Broken Tasco PDP3?

[RussB]

While playing at the range today with my new-to-me circa 1993 open gun, I suddenly went from shooting nice little groups to spraying shots around in a 2 foot pattern.

The mount is tight to the frame, and the scope tight in the WCPI mounting rings. The red dot is still glowing red, but the shots are scattered.

Is this the symptom of a Tasco PDP3BD that has busted internally?

[RussB]

I also dis assembled the gun, and everything looks in order. Comp is tight, nothing out of the ordinary.

[RussB]

In another thread, this member said,

Good luck with the PDP3 scope. When I started IPSC, I went through 5 PDP3s in about a year, 2 of them that were supposedly "bullet proofed" by a then-well regarded person.

[ramirezerwin]

if gun and the scope seems to be in order, did you check the ammo, did it came from the same batch?

[AlamoShooter]

it would be a very special Tasco that could last more than two years shooting Major loads. Even with steel loads two years/ 10,000 rounds was a an over-load.

Most of them had the wires brake louse in side and stop lighting up

[RussB]

if gun and the scope seems to be in order, did you check the ammo, did it came from the same batch?

Yes, all ammo from the same batch, 5gr of 231 over a Berry's 130 plated RN, starline Brass, CCI primers

[RussB]

it would be a very special Tasco that could last more than two years shooting Major loads. Even with steel loads two years/ 10,000 rounds was a an over-load.

Most of them had the wires brake louse in side and stop lighting up

That has been my understanding as well, the dot stops lighting.

[calishootr]

your dot is shot and your just dont know it, the mount is holding it together, saw a guy yrs ago running one ofthose mounts and the mount was actually holding the broken tubes together...also the intensity knob generally is the weak link, with more use you will find that certain numbers will not 'light' i had onethatthe highest position would not come on, or it was intermittant 'disco-dot' as we called it back then...the 'good' news is that PDP3's can be had for as little as 50 bucks or less

I ran PDP3's on mine and got more than 10k out of em, but yes eventually you will lose the tubes or the lectrical connections on em...for some odd reason that mount was the culprit on more than a few broken tubes....dont know why???

[Service Desk]

I would also check the comp baffles for a build-up of fouling... some gunmakers used very tight tolerances on the bore hole in the comp. Light loads seem to lack the gas blast to keep the fouling down and can allow the crap to build up,oddly enough, ballsy loads in the 180pf mark can cause gas peening on the port separators and close the hole up...

Nowlin and EGW make a piloted tool for opening the comp hole up a tad - very handy.

The best PDP3 mount I could find was the one made by Noel Alfaro, I think it was the Phase 2. It was made from Delrin and kept the dot alive for a lot longer than the metal mounts. Kerby Smith used to sell them when he was Gunracer.

BTW - Great looking gun...

Edited March 8, 2010 by Service Desk

[RussB]

I would also check the comp baffles for a build-up of fouling... some gunmakers used very tight tolerances on the bore hole in the comp. Light loads seem to lack the gas blast to keep the fouling down and can allow the crap to build up,oddly enough, ballsy loads in the 180pf mark can cause gas peening on the port separators and close the hole up...

Nowlin and EGW make a piloted tool for opening the comp hole up a tad - very handy.

The best PDP3 mount I could find was the one made by Noel Alfaro, I think it was the Phase 2. It was made from Delrin and kept the dot alive for a lot longer than the metal mounts. Kerby Smith used to sell them when he was Gunracer.

BTW - Great looking gun...

Thanks

You suggestions intrigue me. While staring at this gun for a couple hours after the meltdown, I can see traces of copper around the holes in the comp, which leads me to think that the bullet may be contacting the comp on it's way to the target. I had mentioned in another post that I had to re-install the comp with fresh loc-tite, as it had loosened while getting re-blued.

I have clamped the frame in a vice, and turned the adjustment knobs of the PDP3, the dot moves up/down and side-to-side like it's supposed to. I was tapping it with a small hammer, and I could not make the dot jump around or lose position?

[Toolguy]

Shooting a revolver, I got very bad leading with Berry's and Rainier bullets. I would check for leading in the barrel and comp. It sounds like a bullet problem. Try shooting a box of jacketed and see if it straightens out.

[major9]

I've usually had two failure modes on PDP3s.

The dot goes intermittent. Broken traces or wires.

And failing to zero. That is "shifting the group" rather than "suddenly shotgun pattern"

The failure to zero is due (I'm told) by the "o-rings drying out" and the inner aiming tube not moving when you turn the adjustment knobs.

Try this, clamp your frame in the vice and turn the adjustment knobs, but don't tap with the hammer.

You should see the dot move smoothly in both axis and direction.

If not, maybe your inner tube is swinging all over the place with the recoil.

I've also had ONE failure (with a PDP4) where the LED mask fell off. Suddenly I had like a 10 hour dot.

It could be that your mask is moving and causing your pattern.

[RussB]

Try this, clamp your frame in the vice and turn the adjustment knobs, but don't tap with the hammer.

You should see the dot move smoothly in both axis and direction.

If not, maybe your inner tube is swinging all over the place with the recoil.

I did try that, and the dot moved just like it should. I also tapped on the tube, and the dot would not shift around.

What I did find was the bullets were hitting the comp, throwing them all over the place. In the end, the PDP3 is doing fine, and I opened up the holes in the comp by .005"

Thank you all for the fine advice and recommendations