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Old July 17, 2011, 12:31 AM   #1
Rustle in the Bushes
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How to determine OAL?

Im just making my first batch of 7.5 swiss for my K31. Published Info for this cartridge is for the 1896 rifle is way off, so tell me what you think about this method of determining OAL for MY rifle.

1. Cut the neck of a cartridge open with tin snips so the bullet can slide into it alot easier.

2. feed the bullet in and close the bolt

3. measure how deep the bullet was shoved in, this is probably where it is CONTACTING the rifling.

4. Back off about .023. This is where i am unsure, I wonder how much space should be between that bullet and the lands?

5. reference this to what people give as an acceptable OAL.

Any thoughts, opinions?

Note- Ive already been on swiss rifles forum.
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Old July 17, 2011, 01:00 AM   #2
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Here is the fast and dirty method.

1. Take your cleaning rod and with the bolt closed put it down the barrel till it hits the bolt and with a felt tiped marker, mark on the rod at the crown of the barrel.

2. With the bolt open, push a bullet by it's self with a pencil till it hits the line and groves. Then put your cleaning rod back down the barrel till it stops at the bullet and again mark on your rod at the crown.

3. Push the bullet out with your rod and measure (with caliper) between the two lines.

This is your Max OAL for YOUR rifle. Take the number and subtract 0.050 from it and this is where you want to be.

BUT, depending on how old the rifle is and how much action it has seen, this might be a bit too long of a OAL to use. You will need to use your own judgement as to if there will be sufficent tension on the bullet at the case neck to safely load to that OAL.

You will still need to reference your loading manual as to what the tested OAL and load should be. If the OAL is shorter than MAX OAL for your rifle that is ok depending on by how much. If the barrel has been worn out due to use, you should consider re-barreling that rifle because accuracy will be poor.

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Old July 17, 2011, 01:37 PM   #3
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Another consideration is that many military rifles have extra long leads. Therefore if you set the bullet out to the max it may not feed correctly from the magazine. The reload must feed correctly from the mag.
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Old July 17, 2011, 08:43 PM   #4
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Use Jim's way above, but improve it a little by purchasing two drill collars that fit your cleaning rod, the set screws allow them to hold their position . Measure between the collars with your caliper and get the max OAL.
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Old July 17, 2011, 09:12 PM   #5
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I do the same but grind off the rim so the bolt does not pull the dummy round out. I then use a cleaning rod to gently push the round out.

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Old July 17, 2011, 09:36 PM   #6
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I do it basically the same as the OP.
It works excellent, very simple and dont cost anything.
Just have to be gentle opening the bolt to be sure the bullet dont get moved.
It only takes about 3 seconds to get an OAL.
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Old July 19, 2011, 05:23 PM   #7
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Ok if you have bullet puller the hammer type follow this if not do the top replies

Take a resize case, neck sized will be better but not necessary ,
Set a non charged (no primer no powder ) and set bullet as deep as you can,then take the bullet puller and extract the bullet, do this 3 to 5 times .

Now take that case and set a bullet with your fingers and run it trough the chamber and close the bolt .
Now you can go .010- off and you will have your OAL and a set a custom OAL gauge.
Now like the other gentleman were saying on military calibres yours may have a long trout and may have to go by judjment.

Hope this will help you since after I bought fancy gauges at the end this was a lot easy.
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Old July 19, 2011, 11:52 PM   #8
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For my semi-auto, it has to feed cleanly from the magazine. These rounds have the bullet seated to it's cannelure. For my target bolt gun, I used a Hornady OAL guage and a comparator to get the OAL to the ogive of the bullet. These sit .020" off the lands and, when I do my part, are very, very accurate. Hope this helps.
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Old July 20, 2011, 09:51 AM   #9
F. Guffey
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"4. Back off about .023. This is where i am unsure, I wonder how much space should be between that bullet and the lands?"

I am not a fan of the 'standing still start', I want my bullets to have a running start, I favor the jump start, If I jam the bullet into the lands I feel it necessary to compensate by reducing other factors.

As to shredding the neck of the case for what ever purpose, sounds like busy work, I am a fan of making one measurement then taking that measurement from the chamber to the die and back to the chamber, that is possible with a transfer, a case with a shredded neck does not make a good transfer because of the squid looking neck, I know it sounds impressive "here is what I do, I shred the neck..." I don't, I am a fan of bullet hold, I can measure bullet hold, I can not measure neck tension, nor can anyone else, but 'crush and interference fit' are not in a reloaders vocabulary.

And head space, it is not fair, my rifles have head space, one has .016 thousands head space, that is .011 thousands more than the perfect go-gage length chamber, that means if I chamber the perfect over the counter, new, commercial unfired minimum length case the difference between the length of my case from the head of the case to the shoulder is .016 thousands shorter than the length of the chamber when measured from the bolt face to the shoulder of the chamber is .016 thousands, not a problem, my favorite 30/06 case is the 280 Remington case, or, a case that has been fired in a trashy old chamber, If I wanted trashy old long cases I could fire new cases in my rifle with .016 thousands head space, I would explain why but I can not type that slow.

Again, I am a fan of bullet hold, I make tools out of just about anything and my firing pins crush the primer before the bullet, case and powder know their little buddy, the primer, was hit, AND, time is a factor.

F. Guffey
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Old July 20, 2011, 03:13 PM   #10
F. Guffey
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How to determine the maximum overall length for the chamber: WHY? Because if a reloader is going to seat 'off the lands he/she must know where it is located in reference to the bolt face I do appreciate the bench rester taking the time, in my opinion he was not much help, but the next group of helpers will have you shredding the neck, again for what reason? I do not know, that is because I want to transfer the maximum overall length of the case from the chamber, to the seater die and then back to the chamber as I said that is most difficult with a case that looks like a squid, so, I use bullet hold, that is determined by the ability of the case neck to hold a bullet, a case with good bullet hold is a case that makes a good transfer got setting up the seater die, a hose clamp around the shredded case neck could improve bullet hold but will it fit into the seater die????

I drill the flash hole/primer pocket, some insist on using a .250 (1/4") drill bit, I reach for the .375 (3/8") drill first (depending on the diameter of the case head). Then it is a matter of removing the bolt, chambering the test case then with a cleaning rod, I push the bullet out of the case and into the chamber, when the bullet stops I remove the cleaning rod, remove the test case THEN install the test case in the shell holder, back off the die and seater plug then raise the ram, after raising the ram I adjust the die top the test case, and that is how I transfer the dimensions of the chamber to the seater die.

After transferring the measurements to the press I measure the height of the seater stem with a height gage and that measurement (.000) is off the lands, when seating off the lands I use a height gage or dial caliper to measure adjustment of the seater stem, lowering the stem .040 thousands would be .040 thousands off the lands, and the distance from the face of the bolt to the ogive does not change meaning it is not a measurement the reloader should find it necessary to find ever day and that is the reason I do not shred the neck of my cases, I am a big fan of bullet hold.

F. Guffey
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