Hornady OAL Gauge

[swt5]

I've been pointed in the direction of this gauge and the accompanying modified cases to establish seating depth for my reloads. I think I know how it works and understand it's operation but...I don't see how not having the bolt face somehow included in the measurement process, as being accurate? Is it a given one has to measure the difference in dimensions between the modified case and brass fired in the chamber of what I'm loading for, then subtract/add the difference when determining a seating depth?
I was thinking of getting appropriately sized collars something like this:

and putting them onto a nylon coated rod. When the rod bottoms out on the bolt face of my empty chamber (when coming from the muzzle), I would carefully slide the collar against the crown and lock it place. Then with the bolt removed, insert a bullet up the throat and gently hold it against the lands. Again probe down the barrel with the nylon rod until contact with the bullet tip and then slide a second collar against the crown and lock into place. Measuring from the appropriate surfaces of the collars will give a very accurate OAL reloading measurement...right? (needless to say, this measurement is the first step in determining loaded length from base to ogive using a comparator on calipers) The second measurement method I mentioned seems it would reflect a measurement more in line with my chamber/throat relationship?
Non? Or is this what a lot of guys are doing already?

 

[jo191145]

I've always looked at it this way. Find DTL with my hornady gage. Conduct seating depth tests to find what the gun, bullet, powder combo likes.
If I find it likes it .020"" past DTL and its really just .015" I could care less.
I don't ask my girlfriend to weigh herself in front of me everyday. She says she weighs 115 lbs I accept that as the truth. Proving she weighs 120 would be of no benefit to me.

 

[bigedp51]

jo191145 , do you know how to tell if your girlfriend is over weight?

If your girlfriend steps on your cats tail and the cat dies your girlfriend is over weight. :

 

[Nomad47]

Good points, Jo.

swt5, your method down the muzzle measures to the bullet tip. There is more error there. Why not make a modified case from a case fired in YOUR chamber?

 

[fdshuster]

swt5: I also tried your method using a rod with stop collars and found it be be less accurate than when I used the ever reliable Stoney Point/ (now Hornady) chamber over-all-length gauge.

As Nomad 47 said you will get more variation using the stop rod because of the great variations in over all bullet lengths. The only way you can off-set that built-in error is by using the same bullet that you took the measurement with to adjust your seating die. The only reason I tried the stop rod was to get seating depth information in my semi-autos (like the M1 Garand) that have no straight-in access to the chamber, and will not buy another Hornady gauge made for semi-autos like the Garand, Mini 14, etc. I very seldom have a need to measure these chambers, because I very seldom fire these rifles.

I use both the Hornady modified cases and also some cases that were fired in my chambers, and later modified. Both work equally well for me.

One of the problems that can give inconsistant depth readings is simply not having the cases all the way forward into the chamber, before extending the center rod to push the bullet forward. it's easy to get a false inpression that the case is fully seated in the chamber, when it is not.

Not pushing the bullet fully forward to a hard stop is another problem. Often times I can feel the bullet make contact with the leade, give it another "extra" push, and I can feel it seat deeper to a hard contact stop.

 

[roadkill61]

I use both ways. I drove myself nuts chasing thses measurements. Now I use them to get me started in "the ball park". Our measuring tools are probably not absolute either. If I measure a distance and use the same device it is my setting and repeatable. Same with powder scales my 34.4 gr may not measure 34.4 on yours. As long as I use mine I am OK. There is so much variance with bullet lenths within the same box it's almost fruitless. There seams to be less variance in the base to ogive than base to tip that I now try to use that for my settings. Hope this helps.

 

[watercam]

I agree with those above that all measurements are relative. The object is to find some repeatable seating depth that works in your rifle. Besides, assuming that your headspace is within SAAMI spec or the equivalent, the maximum difference that your seating depth would be off using the Hornady tool would be the difference between the minimum and maximum headspace dimensions. In other words, less than .005". Using rods/collars down the barrel would induce more error than that.
Measure with the OAL gauge three times to make sure you are consistent. Don't jam the bullet in the throat, push gently. I believe you find you will be successful with it.

 

[Forum Boss]

Measure with the OAL gauge three times to make sure you are consistent. Don't jam the bullet in the throat, push gently. I believe you find you will be successful with it.

This is the secret to getting repeatable measurements with the Hornady OAL gauge. I push very, very gently till I sense resistance. Then I do 2-3 very light taps on the end of the rod. I usually measure 3 sample bullets 2 times each. We generally can get consistent, repeatable results within .0015-.002 or so 4 or 5 times out of six

 

[CatShooter]

I have been using a rod and two collars to get seating depth for years. Fast, easy, one tool does every calibre with no extra expense. It measures to the point, but then you seat THAT bullet in a case until you length is the same and note the micrometer setting. It takes little more time to to do, as it did to type this. Plus, no special cases to keep buying every time you get a new caliber - chamber has no bearing on it.

It is accurate to less than 3 thou.

 

[swt5]

Thanks for all the replies Gentlemen. I will go ahead and buy the gauge with modified case. I think I'll putter around with some of the other ideas too and see what variations I get. I'll measure bullets in the comparator to find 3 that are the same base to ogive and then produce 3 "template rounds" using THOSE bullets and see what we get? I think I will find I'm overthinking this as I tend to do that a lot
I'll let y'all know.

 

[jcampbellsmith]

I've always looked at it this way. Find DTL with my hornady gage. Conduct seating depth tests to find what the gun, bullet, powder combo likes.
If I find it likes it .020"" past DTL and its really just .015" I could care less.
I don't ask my girlfriend to weigh herself in front of me everyday. She says she weighs 115 lbs I accept that as the truth. Proving she weighs 120 would be of no benefit to me.

Superb explanation. Brilliant analogy. 10/10 Thanks JCS

 

[jcampbellsmith]

Thanks for all the replies Gentlemen. I will go ahead and buy the gauge with modified case. I think I'll putter around with some of the other ideas too and see what variations I get. I'll measure bullets in the comparator to find 3 that are the same base to ogive and then produce 3 "template rounds" using THOSE bullets and see what we get? I think I will find I'm overthinking this as I tend to do that a lot
I'll let y'all know.

Overthinking and good performances don't mix. Load some, shoot some, briefly consider the results, then load some more and shoot some more. Watch what the good shots do. They are like the good golfers, they don't look like they are exerting themselves. Good sportsmen (and women) make their sport look easy through lots of practice.

Good luck. JCS

 

[Jnewman]

There is a simple way to do this without the oal gauge you take a case put a bullet with some lube on it seat it long measure ogive remove firing pin from bolt, place the case with bullet seated long in action close bolt pop open quickly measure ogive again, repeat process a couple times to make sure you have same measurement and this measurement should tell you where the bullet is at jam back off 20 thousandths find a charge that looks good and then work in or out of 20 thousandths on seating depth