this has been bugging me for a while, so I've got to ask: what in the hell does .010" 'into the lands' mean?

I'm slowly working on getting a 280AI piece-mealed together and starting to think about fireforming the brass. one phrase I've come across is seating the bullet 'into the lands'. When I set up a dummy round I take a fired/unsized case, use a sharpie on a bullet and lightly seat it by hand. Then take it and jam the bullet/case into the chamber with the bolt. Extract and measure; if the bullet comes out, push it back in until shiny-shiny all gone. I do this 5 times to get an average max length. The way I see it, this is the longest that a particular bullet and case combination can be in that specific chamber. So for the life of me I can't see how to get a bullet 'into the lands'.

I can almost understand the lands scraping some jacket material off, but I would be worried about the lands biting into the jacket and pushing the bullet farther into the case, leading to pressure problems.

Please feel free to set this humble grasshopper on the correct path.

Sorry if this rambled: deschutes brewery 1; larry 0

If you have enough neck tension on your cases you can actually engrave the rifling into the bullet. Pressure does go up some; but not extremely. Arguements center around enhancing consistant ignition and getting a smoother pressure curve. There is debate in the benchrest community as to where the optimum point is; and the concensus is it varies based on bullet, barrel, chamber throat, leade, powder, neck tension; hair color, etc. Unless you are benchrest shooting; most would recommend you find the just touching length and back off 0.01 to 0.02 assuming the round will fit in the magazine.

[ 09-26-2003, 03:20: Message edited by: Old & Slow ]

Remember on push-feeds to load the bolt with the dummy before chambering. You want the bolt face, not the extractor, to seat the bullet into the lands.

Hello L Wells,

So far you're doing fine. Maximum Overall Length may not mean much since bullets have different tapers. Also, a Spitzer is usually going to be longer than a Hollow Point. You don't measure overall length. You measure to that point you mentioned that leaves the shiny spot on your bullet. Thats the lands making that shiny mark. You can't go much beyond there unless you try awfully hard. When you reach that point what is beyond it doesn't matter since it's not touching anything anyway since that's the point at which your bullet taper begins. You can have a Sierra HP that touches the lands and is 3.010". You can have a Nosler Bal.Tip go in the same chamber and touch the lands that will be 3.035". Both bullets will have the same length at the widest point of the bullet. I hope this is a little clearer. Best wishes.

Cal - Montreal

L Wells,

Bench rest shooters have rifles that only hold one round at a time and once they put the loaded round in, it IS going to be shot. Pushing a bullet INTO the lands for a hunting rifle is a bad idea, in my opinion. If you don't have enough grip on the bullet and it is forced into the lands the bullet "could" stick in the barrel when you eject the loaded round, dumping powder inside your action. Another point is that if you don't use the chambered round (at the end of the hunting day) the bullet now has marks on it.

You may want to try several "dummy rounds" when finding where the bullet meets the lands. You will more then likely find that the OAL of those "dummy rounds" vary by quite a bit. The distance from the base of the bullet to the start of the ogive on a swaged bullet vary. Some more, some less.

Groove Bullets don't vary by more then .001" from the base of the bullet to the start of the ogive. This ensures that the distance off the lands is the same for every loaded round.

Don

It gets over-thought, but I believe the idea is to have the round firmly seated against the bolt face for forming. After that, I've found .010 off to be an "accuracy" sweet-spot (or at least a good starting point) for many calibers.

.010 in seems to be excessive and I'd agree that one might stand a greater chance of spilling powder with the lack of grip.

I am try to understand the connection between fire forming cases and bullet seating depth...

Surely the two are not connected?

Richard,
I have seen a very close connection between bullet seating depth and fireforming. Take situation where the chamber is a little long and/or the brass are a little oversized. If one has a sloppy case that is driven forward in the chamber when the firing pin hits the primer, the case may not re-seat itself against the bolt face when the bullet leaves the case. The case grabs on the side of the chamber and leaves a gap between the the bolt and the case head. Thus the primer will come out by that amount. If you are using a stout load when this happens, the case will stretch and shortly will split at the junction with web. I had this situation and could only get 2 firings with a case.

On the other hand, if one seats the bullet into the lands, the case will stay back against the bolt face and will not be driven forward during firing pin contact. Thus the case will be better fireformed by better lands contact.

When jamming into the lands one has to adjust the powder and consider overall case length for your magazine. Once fireformed, one can back off the lands contact, if desired.
Ron

C210

Thanks for the explaination. we live and learn!

Seating bullets long or creating a false shoulder
before fireforming is only necessary if the chamber was done by a butcher. I have a 243,257,
and a 7x57 AIs. All have a crush fit on an unloaded virgin case. If the chamber is done
correctly there is no headspace problem. OK.

YUMAN

Just Curious. Any of you that use an Ackley Improved have you been able to bump the shoulder back with your dies without crushing the case?

Don

posted 09-28-2003 07:51
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Just Curious. Any of you that use an Ackley Improved have you been able to bump the shoulder back with your dies without crushing the case?
Don
I have never had a reason to try.
I use only Lee collet dies
Lyle

With my 280AI,..I used 4895 (fast powder) and a 160 speer (inexpensive and heavy) shoved about .006" into the lands. The fast pressure spike and heavy bullet in contact with the lands moved my shoulders foreward and gave a nice clean 40 degree angle all in one fell swoop. IMHO the bullet needs to be firmly engaged to form the brass correctly.

After the forming,...seating depth is just a function of your rifles accuracy and personality.