Loading into the jam

[aintright]

Have been building some loads for a rifle and came across this load info that recommends seating the bullet .020 into the jam . So does this mean that I should seat the bullet .020 longer than O.A.L. ?
I was always taught to back it off the lands by .010 or so . Just want to make sure I am interpeting this right . I don't doubt the fellows load data as he is a very competitive shooter and probally forgotten more about guns than I'll ever know and really don't have anyway to communicate with him .
Kenneth

[Sunray]

"Into the jam" sounds like some guy making up his own terminology.
'Off the lands' has no exact number. Every chamber is slightly different so every one of 'em will be a different distance. Doesn't guarantee anything anyway. Fiddling with the OAL is a load tweaking technique.

[leftyo]

no, it does not mean to load longer than listed oal. what it means is you need to set up and measure exactly where your bullet gets into the rifling, then load it to a length that is .020" longer. while this can sometimes give excellent accuracy, it is reserved for bench or competetive shooting only, as it can turn your rifle into a bullet puller if you decide not to fire the shot once chambered. it also requires that you start working up your powder charge form the bottom of the page again, as it can it can raise pressure levels greatly. it has its place, but its not something that you should just do without thought before hand. remember the internet is a dangerous place.

[PhillipM]

I take it to mean .020 jammed into the rifling. I would expect high pressure since there is no room for the bullet to jump, so be sure to use a low charge of powder.

[raymeketa]

Jam is entirely dependent on the rifle's chamber. You first need to determine when the bullet's ogive is touching the throat and then you can seat longer (on the jam or into the jam), or shorter (off the jam). It's a technique used by Benchrest and other competition shooters. It often results in improved accuracy but not always. For the average hunting rifle it is usually a waste of time but the Internet has spawned a generation of shooters who think it is the stuff that accurate rifles are made of.

Seating .020" into the jam will usually result in the bullet being pushed into the case because the throat will act as a bullet seater. But, it offers the advantage of not having to adjust the jam as the throat wears. Most Benchrest shooters prefer to re-measure the jam every so often and make the adjustments as necessary. The same can be said of seating off the jam because that will also change as the throat erodes.

The notion that seating on the jam will raise pressures to dangerous levels is very much exaggerated. A typical Benchrest cartridge (6PPC) operates at 60,000 or more PSI and if jamming creates dangerously high pressures you would see a lot of blown primers and sticky bolts - but you don't. Chamber pressure probably does change depending on jam but not to the degree that many would have you believe. Again, it's an Internet myth.

JMHO

Ray

[aintright]

Ok , thanks for all the replies . I did not mean to sound as though I was talking about reloading manual O.A.L. . I was referring to making the Cartridge .020 longer after establishing the length of cartridge once making contact with the lands . But still got my questions answered . The gentleman writing the article is a position shooter and I realize that kind of accuracy is not nessacary for hunting , but I like to squeeze all I can out of my rifles , it's just fun .
As of right now with a Remington 700 Buck Master , 24 inch barrel , H4350 53.5 gr. , winchester brass and 200 gr. SGK .010 off the lands , I am averaging .87" five three shot groups .
I need to replace the trigger as it is a monster and inconsistant and requires working harder at holding therifle with out pull , once I get that done I think this will be my hunting load for this rifle .
Thank all of you again for the replies , I may try the .020 into the jam , but not until I replace the trigger , even then it may not make a noticable difference in this rifle .
Kenneth

[leftyo]

you dont want any jam on a hunting rifle, as you want to be able to unload easily without the potential for pulling a bullet and spilling all that powder down in the action. and yes, if your pushing your loads already, you can run into pressure problems by just seating the bullet out further, and thats not just an internet rumor.

[raymeketa]

. . .yes, if your pushing your loads already, you can run into pressure problems by just seating the bullet out further, and thats not just an internet rumor.

I shoot Benchrest and during a normal routine of tuning a load for the existing conditions, I may make seating adjustments of .025" to .030" (in or out) without making any changes to the powder charge. Sure, there may be minor pressure changes as a result, but nothing to be alarmed about. Those pressure changes are probably part of why the accuracy also changes, among other things. And, Benchrest loads are usually pushing the envelope to begin with because that's where most of them shoot the best.

[leftyo]

good for you.

[aintright]

Thanks for the advice leftyo . But when I decide to load into the jam , it will be for bench shooting only . I have already experienced the dumping of powder in the action at the bench from long throated chambers that you can barely get a 165 gr bullet seated into and am well aware this is not a desirable thing in the field , lol . Quite a mess .
As Ray stated , I have read articles on this loading into the jam and there is no concern of dangerous pressures as long as you follow their advice and back down 2 grains and work up to their working load and this a practice by people who shoot a lot . Again thanks to all for replies .
Kenneth