Dave;Hope this answer reaches you in time.The grub screws I include in the HPM are flat faced, so there is no chance of marring the barrel.They are flat faced because the idea is that they are torqued down to about 12 in-lbs, and THEN you "settle" the HPM with three shots.Because the ORings are ShA75, they DO have SOME elasticity, so setling the HPM without the final torque will allow the HPM to return to an "unsettled" state before you torque the screws.If we accept reality, NOTHING in that size range can actually "AFFIX" the HPM to the barrel upon recoil. Forces are simply too big for any decent sized screw. And putting humongous screws would only add more variable masses all around.So:Add or remove ORingsPress the HPM into the barrelTorque the screwsFire three shotsRun test groupRepeat.One more thing: As it was explained to me, Linas CHANGED the barrel of his ProSport to a L-W of conventional length. He did not only remove the shroud, he CHANGED the whole thing and threw away the AA parts.Hugh.-the problem with things that are elastic (ORings with ShA hardnesses larger than 30), is that they let the device act as a "loose weight", and that can AMPLIFY the vibrations.Kirk.-I am working on a design for smooth sided barrels, if you want one, let me know in a PM.Keep well and shoot straight!HM
Morning dtdtdtdt. Down here Repco, an automotive supply shop sells copper washers. Expensive but everything here is. Copper as you know is very easy to work with simple tools. Might be just the thing you need.You mention having a sleeve on the barrel. Is there a sleeve between the barrel and the brake/HT or is there a sleeve over the D54 barrel that is cut short to accommodate a brake for direct contact with the barrel.Tried the internal threaded weight on a brake. Complete failure; a weight interferes with the gas flow and who knows where the pellet went. It might work with an external threaded weight. An airstripper works but the position of the internal cone is important so not much use.
I did three different installation methods. ssMost important conclusion: Torquing to 10in/lb or using a Allen wrench tightened just enough that the wrench flexes enough to be felt sets the Harmonic Tuner so it won't move more than 0.001". It would be worthwhile to check the depth occasionally.I think Method 1 makes good sense to settle the rings tightly in the HT and compress them. The friction of the the HT on the barrel sleeve is likely enough to hold it while you tighten the screws.Measurements were taken from the outside flat edge of the muzzle crown to the flat outside of the harmonic tuner. Installation of the HT for tests. Push barrel sleeve firmly towards the action to seat it. Insert O-rings by stretching sideways to oval shape, slip over barrel to the edge of the barrel sleeve. Take care to not roll the ring so it twists. Repeat for each ring. Push rings together so there is no space. Slide the HT onto the barrel all the way until it mates with the sleeve. Adjust position so one screw hole is aligned with the top of the barrel and action. Check to make sure the barrel sleeve is firmly set against the action, push firmly on the HT to hand seat it on the barrel and barrel sleeve. This was done for each of the following tests.Test 1: 1. Add rings and install HT as above. Measure the barrel setback: 0.126"2. Shoot three settling shots. Measure: 0.118"3. Torque to 10in/lb. Shoot three settling shots. Measure: 0.117"4. Shoot 3 five shot strings measure after each: 0.117", 0.116",0.117"Test 2:1. Add rings and install HT. Measure barrel setback: 0.124"2. Torque to 10in.lb. Shoot three settling shots: 0.124"3. Shoot 3 five shot strings measure after each: 0.123",0.123",0.123:Test 3:1. Add rings and install HT. Snug screws with Allen wrench. Measure barrel setback: 0.127"2. Shoot 3 settling shots. 0.124"3. Torque to 10in/lb. 0.123"4. Shoot 2 more settling shots. 0.123"5. Shoot 3 five shot strings. 0.123",0.123",0.123"Next step it to go back the range and confirm that 4 rings is the "right" number for my rifle. I will do 3, 4, 5 to bracket the number.