How do you fellas find the lands without a modified case?

[Varmint Master]

Hey fellas,

I am wondering the best practice to go about finding my seating depth/jam/jump length in a 6AI. I have a modified case for 6mm but they do not make one for a 6mm AI. What method would you recommend to find the length to the lands with a particular bullet?

Thanks,
Chris

 

[rmist]

Make a modified case from your fireformed brass. Or lightly seat a bullet with marked on the bullet, load shell in chamber and see where the lands are. Look for small horizontal lines from the lands.

 

[BoydAllen]

Sinclair sells a gauge that uses a rod, stop collars, and an adapter that goes in the back of the action. I have had one for years. They are not expensive. Check it out.

 

[ar10ar15man]

make one yourself..
drill and tap the primer hole for the handle..
use a fired case...
if you have a bushing die you can reduce the deck dia and still have a free moving bullet

my OPINION is to stay away from people that CLAIM they can measure RELIABLY from a JAM...
they claim they can tell from a pattern that is x as wide and 2x long or such silly schit...'IT IS NOT PRECISE.
stick with MEASUREMENTS.
just like using a micrometer(mic), it requires practice to develop a FEEL/TOUCH for when the bullet is touching the lands vs jammed into the lands.....keep the bullet you use and use it over to track throat wear.

you are measuring to the ogive(ojive)..not oal...get concerned with oal only when a magazine is involved.

 

[BoydAllen]

Tony Boyer, who has the most Benchrest Hall of Fame points, by a wide margin, uses marks on bullets as a reference seating depth when working up loads. Using that sort of refernce, I was able to set a friend's Wilson seater. well enough that he was able to shoot a sub .2 five shot group. with only a couple of tenths adjustment of the starting load of 322 that I gave him. Perhaps you do not "know" as much as you think you do. I could give more examples. Understand, I am not at all opposed to using touch as a starting point, but am suggesting that your remarks about using marks are not based on the best information. As the saying goes, there is more than one way to skin this cat. I have given the advice of using marks that are half as wide as long for specific bullets and applications, primarily for new 6PPC shooters, and have received multiple reports of shooters' success doing it that way.

Added later: What we are talking about is a starting point for a load workup. I always measure and record my seating die setting (total length of stem and cap for an ordinary Wilson seater) after I have the marks that I was looking for, and whatever changes that I make during my load workup are precisely done, measured and recorded in thousandths of an inch.

Recently a friend has gotten some excellent results, for his 6PPC shooting Berger's new Column bullets, within a precise range of slight jump, so for that application, I will be working from touch, and will use my Stoney Point tool and case to make that determination, with great care.

Some time back, I used another Hornady tool to measure a fully fire formed case, from the barrel that I am currently shooting, and the the modified case that I bought in 6PPC. The fire formed case was .006 longer from datum line to head than the factory modified case, so of course I will add that much to my measurements to come up with a reasonably accurate seating depth at a length that just touches the rifling. I reserve starting with marks for bullet and powder combinations that have a history of doing well when seated longer than touching, which takes in most of my 6PPC experience.

 

[people]

I cut the neck of a fired casing then put a bullet it and chamber it. So it three or four times and you will have your length. Takes no more than a dremmel with a cutoff wheel or a fine tooth saw.

 

[Varmint Master]

Thanks for the imput fellas.

People,
I don't know why I have never thought of that. Seems like a fool proof way that should yield consistent results.

 

[Tim Singleton]

Varmint master
you may find this helpful
http://forum.accurateshooter.com/index.php?topic=3810672.msg36201397#msg36201397

 

[ar10ar15man]

boyd,
i do not think the average shooter on these forums are in tony boyer's league....
i know br shooters do it all the time..but it is not a skill the average guy can use on multiple guns..with repeatability.
tools work best for the average guy ..take a measure ment write down a number and adjust from there///

 

[BoydAllen]

My point is that once you have your starting point, your can measure and GET a number to record and vary from in your tests. Generally I only write about bullet marks when helping a new 6PPC shooter. For the rest, .22 caliber varmint shooters for instance, I usually advocate dropping down the list of powder charges to the middle, and working up starting .006 to .010 into the lands, which of course requires an accurate determination of where the bullet just starts to touch the rifling. I understand the different needs of shooters at different levels of reloading expertise and experience, it was just that you made a general disparaging remark about using marks on bullets, that seemed a bit much.

 

[Raythemanroe]

this is good


http://www.youtube.com/watch?v=Jv-D1mEI514

 

[aj300mag]

Two collars that fit over a cleaning rod and a cleaning jag that the front has been faced off flat in a lathe.

Strip the bolt and install it into the action. Slide one collar onto the cleaning rod that had the jag installed. While holding the rifle vertical slide the cleaning rod into the muzzle and let it contact the bolt face. Tighten up the screw on the collar locking the collar in place. Pull the rod out of the bore and remove the bolt. Drop the bullet down the chamber, tap it into place against the lands. Slide the other collar onto the cleaning rod, carefully slide the rod down the bore until it contacts the bullet tip. Lock the second collar. Withdraw the cleaning rod, measure the distance between the collars and add to this dimension the thickness of the last collar. Load a dummy round to this dimension using the bullet you used. I'll take this round and stick it into a ziploc parts bag and write on the bag the date this cartridge was made and also the OAL dimension that was measured with a bullet comparator.

 

[ar10ar15man]

and how do you account for the fact that bullets in a given box can vary from .005 to .010 or more ??

i suppose for hunting accuracy...min of deer..its ok, but not when one is trying to make small holes in paper...

hi aj

 

[BoydAllen]

With the sinclair setup that was described, you measure the collars to get a back of bullet to case head dimension, which gives a back of bullet to back of fired case number, then you measure the same bullet from base to ogive, and add it to the first base to head number. Now you have a ogive to head measurement. Then you use the same bullet to set up your seater, and if you want to load off or into the lands, add or subtract the appropriate amount from your head to ogive number. As long as you use the same ogive measuring insert or tool, you are good to go. Any ogive to base differences in the box should be pretty well compensated for. Obviously having the rifling and seating stem contact the ogive as near as possible will help to minimize any dependencies, and yes, I primarily use this for varmint and hunting rifles that I do not have a case for for my Stoney Point/Hornady tool. I have gotten excellent results this way for these type rifles.

 

[Coolhand]

People , your method works which is a slight variation on mine , which was demonstrated to me by an old shooter long since passed. In fact I inherited his jewellers saw which he used to cut two slots in the case neck half way down . Resize the neck and then seat a projectile , you will have a fair idea of how deep , then dip the entire exposed projectile into '' bearing blue '' allow to dry , slightly lube the throat , insert the round into the chamber and very carefully close the bolt . You will know if the projectile needs a bit more seat , with a bit of practice, you can achieve a depth where the projectile will just kiss the lands and leave tell tale marks on the bearing blue.
You can also smoke the projectile in a candle flame or paint the ogive area with a black marker .

I have been using this method for longer than I care to remember and the beauty of using a jewellers saw is that the kerf is around 0.5mm and provides just enough looseness for the closing of the action to push the projectile backwards into the case neck. Make sure the throat is lubed .

regards
Mike.

 

[aj300mag]

and how do you account for the fact that bullets in a given box can vary from .005 to .010 or more ??

I've got the old stoney point bullet comparator but took it a step further. Instead of using the aluminum bushings supplied with the unit I make custom bushings out of barrel stock and use the chamber reamer to cut the throat area into the bushing. That gives me an exact reference dimension of where the ogive contacts the throat.

 

[chevi_guy]

Chris
I have the Hornady and I bought a tap and a drill and make my own.
I think it is a 5/16-56 tap. It's a special. I had to order it.

Ben

 

[Nomad47]

and how do you account for the fact that bullets in a given box can vary from .005 to .010 or more ??

i suppose for hunting accuracy...min of deer..its ok, but not when one is trying to make small holes in paper...

hi aj

You make small holes with small bullets. But, seriously, what did you do with the money, sonny?

 

[ar10ar15man]

go look at the pic in "Precision 223 Wylde AR Build "
in the small stuff forum

and how do you account for the fact that bullets in a given box can vary from .005 to .010 or more ??

i suppose for hunting accuracy...min of deer..its ok, but not when one is trying to make small holes in paper...

hi aj

You make small holes with small bullets. But, seriously, what did you do with the money, sonny?

 

[CZ550]

Remove your firing pin assy. Bump the shoulder back so bolt drops effortlessly on a empty case. Seat the bullet long and gradually seat the bullet deeper until bolt drops like it did without a bullet.