How long can i go with my 308?

[alpha6164]

I mainly shoot my GAP 308 which is based on a 700 Rem action with a 26" Bartlein 5R 11.25 twist and has had George's magic powder dust sprinkled over it

I currently load 175smk with 44.0gr of varget and winchester primers with COAL of 2.830". I get 2660 ft/sec with single digit ES. The rifle is a hammer and has shot 0.3moa at a 100 yards and has maintained 4" group at 850 yards.

I initially started loading to the standard 2.800" and went up to 2.810", 2.820", and then to 2.830". Each time i loaded longer my groups got tighter. I have not loaded longer than 2.830" in fear of getting too close to the lands and messing something up etc. I really dont have any way to measure just how far the lands are and how much longer i can load these rounds too. Not that anything is wrong with the current load but wondering if it can even get better. As dumb as it sounds, is there a way to estimate from the above setup how much longer i can load these rounds to?

 

[Rob01]

Re: How long can i go with my 308?

Sure you have a way to check the OAL to lands. Partially size a neck of a case with <span style="font-weight: bold">NO PRIMER OR POWDER</span>, seat a bullet long like to 2.900 and then chamber it. Using the lands to seat the bullet. Take a measurement. I like to do it a few times to make sure. It's easy. I measure to the ogive of the bullet.

That said if you are getting good results now then I wouldn't worry and SMKs don't mind a little jump anyways.

 

[madd0c]

Re: How long can i go with my 308?

Well, If your GAP is anything like my Crusader, then MEASURE THE LANDS!

I was seating to 2.830 because I have another bolt 308 that the lands are at 2.878 OAL with 175 SMKs. Magazine length for the other rifle is 2.830, not a thou more, so that is what I seated to so I could use magazine length and they shot very good groups at that length.
When I got my Crusader, I used some previously loaded 175s to start a load workup and they were seated to my previously standard 2.830. shot very well, and I continued load workup seating to that depth.
Long story longer, I had my stony point gauge out for an AR build, and decided while I had it out to measure my GAP. The OAL for MY rifle with 175s is EXACTLY 2.800. Which just so happens to be the seat length of FGMM. I had been jamming the bullet into the lands 3 HUNDREDTHS, not 0.003, 0.030! Surprised I wasn't pulling bullets when I ejected an unfired round! Come to think of it I might never have ejected an unfired round from the GAP.
Anyway, I haven;t been able to go shoot my newly loaded rounds with a proper seating depth, but obviously will need to begin my load w/u all over again.
Shouldn;t have been lazy to begin with, and measured the Lands when I got the rifle.

Lesson learned, and you might be surprised when you measure the chamber. Use the method Rob01 spelled out, and you should have no problems, other than occasionally it WILL leave the bullet in the lands when you eject. Need to play with the neck tension to get it so when you close the bolt and eject, the bullet stays in the neck and not in the lands.
YMMV,
madd0c

 

[vman]

Re: How long can i go with my 308?

alpha, in my opinion considering you have invested in such a nice rifle I would get the tools to help you measure coal from the ogive.. they arent too expensive if that helps.

What you need

1) Hornady OAL Tool
2) Hornady modified .308 case for OAL tool
3) Hornady Bullet Comparitor with .308 insert

These tools allow you to measure precisely, from the ogive.

I would then set up a few dummy rounds and compare them to what your rifle reads and set up your seating die accordingly.

Also, I would not be affraid to go near the lands. It wont do any harm, however you might want to do some small load development work but it may not be needed. Just watch out for any pressure signs.

Generally speaking the closer to the lands the better the rifle will shoot.