Well, I've got all 3 strain gages now and only one rifle ready to hook up. My 45-70 is on its way back to the factory for correction of a defect, and my 458 Lott is a blob in a pot of molten Montana chrome-moly.

I am glad my Browning 30-06 is not a 308. Boy, am I glad. This gage, ideally, is supposed to be attached to the barrel, over the chamber at a point halfway between the case head and shoulder. Well, that point is about where the receiver starts to hide the barrel threads. I think I can get away with being 2/3 the way up the case, but a 308 would have been half an inch shorter, and I doubt I could have put the gage over any part of the chamber below the shoulder. I guess I could have checked that before I ordered the device.

I know RSI has tested the Pressure Trace on 223's and 6 mm PPC's, so somehow they found a spot to test on a fairly short chamber. Maybe Brownings are just made funny like that. Well, if the rifle had a quarter rib, that could make things difficult, I suppose.

H. C.

Henry,

Don't sweat it on the short cases. They way it's recommended from Oehler in the manual is to figure where the half way point from the face of the reciever to the bottom of the shoulder, this is where to center the gage at and glue it on.

The way I do this is to put a cleaning rod down the bore and against the inside of the head on an empty case in the chamber which is backed up by the boltface, and place a piece of tape on the rod flush with the muzzle to mark the spot that indicates this length.

Pull the rod out, slip the case on the end of the rod and hold the tape up to the muzzle on the mark, now mark on the barrel at the point where the lower edge of the cases shoulder is "as it sit's in the chamber."

Measure the distance between the reciever face and this mark, divide by 2 and this is the distance the gage is glued on away from the reciever.

This allows for the barrel steel to expand evenly on both sides of the gage the same amount, not being strengthened by the reciever on just one side and altering the reading.

So you want the gage centered on the portion of the case that will expand the bbl evenly, which is "beyond" the reciever face, which would act as a strengthening sleeve.

I believe that even half way between the forward edge of the recoil lug and the shoulder would even be more accurate too.

I have seen these devices and wondered about them. Since they are a resistive device and not a crystal when the temperature of the chamber goes up as you shoot how do you correct for the change in temperature of the resitor? Does the software automatically "zero" the resistance at each shot?

PaulS

I just recieved mine and I'm very excited. Like most everyone else.

I understand that the attachment technique recommended by Oehler has you doing an acid etch on the spot where its going to be attached. I suppose this would give the adhesive a better grip. Using the adhesive supplied with the Preasure Trace would this help? If so what is the acid used. Could you use a Muratic acid?

Just looking for the best ideas.

DO NOT acid etch your barrel. It is unnecessary. Clean the spot well, with something like acetone, and use the special cyanoacrylic adhesive supplied with the PressureTrace. It will work fine.

Strain gauges are quite insensitive to temperature change. The error induced by a fairly warm barrel is too small to be a problem.

Thanks for the quick response Denton. With your previous experience with this product do you adivse anything different or outside of the packaged instructions?

Ray,

Like Denton suggests, I doubt the etching is really necessary... a super clean surface IS. I use the etch and neutralizer Oehler sells just because I have it, same with their glue and accelerator too. I'd use a good super glue if it's all I had and I bet it would work just fine too. A very thin and consistantly thick layer of glue under the gage is what I think is absolutely most important. One thing about super glue is that it bonds quickest the thinner the glue layer is.

Denton,

Any thoughts or test been done on the placement of the gage in relation to the shoulder-body junction and the lug or reciever face concerning it's accuracy potential?

Here's a tip to keep your glue from absorbing moisture and hardening up on you that I always use with super glue: Instead of clipping off the tip of the applicator to dispense the glue, and you don't need but a couple drops anyway, unscrew the applicator tip or cap... whichever seals the top up BEST and use a toothpick to dip in and then dispense the drop for use on the gage. The applicator tip usually seals up the tube or bottle best so, if you don't cut the tip off it will last a long, long time. I store it inside a ziplock bag in the refridgerator to prolong it even longer as well. Keeping ALL moisture away from the glue is the goal...

Ray...

The instructions are well thought-out, and should work just fine as they stand.

All adhesives do not work equally well. Not all "crazy glues" will work. But they do supply the correct type, so you don't have to worry. In any event, you do have to let the glue cure overnight, even if it is a "60 second" type.

JB Weld works well. Since it cures slowly, I just put a taut piece of electrical tape over it. That tends to help the epoxy form a thin, uniform film.

And... Thanks for the idea on storing "crazy glue"!!

Oooops... forgot. Brent, I don't know if anyone has done the test you mention. In my own case, I felt like "corners" have a tendency to behave differently from material that is uniform. So I fudged a little, and put my gauge about 2/3 of the way down the casing. That gets the gauge away from the shoulder of the barrel. Can't tell you if that's brilliant insight or a big mistake.

CIP in Europe takes their pressure measurements at the mouth of the casing, and their system does produce results that are significantly different from SAAMI, which we use in the US. So, for sure, you can't go that far down the case.

Thanks Denton.

Oehlers gages are cheap enough that a test might be in order to see if specific placement behind the shoulder makes an appreciable difference. I wish I could say the same about the price of the CA glue that Oehler sent, I think it was 40-50 bucks for a bottle that's practically half the size of a soda can!! For that much CA glue, that's really not that bad of a price really, it's just that they say that the shelf life is 6 months and you need only two drops for a gage, get real, I thought. I been using the stuff for longer than a year but, it's only had the cap off for less than a minute 10 times so far and has been sealed up very well each time.

I'll put two gages on the new barrel for the 30/338 Lapua Imp that will be done in a week or two, one half way between the case shoulder and the reciever, the other half way between the from front of the recoil lug and the case shoulder. Should amount to less than 1/4" difference in placement but, we'll see what they both show for psi.

What's the best way to get a gage back off that I'm not using from this 300wm take-off bbl of mine to use it over? I've never tried it but I think I remember acetone was the answer? I'm not sure what's in CA remover itself, maybe it is mostly acetone...