distance to lands ?????????/

h2447intx

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ok i get the idea behind seting a spesific distance from the lands my question is this

what is the max and min distance the standard , when they ream the chamber out

and also i was checking my over all chamber lenght to the lands

took a new brass set a bullet in it and put it in my die just enough to get it started , checked over all lenth befor i loaded to my rifle it was over 2.9xx any how went ahead and run it into the rifle and removed it rechecked and the over all was now setting at 2.883? i think i did this last night so i may be off a little ,, any how is that a good chamber distance ?

most i see are over that any how any iput would be great , most of my loads are set at 2.810 so that is only a .070 jump
 

QuiggyB

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Re: distance to lands ?????????/

Couple of things. As far as I know there is no standard for how the chambers are created other than from the factory they are bigger than the biggest SAAMI spec round possible so that anything you would buy off the shelf would fit. Multiple identical guns from the same manufacturer will most likely have variances here. When a gun smith chambers up a rifle they are free to set it up how they or the customer likes as well. For this reason you end up measuring your specific rifle so you know. This is if you are loading longer than the max COAL in the load books. I think its safe to assume rounds loaded to that max length will not be in your lands.

Three common ways of making the measurement

1) Basically what you did - load a round up, close the bolt and look for marks on the bullet. If you are trying to be precise this isnt the way to go. Even the way you described the lands will dig into the bullet a good bit before the bullet is actually pushed back into the case. I expect you will see marks on the bullet if you look at the round you used.

2) Cut some slits in the neck of the case so there is less resistance. Carefully insert and remove the round and you'll have a good measure.

3) Use a tool like this one from Sinclair. There is a video showing how it works on their site as well. Super simple and precise.

http://www.sinclairintl.com/.aspx/pid=35491/Product/Sinclair-Bullet-Seating-Depth-Tool

Along with this you will need a way of comparing bullets once you have these measurements. You can't measure to the tip of the bullet because that varies bullet to bullet. You need to measure to the ogive. Here is a good tool for that.

http://www.sinclairintl.com/.aspx/pid=33236/Product/Davidson-Seating-Depth-Checkers

Why you may care about all this. Some bullets perform better seated closer to the lands. If you accidentally shove a bullet into the lands two things could happen. Pressure will go up and you run the risk of pulling the bullet out of the case and dumping powder in your rifle if you chamber a round and then try to remove it. I generally have good luck with bullets seated .010 off the lands when I'm using VLD bullets. For them to feed out of my magazine I set them back to .060 off. The last rifle I had chambered up I asked the gunsmith to set it up so the max length in my mag was .010 off.
 

QuiggyB

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Re: distance to lands ?????????/

For hunting situations or situations where you will be shooting in very cold or conditions where your rifle could get very dirty (sand, dust, etc) and you aren't concerned with extreme accuracy as much as good accuracy and high reliability I would seat the bullets further back, say .060 or further off the lands. I also would not be as tight with how I resized my brass here either.
 

h2447intx

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Re: distance to lands ?????????/

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: QuiggyB</div><div class="ubbcode-body">For hunting situations or situations where you will be shooting in very cold or conditions where your rifle could get very dirty (sand, dust, etc) and you aren't concerned with extreme accuracy as much as good accuracy and high reliability I would seat the bullets further back, say .060 or further off the lands. I also would not be as tight with how I resized my brass here either. </div></div>

got it ,, so you say " not be as tight with ow you resize"

what do you mean , more neck sizing and not so much full length ?
 

QuiggyB

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Re: distance to lands ?????????/

I mean with how far I push back the shoulder with my size die. For competition shooting you may only push it back .001 but if I was hunting in the cold or in a condition where things will get dirty I'd push it back further than that so I didnt have any issues closing the bolt (or opening the bolt after my shot).
 

.375Mojave

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Re: distance to lands ?????????/

A couple things I would add.

Resizing, whether shoulder bump or neck only, can be a matter of choice. Chambering may get tighter with multiple neck-only sizing, but this will be apparent when you are at your bench. I really do not subscribe to loose loading to accomodate dirt. If we were in Afghanistan and dragging our weapons around with our lives depending on chambering a round in a semi auto it is one thing. For hunting if you are getting enough dirt in your weapon to prevent chambering a round you are really screwing up. If you are hunting dangerous game at close range by all means full length resize as 1/2 MOA is not the critical issue but a follow up shot may be. If you are taking ELR shots at Elk make it a tight fit. It is probably prudent to test chamber the rounds you put in your mag if you are running very tight chambering but that should cover your bases.
In a hunting situation, magazine length is likely to dictate OAL of your rounds. Often seating .010 off the lands (which is generally a good starting point) will produce a round that wont fit in the mag. You can always run single shot and have a round that fits the magazine for a backup. It is likely that a followup shot that has to be quick will be on a moving target so .5 MOA may not be at issue.

On determining OAL another easy method utilizes your cleaning rod. I have a small collar with set screw (mine came out of a doweling kit I got at Home Depot) that I can lock on my cleaning rod. I make sure the firing pin is retracted in the bolt face (ready to fire) slide the rod in with and end that stays well centered like a cleaning jag with a flat nose and touch the bolt face and lock the set screw (gently so you dont damage your rod coating). Remove the bolt, slide a bullet in until it touches the lands (don't force it because it really doesn't take that much pressure to engage the lands), run the rod in until it touches and use a vernier to measure the distance between the muzzle and lock ring.

I would do it on several bullets to get a good average as you are measuring to a projectile tip which may vary slightly and it can take a couple to get a good feel for it. Once you have this dimension you should use a Comparator to check your length as bullet tips do vary and what matters is the portion of the projectile that will contact the lands, not really a tip that may be deformed.

Hope this is useful.
 

jkonzal

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Re: distance to lands ?????????/

I use the Hornady O.A.L. gauge and Hornady Bullet Comparator for doing this. They aren't very expensive and work very well for me. In my 308, I seat my bullets .005 off the lands.
 

QuiggyB

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Re: distance to lands ?????????/

With .375Mojave's method, rather than doing several samples and averaging to account for differences at the tip, couldn't you use a bullet comparator to do it in one step?

The measurement tells you the length from case head to bullet tip if you actually seated that specific bullet in a case.

Using the same bullet from the first step, measure the bullet overall length. Then measure the bullet with a comparator. Subtract those from each other to get the distance from ogjve to the tip. Take that answer and subtract it from the first measurement (case head to tip) to get the length of a loaded round that hits the lands measured with your comparator. This should be a consistent value bullet to bullet. Use that to setup the seating die.
 

.375Mojave

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Re: distance to lands ?????????/

The answer is you absolutely could.

I only suggest a couple to get a "feel" for it. Pushing a projo in to contact the lands firmly is a touch thing and it is not hard to be a litle heavy handed and lose a couple thou in the process.

Doing it once (carefully)and seating that same bullet will absolutely produce a good reading. I use a Sinclair Comparator once I have a specific projectile seated to OAL. This will give you a useful dimension when you change projectiles as the ogive is all that matters and a Comparator utilizes this cross sectional dimension when used.
 

h2447intx

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Re: distance to lands ?????????/

well i think im going to start sizeing closer to lands,, i have been seting them at 2.810 and i did check the rifle , so i think that im going to load some at 2.850 +- give me about .035 off the lands

then do some shotting and see what it looks like