Strange Issue with OAL Gauge

[earthquake]

I have a Hornady OAL gauge I have been using for a couple of years now. It has always worked fine. A few weeks ago I chambered a new barrel (Bartlein 6.5mm Creedmoor) and did a load test at 100 yards, then tested the winning load out to 1,175 yards, shot a match, all was good etc.

The gun got really dirty, andd now has 287 rounds down the tube. While cleaning it, I decided to measure the throat/chamber-length again for no other reason than curiosity and found that the chamber got SHORTER by 0.10" according to my OAL gauge! That's not a mis-type...a tenth of an inch!

Now I'm no astrophysicist, but I know a chamber does NOT get SHORTER by 100 thousandths?!?!

I tried several different bullets from the same box I used in the original load development and at the match...all gave the same reading. I then thought maybe the chamber was really dirty and there was a carbon "ring" or something in there so I scrubbed the heck out of it and there was no change.

My last effort was to chamber a few of the live rounds I had left over from the previous weekends' match...they all chambered and cycled fine. I'm loading 42.9 gr of H4350 and jamming Berger 140 gr Hybrids 0.010" into the lands. OAL from base to Ogive is 2.217" when jammed or 2.207" to the lands.

It has to be something wrong with the Hornady gauge...correct? What gives? I'm really scratching my head here.

 

[jlow]

When you say "all gave the same reading" with different bullets, does that mean the lengths you got were exactly the same, or just close?

 

[hogpatrol]

What measuring instrument was used, digital or dial calipers?

 

[Eddie Harren]

I have a Hornady OAL gauge I have been using for a couple of years now. It has always worked fine. A few weeks ago I chambered a new barrel (Bartlein 6.5mm Creedmoor) and did a load test at 100 yards, then tested the winning load out to 1,175 yards, shot a match, all was good etc.

The gun got really dirty, andd now has 287 rounds down the tube. While cleaning it, I decided to measure the throat/chamber-length again for no other reason than curiosity and found that the chamber got SHORTER by 0.10" according to my OAL gauge! That's not a mis-type...a tenth of an inch!

Now I'm no astrophysicist, but I know a chamber does NOT get SHORTER by 100 thousandths?!?!

I tried several different bullets from the same box I used in the original load development and at the match...all gave the same reading. I then thought maybe the chamber was really dirty and there was a carbon "ring" or something in there so I scrubbed the heck out of it and there was no change.

My last effort was to chamber a few of the live rounds I had left over from the previous weekends' match...they all chambered and cycled fine. I'm loading 42.9 gr of H4350 and jamming Berger 140 gr Hybrids 0.010" into the lands. OAL from base to Ogive is 2.217" when jammed or 2.207" to the lands.

It has to be something wrong with the Hornady gauge...correct? What gives? I'm really scratching my head here.

Borescope and look for copper fouling.

 

[Mozella]

Chances are you made an error when you made the first measurement. Unfortunately, you can't hit rewind and do it again.

Some of my guns give vague readings and some give "crisp" readings when using the Hornady tool. I always make plenty of readings.

It is VERY unlikely there is something wrong with the tool. It's a simple device and unless the stop rod is slipping because the knurled lock screw is stripped or something like that, there's really nothing to go wrong.

 

[jlow]

I agree with Mozella that it is very unlikely that the tool is bad – almost always user error.

I can share with you my own experience doing pretty much the same thing. Hornady OAL gauge, Berger 140 Hybrids, in my .260 Rem Bartlein barrel. Tried to check OAL using the prescribed method which is to seat the bullet short in the case, push case/bullet into the chamber, push on the rod until it stops to get a measurement. What I got was rubbish with measurements that varied by 50 thousands or more.

Tore my hair out until I figured out why – it turns out that with a high BC bullet like the 140 hybrid, when you use the tool via the prescribed method, the long nose bullet can come in very slightly cockeye and get stuck in the neck without actually going all the way through and give you a bad inconsistent reading.

Changed strategy by seating the bullet in long, push the bullet/case in and letting the throat push the bullet into the case. Once done, made sure the flex rod is tight against the base of the bullet, lock it in, and use a wood dowel via the muzzle to push the whole contraction out. Got good reproducible reading via this method with variance of around 2 thousands.

BTW, this was the reason why I ask how consistent your measurements were? When doing this stuff, never do it with one bullet, I usually do 10 and I measure each 3 times to make sure the readings are REAL. Bad readings that you don't catch can drive you crazy....

 

['Freak]

I get a much better feel of what’s going while using Sinclair’s Bullet Seating Depth Tool, #749-004-650, working its solid stainless steel rod through a Delrin action guide (and no “special case” involved) shoving it directly against either the base of a bullet or, in the next step, shoving against the head of any case you choose though preferably a designated case that’s been fully formed to the extents of that particular chamber.

Two stop collars get positioned on the rod, the first one indicating length to the base of the bullet and then the second one indicating length to the head of a case whilst it’s seated fully against the chamber’s shoulder. A measurement betwixt the two stop collars is the length from the case head to the base of the bullet. Add to that bullet base to ogive length obtained with aid of a comparator, and the final result is your target case head to ogive length of a round with the bullet’s ogive positioned relative to the lands however you wanted it in the check.

 

[fguffey]

It has to be something wrong with the Hornady gauge...correct? What gives? I'm really scratching my head here.

A reloader with a solid understanding of ‘the datum’ can verify any gage that is a datum based tool. To most the datum is a line, I make datums, I never agreed with Sinclair and Horndsay because they use a case friendly datum, they have datums with a radius.

When using a datum I always have to ask if you are measuring off of the bullet for maximum overall length or are you measuring the length of the case from the shoulder to the4 case head.

F. Guffey

 

[hogpatrol]

 

[earthquake]

When you say "all gave the same reading" with different bullets, does that mean the lengths you got were exactly the same, or just close?

I mean they were all around the same ridiculously short measure, a tenth inch short, +/- a thousandth or so. Like I mentioned, I've never had an issue using this tool, with the same bullets. I only shoot and reload for one caliber. Have been using it for 3 years now. They are never exactly the same, usually +/- 0.002" and I take a dozen readings, toss the high and low, and use the average. Never has the tool given a reading so far removed from what I've measured before.

I placed a loaded round from last weeks' successful reloading session next to the case from the OAL gauge with the weird measurements and it's so obviously short that anyone can see it with the naked eye...it's 1/10 of an inch! It looks obviously wrong and none of the loads I've done on three barrels were ever this short. It's 2.130" base to ogive on the same brass, bullet and tool I used for all the stuff I made only two weeks ago.

I took the tool apart, lubed it, cleaned the gun etc....repeated it several times with other bullets from the same box/lot#. When the loads I did last time still chamber and cycle, it has to be the tool or a gremlin.

I used three different calipers. I like dial calipers and have Mitutoyo dial calipers and then I confirmed with my digital calipers too...because sometimes yeah, the dial ones can be confusing if you don't pay attention. All gave the same reading.... I'll try and track down a bore scope...but I scrubbed the chamber and bore and the patches are clean.

 

[hogpatrol]

WAG here. Are you using the proper insert in the calipers? I got gaffed up once when I used the 6mm for a 7mm bullet. Talk about dazed and confused!

 

[ireload2]

There was once a mystery like this with a new Contender barrel that would hit nothing. The owner assured all of us that everything was correct but he could not hit the backstop. Page after page of speculation and discussion ensued.
The owner was finally asked if he checked the new barrel for fit with his bullets. He took one of the bullets he was trying to shoot in his 257 TCU and it dropped right through and hit the floor. It seems he had a 6.5 TCU marked .257 and he had overlooked a very obvious check.

It happens.

 

[dkhunt14]

At 287 rounds I would look for carbon in the throat. Depending on powder it could be built up. Especially if the loads were on the cold side. I think you need to have a look with a borescope. Is it the same lot of bullets? Matt

 

[1lnbrdg]

Sounds like some kind of trash in the chamber for the 1st measurements.

No way to un-ring that bell now.

 

[jlow]

I’ll tell you guys another story as it relates to OAL treouble that I witness just last month.

Was at the range doing some load development with my .260Rem. When I got there a friend of mine showed up at the same time and told me he was going to check the OAL of his FTR rifle. He mentioned that he was unhappy with the Hornady gauge because the headspace on the case was short and he had arranged to have a friend tap out a few of the cases that was fired out of the rifle.

I went to work on my load and 1/2 of the way through came out to take a break and found both of them struggling to get a consistent read. I tried my method of pushing the bullet in and it also was unable to get a consistent read. Went back to my stuff and when I was done I found they were still out there tearing their hair out.

Long story short, what I found was when the case was tapped, the 3-jaw chuck had slightly distorted the case and of course a distorted case is not going to fit properly in the chamber… It was obvious when I asked him to chamber the tapped case and he could barely get the case back out….

So OP, if you somehow had distorted your OAL case, the same could happen to you. Not likely but this is a true story..

 

[Dusty Stevens]

Carbon ring is the culprit. Matt beat me too it.

 

[waldo1979]

I've never had any luck with that gauge. I now use the sinclair OAL gauge.

 

[rudysts]

Changed strategy by seating the bullet in long, push the bullet/case in and letting the throat push the bullet into the case. Once done, made sure the flex rod is tight against the base of the bullet, lock it in, and use a wood dowel via the muzzle to push the whole contraction out. Got good reproducible reading via this method with variance of around 2 thousands.

This method works well for me been doing it for a few years now.