loading for a ar10?

[huntxtrm]

Hey guys. I have never loaded for an automatic before. I just acquired my first AR10. I want to develop a load for it. What should I watch out for? Any advice? I plan on starting at the bottom of the load spectrum, as allways, to be safe. But, in the case, I start getting hot? What are some signs to look for, telling me to back off?

 

[huntxtrm]

Oh, and it is a 7.62 x 51(.308)

 

[scrmblr1982cj8]

Have you reloaded before? What brass will you use? What bullets?

It's basically the same as reloading for a bolt action gun. Many people add a crimp to stop bullet migration within the magazine due to the movement of the bolt as the action cycles. I don't crimp, and have never had an issue with the bullet moving deeper into the case. Not to say I shouldn't, but I haven't seen the need yet.

Be careful with your powder load. Watch for flattened primers, head case separation, and split necks.

I've got a chrono, but rarely use it. I'm more interested in grouping than speed and adjust powder charges on groupings rather than fps readings.

 

[rcoody]

you have to full length resize for an autoloader instead of just neck sizing.

the rest is pretty much the same.

 

[huntxtrm]

Yes, I reload primarily for my 300RUM right now. I do reload some for my wifes 30/30. But never for and automatic. As far as brass and bullets, and powders. that's where I'm also looking for direction. I want to shoot out to distance with it. It's going to be primarily a range toy. We have a 1200 yard range, where I shoot. Shooting my 300 out there is quite expensive on ammo and wear and tear. So, I got this as a fun way to keep my skills somewhat sharp. I'm leaning toward around 180gn accubond. I shoot 200gn accubonds out of my 300 and love them. But, then again, I have never loaded for an automatic, so it might not be the best choice?

 

[huntxtrm]

I do crimp my wifes 30/30, because it's tube feed. And, I will full length size. I am also after accuracy, I don't really care about speed either. Speed kills a barrel, from what I have been told anyway. Accuracy is what kill Elk! lol

 

[Bart B]

Full length size your fired cases for best accuracy; that's been proved for decades. It's important that the fired case shoulder be set back about .003" for good functioning in semiautos as well as decent case life; 4 to 5 reloads is about maximum. You'll need a case headspace gauge to measure cases; RCBS Precision Mic or Hornady LNL, for example. Or just use a half inch long nylon bushing with a 3/8ths inch hole in it to put on the case shoulder then measure with calipers.

RCBS or Redding full length bushing dies are good, but use a bushing diameter about .002" smaller than that of a loaded round's neck diameter. Don't crimp case mouths into bullets; a sure cause of accuracy loss. Seat bullets to function well when rounds are used with magazines. For single round loading, seat bullets about .010" short of touching the rifling.

It's almost impossible to tell real pressure levels without a real piezo transducer pressure system, such as those from RSI. Visible signs of primer or case changes are only approximate, but better than nothing. If you stick to near max loading data, you should be fine.

Powder wears out barrels, bullet speed does not. A .308 Win will get 3000 rounds of best accuracy shooting 150-gr. bullets out at 3000 fps from a long barrel with 45 grains of powder. A 30 caliber magnum shooting 200-gr. bullets out at 3000 fps with 65 grains of powder has 1200 rounds of barrel life with equal accuracy. Shooting 140's from a 6.5x.284 out at 3000 fps with 47 grains of powder gets 750 rounds of barrel life with the same best accuracy. All of them having the same peak pressure.

Unless your AR10's bolt face has been squared up properly with the chamber axis, new cases will typically shoot bullets more accurate than reloaded ones. When first fired, case heads tend to flatten against the bolt face; if that face ain't square, the case head's now out of square. Resizing them doesn't square the head back up. They'll slam at different places around the bolt face each time they're fired. That can cause up to 1 MOA accuracy degradation.

I don't know how long your barrel is, so I suggest using bullets in the 175 to 185 range. Sierra or Berger match bullets will shoot most accurate, but only if they're a few ten-thousandths inch bigger in diameter than the barrel's groove diameter. 42 or 43 grains of IMR4064 under either one should do well.

 

[scrmblr1982cj8]

When using commercial brass, I use 42.5g IMR4064 I consistently get 3 shots touching at 100 yards. I reload for hunting and plinking, so that is plenty accurate for me.

I have never attempted a 1,200 yard shot with a .308. From everything that I've read and heard, 1,200 yards is going to be difficult for a .308. I often hear that the 800-1,000 yard distance is the outer edge of effective range for a .308, but that is with a 168g or 175g bullet. You may be able to stretch that out with a heavier bullet. Case capacity for enough powder to get it to 1,200 is an issue. You will most likely have a very compressed load for that distance.

A .30-06 or a 300WM would be a better .30 cal choice for that distance.

 

[barefooter56]

Hey guys. I have never loaded for an automatic before. I just acquired my first AR10. I want to develop a load for it. What should I watch out for? Any advice? I plan on starting at the bottom of the load spectrum, as allways, to be safe. But, in the case, I start getting hot? What are some signs to look for, telling me to back off?

huntxtrm,
Suggest you use the .308 SERVICE RIFLE DATA in the Hornady manual as a guide. Dont use "range" or brass that has been fired in another rifle. Start new. If you want to use Berger bullets stick to the .30 caliber CLASSIC HUNTER or .30 caliber OTM bullets. You will be full length sizing and trimming every time. Also suggest that you get an L.E.Wilson cartridge case gauge in .308 Winchester as a quick check of sized/trimmed rounds. Bullets in the 150- 175 weight range are the most commonly used. Dont expect bolt action rifle accuracy right out of the box. Most military style rifles like this are guaranteed 2 MOA. Anything more is a gift. If you want bolt action rifle accuracy out of this style of rifle. Stand by to spend some $$$. Of course you MAY luck out ant its a tack driver right out of the box. Lets hope so!

 

[engineer40]

Only other thing I will add is to make sure all of your primers are fully seated to avoid having any slam fires.

I've never had it happen to me but that came up a lot when I was researching reloading for semi autos.

 

[HNDLDR]

Go on then, tell us what you bought.

 

[huntxtrm]

Full length size your fired cases for best accuracy; that's been proved for decades. It's important that the fired case shoulder be set back about .003" for good functioning in semiautos as well as decent case life; 4 to 5 reloads is about maximum. You'll need a case headspace gauge to measure cases; RCBS Precision Mic or Hornady LNL, for example. Or just use a half inch long nylon bushing with a 3/8ths inch hole in it to put on the case shoulder then measure with calipers.

RCBS or Redding full length bushing dies are good, but use a bushing diameter about .002" smaller than that of a loaded round's neck diameter. Don't crimp case mouths into bullets; a sure cause of accuracy loss. Seat bullets to function well when rounds are used with magazines. For single round loading, seat bullets about .010" short of touching the rifling.

It's almost impossible to tell real pressure levels without a real piezo transducer pressure system, such as those from RSI. Visible signs of primer or case changes are only approximate, but better than nothing. If you stick to near max loading data, you should be fine.

Powder wears out barrels, bullet speed does not. A .308 Win will get 3000 rounds of best accuracy shooting 150-gr. bullets out at 3000 fps from a long barrel with 45 grains of powder. A 30 caliber magnum shooting 200-gr. bullets out at 3000 fps with 65 grains of powder has 1200 rounds of barrel life with equal accuracy. Shooting 140's from a 6.5x.284 out at 3000 fps with 47 grains of powder gets 750 rounds of barrel life with the same best accuracy. All of them having the same peak pressure.

Unless your AR10's bolt face has been squared up properly with the chamber axis, new cases will typically shoot bullets more accurate than reloaded ones. When first fired, case heads tend to flatten against the bolt face; if that face ain't square, the case head's now out of square. Resizing them doesn't square the head back up. They'll slam at different places around the bolt face each time they're fired. That can cause up to 1 MOA accuracy degradation.

I don't know how long your barrel is, so I suggest using bullets in the 175 to 185 range. Sierra or Berger match bullets will shoot most accurate, but only if they're a few ten-thousandths inch bigger in diameter than the barrel's groove diameter. 42 or 43 grains of IMR4064 under either one should do well.

Now that's some info! Thanks! If the bolt face isn't square, would you be able to tell by looking at a fired round? Shouldn't the case head be out of square? If that's the case? I'm just trying to figure out a way to check it.

My barrel seems to be 18", if you measure from the bolt face, about 20" Not counting the flash hider. It is a heavy barrel. Not a bull barrel.

 

[huntxtrm]

let me phrase that better. My barrel, measures about 20" from the bolt face to muzzle. Not counting the flash suppressor.

 

[huntxtrm]

When using commercial brass, I use 42.5g IMR4064 I consistently get 3 shots touching at 100 yards. I reload for hunting and plinking, so that is plenty accurate for me.

I have never attempted a 1,200 yard shot with a .308. From everything that I've read and heard, 1,200 yards is going to be difficult for a .308. I often hear that the 800-1,000 yard distance is the outer edge of effective range for a .308, but that is with a 168g or 175g bullet. You may be able to stretch that out with a heavier bullet. Case capacity for enough powder to get it to 1,200 is an issue. You will most likely have a very compressed load for that distance.

A .30-06 or a 300WM would be a better .30 cal choice for that distance.

I hear ya. I have a 300 rum I shoot way out there with.. I am not sure how far I will be shooting this AR10? The range is 1200 yards, in 100 yard increments from 300. I'll giver her a go, until she runs out of steam! LOL. It will be fun, that's what maters. I wouldn't ever dream of shooting an animal out that far. Just steel.