OAL question

[jermy01]

Hello guys, this is my first post and i am semi new to reloading. Have been reloading a lot of 357 but just got a 7mm-08. I loaded about 40 rnds the other day, min load, no problem. anyways one of the guys at the range told me to start at min load, work my way up to max load in increments and find the best grouping. then after that to play around with overall length.

so to find the max overall length for my rifle, i was told to use a resized shell, no primer, no powder, and play around with the overall length until i found where the bolt would not close.

in my lee manual it tells me the OAL dimension is 2.800". So i started there, made one 2.800", put it in the chamber, bolt closed with a little friction, took out the dummy round, and remeasured to 2.794". so i repeated with a pretty decent crimp to make sure nothing was just slippin around and same result. So im assuming thats gonna be my max OAL but min OAL for a lot of the loads is 2.800". What should i do?

[mehavey]

If you are speaking of finding max OAL of a full up cartridge, then you definitely got a bum steer from the guy who told you to find "...where the bolt would not close."

A bolt action will ALWAYS close on a round... even if it has to shove the bullet into both rifling and back in the case while doing so. The camming action of bolt closure will do this and you might not even be able to feel the difference. Politely thank whoever gave you this info, cough slightly, and walk away shaking your head.)

Do this instead for a field technique:

Gently push a bare bullet into the chamber and up against the rifling using a wooden dowel. Use a cleaning rod from the muzzle to slightly push the bullet back & forth on-again/off-gain from the rifling against the dowel. when satisfied that the bullet is just barely contacting the rifling, mark the cleaning rod w/ a razor blade right at the muzzle.

A good starting point for OAL is then an assembled cartridge 20-30 thousandths shorter than that -- i.e, the cleaning rod will sink deeper into the barrel by the diameter of a small paperclip before the bullet stops it.

[oneoldsap]

I always make a Dummy with the bullet longer than the published COAL for that Bullet . Put the cartridge in the gun and close the bolt , if it won't close shorten the round up .010 and try again . Once you get the lugs engaged you should be able to close the bolt , which will push the Bullet back into the Case . Remove the Dummy round and measure it for length . Subtract .015" and you have a starting point . Make sure to write things down so you aren't chasing your tail !

[wncchester]

"What should i do? "

Step one is to ignore book OAL. As info, a book OAL is only a starting point for those who have no idea of where to start. I've been reloading since '65 and have never even looked at a book OAL. I know it's only the length the book makers used to develop their data. It's not a law, or even a strong recommendation, for anyone else.

[603Country]

jermy01, do it mehavey's way, which is also outlined in detail in the Nosler loading book (at least it is in my oldish one). Buy or borrow the Nosler book and read it. Or you can buy one of two types of rigs that'll do an even better job. I think the Sinclair catalog carries them both.

[jermy01]

great.....thanks for your help guys. So if i do that, any my OAL is in fact less than 2.800" can i still use the data for min OAL 2.800" making sure to start with low powder charge and watching for signs of pressure as i increase powder charge? will definately pick up Nosler manual. thanks again for the input

-Jeremy

[mehavey]

While pressure does increase as bullets are seated deeper into the case, it does so at a predictable rate.
This QuickLoad analysis should give you an idea of your margins:



Your mileage may vary, of course.
But you get the picture.

[Jim243]

You didn't say which book you were using. Most books will give you MAX OAL. However if it is listed at the top of each load, it means that the info in that load chart was produced at that specific OAL.

A variance of 0.006 OAL on rifle loads will not change your preasure that much that you need to be worried about it. If it does concern you, you can drop your powder load by 0.2 of a grain to compensate for the shorter OAL. Since I know you will be working from min to max load in increments, you will stop way before you reach the max load anyways. Always check after each shot for overpressure signs on the case till you get the just right load.

While we are on the topic. Setting the OAL to the max length of your chamber is not a good idea. The bullet sitting right up agains the line groves will increase the amount of pressure in your chamber when you fire that shell. It is easier to get started from a running start than a dead stop. Best Idea is to set your OAL 0.050 or 0.020 from the max of your chamber. For this purpose I use Honady's LNL case length gauge and dummy case (purchased for the caliber you are loading for, sold seperate $7.00 per case)
and the bullet you are loading.

But since you know the Max OAL for your chanber for that bullet (2.794) I would use a OAL of 2.744 for that load and drop the min powder amount by 0.2 grains of powder and start there and work your way up.

Just a thought.
Jim

[jermy01]

thanks for all the replies! I am going to try to make it out to the range this weekend with the knowledge i gained here and will report back. This seems like a great community with a wealth of knowledge. Im sure you'll see me around these boards

someone asked which data i was using and OAL in data. I am going off the 2nd edition of Modern Reloading by richard lee. the min and max overall length are both 2.800" for 150 gr bullet for almost all powders. So far i have only purchased 1lb of H414

[NWPilgrim]

2.800" is the SAAMI specification for the max COL. That just means that chambers/throats need to be reamed to accommodate at least that length. Most rifles, especially bolt actions will have a longer throat. You may be limited to the COL that fits in the magazine. If you are loading one at a time then you can load to near max that fits in the throat as described above. You don't want the bullet to contact the rifling (big jump in pressure), yet the longer gap there is between bullet and rifling the more chance for wobble.

I think you will want to establish the COL for your rifle FIRST, then work up a load. If you are loading to a COL greater than 2.800" then you will have less pressure than the listed load.