.308 AW case length to lands and Grooves

rickp

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I need some help getting my OAl to the lands and grooves.

I've tried the guide rod method, I've tried the Hornady lock and load OAL rod method and I'm still not sure what the measurement is.

I'm shooting .308 with 175gr SMK and Win. brass.

with the rod method I got 2.740 and that seems long considering the case is 2.800 OAL.

i went as far short as 2.725 and i still get marks on the bullet with magic marker on it.

How are you guys getting that number?

and if I cant get it, what's a good number to start with?

R.
 

Bob 964

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Feb 10, 2011
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Re: .308 AW case length to lands and Grooves

I struggled with this as well. When I bought my L-N-L OAL gauge I had no idea whether I was using it correctly because I was being asked to "feel" something I had never felt before. I took 10 separate measures of the same bullet and got a wide range of measurements. I had no idea whether I was even in the right ballpark.

I followed some advice I got on this forum and took an empty case and, using a Dremel tool, cut a slit in the case neck almost to the shoulder. This relieves neck tension enough to let you put a bullet in an empty unprimed case and then slowly chamber it in your gun. The relieved neck tension will permit the bullet to move up to the lands as you close the bolt. Carefully remove the cartridge from your gun so the bullet doesn't move and take your OAL measurement.

I repeated this 8-10 times until I got a consistent and small range of variance. This gave me some idea of what measurements I should be getting with the OAL gauge. Then I took repeated measurements with the OAL gauge until I started getting measurements that were close to what I got with the slotted cartridge.

It's unclear whether your 2.725 - 2.740 is measured to the ogive or is the overall cartridge length. Using a bullet comparator and caliper, I measured the length of the SMK 175 to the ogive to be 2.293". This is the median value of 10 separate measurements in my Savage 110FP. The overall cartridge length measured the same way was 2.876". Caution... these are my measurements in my gun.

Good luck. There are numerous posts on this forum where people have used the slotted case neck and there are some youtube videos that might help as well.

Bob
 

19Scout77

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Jun 9, 2007
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Re: .308 AW case length to lands and Grooves

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rickp</div><div class="ubbcode-body">I need some help getting my OAl to the lands and grooves.

I've tried the guide rod method, I've tried the Hornady lock and load OAL rod method and I'm still not sure what the measurement is.

I'm shooting .308 with 175gr SMK and Win. brass.

with the rod method I got 2.740 and that seems long considering the case is 2.800 OAL.

i went as far short as 2.725 and i still get marks on the bullet with magic marker on it.

How are you guys getting that number?

and if I cant get it, what's a good number to start with?

R. </div></div>

WIth 175s just load them to 2.8" OAL and run with it. If you really want to make it easy, seat the 175 over 44 grains of varget and call it a day. IME AWs are anything but finicky.
 

jackinfl

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Dec 19, 2008
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Re: .308 AW case length to lands and Grooves




WIth 175s just load them to 2.8" OAL and run with it. If you really want to make it easy, seat the 175 over 44 grains of varget and call it a day. IME AWs are anything but finicky. [/quote]


Wow,
Sounds strangely familiar!!! 19 scout77, you took the words out of my mouth
 

Rolygmt60

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Re: .308 AW case length to lands and Grooves

Plus 1 on square nut. I use a wooden dowel to push the round out of the chamber. I have better feell using the dowel. You have to use the original bullet that you use the measurement when seating the distance from the lands because there are variances to the lengths of bullets. I have the Sinclair tool and the hornady tool and I cannot get consistent measurement because w hornady tool itand Has too much flex. And w Sinclair you have to account of the primer depth because the tool smaller than primer pocket in 308mines and the rod wiggles which gives some variances.
 

427Cobra

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  • Nov 24, 2005
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    Re: .308 AW case length to lands and Grooves

    Case - is a piece of brass, no powder no bullet

    Cartridge - Loaded round
     

    Graham

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    Oct 30, 2007
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    Re: .308 AW case length to lands and Grooves

    With VLD's you'll need to play with seating depth, but like everyone is saying, with 175SMK's just run them at 2.8 or 2.810 - they like to jump and they jump just fine in an AW chamber.

    If you want VLD's to touch at the origve, though, you'll probably need to go 2.890+, so first make sure you have room in the magazine.

    I load VLDs in my AE to 2.925 OAL, and they're not at the lands yet.
     

    427Cobra

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  • Nov 24, 2005
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    Re: .308 AW case length to lands and Grooves

    Start with a clean weapon, make sure the throat is spotless, any carbon/gunpowder residue will skew the reading, the only other tip I can give after a clean bore is push the bullet in exactly the same every time, or insert the tool in and let gravity do the work, the readings will be repeatable and keep that bullet you used with the tool, I like to call them manic bullets.
     

    Bob 964

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    Re: .308 AW case length to lands and Grooves

    Thanks 427Cobra. That's an important distinction, one that was obviously lost on me. I will choose my terms more carefully from now on.
    Bob
     

    plh

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    Re: .308 AW case length to lands and Grooves

    <span style="text-decoration: underline">Extra</span> emphasis on the 'spotless throat' part.
     

    rickp

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    Re: .308 AW case length to lands and Grooves

    After some information from another member I reused the Hornady lock and load OAL gauge and I got a measurement of 2.870 to meplat and about 2.147 to the ogive, so I guess I have a long freebore / throat.

    When I get to the point of playing with my bullet seating I'll load some rounds just short of that and some at that OAL and see what I get for results.

    I guess what threw me off was knowing that all typical 175gr rounds have a OAL of about 2.8 I didn;t think a chamber/throat would be much longer than that.

    If i had just settled for loading to 2.8 i wouldn't have learned that. At my level of reloading experience I can't afford to not learn something new that can help me in the future. Besides, I'm not one to just settle for things either.

    Thanks
    R.
     

    codlinjr

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    Re: .308 AW case length to lands and Grooves

    rick, another benefit to knowing how to use this method properly, is so that you can measure and track throat erosion... if you are so inclined. when i got my rifle new, i took these measurements, and its interesting to me to get new numbers every so often to see how the length grows after x-number of rounds.
     

    rickp

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    Re: .308 AW case length to lands and Grooves

    true. It's not something I'll get too wrapped around the axle about but again it terms of knowing and being educated about something I'm doing, absolutely. If accuracy becomes an issue then I'm sure I'll address it.

    thanks
    R.
     

    rickp

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    Re: .308 AW case length to lands and Grooves

    Gunner0812,
    for some reason I can't pull up your post on this site, so I'll paste from the email notification I got with it.

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gunner0812</div><div class="ubbcode-body">my 2-cents, based on my own mistakes... just make sure you keep VERY accurate and detailed notes, and save them. when i was working up loads i remember a couple times when there was data i didn't annotate and remember thinking more than once "damn, i wish i would have written that down". similiar to that, i would also caution about throwing in too many different variables such as different powder chages and different OALs. you might find yourself with too much data and actaully end up getting "lost" in all the numbers and end up not really knowing what variable made the difference good or bad.

    "lastly, something to consider about doing this test at 400+ yards... the farther out you go, the more you introduce external factors that are not related to your actual loading variable. for instance, you shoot your 42 gr 5-shot group with no wind and it turns out pretty good. then you shoot the 44 gr 5-shot group with a little stronger wind and the group opens up a bit, you are gonna be wondering if its because of the wind or because of the powder charge. I prefer to do my testing at 200 yards, but YMMV."</div></div>


    I agree with you. The reason I was planning on shooting at either 400 or 500y is because that's the distance I keep reading about. I read the further out you go the better data you get.

    Now that I think about it, I wonder if that distance is more for BR shooters. The one's I've seen lock down their rifles on a very solid support device and I think that removes some the shooter error variables. What do you guys think?

    R
     

    codlinjr

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    Nov 5, 2005
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    Re: .308 AW case length to lands and Grooves

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rickp</div><div class="ubbcode-body">Gunner0812,
    for some reason I can't pull up your post on this site, so I'll paste from the email notification I got with it.

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gunner0812</div><div class="ubbcode-body">my 2-cents, based on my own mistakes... just make sure you keep VERY accurate and detailed notes, and save them. when i was working up loads i remember a couple times when there was data i didn't annotate and remember thinking more than once "damn, i wish i would have written that down". similiar to that, i would also caution about throwing in too many different variables such as different powder chages and different OALs. you might find yourself with too much data and actaully end up getting "lost" in all the numbers and end up not really knowing what variable made the difference good or bad.

    "lastly, something to consider about doing this test at 400+ yards... the farther out you go, the more you introduce external factors that are not related to your actual loading variable. for instance, you shoot your 42 gr 5-shot group with no wind and it turns out pretty good. then you shoot the 44 gr 5-shot group with a little stronger wind and the group opens up a bit, you are gonna be wondering if its because of the wind or because of the powder charge. I prefer to do my testing at 200 yards, but YMMV."</div></div>


    I agree with you. The reason I was planning on shooting at either 400 or 500y is because that's the distance I keep reading about. I read the further out you go the better data you get.

    Now that I think about it, I wonder if that distance is more for BR shooters. The one's I've seen lock down their rifles on a very solid support device and I think that removes some the shooter error variables. What do you guys think?

    R
    </div></div>

    well I actually wrote that before I had a complete understanding of what exactly the "ladder test" was. after reading some detailed info about it, i went back and deleted my comment because it didn't really apply to the actual test you had inquired about. from what I found, it does seem that the farther out you can do that specific test at the more accurate results you will get. and since this test does not really account much for horizontal dispersion, my comment about the wind factor didn't fit either.

    if there is anything I can stress, based on my personal experience, is do like you mentioned and try not to get too wrapped around the axle on all the tidious details of relaoding for accuracy. at one point i started getting so deep into the weeds and it made my head spin. i finally decided to focus on the things i could control without too much time/tools/effort, yet still seemed to give me acceptable accuracy. there is definately a difference in relaoding for bench rest style shooting, and reloading for PRACTICAL precision shooting.
     

    glocksig40

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    Re: .308 AW case length to lands and Grooves

    I use the hornady lock and load OAL tool. I also use the clamp on tool to measure from the ogive. Bullets out of the box will vary =/- .005 or more so using the OAL leaves a variable of .010 possible. As 427Cobra said, clean it good. Use the lock and load tool and measure 3-4 times. Use the Ogive to measure from. I always save the bullet as my "magic" bullet too. I take a new piece of brass and run it thru the sizing die. Then open up the seating die until I know its going to seat the bullet too long. Seat a bullet from the box and measure to the ogive. Keep adjusting the die until I get the seating die where it will seat the bullet at the measurement I want. Now I have a case with the specific bullet seated to the correct length. I use different bullets in the same die so I make the same set up with different bullets so i can reset my seating die easily by picking the particular dummy round and using it to adjust the seater. Once the dummy round is done, I will put it in the rifle to see that it chambers correctly and will fit the magazine properly.
    On the .223 bolt gun, I can chamber and magazine feed the 75 grain Amax but not in the AR .223 because of magazine length.
    Once im happy with the load developement and the length is working like I want it, I will take my air pencil and scribe the length and bullet info on the case so if I drop it and screw it up, its easy to redo.
    Many different ways will work. Good luck

    SP