Accurate #31-260B hardcast 1:10 twist .30-06 Springfield - Test #1

[CometJo]

This is my first foray into casting my own boolits. Cast up a bunch of the Accurate Molds #31-260B (.300 bore ride instead of default .305) with 92-6-2 hardcast alloy, water quenched. Don't have a hardness tester yet so I'm not sure the BHN. Sized to .311 with White Label red carnuba wax lube and gas checks. Trimmed the cases to 2.494 after resizing, and expanded necks with a .311 neck sizer from NOE in a Lee expander die before filling powder and seating bullets. Winchester large rifle primers, standard, not magnum.

Loaded up 5 sets of 10 rounds each, with IMR 8208 XBR in increments of 36.0, 37.0, 38.0, 39.0, and 40.0 grains. Seated bullets to crimp groove, light roll crimp. COAL 3.084 inches. Used QuickLoad v. 3.4.04 to develop initial test load data. QL data pretty consistent with actual results; low by maybe 100fps.

Shot out of a Ruger Guide gun in .30-06 with the "perforated" muzzle brake installed; has a 1:10 twist rate. I had previously used Tubbs Final Finish to fire lap the rifling. Used the iron "express" sights only, target at 50 meters.

The 38 grain load seemed to shoot the most consistent velocities.

	Set 1 (36.0 gr)	Set 2 (37.0 gr)	Set 3 (38.0 gr)	Set 4 (39.0 gr)	Set 5 (40.0 gr)
Shot 1	1990	2029	2060	2160	2160
Shot 2	1984	1984	2070	2093	2175
Shot 3	1987	2041	2070	2116	2178
Shot 4	2044	2041	2086	2086	ERR
Shot 5	1993	2008	2063	2126	2116
Shot 6	1981	2032	2063	2119	2136
Shot 7	1960	2038	2044	2109	2116
Shot 8	1960	2005	2051	2099	2189
Shot 9	1987	2029	2083	2129	2175
Shot 10	1975	1999	2054	2096	2175
SD	23.41	20.03	13.34	21.88	27.94

Range conditions about 60 degrees, no wind, and approx 400 MSL. 29.48 inHg.

I mostly wanted to find the load with the most consistent velocities and I think load #3 nails that pretty well. But I was unpleasantly surprised by the bullet printing on the target when I recovered it.

See pic of target for all 50 rounds. I see a LOT of what appears to be keyholing. I was seated on a bench but used no rest of any kind. Sights are obviously off, and the express sights are not super good for target shooting, either. I need to get a scope and a rest for this rifle to do any better grouping even with jacketed bullets, that much is obvious. But my main concern is the oblong holes in the target.

I had previously used the Berger Twist Rate Calculator at http://www.bergerbullets.com/twist-rate-calculator/ before I even bought the bullet mold to see if it was worth buying such a long bullet for the 1:10 twist .30-06. Calculator says it should be plenty stable at 2100 fps, though. BC calculated to .758 based on http://gundata.org/ballistic-coefficient-calculator/ -- 1.37 inch bullet @260 grains and .31 diameter for the Accurate #31-260B

This calculator also says the bullet will stabilize with an 11.3:1 twist rate, so 1:10 should be plenty tight. http://kwk.us/twist.html

So I guess I'm not sure where I went wrong. Today I also shot 50 rounds of NOE 311299 (1.175 bullet length @ 202 grains) hardcast in a Stevens 200 .308 Win, and none of those boolits keyholed at the same velocities +/- 50fps. It's also a 1:10 twist, sized to .311 with same lube and gas checks, case necks expanded the same way, etc. Powder for 308 was IMR 4064, though.

Maybe they will stabilize further out? - 50 meters too close in? Or load up some NOE 311299 in the .30-06 and see if the problem is just bullet length?

I've not shot any other bullets through the Guide Gun other than the 50 fire-lap rounds. I should get a good baseline with a scope using jacketed rounds, I suppose. Going to try some 220 grain Hornady round nose and see how they perform, being longish bullets themselves.

PS -- No leading of barrels for either NOE or Accurate boolits at those velocities, which was a relief. Not a very successful trip to the range, but at least I now know that hardcast water quenched can handle rifle velocities without leading.

[CometJo]

A few more things I'm going to try to get this boolit to work:

1. Seat farther forward so nose lightly engages the rifling. Add to wishlist: Hornady bullet seating depth gauge.
2. Load for 1500 fps on up to 1800. Twist calc makes it look like anything above 1000 fps should stabilize this bullet. Who knows?
3. Try goodsteel's advice on the "just a few tips for new rifle casters" sticky.

[sharpshooter3040]

Try Softing your alloy to allow proper obturation. Try 18-22 grains of IMR 4759 if you can find it. If you push this bullet too hard you will have issues. The sweet spot for this bullet is 2000fps

[runfiverun]

they ain't gonna stabilize at any distance.
I'm not familiar with the boolit your using there but it seems to be a shorter one.

tumbling is caused by only two things.
1. you ain't going fast enough.
2. or your not gripping the rifling.

I'd go with number 2 in this case.
or number 1 is being exceeded causing number 2.

[CometJo]

Thanks folks for taking time to reply.

Have access to a huge bar of pure lead -- will try adding some of that to the hardcast alloy to soften it up.

I also wondered if I was pushing the bullet too fast causing it to lose grip on the rifling.

Will also try it in a .308 Win and see if the gun makes any difference. Probably won't but I'm curious.

Here's a pic of the bullet's design (but like I said, mine's got a .300 bore ride not a .305)

[popper]

I've shot up to 36 BHN in 1:10 308W, sized to 3085, @ 2700 fps. Makes no difference. I'd say you are going too slow. Like SS says, boolit may have a fps max for performance.

[runfiverun]

okay you got ton's of length there.
your not spinning it fast enough to stabilize the boolit.

[CometJo]

Yeah maybe those twist calculators are a bad idea for cast boolit work. I'm not sure I can safely get more velocity out of the .30-06 with that 260 grainer per QuickLoad, so I guess I'll save these bullets for the day when I get a magnum .30 cal rifle.

In the meantime, I have several other molds from NOE and Accurate ranging from 170 to 220 grain that I can play with in the .30-30W, .308W and .30-06.

[wmitty]

You mentioned sizing to .311 but I didn't see what your groove diameter measured. Any chance the Ruger might have a slightly larger than normal groove dia?

[w30wcf]

Years ago I had a 252 gr bullet (Lino) made to shoot in my Rem 788 .30-30 (1/10) so most of it was riding on the bore. The bullet was 1.53" long and had a semi pointed nose. My main goal was 100% positive takedown on the 500M steel rams. It shot well at that distance.

I tried different loads and it was stable at 1700-2000 f.p.s. velocity...from that rifle.

I gave some to a friend to try in his .308 and, for whatever reason, his rifle would not shoot them very well. I suspected his rifle had a 1/12" twist but he steadfastly claimed it was 1/10.

Good luck,
w30wcf

[CometJo]

I slugged my Ruger Guide Gun rifle recently. Groove came out .308 or .3085, IIRC.

Tested it a few weeks ago with some hand-loaded Hornady #3090 220 grain round nose bullets. They are 1.26 inches long; only .11 inch shorter than the Accurate #31-260B. Used from 41 to 45 grains of Varget for 5 sets of 10 rounds each. From about 2000 fps with 41 grains on up to 2300 fps with the 45 grain loads. Shot them into far tighter than the cast boolits, and no keyholing.

Wonder if the nose of the cast boolit is deforming on the way down the barrel. Maybe need a harder alloy for shooting skinny .30 cal bullets that fast? The 92-6-2 hardball alloy supposedly casts at 18 BHN, and maybe a bit harder since I water quench them immediately out of the mold. Seems like it should be plenty hard, but then again I am new to shooting cast bullets smaller than 44 or 45 caliber, and faster than 1500 fps or so.

w30wcf -- your long bullets were linotype, right? Maybe I need to try that alloy for my faster rifle bullets.

[frnkeore]

Your bullet is 1.385 long with the GC installed. With your bullet and case combo, you have .410 of the bullet below the case neck.

I believe that this is the reason your getting keyholes, the base of the bullet gets damaged at ignition and that causes gas cutting in the barrel, causing the keyholing.

Frank

[LAH]

FWIW I have WQ 92-6-2 alloy & mid 20s isn't hard to obtain if you use cold water & dump the mould soon as the sprue hardens.

[CometJo]

Well, tried the linotype versions today both water quenched and air cooled. They shot even worse than the water quenched hardball.

Also tried to seat some to the max allowable length but they won't chamber in the rifle.

For this .30-06 I'll start loading up my 150-180 grain boolits like I should have done from the start, get some more experience, and then come back to these long bullets later.

I might also try these 260's in different 30 cal rifles to see if they like em better.

Thanks for all the suggestions!

[w30wcf]

CometJo,
Sorry to hear that accuracy with the 260 gr has been elusive to date. Perhaps switching to 4350 or 4831 might help.

I have used the 252 in Lino and also in HTWW (267 grs.). As these pics show, the bullet I'm using, is mostly into the barrel with everything forward the last two driving bands riding the bore. I'm using H414 in the .30-30 case.
Accuracy has been very good out to 500 meters.




Left - 311620 - 212 grs Lino / 225 grs HTWW +2% tin
Right - 311620 modified - 252 grs / Lino / 267 grs HTWW + 2% tin

w30wcf

[W.R.Buchanan]

That boolit is too long for your .30-06. You can't spin it fast enough to stabilize it with that twist rate. You also can't run it faster to make it spin right because it is a cast boolit.

I have a Guide Gun as well and it shoots Lyman 311299 GC sized to .310 just fine. The Barrels are Hammer Forged and most all of them are right on the money. It could use about 200 jacketed bullet loads ran thru it to make sure it is broke in completely. My Ruger Scout has a 1:10 twist barrel as well, and it shoots better every time I shoot it. They keep getting better until the throats erode which in the case of a .30-06 or .308 will be about 10-15,000 rounds down the road.

But you need to realize that not many guns of this caliber will shoot any Cast Boolit very well above about 18-1900 fps. And with that limitation boolits bigger than about 200 gr are going to be very problematic.

I have some Berger 240 gr .30 cal Bullets that I was given at the SHOT Show They require a 1:7 twist barrel and a speed no less than 2700 fps to work. So how are you going to get a 240 gr Lead Boolit to go that fast? The boolit can't survive the pressure needed to accelerate it to that speed, and if it could, it would probably strip the rifling since the lead isn't strong enough to maintain it's shape.

Why don't you try a Lyman or NOE 311299GC with about 25 gr of 5744 or 18 gr of 2400 I think you'll achieve success much more easily.

One last point: I have not seen "twist rate calculators" produce anything accurate yet. There are variables that are not considered that have a negative effect on their results. They could be used as a starting point but all results would have to be confirmed by testing.

All of this stuff was figured out a long time ago and what works and what doesn't is well documented here at the site. A perfect example of an earlier Twist Rate Calculator that doesn't work right is the one that figured out that for some reason .44 cal. rifles should have a 1:38 twist rate, but .45 cal. rifles need 1:20? Kind of contradictory isn't it? I understand the nuances here and don't agree with them and many here and elsewhere don't as well.

Randy

[w30wcf]

Randy,
1.53" long 252 gr. cast bullet shoots fine from my 10" twist 788 .30-30.

w30wcf