loading manual seating depths

[1000yardstare]

I have been reloading rifle since 1963 while a University student. Have owned just about every reloading manual ever published including the latest. Most manuals give an oal for each bullet/cartridge combo but I never see any reference to 'distance from the lands'. One question that has always bugged me is 'How far do the bullet manufacturers seat their bullets from the lands'. I am mainly an F Class shooter in the present tense so reloading .223, .243, 6AI, .308, .300WSM is a major part of my hobby. I have sent e-mails to the various companies concerning 'jump to the lands' but the silence has been deafening. There are many skilled and talented members answering questions on this website and I would be very interested in reading their opinions on the matter.

 

[billmo]

OK PAL, I'LL TRY TO HELP YOU OUT HERE. THERE PROBABLY IS A SET COAL,CARTRIDGE OVER ALL LENGTH) WITH THE FACTORY AMMO AND OF COURSE THERE IS A SUGGESTED COAL IN SOME IF NOT ALL MANUALS. JUST GUESSING ON THAT. DID NOT LOOK AT ALL OF MINE. BUT HERE IN LIES THE ISSUE. EACH RIFLE WHETHER FACTORY OR CUSTOM BUILT WILL OWN IT'S OWN PERSONAL FREEBORE DISTANCE IN THE THROAT AREA OF THE CHAMBER. THERE MAY NOT BE BUT JUST A VERY SMALL FRACTION DIFFERENCE BETWEEN TWO OR EVEN MORE RIFLES BUILT BY THE SAME BUILDER AT THE SAME SESSION BUT THERE WILL BE SOME. SO, I THINK IT WOULD BE VERY CLOSE TO IMPOSSIBLE TO GIVE YOU OR ANY OTHER RIFLE OWNER A SPECIFIC MEASUREMENT THAT YOU COULD REALLY DEPEND ON WITHOUT A MEASUREMENT OF YOUR PARTICULAR RIFLE CHAMBER. I HOPE THIS HELPS YOU UNDERSTAND WHY NOBODY HAS RETURNED YOUR ANSWERS. AND, THERE ARE ALOT OF GUYS ON HERE THAT HAVE FORGOTTEN MORE THAN I KNOW ABOUT THIS SUBJECT, I SUPPOSE. MAYBE SOME OF THEM WILL CHIME IN FOR YOU. BILL

 

[RJinTexas]

As both Billmo & gunamonth stated all rifles vary somewhat. The best advise I can give you is to purchase a oal gauge with a modified case for each cartridge you load for and a insert style bullet comparator and a inset for the each caliber you load. That way you will know the needed measurements for each particular rifles. Both are inexpensive and can be viewed on Sinclair's on line catalog. Hope you find this helpful.

RJ

 

[1000yardstare]

Thanks for the responses guys. I have a Sinclair OAL guage and start loads 20 thou off the lands of my individual rifles. The question that has been on my mind for 45 years is why the reloading manuals make no distinction between the OALs specified in the manuals and the real life variation in rifle chambers? Could be that the lawyers are specifying OALs and not the ballisticians. But I just bought a Savage M11 .243 that seats Sierra 75 hps .05 deeper than the OAL specified in the Sierra manual which has re-awakened my 45 year old thought stream. All of this may be 'angels on the head of a pin' but we all have a windmill to tilt at,pardon the sentence structure).

 

[billmo]

'How far do the bullet manufacturers seat their bullets from the lands'.

The problem with the question is that the ammo manufacturers don't know. If you're talking about a factory rifle the rifle manufacturer will have some idea what they're trying for but it will vary.

Factory ammo is loaded to SAMMI specs,almost always) which includes a maximum cartridge overall length. Helpful info since the rifles magazine can be built so the loaded factory round fits. Also makes the round short enough you shouldn't generate excessive pressure because the bullet was jammed into the rifling.

The down side is the bullet usually has a pretty long jump to the lands. Some cartridges seem to like this. A gunsmith buddy told me the 6.5X55 like .120' jump. In some you can't reach the lands even if you try, like some of the Weatherby cartridges which have a very long freebore.

If you're loading your own and using something like a Berger VLD bullet and want a jam into the rifling there's a real good chance the round won't fit in the rifles magazine. In the Sierra manual, at least the old ones I have, there are 223 loads listed with heavy bullets that have a notation that they will need to be fed one at a time.

And BILLMO, the Caps Lock Key. Right above the Shift Key? OK?

 

[billmo]

'How far do the bullet manufacturers seat their bullets from the lands'.

The problem with the question is that the ammo manufacturers don't know. If you're talking about a factory rifle the rifle manufacturer will have some idea what they're trying for but it will vary.

Factory ammo is loaded to SAMMI specs,almost always) which includes a maximum cartridge overall length. Helpful info since the rifles magazine can be built so the loaded factory round fits. Also makes the round short enough you shouldn't generate excessive pressure because the bullet was jammed into the rifling.

The down side is the bullet usually has a pretty long jump to the lands. Some cartridges seem to like this. A gunsmith buddy told me the 6.5X55 like .120' jump. In some you can't reach the lands even if you try, like some of the Weatherby cartridges which have a very long freebore.

If you're loading your own and using something like a Berger VLD bullet and want a jam into the rifling there's a real good chance the round won't fit in the rifles magazine. In the Sierra manual, at least the old ones I have, there are 223 loads listed with heavy bullets that have a notation that they will need to be fed one at a time.

And BILLMO, the Caps Lock Key. Right above the Shift Key? OK?

Sorry Gunamonth, Did not realize the caps would irritate you. Billmo

 

[Ackman]

They're not concerned with distance to lands. Since that's all over the place from one gun to another how could they possibly know? And it doesn't matter anyway....your chamber is all that matters. The loading manuals also have to deal with SAAMI spec's, you don't. Sierra's criteria for seating depth isn't about distance to lands or freebore. They just seat to have a certain percentage of bullet length held by the caseneck and although it's been awhile since talking with them I believe it's according to bearing surface.

 

[KevinThomas]

Looks like it's already been touched upon here, but the real issue here is the maximum SAAMI dimension. This usually relates to the ability of a loaded round to feed from/through a magazine, bearing virtually no relationship to the leade/throat issue. It wasn't until the advent of the LR specialty bullets that we began to run into issues whereby we needed to drastically exceed the 'max OAL' dimensions in certain circumstances. The .224' 80s being used in LR competition for example. Since this stage is strictly slow-fire, and the cartridges MUST be sinlge-loaded, the magazine limitation no longer applied. The relationship to the rifling, however, is something that the handloader himself has to determine.

Spent a long time with Sierra, but no, that wasn't me. At 40 years back, that might have been Jim Hull, or possibly one of the owners.

Hope that helps . . .

Kevin Thomas
Berger Bullets