How far off the lands is my boolits?


About 600y, 24", plus or minus a few thou.

Loaded up my first rounds for El Kabong last night. Out of curiosity I stuffed a bullet in a decapped, spent case, stuck it in the chamber, closed the bolt, pulled it out and I think I could see rifling marks on the bullet. I measured the OAL and compared it to the book. I think the difference was close to .100". Could that be right? I then put a bullet in a sized, unprimed case and left it long by a BUNCH- more than I'd seat one at, repeated and the OAL didn't change. Mind ya this is with a 200gr Sierra MK, pretty long slug.

Is this 'just off the lands' thing subject to caliber/chamber size/tightness/freebore size cuz I'm not too sure I'd try to seat one sticking way out of the case like that, esp a light/short slug. Wouldn't that affect pressure, by a lot, if I increased OAL by say .090"?

I loaded them up to min OAL = .005", which was much longer than comparable factory ammo I had laying around, and called it good. Rolled 'em on some glass and no runout, at least that I could detect.

Yes, Chambered, these are START loads going up in .5 grain increments, to 1gr over START . (3 diff loads)

Depends on your rifle, caliber, bullet, load and powder. Too many variables to give you an answer. This is one thing that you have to find out for yourself as different rifles like different depths.

Cheers & Tighter Groups: Eaglesnester

I think I overloaded my post.

I think my main question was: would pressure be significantly reduced by increasing OAL by .090" or so?
The 200gr .308 SMK has plenty of shank so one could pull it off- cutting down the jump, in theory.

I think pressure would be affected significantly by increasing the OAL a bunch trying to reduce the jump, esp START loads with slow powders.

stovepipe wrote:

I think the difference was close to .100". Could that be right?

I've seen it with more than that with light for caliber bullets !!! (Remingtons are known for a lot of free-bore.)

As a general rule of thumb.......All you need in the case is the diameter of bullet your working with. Measure a case and a bullet, add them together and subtract .308 this will give you a starting point for OAL.
If your going to use the magazine set OAL as long as possible for it and start your development.

The amount of pressure drop or increase from moving the bullet in either direction would be in direct proportion to the size of the cartridge. A smaller case capacity will react quicker than that of a larger one.

chambered221 wrote:

As a general rule of thumb.......All you need in the case is the diameter of bullet your working with... The amount of pressure drop or increase from moving the bullet in either direction would be in direct proportion to the size of the cartridge. A smaller case capacity will react quicker than that of a larger one.

Interesting! And vaild point I overlooked on pressure. I was concerned with my START loads not having enough/correct pressure should there be a ton of new space in the case from moving that big ol' bullet out too far.

No doubt you'll have less pressure !!! How much less ??? IMO I could care less..... As you already know the goal is to have a safe starting point !!!

Copy on the START load and being safe.

I feel the need to share an event I had with a starting charge (minimum recommended charge) a medium range bullet (165) and a 30-06.
The powder was WW760 and I basically did the same thing that StovePipe is doing. The first round fired OK but sounded "funny". The next round fired the primer - and then the powder (a full second later) detonated!
The case was completely destroyed. The bolt was stuck shut. The noise was deafening even with muffs and plugs.
I took my gun from the range to my gunsmith and he opened the action and showed me the case - It looked like a cross between a 300 mag and a 303 British! After checking the rifle over he didn't find any problems and we talked about the load I used. He told me that using slow (760?) powders and too much air space allowed the powder to lay in the case and the primer would only ignite a few grains in a line. It burns very slowly until enough of the powder is burned that it spontaneously ignites the rest of the powder all at once causing an explosion.
I was told to use the listed components and the listed OAL for the starting load. If I wanted to exceed that length to add powder to make up for the added air space.
I have since used the listed OAL when I reload and have never had a problem since.

That's called a Shaped Charge. Thought about that too.... and same is one reason I don't reduce slow powder recipes or want a lot of room in the case.

Good thing you did not whip open the action right after the dud didnt light....yikes.

If I had opened the action I probably wouldn't be here talking about it.
Keep in mind though, that this was a listed starting load - the only reason it detonated was because I had moved the bullet out to get close to the lands. In my gun, an 03A3, that positioned the bullet about 1/2 caliber into the case - I loaded then one at a time so I am unsure if they would have fit in the magazine or not. It was one of my early attempts at getting smaller groups with a gun that normally produced groups in the .5 to .75 MOA range at 100 yards. Needless to say it didn't help with groups....

Yepper. Dang good thinking at a very good time for it.

I've cleared duds on pistols before doing drills then thought "oh crap!" and cringed and waited for the bang. Lucikly nothing happened. Sloooowww down stovey.

After I did the chamber check thingy I was thinking no way am I gonna start with the bullet that far out as nothing has been verified. I'll do seating stuff for groups, if even nec, and in very small increments after I verifiy the load I want. I'll be looking for complete combustion/pressure signs primarily the first outing w/ 3 loads: START, plus 0.5 gr, plus 0.5 gr again.

Paul, Do you remember if the bullet was seated into the lands or maybe how far off the lands it was ?




It was my understanding that laboratory test have been conducted and they have never been able to recreate the excessive air space theory.
I quit loading light handgun loads because of this but I've never found any documentation that proofs or dis-proofs the theory.
I'd be interested in reading any fact based info if anyone can provide where to find it.

chambered221 wrote:

Paul, Do you remember if the bullet was seated into the lands or maybe how far off the lands it was ? It was my understanding that laboratory test have been conducted and they have never been able to recreate the excessive air space theory. I quit loading light handgun loads because of this but I've never found any documentation that proofs or dis-proofs the theory. I'd be interested in reading any fact based info if anyone can provide where to find it.

My load was no more than .01" and no less than .005" off the lands.
I have seen the studies too - all I can say is that it happened to me and I am a believer. There was no overload or double charge (not possible), my reloading technique precludes any possibility of low or high powder charges - each is visually inspected when they are all together in the loading block - it is easy to see even 1 grain difference.

chambered221 wrote:

I quit loading light handgun loads because of this but I've never found any documentation that proofs or dis-proofs the theory. I'd be interested in reading any fact based info if anyone can provide where to find it.

Reducing for HG is cool. It's more accurate in a lot of cases, saves a bunch of wear etc. I just use a powder that moslty fills the case, is NOT a slow mag/ball type powder and use publshed loads. Most published HG loads are pretty light compared to factory/hunting stuff.


I didn't get to test my rifle loads in El Kabong yesterday. Windy, rainy and I had the sniffles so...I stayed in and reloaded, organised supplies etc. Argh, gotta wait till June now.