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What's the better sizing for accuracy..???
cliffgriffin
Member Posts: 8 ✭✭
I am new to reloading and have recently purchased the RCBS Rock Chucker Supreme Kit. My question is this: are rounds made close to the maximum overall length more accurate than rounds made nearer the min. OAL. Again, I'm relatively new to relaoding and have not been able to find information in this area. My rifle data is as follows:
Model: Remington M700SS 5R Milspec
Barrel Length: 24 Inches
Caliber: .308 Winchester
Weight: 9 Pounds
Twist Rate: 11.25
Capacity: 4
Any help in the right direction would be greatly appreciated..
Thanx in advance, Cliff G
Model: Remington M700SS 5R Milspec
Barrel Length: 24 Inches
Caliber: .308 Winchester
Weight: 9 Pounds
Twist Rate: 11.25
Capacity: 4
Any help in the right direction would be greatly appreciated..
Thanx in advance, Cliff G
Comments
Always? no.
I always start load development with MAX OAL. Then work to max length will fit in magazine and bolt close.
Just remember when changing OAL many dynamics change, just a few are:
1. Powder compression.
2. empty volume in the case
3. Contact (pushing on the rifling of the bore)
4. Neck tension on the bullet
In my view the 308 will perform better at or above MAX OAL and with near max Powder charges.
Your rifle was designed with a specific purpose in mind. 168-175gr HPBT pushed at the highest velocity the 308 can go. Why? Military stuff is cool.
Good luck and be safe with your first reloading attempts.
Your question is hard to answer because every rifle is different. your first decision is if you are going to single load or use the magazine. If you are going to magazine feed, then the max is the max for feeding purposes.
However; with all that said; Determining the location of YOUR rifling is important. If you take a bullet, remove the bolt and drop it into the chamber so it is sitting in the barrel, hold it there with a dowel rod and sit the rifle in a cradle. Next; take a cleaning rod with a junk plastic jag and push it into the bore until it just touches the tip of the bullet.CAREFULLY mark the cleaning rod with a sharp knife, just a light scratch is all that is needed. Now, remove the bullet and reinstall the bolt. Push the cleaning rod all the way in until it touches the bolt face. Mark the rod again, being careful to not harm the muzzle. Using your dial calipers, measure the distance between the marks. That is the OAL to YOUR rifles Lands!
Some rifles love a .0020 jump to the rifling. Some like it Jammed into the rifling by .0020. It will take experimentation to find your sweet spot.
The .308 is a very well researched round. Do some searches on the web for some favorite loads using match grade bullets and work from there. It is always best to back off load recommendations to determine if the load is safe in your rifle. Once you get ROUND groups, with no fliers you can adjust charge weights and OAL to gain the ultimate accuracy.
Then back the MAX by .002" (some say .001")to get OAL. This round should only be used for that rifle. Although I mainly reload for pistol and shotgun, I have found this method to improve accuracy on my rifles.
Hopefully more of the "rifle guys" on this forum can give you better instructions. The main thing is to realize that, as reloaders, we can customize our ammo to an exact requirement or gun, so do a little up front work and it will pay off big.
Didn't mean to be redundant to BPOST, I was writing and didn't see his reply above before I posted mine.
I am new to reloading
THAT is the important bit of information.
As your probably going to be using Sierra (Matchkings), or possibly Nosler (Balistic Tips) bullets (both are noted for their accuracy BTW), get the manual put out by the maker of the bullet you decide on.
Use the powder they suggest as being "most accurate" AND the OAL that they tested that bullet at. Start at the minimum charge they recogmend, and work up in (approx) .5gr increments towards the maximum charge they list, watching both your group sizes and obvious pressure issues.
AFTER you have a thousand rounds or so under your belt, THAN start playing with the "advanced" stuff. IOW you gotta learn to walk, before you can run with the big dogs.
As you may have noticed a couple recurring themes here: your rounds are tailored to your rifle. So that means is how do the rounds work in your rifle. SAAMI spec OAL is a lot less important than SAAMI spec pressure. If you don't watch what you do too long of a cartridge, or too short can cause pressure problems. The other main issue of SAAMI spec OAL is so it fits a standard magazine length. That doesn't mean you aren't going to find the odd rifle with a magazine that is a little short of SAAMI spec. You can load the bullets out into the lands if you want, as long as you understand what happens when you do. You most likely won't ever get to the max published load putting bullets into the lands before showing pressure signs. I usually start a grain under minimum when doing this. I usually end up at max pressure about 1.5 grs. under published load data.
The reason you push the bullet into the lands is for increased accuracy. Long bullets like VLD's that is almost necessary to make them accurate.
As far as pushing the bullets down to the minimum OAL, you need to know if you are compressing the load. In most cases it's not a big issue. But some powders tend to spike pressure when compressed. That is why you work up slowly and carefully. Inspect all cases for any sign of pressure when loading this way. test new lots of powder by working back up to old loads with older lots of powder.
I think it's great that you're learning all you can about the reloading aspects but I think that there is one thing to take care of before departing on your journey through the pursuit of reloading accuracy.
If this came with the HS stock that has the aluminum bedding block, you need to skim bed the action so it is stress-free and will be be repeatably consistent. The action screws should be torque-set at 65 inch pounds and that's it.
Best.
meeting with my gunsmith this week to discuss "tweeks" that the gun may need. he did mention the 65# torque settings. i'll bring up the bedding & try to keep the mouth shut and take in what he has to say. thanks for the advice.
CG [8D]