Reloading for 308 semi

[M1911a1g17]

Hello all. I want to get into reloading 308 for a semi auto. Specifically a LR-308 platform rifle. I have some varget and imr-4064 on hand. I was planning on using sierra 168 gr match king hpbt. With factory ammo my rifle seems to like them. I was wondering if anyone had any tips? With the data I am seeing they have 308 win and 308 win service rifle. I have heard that is more for M14 platforms. Just curious what you guys have to say. Thank you.

 

[jpm]

The Federal Gold Medal Match loading is 168gr SMK bullet that you have and 42.8gr of I-4064. It would also use Federal brass and a Federal GMM primer but should be quite good even with regular primers.

 

[M1911a1g17]

@jpm they use 4064 for that cartridge? I have only been able to get my hands on S&B primers for large rifle.

 

[jpm]

@jpm they use 4064 for that cartridge? I have only been able to get my hands on S&B primers for large rifle.

I don't know if that's the actual powder they use in those cartridges, but that's the equivalent loading with commercial powder.

Those primers are good, I use them.

 

[M1911a1g17]

@jpm oh ok. Gives similar results? That’s good to know. Thank you! Do you have a preferred load for 308?

 

[daekken]

Think of 308 Service Rifle as 7.62 NATO. So, M14/M1A, FAL, etc.

When I load for my FALs I use 308 Service Rifle data and not 308 Winchester data.

Unlike .223 and 5.56, 7.62 NATO is a lower pressure round than commercial 308 Winchester.

 

[M1911a1g17]

@daekken ah ok. So stuff marked for 7.62 nato more so?

 

[daekken]

@daekken ah ok. So stuff marked for 7.62 nato more so?

Basically if you're loading for a M1A, FAL, .308 Garand, etc.

If you're loading for a .308 Winchester marked recently produced gun, .308 data should be fine.

 

[M1911a1g17]

@daekken ok that is good to know. Thank you.

 

[jpm]

@daekken ah ok. So stuff marked for 7.62 nato more so?

If the gun/barrel is marked .308 Win, you can use .308 win or 7.62x51 ammo and brass. If its a 7.62x51 marked gun/barrel, then you should NOT use .308 Win ammo/brass in it because the headspace is longer than .308 and the pressure in .308 is higher which could lead to a case head blowout.

 

[paul73]

which could lead to a case head blowout

it is an extremely hypothetical. a practical probability for such thing to happen is minimal, if ever even possible.
but, if one would indeed take an extremely hot custom 190gr load made for a 16" hunting .308 ar10 to spit it out at 2700fps, and then places that into a 24" 7.62 gun, well. who knows.
but to blow up a stock 7.62 gun with a typical commercial 308 round - it is not probable at all.

 

[M1911a1g17]

@jpm I have read a bit about that. That has to do with the case itself right? 7.62 is slightly thing and longer. And headspaces different? Mine is marked 308 win.

@paul73 oh really? So it more so comes into play with spicy rounds?

 

[jpm]

@jpm I have read a bit about that. That has to do with the case itself right? 7.62 is slightly thing and longer. And headspaces different? Mine is marked 308 win.

No, 7.62 is actually slightly thicker with a longer headspace. 308 is thinner. You can use either in yours without concern.

 

[PatMcD]

The LR-308 will take anything you care to feed it.
Maybe go easy on the 200-220's, but other than that.....

 

[paul73]

@jpm I have read a bit about that. That has to do with the case itself right? 7.62 is slightly thing and longer. And headspaces different? Mine is marked 308 win.

@paul73 oh really? So it more so comes into play with spicy rounds?

Blowing up a 7.62 gun is possible but not very probable.
You really have to do a major powder mismatch error to do it. With sticking to varget, even with a full case of it - it is unlikely to exceed the max chamber limit.

I do not say it is a thing one can feel safe experimenting with, I mean finding that threshold of over than max super hot loads. You need to respect amount of pressure it makes.

 

[M1911a1g17]

@jpm ah ok. Just close enough though?
@PatMcD thats very good to know! Want to experiment with different projectiles. Just curious. Why go easy with 200-220’s?
@paul73 how about with a 308 gun? Is the process of loading 7.62 nato the same as 308 win? What data would you use?

 

[PatMcD]

@PatMcD thats very good to know! Want to experiment with different projectiles. Just curious. Why go easy on the 200-220's

Those bullets are primarily used in bolt guns for long range targets at as high a velocity as the case will take. I've just never heard of them being used in a 308 AR, so that's why I said go easy. I could very well be wrong. I'd do more research before I used them.

 

[M1911a1g17]

@PatMcD ah I see what you I mean. Kinda like in 556? Can’t load certain for semis?

 

[paul73]

@jpm ah ok. Just close enough though?
@PatMcD thats very good to know! Want to experiment with different projectiles. Just curious. Why go easy with 200-220’s?
@paul73 how about with a 308 gun? Is the process of loading 7.62 nato the same as 308 win? What data would you use?

You use common sense.
Gas guns can be loaded somewhat hotter than longer bolt guns.
Like this loading data below - it is using 26” savage rifle.
So, I load for my 308 20” ar10 with 45.5gr varget and it is still under 2700fps. And no pressure signs.

 

[M1911a1g17]

@paul73 ok I get you what you mean. Use standard procedure still. I have a ton of 7.62 nato brass. What would be the process of losing that though? Would I use 308 data or 308 service rifle data?

 

[paul73]

@paul73 ok I get you what you mean. Use standard procedure still. I have a ton of 7.62 nato brass. What would be the process of losing that though? Would I use 308 data or 308 service rifle data?

i presume you load it for the 308 AR10 build. what bullets do you use? i attached here sierra file.
see in there what are the max speeds for bullets of specific weights. use a chrono to control your loads, and watch out for pressure signs.

 

[M1911a1g17]

@paul73 yes and 168gr sierra match king for now. I am thinking of trying some other brands and weights and whatnot. Just for kicks. Thank you. I appreciate it.

 

[jpm]

@M1911a1g17 do you have a reloading manual? If not you should get one and read through it before you start loading anything.

 

[M1911a1g17]

@jpm yes I do. I just like to try different weight projectiles and types and brands to see what my gun likes best.

 

[paul73]

@jpm yes I do. I just like to try different weight projectiles and types and brands to see what my gun likes best.

look at the sheet i sent you and other reloading data points. the bullet you stated is optimal to be loaded for in between of 2500 and 2600fps.
make sure you have a chronometer for all the tests, start with a grain under the max load published in the sheet i sent, as it is on a very low side for an AR10 - i presume you do it for a gas gun.
then load groups of 5 in .5gr increments, shoot it monitoring speed and overpressure signs.

if your gun is not completely broken in yet - under a 100 shots - then your speeds will be lower. i found for my gun the clear overpressure signs began at the 46gr varget for the 168gr bullet. the posted max load in there for that bullet was 43.5gr.

it is relevant for my gun, IT DOES NOT mean it will/may be relevant for yours. but it gives an idea of how a 20" AR10 differs from pressure build up in the 26" bolt savage.
with a a 7.62 barrel you must go gentler than with a 308, and listen to the bolt, check brass after each shot and, express respect to the weapon you are trying to force to the limit.
also, again, it is not the goal to load to the max. the goal is to find a node that works best accuracy wise with the acceptable speed out of the muzzle, for the given application.

 

[mac1911]

308/762 NATO
1. First wrap your head around powder burn rates and such
A. Case differences 7.62 nato brass is or was thicker and IIRC has/had thicker webs so powder capacity can be a issue.

2. Now loads with in “restrictions” of the platform.
Semi vs bolt, twist , chamber, throat specs ectect.

Can you damage a gas gun in “7.62 NATO” with a heavy slow powder load. Sure might “over gas” the system causing un wanted stress on the parts associated with a gas gun.

Now look up 308 vs 762 NATO reamers.
What your going to find is NATO is just a bit sloppy to account for NATO ammo that can/will come from anywhere in the NATO world

 

[mac1911]

look at the sheet i sent you and other reloading data points. the bullet you stated is optimal to be loaded for in between of 2500 and 2600fps.
make sure you have a chronometer for all the tests, start with a grain under the max load published in the sheet i sent, as it is on a very low side for an AR10 - i presume you do it for a gas gun.
then load groups of 5 in .5gr increments, shoot it monitoring speed and overpressure signs.

if your gun is not completely broken in yet - under a 100 shots - then your speeds will be lower. i found for my gun the clear overpressure signs began at the 46gr varget for the 168gr bullet. the posted max load in there for that bullet was 43.5gr.

it is relevant for my gun, IT DOES NOT mean it will/may be relevant for yours. but it gives an idea of how a 20" AR10 differs from pressure build up in the 26" bolt savage.
with a a 7.62 barrel you must go gentler than with a 308, and listen to the bolt, check brass after each shot and, express respect to the weapon you are trying to force to the limit.
also, again, it is not the goal to load to the max. the goal is to find a node that works best accuracy wise with the acceptable speed out of the muzzle, for the given application.

Exactly my friend was loading hot loads on his AR10 I swear you could hear the lugs screaming as they where trying to force open!
He cracked a few lugs before I told him to use a different powder and charge weight.

 

[M1911a1g17]

@paul73 will do. I always work up my loads. Sorry bad at messaging haha. I realize they don’t always make sense.
Ok that is good to know. That’s where I was getting lost a bit on the 308 vs x51.

@mac1911 thank you. That is very good to know. I was unsure of how the process works. I was given a ton of surplus x51 brass. ~1000. Will do. Wow that is nuts. That is because the difference in cases?

 

[mac1911]

@paul73 will do. I always work up my loads. Sorry bad at messaging haha. I realize they don’t always make sense.
Ok that is good to know. That’s where I was getting lost a bit on the 308 vs x51.

@mac1911 thank you. That is very good to know. I was unsure of how the process works. I was given a ton of surplus x51 brass. ~1000. Will do. Wow that is nuts. That is because the difference in cases?

Theres a lot of small diffetences.
I dont know if NATO brass today is still thicker at the web vs “regular” brass these days.


To add to confusion chamber pressure and cartridge load pressure testing is different methods and equipment
SAMMI vs CIP vs NATO EPVAT

All vary slightly and there is no Direct Conversion.

Stay with in published data and always start shy of max and look for any pressure signs.

In a nut shell loading with in safety margins of powder /bullet data and your chamber is cut correctly and tour not cramming bullet into lands you will be ok.

Load for the task/node/end result

I shoot at 200 yards alot so my loads are based on that and im hardly ever even close to the upper range of powder charges

 

[paul73]

@paul73 will do. I always work up my loads. Sorry bad at messaging haha. I realize they don’t always make sense.
Ok that is good to know. That’s where I was getting lost a bit on the 308 vs x51.

@mac1911 thank you. That is very good to know. I was unsure of how the process works. I was given a ton of surplus x51 brass. ~1000. Will do. Wow that is nuts. That is because the difference in cases?

you still did not say what gun you`ve got. is it s 7.62 or 308 barrel? which one? what length gas tube?

now, IF it is a 7.62 barrel - get a bit of a standard 7.62 nato ammo in mid-weight, like this - plus it is on sale now.
run it, considering your gun cycles on it fine. while running it - chrono it and LISTEN to how your bolt behaves. compare the actual measured speed with the expected speed on the box and make a mental note of it.
once you learn how it sounds and feels, it will become quite natural to sense any abnormalities when your hot loads start breaking the gun. you do not need a ton of that ammo and it does not matter much which bullet weight it is.
i have a small stash of 150gr 7.62 nato i always check a gun with to see if it will cycle of not. some 308 in rifle length gas do not.
this 175 i think should cycle any 308 system fine.