Bullet seating Depth and roll crimping

FromTheNorth

FromTheNorth

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I'm new to the reloading world and I'm reading Lymans reloading book and I'm at the part of Bullet seating Depth, then it says something about "jump"(pg 76. 49th edition). I don't really understand this part because it sounds like I'm suppose to seat the bullet more then what the overall length of what the round should be... another question is about roll crimping. it says for large caliber rifles i should roll crimp because the recoil will un seat the bullet, but what is the starting point of a large caliber round? is it absolutely necessary to roll crimp because it all comes down to buying the crimp die for it...im shooting a 270 WSM and i can't really find a crimp for it, or is the reloading/seating die its self enough to crimp it? can some one please help to clear this up for me. :confused:
Greg:sniper:
 
Jump is the distance between the bullet and when it's fired to ware it in gauges the rifleing.
I don't crimp my rounds even on my 375 ruger

The bullet seating depth in the Book is a standard. So the rounds will chamber in all guns.
Seating the bullet long is like tailoring your rounds to your rifle.
It effects accuracy and presures. ( usialy in a positive way)
 
regulate34 said:
Also you should be able to crimp by lowering the seating die.
Do your bullets have a cannelure for a crimp?
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i haven't bought any bullets yet, I'm just reading at the moment and was a little confused, but it will depend on what my objective will be is when i choose a bullet to use. on that note, your saying my seating die will work as a crimp die if need be on cannelure bullet?
 
FromTheNorth said:
i haven't bought any bullets yet, I'm just reading at the moment and was a little confused, but it will depend on what my objective will be is when i choose a bullet to use. on that note, your saying my seating die will work as a crimp die if need be on cannelure bullet?
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I could be mistaken and maybe some brands offer it, but none of my lee rifle dies have a crimp ring in them, That's a separate step.
All my lee pistol dies do have a crimp ring built into the seating dies. That way you can set and crimp in 1 step.
 
Spawn-Inc said:
I could be mistaken and maybe some brands offer it, but none of my lee rifle dies have a crimp ring in them, That's a separate step.
All my lee pistol dies do have a crimp ring built into the seating dies. That way you can set and crimp in 1 step.
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yea it seems if i want to crimp I'm going to have to buy a crimp die separately if need be because lee only sells a 2 piece die set for the 270 WSM and it doesn't come with a crimp, and it doesn't say wether or not the seating die has the crimp ring.
 
A .270 WSM isn't a large calibre. It's talking about cartridges with heavy recoil like the .375 H&H or .458 Win.
For your .270, neck tension is usually enough to keep the bullet in place. The big bruisers have physics acting on 'em(the 'objects in motion' stuff that Newton guy prattled on about.) that can cause the bullet to move backwards under recoil. Happens sometimes in lever actions and semi-auto mags too.
No special die is really needs as the seating die can be set up to crimp. You adjust the seater die down a wee bit at a time until you have enough crimp by trial and error. You really don't need it though. However, if you opt to crimp use as little as possible. Crimping is detrimental to accuracy and should be only enough to hold the bullet in place.
The 'jump' is about how far the bullet had to go upon firing before it hits the rifling. This is the OAL to be 'off the lands' stuff you hear about. There is no actual number for being off the lands. Every chamber is different, so every rifle will like a different distance off the lands. It can be 20 thou or 10. Don't worry about it too much. It's a load tweaking thing.
 
When you are starting out, do everything simple.
Seat the bullets deep enough so there is no danger of them hitting the lands (rifling) when seated. This is what your book refers to a "jump," meaning the bullet has a bit of travel before contacting the lands.
You don't need to do any type of precise measuring to achieve this, just use the old fashioned, tried and true method, as follows. Use an empty case that has been fired in the rifle you are loading for. Check to see that it will seat smoothly in the chamber.
Squeeze the neck in a bit, just enough that you can push the bullet you will be using, into the neck a bit, with your fingers, with some difficulty. Now, carefully chamber this dummy round and fully close and lock the bolt handle down. This is the seated depth of the bullet used, to just touch the lands. Remove the dummy load from the chamber and carefully set it aside.
We are presuming you have a bolt action rifle, so there is no need to crimp.

Screw the seating die into your press. With the handle down, turn in the die until it is about an eighth of an inch clear of the shell holder. Turn the locking ring down and solidly lock the die at this setting.
The centre screw on the die adjusts the seating depth. Turn this well up and seat your first loaded cartridge.
The bullet should be started in the neck, but obviously out too far. Compare this new round with your dummy round. The loaded round will have to have the bullet seated a bit deeper than the dummy round, so adjust the centre screw on the die, turning it down a bit at a time, while comparing it with the dummy round. Do this until the loaded round is seated a bit deeper than the dummy, as viewed by your eyes. A "bit deeper," could be the thickness of about 8 pages of writing paper.
Lock the centre screw at this setting and you are good to go.
I have purposely kept away from caliper measurements because there are more new reloaders who get confused by these precise measurements and seek help on these threads, than ask for help for any other reason!
 
Well, Bruce, once again our methods differ but the ends are the same. I make the dummy. Install the seating die the same way. I then put the dummy round in the press. I lower the press handle fully then turn the screw until it gently contacts the bullet ogive. Raise the press handle and turn the screw down 2 full turns. Lower the handle to seat the bullet deeper. Remove the round and check magazine fit. If it fits in the mag, you are good. Your dummy is set. I now crimp it, mark it with proper info using a paint pen. Any time I need to reset the die after loading a different bullet, I just install the die, insert the dummy, raise the ram fully, and turn the seating die screw down until it contacts the bullet ogive. Now, I can seat on the new batch.

Ted.
 
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