Bullet Seating Depth

[RHarris]

what can you guys tell me about bullet seating depth. I am shooting a .270 and until today have always gone with a book learned over all cartridge length of 3.34. This is with a 150gr nosler partition, and I have had good results. Today I loaded two different powders five rounds each at 3.40 overall cartridge length which is .03 less then the overall bullet seating depth test. This is actually the starting point that my Nosler hand book suggests. I measured a factory Federal cartridge with the same Nosler bullet and they had an overall cartridge length of 3.31.
What can you guys share through your experimentations.

Thanks!
Rharris

 

[Hankenstein]

I'm not an expert by any means, but I'll have a go at it. When you say "Today I loaded two different powders five rounds each at 3.40 overall cartridge length which is .03 less then the overall bullet seating depth test.", I will assume you mean .03 short of hitting the lands. Only thing you really don't want to do is get the bullet into the lands unless your shooting moly bullets. Bullets seated into the lands may cause pressure problems dependent on the powder charge. I would just start shortening the OAL from that point .010 (or so) per decrement. If that doesn't work, I would increase the AOL to a point just shy of hitting the lands (.005 or so). In all likelyhood, you'll hit a "sweet" spot somewhere along the line. Guns are like people, they're all different. Give it what it wants. If it likes it a full tenth off the lands, shoot it there. If you're anything like me, I like to squeeze everything out of a gun that I can, even if I can't shoot the difference. Just having fun...


Hank

 

[TheKnack]

Start a bullet in a case with no primer or powder so that it is seated higher than you think it will chamber.
Mark the first half of the bullet with a black marker and insert the round into your rifle (SLOWLY push the bolt forward) If you feel the round beginning to hit the rifling STOP DO NOT GO FURTHER! Move the bolt back and seat the bullet another half turn down on your die and try again after remarking the bullet with the marker.SLOWLY repeat the process till you you can close the bolt handle on a round without feeling any resistance.
Then make sure you see no marks of contact on the marked bullet.
Back off so that you have a small clearance and that the bullet is not touching.
Then pick a load that you want to try and subtract 5-10% the given powder charge and see how they shoot at the range.
The reason to reduce the powder charge is that seating the bullet closer to the lands increases a loads pressure.
After you have fired the round at the range check for pressure signs IE-sticking bolt on extraction/shiny extractor mark on a case head/blown primers and such.
A good loading manual will describe this in better detail.
One of the benefits of loading closer to the lands is usually better accuracy.
Good luck loading and be safe.
Best,
TheKnack-Jerry

 

[elkslayer54]

see www.nosler.com/faq.html

 

[RLH]

what you're trying to do is determine the "throat" of your rifle. the throat is that space in the chamber between the end of the case and the beginning of the lands of the riflings. what the knack described is a tried and true method of determining the throat of a rifle. keep in mind that not all rifles are exactly the same, even ones of the same brand and caliber made at the same time. there can be few thousandths difference. there is a big difference between different manufacturers, in the throat length. loads for my .270 will blow the primers out and jam the action on a ruger because the throat is about 30 thousandths shorter. brings the pressure way up. i shoot my .270 at 3.355" overall length. i've shot 140gr. hornady boattails for years and the cannelure used to be where it would be right at the end of my cases. i bought some bullets a few years back and the cannelure was moved way forward, like 35 thousandths. called hornady and they said they had to do that because some manufacturers made the throat so short and guys were using the cannelure as a convenient place to set the bullets at and were jamming their guns up. i still use the same bullets, but the cannelure sticks way out past the end of the case. looks stupid, but it works. when you used solid copper bullets, be real mindfull of the bullet seating depth. copper bullets, being much lighter than lead bullets of equal length, are much longer and must be seated much deeper. most of them suggest that you have about 30 thousandths of freebore, to reduce pressure. the long copper bullet has so much more bullet in the lands causing friction and drag that the pressures go up considerably over a lead/copper jacket bullet. finding the right overall length does more for accuracy and velocity than any single thing you can do for your rifle. they're all different and require a little work to find, but well worth the time. and don't pay much attention to what your reloading book says. figure it out for your rifle. the reloading books have something called "liability" they're trying to keep away from. so the info you get on overall length is quite generic. have fun.

 

[shotgunjim]

LAST EDITED ON May-21-03 AT 09:02PM (MST)[p] WOW, what great info guys, who needs a reloading manual with this forum around. I used the method described by the Knack to detirmine bullet seating depth. I shoot an A-bolt, which has a removable clip type magazine, which I Like. But the bullets wouldn't fit in the clip. I either had to use it as a single shot or seat the bullet a little deeper.I choose to seat a little deeper. I thought about trying to see if a magazine from a 300 Mag. or something like that would work, oh yea I have a 7mm Rem Mag. Anyone Know if that would work?



GO DUCKS!!!!!!

 

[Buckrub]

How about "crimping" bullets? I've never done it and I load both pistol and rifle. What are the advantages, if any? I always thought crimping was to keep your bullets from seating deeper in the magazine as a result of recoil, or with a tube magazine(30/30) from the same inertia. Can anyone explain the the "what and why" ???

 

[RLH]

crimping does several things. most factory ammo is crimped. it helps in waterproofing it and pretty much stops any chance of a bullet coming loose. i used to have problems with my .264 mag losing bullets in the magazine or shaking loose in the boxes. the recoil is quite substantial and would work them loose sometimes and they are especially prone to it when they bounced around in boxes in my ol' pickup a lot. the necks on that particular case are real short and are sorta prone to that. the .300 win mag has a fairly short neck too, but i've never had a problem with it. instead of crimpin them i'd use a drop of real thin clear fingernail polish. seemed to work. all military ammo is crimped for these same reasons. pistol ammo is a little different. you really should crimp it a little. especially big calibers. the caliber is real large and the bullets are really quite small when you consider the diameter and they don't have very much seated at all in the case and they can get dislodged by recoil or temperature change or just knocking around. the reason for crimping is to make the odds of it going off when you want it to a little better. i've never seen crimper dies for bottle neck rifle cases either.