AR-10 and Cast

[Winelover]

The last couple of Springs, I've been working with a Armalite AR-10 Carbine and cast. I started with NOE's 200 grain 311365 SP, one of the few bullets that would feed with 100% reliability. I air cool my alloy, size and check on a Star then heat treat before lubing with Carnuba Red. BHN @ 18, after HT-ing. I gave up on this bullet, when the best 10 shot/100 yard groups were 2 MOA. I tried it with a multitude of powders ranging from IMR-4198 (fast on burn chart) to AA-4350 (slowest). Military brass (LC-05), CCI 250 magnum primers and 36.5 grains of AA-4350, yielded the 2 MOA groups. Tighter groups can be gotten, but at the cost of cycling the auto-loader.

Next bullet I played with is Miha's 180 Silhouette bullet. This is a much friendlier design when it comes to accuracy. Shot many 10 shot/100 yard, 2 MOA groups with powders ranging from N-135 to AA-4350, including AA-4064, N-140, Varget, IMR-4320, and N-150. Again, heat treated alloy, military brass, CCI 200's (except for AA-4350). Many of these powders gave 1 MOA groups for the first 5 or so shots, but subsequent shots opened them up to 2 MOA.

This year I'm focusing on NOE's 160 grain 311414 SP, basically a shorter version of the 311365 SP.....so much so that I use the same seating die depth setting for both bullets. My COAL (o-give) is 2.254 inches.
So far, H-4895 and N-135 have yielded 10 shots in 2 inches. Still have to test AA-2495, AA-4064, Varget, IMR-4320 and N-150...trying to find that illusive 1 MOA, 10 shot group @100 yards.



These are some of the 414's that I just finished up lubing for the upcoming testing. Sized on a Star, averaging .3118 diameter. Using Gator gas checks.

I use RCBS X- sizing dies, including their cast neck expander and seater. AR taper crimp in separate step .

 

[Ian]

John, that's pretty good for what you're working with. Loads that will cycle the action tend to push the bullet beyond a ten-twist barrel's velocity "comfort zone". Your alloy sounds like it should be about perfect for what you're doing, but I'm betting the challenge you're up against is the elusive straight start into the rifling.

Something that helped me a lot was the combination of ball powder (H414, Ball C2, etc.) and granulated poly shotshell buffer. H-414 around 41 grains and buffer at very slight compression (sift in the case though a powder funnel to the level that it is compressed by about 3/32" when seating the bullet) helps push the bullet into the throat straight and prevents gas loss between bullet body and case neck in the sloppy .308 chamber. The buffer also boosts the powder burn speed a good bit and promotes consistent ignition and initial burn by putting a little extra load on the powder. After you get your other knee rebuilt I think that might be worth a try.

Also, see if you can beg some LBT Blue from Rick and give it a go, I think it will do better for you than Carnauba Red after the first five shots. With buffer, I've found a very soft lube works the best.

 

[Winelover]

Getting LBT Blue from Rick isn't a problem. I thought Carnuba Red was softer. As far as buffers go.....not going to happen....same as duplex or triplex loads. Believe it or not......I have done a lot of testing with cast and AA 2520, a ball/spherical powder at way less than 85% capacity and got very good consistent groups..... but I was warned off by Outpost. J-words in either 168HPBT or 150 SP and stout loads of AA 2520, does one hole groups at 100 yards....off a tripod. There is a cast/ powder combination out there that will come close, and I intend to find it, without jumping through hoops.

 

[Ian]

I thought the same thing at one time. If you can figure out how to get the bullet started straight enough to handle 2200 fps and still group 1 MOA without jumping through some hoops I'm all ears. There's another way you can do it, but it involves special brass with very thick necks. Or you could throat the rifle to .314" and size your bullets to about .313".

Rick must have the hard LBT lube. About 10% Vaseline will soften it up nicely, but if you aren't using buffer, Carnauba Red is probably just fine IF it is departing the bullet at the muzzle. If not, you may need a softer/less tacky lube.

 

[Rick]

I happen to know for a fact that Rick has never tried LBT hard lube. I also know that Rick doesn't like hard lubes.

 

[Missionary]

Greetings
I am going to follow along on this. Just maybe one day an AR 10 will com along and any head start will be welcome
Mike in Peru

 

[Winelover]

I happen to know for a fact that Rick has never tried LBT hard lube. I also know that Rick doesn't like hard lubes.

Everything is relative, however........you gave me a bunch of different styles 30 cal bullets, lubed with LBT Blue and they were less tacky than Carnuba Red. There might even be a few left, lying around. Now, if I could only remember where I put them.

 

[Winelover]

Found them and the lube is soft and less tacky than Carnuba Red. IMO

 

[Ian]

I happen to know for a fact that Rick has never tried LBT hard lube. I also know that Rick doesn't like hard lubes.

Stands to reason, that Rick guy knows what the good stuff is. Carnauba Red is good lube but has some quirks. It needs warm weather and full-tilt loads that burn very clean or else it can start accumulating gummy residue in the barrel. In one gun it will work great and the next not so much, too many variables to predict. Softer lubes that still contain some sort of soap to control oil release and viscosity fade at the far end of a rifle barrel have served me the best overall.

 

[Winelover]

Couple years ago, when I started this project.....Rick was gracious enough to donate about dozen different styles of cast bullets for dummy rounds. Only two styles would feed, manually in my Armalite, the RCBS 165 and 200 grain SIL's . I did test them with promising results but I used up that limited supply before trying all the powders in mine and also Rick's stashes. Decided not to purchase either mold because I really didn't want to deal with two cavity moulds and wasn't sure the current runs would cast .311 with my alloy. Much more economical, nowadays, to purchase custom moulds from NOE, Accurate or Miha and drop larger diameter bullets. Easier to size down than up!

 

[Winelover]

Carnauba Red is good lube but has some quirks. It needs warm weather and full-tilt loads that burn very clean or else it can start accumulating gummy residue in the barrel. In one gun it will work great and the next not so much, too many variables to predict.

Not in my case.......barrel is the cleanest part of gun and I have tested in all kinds of temperatures in this fickled State. Now the chamber, bolt carrier and magazine is a different story. Mostly due to unburned powder and or sooty powders. AA-4350, the slowest I've tried is very dirty.....and I use magnum primers with it. Seems like the slower powders tend to be dirtier.

 

[Ian]

I'm fiddling with three different designs for Tom to cut when I get them all worked out, but some of my NFA stamps have come through and I've been tinkering with that stuff at the moment because it greatly increases the amount I can shoot at home and not PO my neighbors. I have a lot of shooting to get out of my system! Now I need to build better bullet traps at 50 yards and maybe a woods-walking course....

Anyway, one of the designs I'm planning is a modification of the 31-157G. I want to keep the nose just as it is but add a shallow crimp groove just ahead of the current lube groove and make two, small radius lube grooves and put a normal, .284" straight lube shank on it. To work in the autos, the nose will need to be pointed but I have a tool for that. Should be about 180 grains before pointing. When I get back to the HV challenge I'm going to explore this more, probably work with two .308s, one a bolt rifle and the other my M1A, just to keep it interesting.

You say your barrel is clean, but why does the accuracy deteriorate with some loads after five shots? Have you friction-tested with a dry patch after each shot to see if there's a change? I'll bet there is. The LBT Blue will improve "consistency of residuals encountered" in your bore, just something to think about.

Dirty powder never seemed to bother anything with my guns, it's just a bother when you get black oily mess all over everything. It's ten times worse with a suppressor when shooting subsonic loads that require powders be run well below their ideal burn pressure.

 

[Winelover]

Anyway, one of the designs I'm planning is a modification of the 31-157G. I want to keep the nose just as it is but add a shallow crimp groove just ahead of the current lube groove and make two, small radius lube grooves and put a normal, .284" straight lube shank on it. To work in the autos, the nose will need to be pointed but I have a tool for that. Should be about 180 grains before pointing. When I get back to the HV challenge I'm going to explore this more, probably work with two .308s, one a bolt rifle and the other my M1A, just to keep it interesting.

You say your barrel is clean, but why does the accuracy deteriorate with some loads after five shots?

If I knew the quest would be over. I don't weigh my bullets, I cull, visually. When I shoot 10 shot groups, there is no waiting for barrel to cool. I have observed a group opening up with as little as 1/2 grain of powder change. I don't mean gradually......2 MOA to a group that doesn't deserve measuring.

Tom doesn't do pointy or small meplats so he has nothing that interests me. At least where bullets for the AR, are concerned. I don't think the M1A is as picky with bullet design......now if and when Rick decides to work with his.......I could be more definitive.

 

[Rick]

I don't think the M1A is as picky with bullet design

I don't think it is either. I haven't tested nearly as many bullets as John but haven't had near the problems feeding from the magazine in the M1A that John has had in the AR 10.

now if and when Rick decides to work with his.......I could be more definitive.

Soon lover of the grape . . . Soon!

 

[Pistolero]

Have you ever tried using std primers instead of Mag primers in those loads to see the effect
on accy?

Bill

 

[Winelover]

Started with standard primers, with AA-4350 and switched to magnums, per Rick's suggestion. There was some measurable accuracy gains. Using standard LR in everything else, at this time. There are a lot of variables that can be addressed.

 

[freebullet]

I would suggest single loading your best performing rounds.

Ar's tend to be unforgiving to lead upon entry and I'd try to rule out entrance damage when I'm as close as you are now. It's like shoving a feather through a blender and expecting the down to be undamaged. These guns in particular(308) are razor claw bolt having lead smashers. They mangle Jax well enough sometimes. It'd be worth a try.

 

[Winelover]

I would suggest single loading your best performing rounds.

That's like changing to a bullet design, that won't feed or a powder level that won't cycle the action. Easier to attain good groups, that way......or I could shoot five shots and wait till barrel is cool, to shoot the other five, in a 10 shot group. Not interested in a single shot auto-loader.

 

[Rick]

I don't think the suggestion to single load the test rounds was a suggestion to shoot it that way. It was meant as a testing tool to check accuracy and possibly eliminate one cause of the groups and what the accuracy really is. Once you find the bullet that will cycle single load some and see where the accuracy is.

 

[Winelover]

Moot point.... cause if cycling though the action, affects accuracy...what's the cure? Already heat treating the bullets.