What am I doing wrong... OAL ?

[okbob51]

I'm using a Hornady OAL gauge and comparator to find my lands.
I've used the OAL tool with the modified case in the chamber and barrel using a Berger 105 for my 6BR

I've measured the modified case and bullet using the comparator to find case base to bullet ogive length.

I made up a dummy round to exactly match the length of the modified/Berger case round.

The dummy round must be jammed hard (probably .050) into the lands to get the bolt closed.

What gives? Why, with the modified case and bullet does it fit the chamber and with the dummy round I have to force the bolt closed? I must be missing something.

 

[expiper]

Make the loaded rounds fit!!!

Throw all those gadgets and gizmos away and just make the rounds fit your chamber.....run the bullet out till you get the classic square to rectangular marks from the lands....and you will be perfect....dont complicate something that is very simple...just enuff contact to slightly feel it ...not enuff to rock the gun in the bags and "then" start fiddlin with the powder charge....Roger

 

[deadlyswift]

Your not trying to close the bolt when the mod. case is in the chamber. Back the bullet off until the bolt will close with ezz. That should put you close to just touching. Or use the cleaning rod or wood dowel rod method. Put your bolt in and close it. Run the rod down the muzzle until it touches the bolt face. Mark the rod. (pen, paint maker etc.) Then take the bolt out put your bullet of choice into the bore. use a pencil with the eraser end hold the bullet in place. Then run the rod back down the muzzle marking it again where the rod touches the bullet. Messure the space between the two marks. I have found that this works better for me that the Mod. case procedure.

 

[tenring]

I have found that the Hornady OAL guage does a poor job on all boat tail bullets (i.e. Berger 105 VLD and others). It is usually way off. The method suggested by deadlyswift is what I use. I have two aluminum cylinders with hold down screws that attach to the cleaning rod. Had them for many years, no manufacturers name on them.

BTW the Hornady tool is fine for flat base bullets.

 

[Steve Blair]

I have not had any problem using the Hornady/Stoney Point tool to measure land engagement. Following are the steps I use. Make sure that the collar set screw is tightened on the tool's back end, first. Also verify that the case is tightened snug against the tool shoulder.

1. With no bullet in the case but with the case mounted on the tool, insert the case into the chamber and verify that the shoulder touches. You can do this with a Dykem pen or a magic marker. Look for circular scuffing on the shoulder after rotating the case clockwise against the shoulder. If you do not see any scuffing on the Dykem, the case neck may not allow the case to fully chamber. If you have a tight chamber, it will be necessary to turn the neck. Remember that the neck must be turned more than usable cases because the I.D. is large enough to allow a bullet to slip freely. It might also, but more rarely, be necessary to size the case body. Try not to touch the shoulder.

2. Place a bullet in the tool with the plunger set to allow about half the ogive to protrude. Insert the tool into the chamber and twist it one full turn clockwise to seat it until the knurled collar screw is facing up. Loosen the collar screw and push the plunger forward until the bullet seats against the lands. Maintaining a little pressure, tighten the collar screw. Withdraw the tool. You may need to elevate the muzzle and drop a brass rod or jag (base first) down the barrel to dislodge the bullet. Catch it with a shop rag.

3. Place the bullet back in the tool and measure the ogive with a caliper and tool like the Sinclair Comparator. Make certain that your caliper jaw is square to the case head. Remove the comparator and measure the OAL for reference. Record both measurements. Use these measurements when seating bullets.

4. I take an additional step to obtain a true chamber measurement. The case supplied with the Hornady tool is a new, unfired case and reflects factory dimensions that tend to have shorter headspace than a chamber. I use the Sinclair Case Comparator to obtain the headspace difference between the Hornady case and a case fired in that chamber. I then add the difference (usually .002-.005") to the previously obtained dimensions. If you make your own cases from fired brass and tap them 5/16-36, you can skip this step.

It pays to repeat the measurement occasionally to monitor throat erosion and change your die settings accordingly.

 

[deadlyswift]

Steve good post! It makes a lot of since! I have been thinking about just taking a fire formed case in my chamber or chambers and making my on modified case. I'll have to try this myself with the stoney point gauge.

 

[okbob51]

Sleepygator,

Thanks for the great reply and ideas! I'm going to try sooting the modified case and making one complete revolution. I'll post results.

Bob

 

[Moderator]

I've found the Hornady tool works fine with any kind of bullets. However, some guys, when they start to use the tool make two mistakes.

First you must make sure the modified case shoulder is FIRMLY seated against the front of the chamber. Also make sure that the modified case is screwed down securely to the OAL tool (red rod). As sleepygator notes, if you have a tight neck you may have to turn your modified case to allow it to seat all the way foreward.

Second, and this is key... do NOT push the OAL tool rod in hard. Slide it VERY gently. Then back it off, slide it again (till you feel resistance). Then (and this is my secret), give the end of the rod a couple very LIGHT taps.

Using this method, with a 6BR I can get repeatable measurements over and over again... and I have 5 years of logs to prove that.

If, when using the OAL tool you are getting any more than a tiny dot of engraving, you are pushing the bullet in too hard.

If you practice with the tool you should be able to get repeatable results to about .001-.0015.

NOTE: When measuring the base of cartridge to bullet ogive with the comparator tool, make sure the comparator body is installed correctly on the jaw of your calipers. It can be flipped 180 degrees. If it is is set incorrectly it will not align straight with the OAL tool when you place the notch in the tool on the opposite jaw. If you eyeball the set-up you should see one orientation that works better than the other.

CAVEAT -- if the throat is off-axis or if there are burrs or heavy chatter marks on the entrance to the lands, all bets are off. If you can't get the OAL tool to work consistently, inspect the throat and entrance to lands with a borescope.

 

[Steve Blair]

I agree completely with our Moderator's comments. When Jim Borden recently shipped my barreled Tube gun action to me with Stoney Point measurements, they agreed with my own within .002. The earth's rotation and space-time differences between California and Pennsylvania probably account for the difference.

 

[Moderator]

I would also add that before starting a reloading batch I always repeat the measuring process and I measure at least 3 bullets from the box I'll be loading with. I'll usually measure length to lands with each bullet twice. That typically gives me a range of say, .003 with six measurements, but you'll see the majority of measurements cluster around the same point.

It is possible to get a measurement much longer if you really shove hard. What you want to do is develop a "gentle" technique that produces repeatable results with nearly zero engraving on the bullet.

 

[okbob51]

The problem has been found but not solved. The soot test revealed that the outside neck diameter of Hornady's modified case is too large and does not allow the case to enter the chamber completely. The outside neck diameter, at the shoulder, is .004-.005 thicker than new Lapua cases.
Unfortunately, I don't own an outside neck trimmer. Would running it through a FL resizing die solve the problem? I know Hornady's instructions clearly state not to do so.

 

[Steve Blair]

I am afraid it must be turned or make you own case from Lapua. If you size the neck, the bullet cannot slip freely and will not provide accurate measurements.

 

[okbob51]

Thanks Steve for all your help. I have another solution....it involves returning the modified case to the store and trying a different one. I can't believe it but, I actually found the receipt, packaging and bag. ;D

Bob

 

[Steve Blair]

Take your caliper with you.

 

[cheek9075]

i had problems using the modified case in my 6 br. it is a .270 neck, the modified case was not!!! i had to turn the neck on the modified case so that it fit the chamber. after i done this it worked fine, just a thought.

 

[Steve Blair]

Same here, John. Hornady made the case I bought from Lapua brass but my chamber is .269, so required turning. Attached is a pic of the well-worn case. I had to neck-size the case, expand for turning and then expand again to allow a bullet to easily slide.

 

[dreever]

I go along with Roger.
I've used the Hornady tool, didn't like it, sold it.
I then bought the Sinclair tool, better, but still wasn't satisfied.
I now use a Sinclair expander mandrel which gives about .001 tension on the bullet. I then seat the bullet a little long, steel wool it nice and shiny and let the bolt seat the bullet. I keep adjusting my seating die down and repeating the process untill I get nice square land marks and go with this measurement.
Simple, cheap, and works every time.

Danny

 

[jo191145]

All excellent advice. With a little careful fitting and handling the Hornady tool is very accurate.

I just recently fitted a 6BR case quage to a .270 neck. Had my turner set up for my 30BR and did'nt want to mess with it. Lightly chucked the 6BR in my drillpress and using a small wooden block and 220 sandpaper I turned it down that way. Works just fine. Remember they don't have to be perfect they just need to fit the chamber.

Another thing I just found that can give erratic readings. Theres a small allen set screw on the rear that holds the knurled finger set screw assembly to the body. If that allen set screw gets loose it can mess with your mind for awhile ;D

 

[GSP7]

I just use a used case, neck size it, cut a slit length of the neck with a thin dremel cutting wheel so the bullet can be pushed in and out, but still holds the bullet firm, if it gets looser with repeated use, I just pinch the neck with my fingers to tighten it. Chamber it with a bullet just started and let the lands push it in, then measure the OAL. I use 3 bullets when measuring. Good enough for me. No fancy gizmos. I keep a dummy case with each set of dies and caliber

 

[okbob51]

I modified Hornady's modified case in order for it to fit my chamber. I'm now confident the Hornady tool is giving repeatable measurements and I can move on to tweeking my seating depths.
Even with the early hassles I'd buy this tool again. I like having the exact numbers measured and recorded.