Seating depth with DBM

[Ksmirk]

Ok fella's my search fu doesn't seem to be working as I made a couple searches and didn't come up with anything so thought I would just ask. Ok what I'm wondering is say you have a rifle and you didn't get to spec out the reamer and you have a detachable box mag like say an Accuracy International so your COL is stuck at X.XXX do you tune the loads with changes in powder charge weight or do you have some other magical system?

So far what I have been doing is to just come up with an COL that fits the mag and then jack with the powder charge weight to adjust to get the smallest groups I can and I was just sitting here thinking "Is there a better way?" I'd like to hear your thoughts and the ways you folks adjust loads to gain that magical LR load Later,

Kirk

 

[Ksmirk]

Maybe one of these days I'll be one of the cool kids and we can discuss questions. Later,

Kirk

 

[g0rd0]

put on your sunglasses, you have reached cooldom.
what I do is size 1 brass, lube the inside of the neck and sat a bullet in this dummy just enough to hold it in place then chamber it. When the ojive of the bullet contacts the rifling the rifling will be a seat die, after your bolt closes withdraw this and measure, subtract 30 thou and that is where I start
lets say that the dummy is oal 4.150" adjust your seat die to reseat this dummy to 4.120. Find your sweet spot with your powder charge
so now you are at 4.120" cci mag primer and 66.5 grn of XXX and you have .75" groups at 100 yards I will now try increasing the oal 5 thou and see if there is any change with the group then I will subtract 5 thou check group,ect till I see positive or negitive results

My favorite rifle likes 150grn ETIPS at 10 thou from the lands, 175 grn speer sp 30 thou 150 grn sp 30 thou and 139 grn hornady sp 35 thou. Dont ask me why the ETIPS like 10 thou I cannot hope to answer that, it is what it is

 

[Predator 22]

put on your sunglasses, you have reached cooldom.
what I do is size 1 brass, lube the inside of the neck and sat a bullet in this dummy just enough to hold it in place then chamber it. When the ojive of the bullet contacts the rifling the rifling will be a seat die, after your bolt closes withdraw this and measure, subtract 30 thou and that is where I start
lets say that the dummy is oal 4.150" adjust your seat die to reseat this dummy to 4.120. Find your sweet spot with your powder charge
so now you are at 4.120" cci mag primer and 66.5 grn of XXX and you have .75" groups at 100 yards I will now try increasing the oal 5 thou and see if there is any change with the group then I will subtract 5 thou check group,ect till I see positive or negitive results

My favorite rifle likes 150grn ETIPS at 10 thou from the lands, 175 grn speer sp 30 thou 150 grn sp 30 thou and 139 grn hornady sp 35 thou. Dont ask me why the ETIPS like 10 thou I cannot hope to answer that, it is what it is

This is what I do as well with the exception of I start 10-15 thousands off the rifling and just go farther back from the lands in 5-10 thousands at a time. Or if I'm restricted by mag length I start as long as the mag will allow find the best powder charge then start with jumping. Hope it helps

 

[Ksmirk]

Well thanks for the pointers fella's, I've got the OAL thing down I was just wondering if say my max COL is say 2.895" (not sure what it is just yet but sounds close) and my AI mag won't let me go over 2.885" so right off I'm .010" off the lands which for the most part is just about right from past experience so normally I'd just adjust the powder charge by .5gr increments until I find a load node then go back and adjust .1gr until I figure out what prints the best group with the lowest ES and run with it. Well so far so good BUT I find myself getting a touch more picky so thinking about say I find a good powder charge weight with the low ES I'm after THEN start playing with the seating depths but within' the restraints of the AI mags OR then again I could just be wasting my time with crazy thoughts lightbulb Later,

Kirk

 

[DocDoc]

You are better off to measure to the ogive, BTO, than COAL, as the length of tips vary more.

 

[Ksmirk]

Yes sir you would be correct but well old habits of writing COL yes I measure Ogive not the tips as well your right and even with those expensive bullets I've gotten some crazy differences. Later,

Kirk

 

[sp6x6]

My rifle im at .005 off and it fits my AI mag for my 338 NM and the 300 otm.Different bullets will also give you a choice also due to there different lengths