Measuring the lands
- Thread starter ifsta4
- Start date
It is only important if you are shooting cast bullets and you want to do a better job of matching your cast bullets to the barrel.
The best method is to use a pure lead slug, driven through the barrel.
Depends on the type of bullet, and some rifles prefer one or the other.
Don't understand your question. Perhaps full sentences or paragraphs to explain what you are trying to do?
The best method is to use a pure lead slug, driven through the barrel.
Depends on the type of bullet, and some rifles prefer one or the other.
Don't understand your question. Perhaps full sentences or paragraphs to explain what you are trying to do?
unstableryan
CGN Ultra frequent flyer
- Location
- Beautiful Okanagan Valley
Pretty sure he's talking about bullet seating depth.
Probably the most accepted method of doing it uses the Hornady system, formerly called Stony Point.
Measuring Distance to Lands
I think the only down side of this method is that it uses a dummy case that may or may not match your cartridges. My method is to take a fired and neck sized only case, and cut a slot in the axial direction through the neck and shoulder. Then you can fit a bullet in the neck that slips with moderate pressure. I pull the bullet out long, and then chamber it. Very carefully remove the cartridge without disturbing the bullet. Measure the overall length. Repeat until you get a consistent number. It helps once you get close to just pull the bullet slightly longer than what you suspect is the distance to the lands.
This distance is the only valid for that specific bullet. So you have to use that bullet to set up your seating die with a real load. The reason is that bullet lengths vary from the ogive to the tip. Also you have to add to this distance to get a jam, or subtract to get a jump. And obviously you have to do this for each different bullet weight and design.
As far as jump or jam, my experience is that a .010" jam works best for me. However, there are issues with using a jam. I avoid trying to seat right to the lands. It is very difficult to achieve due to tolerances. You will end up with bullets that have a slight jump, slight jam, and very few that actually just touch the lands.
I have no experience with subsonics in centerfires and can't comment.
Perhaps, but that is an assumption. He could also have been talking about short bullets, or anything.
As for sub-sonic loads, if he is using cast bullets (another assumption!), then touching the lands should not make any difference. But, we don't know what he is trying to do, and it is entirely possible (50-50) that he is using jacketed bullets.
Cannot give meaningful and safe advice without more information.
I use a Sinclair seating depth measuring tool with a comparator, as described on this page:
http://blog.sinclairintl.com/2009/03/26/determining-bullet-seating-depth/
This is the One True Way of doing it, but the Stoney Point tool is okay if you don't know what you're doing.
http://blog.sinclairintl.com/2009/03/26/determining-bullet-seating-depth/
This is the One True Way of doing it, but the Stoney Point tool is okay if you don't know what you're doing.
Sorry folks, Cold medicine is wonderful for colds not so much for clarity of mind..
What I am looking for is the best proven method for figuring out the best bullet seating depth. I have been reading about distance to the lands and it would seem general concensus is 0.001" back off the lands or "jump".
I have been working on subsonic 308 rounds and have tried 150gr RN, 168gr FMJ, and the Lapua 200gr subsonic. I am still working "down" the loads and was curious if seating depth is different when using subsonic loads.
I also have ordered some 200gr all lead cast bullets and am curious if anyone has had experience with these.
http://www.midwayusa.com/viewProduct/default.aspx?productNumber=837126
Currently, similar to Ron Aka's advice, I have used a resized and lenghtened unprimed case with lube in the neck, and seated each bullet slightly, then loaded into rifle, extracted and measured OAL for each bullet type, is this accurate? Is there a potential danger to this?
Also I am using Federal magnum match primers is this safe? Everything seems to be working so far but I am relatively new to this and looking for advice from those with experience.
What I am looking for is the best proven method for figuring out the best bullet seating depth. I have been reading about distance to the lands and it would seem general concensus is 0.001" back off the lands or "jump".
I have been working on subsonic 308 rounds and have tried 150gr RN, 168gr FMJ, and the Lapua 200gr subsonic. I am still working "down" the loads and was curious if seating depth is different when using subsonic loads.
I also have ordered some 200gr all lead cast bullets and am curious if anyone has had experience with these.
http://www.midwayusa.com/viewProduct/default.aspx?productNumber=837126
Currently, similar to Ron Aka's advice, I have used a resized and lenghtened unprimed case with lube in the neck, and seated each bullet slightly, then loaded into rifle, extracted and measured OAL for each bullet type, is this accurate? Is there a potential danger to this?
Also I am using Federal magnum match primers is this safe? Everything seems to be working so far but I am relatively new to this and looking for advice from those with experience.
Like I said, if you want to do the job right, you'll get your credit card out and buy the following parts from Sinclair:
59-4000 Sinclair Seating Depth Gauge
09-600 Sinclair Bullet Comparator #1 or #2 (pick the one with the calibres you use the most)
and, optionally, get a competition seating die that has a micrometer adjustment on the top so you can make precise adjustments.
While there are some that say "kissing" the lands is the best position, I am not a subscriber. I would suggest there is no possible way to measure close enough to consistently have the ogive 0.001" off the lands. I would suggest a jump of 0.005 is a minimum unless you are going to get into measuring every bullet. The bullet length to the ogive does vary. What works best probably has to be determined by experiment in your gun. I suspect many tolerances come into play. The gun I have been shooting likes a 0.010" jam into the lands best.
Your method of sizing the case, lubing it, and then feeding it into the gun sounds a bit suspicious. You may want to colour some bullets black with a marker and try it. I think you will see that you are jamming the bullet a significant distance into the lands, so giving you a false reading.
It is easy to use a dremel cutting wheel to cut one slot in neck and shoulder. That lets you control the tension. You really don't want the bullet to enter the lands, just touch them. I find once I get close with the measurement you can pull the bullet just a few thou out and chamber it again. When the bullet moves a short distance it usually gives you the most consistent result. What you want to avoid is having the lands grab the bullet so it partially pulls out when you extract it.
I have a the Hornady/Stoney Point tool. It worked great at first, but for some inexplicable reason, it is not longer giving as me as consistent results, particulary with Nosler Ballistic tips. I am thinking that throat erosion my be a factor (fired 272 round through my WSM, and have eroded about .010 off the throat. I was thinking of trying the the dremel tool method.
However, I have a Lee collet die. When first using this die, I noticed that I could push the bullet in with my fingers with a little pressue and thought that this might be another method for making a dummy round to find seating depth. Has anyone used a Lee collet die to make a dummy bullet for finding seating depth.
However, I have a Lee collet die. When first using this die, I noticed that I could push the bullet in with my fingers with a little pressue and thought that this might be another method for making a dummy round to find seating depth. Has anyone used a Lee collet die to make a dummy bullet for finding seating depth.
350tracker
CGN Ultra frequent flyer
- Location
- Interlake Manitoba
Check with Mystic Precision and he's located in BC...
Home Made Seating Depth Gauge
I drill out the base of a empty casing and than tap it to recieve a 1/4 ready rod. I soft seat the bullet into the casing by chambering and closing the bolt. I then seat (using any type of seating die) the bullet in small increments until I can no longer feel the bullet touching the lands. What I mean by feeling the lands, is that after each seating I sping the casing with bullet onto the ready rod and then feed it into the chamber (bolt removed obviously). When the cartridge is inserted all the way into the chamber and then spun by hand you can feel if your touching the lands or not. With dilligence, you can be as accurate as your dies allow. If you like to tinker, this is quit accurate and only costs a few dollars to make. Note to wrap the ready rod in hockey tap to ensure you dont scratch the reciever. I also double nut about a half inch from the end of the rod so the casing has a stop. The other MUST to ensure accurate readings is to have an Over All Length Gauge. And ol timer should me this. Its crude, but has worked its prupose for all my rifles. I would post pics but cant figure it out. If you guys really want them, then someone who knows how PM me their email address and I can take some. Enjoy!
I drill out the base of a empty casing and than tap it to recieve a 1/4 ready rod. I soft seat the bullet into the casing by chambering and closing the bolt. I then seat (using any type of seating die) the bullet in small increments until I can no longer feel the bullet touching the lands. What I mean by feeling the lands, is that after each seating I sping the casing with bullet onto the ready rod and then feed it into the chamber (bolt removed obviously). When the cartridge is inserted all the way into the chamber and then spun by hand you can feel if your touching the lands or not. With dilligence, you can be as accurate as your dies allow. If you like to tinker, this is quit accurate and only costs a few dollars to make. Note to wrap the ready rod in hockey tap to ensure you dont scratch the reciever. I also double nut about a half inch from the end of the rod so the casing has a stop. The other MUST to ensure accurate readings is to have an Over All Length Gauge. And ol timer should me this. Its crude, but has worked its prupose for all my rifles. I would post pics but cant figure it out. If you guys really want them, then someone who knows how PM me their email address and I can take some. Enjoy!
I did try this and no matter what I did the bullet would get stuck in the lands, as there was not enough tension in the neck to hold. I took the rifle into a local shop and they were drewling over it claiming it was custom built military spec. so I am not sure if that makes any difference.
