Tubb\'s TMS part 1
I had the opportunity today to really get into an experiment with David Tubbs's throat maintenance system. I have seen excellent results with factory barrels and Tubb's Final Finish break in system and wouldn't buy a factory gun without using it, but I have had limited experience with the TMS system on worn custom barrels.
A little while ago, I used a 22 caliber TMS kit in my 22-250 AI fast twist to bring back accuracy and to smooth out the throat so it would be easier to clean. However, on that gun, it was so far eroded that I could not get 75 grain Amax's to touch the riflings anymore so I wasn't sure if the TMS "erased" the lands out farther or if it just made it smoother. The only absolutely known thing I could say about that experience was that it made the rifle a 3 patch gun with Coppermelt from a blue 6 or 7 patch gun. Cleaning time was cut in half, and I could literally feel that the barrel was smoother while pushing the patch down.
While accuracy never did come back with the 75 AMAX, I went to a slightly less aggressively shaped bullet, the Nosler 80 grain J4 comp and it was shooting excellent. I was getting 1 moa at 100 with them, and about 3/4 moa at 700! I figured that a 3 patch gun that shoots as good as it did when it was new was good enough reason to try the TMS on my 6.5-.284.
Normally, I would just send the rifle back to the gunsmith to have it set back a thread or two but this time, I needed the gun for the remainder of the chuck season and for an upcoming doe antelope hunt in September. So I figured that this was a great time to try the TMS and keep good notes while I was doing it.
My 6.5 has about 850 rounds through it. Accuracy has not fallen off at all, but it now takes about 11-12 patches to come clean compared to about 7-8 when it was new. It also has been taking a few more minutes to get her up to 1k then it used to. The throat is rough enough that it is degrading the BC of my bullet slightly.
So my plan was to clean the rifle completely and then load up some of my normal Bergers at the regular length that puts them about .020" into the riflings. I then "sharpied" all the bullets so that the bite would be very visible on the bullet. I then loaded up 15 TMS rounds way off the riflings like it is recommended. Then I loaded up 5 different charges of Rl22. When the gun was new, it liked 50 grains of RL22 and over the course of the last few years it has had to be loaded down to 48 grains to maintain the velo sweet spot as the throat got rougher. So for the test, I loaded up 48, 49, 50, 51, and 52 grains of RL22 and shot them in sequence after firing the TMS bullets. More on that later.
I shot 5 TMS bullets, then cleaned. Then I stuck the Berger into the chamber to see if the bullet bite had changed. There was still plenty of mark on the ogive so I cleaned and fired the next ten. After that, I checked it with the Bergers again and it still had .020" bite! Very good.
I then cleaned it out completely and it went from 11 patches after the first 5 TMS bullets down to 6 after the last 10 TMS.
At this point I wished I had loaded up more TMS rounds as it was clear that they were perfectly safe to use without fear of erasing the lands ahead of the chamber. But I only had 15.
So on to the Bergers I went. 48 grains shot an average of 2819 for a three shot group and went into a .365" group at 100 yards. That is almost 200 feet per second slower than the same load shot 1 month ago! Obviously, the smoothening throat was not causing as much pressure.
49 grains went average of 2961 and shot .655".
50 grains went average of 3004 and shot a .757".
51 grains went 3022 and shot a .500" even. This velo was close to the magical speed that this gun likes and it also had a standard deviation of 7. It would have shot a much better group I believe if the mirage wouldn't have been moving the target around my crosshair! It was like looking through chicken noodle soup!
52 grains got me 3082 out of the 30" barrel with the 140 bergers and a nice .423" group with an SD of 12.
So after about 20 rounds of load development, it was clear that the smoother throat had got me back to and above my original loading of 50 grains. And instead of taking 12 patches, it only took 7.
Before starting this experiment, I could look down the bore from the muzzle when it was perfectly clean and see a short distance ahead of the chamber that would scatter the light differently than the rest of the barrel. It looked like a little black ring. Now after 15 rounds of TMS, it is completely gone and the whole barrel looks the same. It may even be shinier out towards the muzzle than it has ever been.
So far, I would say this TMS system is worth every penny but I would like to get the gun down to a 3-4 patcher if possible so I am going to go shoot another 20 TMS bullets down the bore later this week and I will report back my findings. [img]/ubbthreads/images/graemlins/wink.gif[/img]
If it's not far, it's boring.