few more .308 questions


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juk
April 30, 2009, 12:11 AM
I finally got my reloading set up going and ran a test batch. I have not had the time to shoot them yet, but had a few questions. First, the specs.

Mixture of black hills match and hornady brass. All were within SAAMI specs.
Sierra 165 gameking soft points
CCI LR primers
IMR 4064

Per the sierra manual, I made my loads start a tad above min and a tad less than max.

I made 5 each of 38, 39, 40, 41, 42, and 43 grains of the 4064 topped with the gamekings at COAL of 2.75"

Now, I have still been reading up on reloading and found that many people start loading the cartridges long. Sierra says don't go over 2.75" COAL for my bullets but I have read that people load them out to (and a few past) 2.85". I know that they are trying to get the bullet closer to the lands, but how does this affect pressure? I know for sure that a friend loads his 308s with IMR 4064 below 150 NBTs out to 2.80". I'm just curious. I doubt I will start messing with bullet depth anytime soon as I am more concerned with just getting safe experience and acceptable accuracy. My gun is a hunting rifle, not a long range boomer, so I doubt I will ever need to stray from the books anyway.

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JDGray
April 30, 2009, 05:30 AM
Federal loads their 168gr SMK, in the Gold Metal Match ammo, out to 2.805", and is only .008" off the lands in my Savage 10 FP. This load is only 2600fps, so its on the mild side, but shoots very well. For a hunting load, I would keep to the book, the longer cartridges may not fit your magazine.

41 Mag
April 30, 2009, 06:00 AM
Per the sierra manual, I made my loads start a tad above min and a tad less than max.

I made 5 each of 38, 39, 40, 41, 42, and 43 grains of the 4064 topped with the gamekings at COAL of 2.75"

Now, I have still been reading up on reloading and found that many people start loading the cartridges long. Sierra says don't go over 2.75" COAL for my bullets but I have read that people load them out to (and a few past) 2.85". I know that they are trying to get the bullet closer to the lands, but how does this affect pressure? I know for sure that a friend loads his 308s with IMR 4064 below 150 NBTs out to 2.80". I'm just curious. I doubt I will start messing with bullet depth anytime soon as I am more concerned with just getting safe experience and acceptable accuracy. My gun is a hunting rifle, not a long range boomer, so I doubt I will ever need to stray from the books anyway.

The OAL listed in most manuals is more or less the standard spec length for ammo which will feed and chamber in just about any firearm and magazine made for this caliber. That said, there are differing lengths on magazines and chamber throats from different manufacturer's that will be longer and allow a slightly longer bullet to function fine. Also the profile of one bullet being different from another will also influence the actual OAL of the load.

The goal in seating the bullet closer to the lands is to gain in accuracy, by reducing the jump the bullet makes from the case to the leade. This however is not always the only accurate load one can get from a set of components. You can take two cases, using the exact same components, work one up with the bullet touching or just at the lands and get one hole groups, then take the other and work the load up with the bullet sometimes .100" back off the lands and get the same degree of accuracy. Depending on the powder and charge weight the shorter load will generally have a bit less pressure as well, due to the bullet not getting jammed up before the pressure starts to move it along.

Case in point, My friends .300 RUM shoots the 185gr Berger into 1" or less groups at 300yds with the bullets seated to the lands. The issue is at this length they will not fit the magazine so he can only shoot single shot. Just out of curiosity, he decided to start seating them in to see how they would shoot at magazine length. After getting progressively spread out groups as he seated deeper, the spreading reversed and the groups tightened back up actually to better than he had to begin with. The final load has them seated some .128" off the lands, and just slightly under what the manual suggest as an OAL.

In a hunting rifle I generally use the mag length as my guide. I then start out my development working up in .5 gr increments shooting 3 shot groups until I see something promising or until I reach the velocity or pressure issues which tell me that the particular powder isn't what I want to use. There are several handles by which this process is called, however this was how I was taught to load long before the internet or fancy handles were assigned to the process. Here is a pic of a load I worked up a few weeks back for a .243, nothing was changed on the load except the powder charge.
http://thumb2.webshots.net/t/62/662/8/59/38/2903859380043012562MDPpbm_th.jpg (http://outdoors.webshots.com/photo/2903859380043012562MDPpbm)

The top row dots three and four, were the final two changes to the powder charge. I only used two shots during this test as I only had a limited supply of the bullets with me at the time. The bottom left bigger stickers, were both 5 shots groups, with the two flyers in each resulting from the barrel heating up and contacting the stock. However you can see that the load shoots great, and after the stock is relieved a bit should work fine from now on out.

In your case your on the right track, however sometimes when you get to a certain weight charge the groups will be say 1.5", you really want to use that particular powder but this is the smallest groups your getting. So at this point you can start changing the depth a little to see if the groups will respond. If you start at your max length for your magazine then seat the bullet deeper in say .005" increments, you might only need to make one or two changes to close up the group. As long as your not overly compressing a charge, or at the max loads listed, you should have no issues going up to around .030" deeper with most bullets, especially the mid weight ones. You might run into issues with longer ones, and with shorter ones when seated out to your max mag length. The short ones might end up being up to .125" or more off your actual max length simply due to the profile.

I will take 1.5" groups and fully functioning ammo any day in a hunting rifle. When I hit the woods I generally like to have at least a full magazine and at least that many more on hand in a pocket. In our area a pack of feral hogs can make for a quick run through of ammo and on more than one occasion I have dumped 5 hogs in 5 shots and had to watch as the rest of the pack simply ran away.

Keep up the diligence in your techniques, but don't be afraid to play with the depth once you get a decent load worked up. It might supprise you at how little a bit of change to the seating depth can make at the target.

USSR
April 30, 2009, 08:26 AM
juk,

Cartridge OAL is more a function of the individual rifle they are to be used in, and the OAL listed in reloading manuals is simply the length that they used. As long as the cartridge fits your magazine (assuming you don't want to single load), the bullet does not contact the leade, and you have atleast 1 caliber of the bullet body in the neck, cartridge OAL is irrelevant. With the brass you are using, your loads are extremely light, and you will no doubt find better accuracy by raising your charge weight. Black Hills brass is manufactured by Winchester (light weight w/high case capacity), and Hornady also is light with a large case capacity. I would suggest loading your bullet out a bit more and bumping up your charge weight in 0.5gr increments to 44.0gr. Hope that helps.

Don

juk
April 30, 2009, 01:51 PM
Thanks for the info guys. I much appreciate it and have taken many notes.

lgbloader
May 1, 2009, 01:00 AM
This is like the fun part of load development. When I started messing around with the COL, a new world opened up. Make sure you keep good records.

LGB

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