gun STILL has a degree of compensation in it because it was never good in the Fps spread department ..When you see a group form at 1000yds with 8 of the ten shots in 1.4ins,5 of those in less than an 1 inch and 4 shots touching and you know that the fps was 23 fps over those 8 shots ,then you also know your not dealing with a straight maths calculation .. The added advantage we have seen with the present light Tensioned barrels is the ability to shoot over a wide variety of weather conditions .. Matt ,imo the 1.250 x 30ins with barrel block will show a greater degree of changes in overall performance as the weather varies than a Williamsport profile that is conventionally bedded.. If you have to use that barrel ,glue a half sleeve to the action just to increase the bedding area and so support that much weight ..JR..Jeff Rogers..ps Guys, please don't shoot the messenger!!