My quest for speed and accuracy with powder-coated cast bullets

Ian

Notorious member
I only used the RX7 because it was the only powder that modeled over 2300 fps from the 18" barrel without obnoxious muzzle pressure which would be bad for my suppressor over time. Pressure is in the 45-50KPSI range which is way more than anyone would normally want for a soft cast bullet, but I had hopes the PC and shape of the bullet would allow the bullet to jet up into the bore without much resistance and that would save the base from being squished. It seems to be working. I would prefer something like 4895, 3031, or Varget, but not in a barrel this short where muzzle pressure would run 10-12KPSI easily. Remember, this is a special-needs situation so I wouldn't say that RX7 is a great powder for the .308, but I made it work due to lack of better options.

CORE is the only thing that has me worried. I started with a patched-out but not solvent-cleaned bore and don't yet know if it was falling apart after eight rounds or it was just me giggling after looking at the chronograph. More shooting will tell. If I can start off clean and get ten rounds into almost MOA that would actually be good enough for the purpose of the rifle and load.
 

Ian

Notorious member
Not if you model them in Quickload in this situation. I was kinda surprised and disappointed myself by the jump in burn length above RX7, and by the big gap on the faster end too. I didn't model many powders other than Hodgdon, Alliant, and IMR because of what I have, what I can get here, and the expense of Accurate and VV powders. XMP 5744 is close but way to spikey past about 35K psi. RX7 doesn't start to really peak out pressure until closer to 45-50K psi which enables it to give a lot more velocity in my particular rifle.
 
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Pistolero

Well-Known Member
Ahh. Another value of computer modeling, which I spent a career doing, but not in combustion
dynamics. Very interesting, and useful.

Bill
 

fiver

Well-Known Member
what's wrong with 50-K? LOL.

other than it sorts things out real quick, and really starts making you look at powders you haven't ever thought about using before.
I never thought about CFE-223 as a good 308 type cast bullet powder until it got up in the 45gr area and then I was like well that one sure shoots smaller groups.
of course AA-2230 wasn't on my radar for anything other than 223 Jacketed use either, until I started shoving it in everything [like silly this shouldn't even be here type everything] and it was actually working in places I thought it would be a total failure in.
 
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Ian

Notorious member
Two more groups today. The LR-308 turned in a 1-3/8" group and the same ammo which was a slap the bolt home fit in my Savage 111 with the Rock Creek 5R barrel turned in a out the same. The dirty LR-308 threw the first shot a little low and worked shots 7-8-9 right to left as it heated up, the Savage put the first one from clean barrel straight into the center of the group. It was cool out and suppressor mirage was getting bad in the light/variable breeze, shifting up to 1.5 moa. Had to use the Zen method of sighting.

8778
 

Pistolero

Well-Known Member
No reason for a pig to complain about either of those. Bang, flop.

Solid, soft or hollow points for the actual hunting ammo?

Bill
 

Ian

Notorious member
Probably the hp, I'm convinced the load is good in the LR-308 so the next testing will involve ballistic media of some sort.

I don't remember if I mentioned it or not but a little strategic filing on the underside and near the front of the right hand feed lip cured the bad jamming problem.
 

fiver

Well-Known Member
it's really,really trying isn't it.
it's like ooohman right on the tip of the tongue wants to shoot some small groups.

I'd be super happy with that sort of LOL, but wouldn't hesitate to take it to the field as it is.
 
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Ian

Notorious member
There's room for improvement and I still need to see how awful it is at 200 yards, but that's meat on the table with either rifle right there. This is the fifth firing on this brass and a lot of it got mangled badly from jams. Still haven't trimmed it and didn't weigh bullets or even check for extra voids formed around the top of the hp pins, bullets are jumping a loooong way to the throat, so I'm sure it could be better but its nice to be getting this much with this little work. I'm a little surprised the Savage didn't shoot better than it did, but it has a .309-ish throat and a Bisley taper that doesn't go with this bullet nose shape at all, I guess I shouldn't be too disappointed. Also the 24" barrel was probably zinging them along at 2600 or so, not too shabby for an 11" ROT.

Oh, and did I mention 14 bhn? If these were heat treated to 20 or so during the coating process they might shoot even better.

On the mag lips. I read all over the net on the problem I was having (rh column, case rim pops under bolt lug as the bullet nose rides up the ramp, bolt crushes case against barrel extension) and it seems I'm one of the very few who ever figured it out or at least few are sharing the solution if they did find it. Dpms saw a LOT of rifles back for this issue and their fix rate wasn't great. One guy using dpms mags said he "bent the feed lips" to take care of it but didn't expound. Most eveyone says the Magpul mags fix the problem but Magpul is all I have. Couple swipes with a file took care of it, now the bolt lug stays behind the rim the whole time and with the same amount of engagement as the left side which didn't jam. With the adjustable gas block someone here recommended installed and tuned, the rifle runs like a swiss watch.
 
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Ian

Notorious member
Photo of the jam. Feed lip geometry is critical to function of any autoloader IME, remember helping me understand the 1911 magazine thing? No different with an AR.

8780
 
F

freebullet

Guest
In that last photo makes me wonder if a little block in the mag bottom might have cured it by way of increased spring tension. Probably a longer term solution on the lip job
 

Ian

Notorious member
I be like...here piggy piggy piggy PEWPEWPEW heeeeeere piggy piggy piggy PEWPEWPEW .......ahschitt now I gotta heap o' work to do...[GRIN].

I don't think spring tension was the particular issue, the case was pivoting on the front corner of the lip as the bullet rode the ramp and it was just enough to pop the case rim under the bolt lug that was driving it. Basically there's a three-point bind between the bullet nose on the ramp, the case body and feed lip, and the case rim riding the cartridge below it. Something has to give and the mag spring was the weak link...but if the spring wouldn't allow the stack to push down then the cartridge would bend or the mag lip would flex excessively. The plastic mag lips are thick and a I had to do was curve the underside and thin it out toward the front so the case rim would tram level and stay in front of the bolt lug while the front of the cartrige tilted up into the barrel extension.
 

popper

Well-Known Member
One guy using dpms mags said he "bent the feed lips" to take care of it but didn't expound. I still use the DPMS metal ones, bent the feed lips to make them work reliably. Break the bottom edge of the lips and mic'd the opening after I got it working. Bent the others to the same dim. No problems in several years. Have some gen I magpul someplace. Don't remember them working well with cast FP.
 
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Hawk

North Central Texas
I be like...here piggy piggy piggy PEWPEWPEW heeeeeere piggy piggy piggy PEWPEWPEW .......ahschitt now I gotta heap o' work to do...[GRIN].

It's all fun and games til they hit the ground.
Then the work begins.
 

Pistolero

Well-Known Member
Ian, sometimes that sort of a jam is the bolt not going QUITE far enough back, too. But,
if only fiddling with the mag has fixed it, must not be that. Any issue with the mag dragging
on the bolt and your changes letting the bolt go back slightly more freely, so a hair farther?

Ever try a tiny bit more gas?

Ok, read your more detailed explanation....the front of the feed lips weren't letting the case go up
enough as it fed without tipping the back down, off the bolt. That wouldn't be related to gas.
I presume you learned this from slow hand cycling?

Bill
 
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Ian

Notorious member
Yes, learned it from slow hand cycling while looking for differences between left and right columns since left side never jammed. The difference and reason was obvious once I spotted it.

My first checks, since this is a polymer, 80% lower, were to check mag seating depth (it is exactly perfect in relation to the clearance grooves in the BCG), magazine well being off-center to the right side (it is not), checking magazine lateral play in the well (mag catch pulls all the tolerance out toward the right hand side, offsetting the magazine slightly to the right, which is actually a contributing problem), bullet profile, seating depth, compared to other "dummy rounds" I had on hand or made with various bullet nose profiles and seating depths, and finally determined that putting a parabolic radius to the underside of the RH feed lip would cure the issue, and it did. Gas settings didn't make any difference except in the violence with which the case was crushed.
 

Ian

Notorious member
Another group today from a clean-ish barrel and using military brass this time but otherwise exactly the same load. The left flyer was the first shot, might have been an oil haze in the barrel because I didnt get it completely bone dry. Barrel wasn't fouled before cleaning before this group, only carbon present which patched out with Ed's Red. 7/8" @ 100, second sub-moa group. :)

8848
 
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