tuning OAL/ steps used to find best group??? plz help

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Dizzle000

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hey guys so i have some questions i am hoping someone can chime in and help me out i have been reloading for about 6 months now by no means am i really good at it, but i got the hang of it but am always looking to get better. i shoot a weatherby vangaurd 308 and have been loading berger bt long range target 175 gr bullets federal brass federal match 210m primers and using varget for powder .the last i shot my rifle was in the fall it was about 12 degrees out. i was testing load development 3 rnd groups. so my best was .137 (to center of holes) my OAL was 2.198 using the hornady ogive tool,and my measurement for my max length to the lands is 2.306 using the ogive tool. these are lengths i decided to start with and i guess it was afluke, so this is where my load developments are at now and the questions begins.

when should one play with the over all length to see wether the groups will tighten up or not? i would like to make the OAL longer or shorter to see if the groups tighten up but if i push the bullet in further then the case pressure will go up and if i pull the bullet out more the case pressure wil go down correct? so i will either have to add more powder or subtract some? which steps do you guys take to find the Best load/case length for your rifle?

im stumped on this one, because now that i reload i would like to make some rounds for hunting this fall, and im not sure if i want them to be able to fit in the magwel or just bomb in one round at a time. ill be using the nosler accubond 180 gr hornady cases federal gold primers and varget. max sammi in the nosler book is 2.810 and the tested was 2.800 OACL ,but id like to play around and make them as long as i can to still fit in the magwell but get the best accuracy i can.
i hope what i am asking makes sense and someone can help me out some.
cheers
kyle
 
Did you just say your COaL was 2.198 for a .308 Winchester round? Factory spec (SAAMI) is 2.80" for the .308 win.

Getting back to your question (I'm new to reloading as well), you can either buy an OAL gauge (I own a Hornady gauge with the .308 modified case), or.......

Grab a piece of brass that WAS FIRED FROM THE RIFLE IN QUESTION, and saw 3 or 4 slits around the neck of the casing using a hack saw...as to have a round seat but that you can pull it out with minimum effort. Chamber said hacksaw round with the projectile you wish to use (minimum of 5 times), and calculate the average from each chambering. Do this slow because if the case neck is too loose the projectile could fall out or become lodged into the lands (easy fix). So you take your 5 readings as an example of 2.8 or larger, divide that by 5, and you get the average of your 5 chamberings. Subtract (FOR SAFETYS SAKE) 2/1000's of an inch and that will give you a COAL to start with.
 
klink1983 said:
Did you just say your COaL was 2.198 for a .308 Winchester round? Factory spec (SAAMI) is 2.80" for the .308 win.

hes measuring off the ogive not the OAL to bullet tip

Getting back to your question (I'm new to reloading as well), you can either buy an OAL gauge (I own a Hornady gauge with the .308 modified case), or.......

he already has one

Grab a piece of brass that WAS FIRED FROM THE RIFLE IN QUESTION, and saw 3 or 4 slits around the neck of the casing using a hack saw...as to have a round seat but that you can pull it out with minimum effort. Chamber said hacksaw round with the projectile you wish to use (minimum of 5 times), and calculate the average from each chambering. Do this slow because if the case neck is too loose the projectile could fall out or become lodged into the lands (easy fix). So you take your 5 readings as an example of 2.8 or larger, divide that by 5, and you get the average of your 5 chamberings. Subtract (FOR SAFETYS SAKE) 2/1000's of an inch and that will give you a COAL to start with.

he already knows his OAL to touch the lands
Click to expand...


any who, OP if youve got your powder charge sorted out (Which it sounds like you do with .137" group) as long as the rest are close youve got it... so now to play with OAL, using your OAL guage, load 5 at touching, 5 -5thou off, 5-10thou off and so on, see what happens

usually when you seat longer pressure goes up, as there is "free space" in the cartridge for gas to expand before the bullet moves, obviously talkng in terms in the tens of thousands of seconds here.

if you plan to load up some hunting ammo, dont forget you will need to load develop for this separately , and id honestly load so they can be mag fed
 
Thanks monkey sorta makes sence. right now my target burger rounds are jumped something like.106 off the lands its just were i desided to start. just wondering if i could make the group tighter. When u start playing with the lengths is that where a crono comes in ?so say u have a charge that your happy with ,but are trying to tighten up the group abit more if u gain case pressure or loose it ur volocity will eather go up or down, then would you compinsate in ether addin or taking away powder?
As for the huning rounds i think i will make them so they fit in the mag well would you recomend making them as long as i can to fit in the mag well or to sammi? This is where im stumped does it just become trial and error i guess or is there a sure method to do without having to throw a bunch of lead down range lol?
 
Klink1983. I use a ogive gauge made by hornady its way more accurate then measuring coal as some bullet the very tip isnt exact bullet to bullet eg burger bt so when i was loading i was getting a deviation in lengths
 
I would say just carry on and load as you were - there are very very very few people that can get a .137 group - if you can replicate that, then stop! If not, then start loading at COL spec for the load, then move it out a bit at a time - you will see groups change one way or another. One thing at a time.

Big thing is to be able to get repeatable groups. Myself, I go to 200yds for load testing, its much easier to see good/bad loads.... You see the evil vertical groups much better.
FYI my rifle didn't like Bergers so much with the powder I use, but does like Scenars - I load them (and SMK's) to 2.15 ogive for consistent 1/2moa - the longer I loaded, the worse they got, including being jammed.
One thing I have found, and learned from others here, is that the best loads for 175ish gr 308 are right at 2600fps. Most are 2.8-2.82"COL. Took me a couple hun rounds to figure that out/heed that advice - guess what - it works 99% of the time!
I also went to 200yd OCW round robin type load testing - works pretty good!
 
Dizzle000 said:
Klink1983. I use a ogive gauge made by hornady its way more accurate then measuring coal as some bullet the very tip isnt exact bullet to bullet eg burger bt so when i was loading i was getting a deviation in lengths
Click to expand...

I've never done that, but now that you mention it I think I have to get one of those. I always just go off of the tip, but then there will be inconsistencies with how far in the bullet seats altering the pressure inside the round when she goes boom.
 
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