Developing 6 MM 350 yd accurate Load pt1

[Bama]

I wanted to see if I could develop an accurate HV load to use in a 6x45 similar to the one developed for a 308W. The 6x45 is a low recoil, cheap to load, and extremely accurate round. The guns used for development are all Savage short actions with Shaw, McGowan, and Lothar Walther barrels all with 1 in 8 twists. To date, only modified PCed bullets based off a RCBS 95 gr mold (98.6 gr after PC) have been used. After casting, a gas check is seated and the front portion (bore rider) is sized and then the drive band/gas check is sized. After powder coating the same sizing sequence is used again. The first picture shows the main stages and the second show the bullet before and after the final sizing (.244/.236).

Observations: Things found during testing that may be of interest.

1. Copper was mixed in the alloy used. Similar to what was found in working up loads in 308W, the bullets will turn to dust at higher velocities when used in a fast twist barrel unless copper is added. It doesn’t take a lot; I am using 6 heaping tablespoons of copper sulfate (25.2% eq metallic copper) in a 20 lb batch. Caution- read threads how to mix safely.
2. There seems to be a very interesting relationship between the alloy hardness, bore fit and PCing. In conventionally lubed bore rider bullets the forward portion of the bullet has no lubrication so if it presses very hard on the sides of the bore, it usually results in leading. When fired, if the pressure builds beyond the working strength of the alloy it will expand into the bore and lead the bore so pressures had to be maintained below the working strength of the alloy (as detailed in Lee Manual). A close tolerance or fit was required to have any accuracy. PCing seems to have changed some of the previous constraints of a cast bullet. Leading is no longer an issue. If the working pressure of the back portion of an alloy bullet is exceeded, it will suffer plastic deformation and retain the bore shape if the pressure falls below its working pressure before it leaves the end of the barrel. The bullet will be a perfect fit to bore and rifling will show full engagement on the bore rider portion. The harder alloys usually have a higher working strength and require higher pressures to cause plastic deformation. The above is based on the bullet staying together at high rotational speeds which is helped by copper addition. In all testing so far on both 308 and 6mm, accuracy makes a significant improvement when recovered bullets begin showing full rifling engagement to within 3/16” of bullet tip. The rifling engagement can be seen on the recovered bullet below which was originally sized .244/.236 (drive bands at .244 and bore rider portion at .236).

1. A very large number of different PC powder coatings have been tried in the last few years. Even when properly cured (temp monitored with thermocouple), the powers tested resulted in varying amounts of buildup when shooting 50 rounds between cleanings which affected accuracy if shooting the higher velocities. At lower velocities and pressure almost any of the different powders work with no apparent buildup. The best powder tested to date is “Smokes” Bacon Grease which normally only requires one more patch than with jacketed bullets at the most. It has a lower ratio of polyester resin and its cross-linker to the other materials having a melting point near 1800’C.
2. The die used for neck sizing is a home shop made holder using a purchased Redding neck sizing bushing. The approach angle was too sharp on the bushing as received, so a more gradual angle was ground using a Dremel tool. The increased angle allows the bullet to be (extruded or swaged) without shearing the bullet alloy or the PC.
3. Bullet seating was done using an old C&H sliding bushing seater-die bored out to match the diameter of the bore rider portion of bullet.
4. On trials made so far, it seems that the smaller 6 mm is more sensitive to neck pull and weight variations than the 30 cal. I have not been weighing bullets, and I use them as cast. More testing is needed to determine if fliers are the bullet or the shooter.
5. Even weighing bullets have been getting one or two fliers in each 5 or 6 shot groups. I have been trying a number of different powders in the 6x45. Only small amounts of load data is available for 100 gr bullets and have found none for cast bullets so loads are started low and slowly worked up. Case volume is usually maxed out before any pressure signs are seen. On recent range trip, cases were checked with RCBS precision mike. Out of each group, 1 or 2 would show lower case length ( ½ thousandth ) which matched up with number of fliers. Crimping and slightly faster powders will be tested next.

[Bama]

Well it can be done. Arsenal now offers a GC 6 mm bore rider designed for powder coating. The 2 cavity is 243 115-NR-BR-GC. With my rough alloy ( added copper as copper sulfate and two slugs of Rotometal super hard) it is ready to shoot with GC and PC at 108 gr. I size at 236/244 and have been shooting in 6X45 using 23 gr of IMR 8208 XBR at 2468 fps. It shoots so well that we (fellow range members who have tried it) now have 5 of the 5 cavities on order. The flyer was the shooter fault but compounded by a yellow jacket which stung me on finger.

[popper]

Out of each group, 1 or 2 would show lower case length ( ½ thousandth ) which matched up with number of fliers. Interesting. possibly crimp related? Good shooting. That color is about the yuckiest I've ever seen, but hey it works.

[vzerone]

Out of each group, 1 or 2 would show lower case length ( ½ thousandth ) which matched up with number of fliers. Interesting. possibly crimp related? Good shooting. That color is about the yuckiest I've ever seen, but hey it works.

Are you saying the 1 or 2 are actually placing the bullet a 1/2 a thou shorter in the throat? If so that may do it. Why not toss those cases out? But then again you're cutting case length less then a hair, isn't that anal?

[Bama]

Popper, you brought up a good point about possible crimp related. I do not normally crimp, just a .002" neck tension. On some powders I do not think there is enough resistance with PCed because they are so slick to get a consistent burn without going up so high in velocity that accuracy is effected. Been debating on having a cutom "Factory crimp made for the 6X45. Have been wondering if added resistance is worth the added cost of custom die

[OS OK]

Hey Bama...nice work, excellent write-up too. We certainly can use a lot more posts like yours.

Couple of Questions...how are you setting up the nose in the bore? Does it just touch the lands slightly or backed off a bit...how much?
Have you ever tried a high quality 'clear gloss' for PC'ing?

Yeah, have to agree with the color statement...they shoulda called it 'mustard'! But...I wouldn't care if it was San Francisco Hot Pink as long as it does the job.

EDIT: Was just figuring RPM on that 2468 FPS velocity...am I correct thinking that's 222,120 RPM?

[vzerone]

Hey Bama...nice work, excellent write-up too. We certainly can use a lot more posts like yours.

Couple of Questions...how are you setting up the nose in the bore? Does it just touch the lands slightly or backed off a bit...how much?
Have you ever tried a high quality 'clear gloss' for PC'ing?

Yeah, have to agree with the color statement...they shoulda called it 'mustard'! But...I wouldn't care if it was San Francisco Hot Pink as long as it does the job.

EDIT: Was just figuring RPM on that 2468 FPS velocity...am I correct thinking that's 222,120 RPM?

You're right if it's an 8 twist. He has better watch it or the rpm police will get on his butt!!!!!

[OS OK]

It makes me think that the fliers he is getting may have slight inclusions in them...they ain't off by very far though!

[vzerone]

Hard to tell, he didn't mention anything about weighing his bullets.

[popper]

If you are using taper crimp die to remove the flare it may cause difference in flare. Those cases may also have an internal 'donut' at the shoulder.

[vzerone]

If you are using taper crimp die to remove the flare it may cause difference in flare. Those cases may also have an internal 'donut' at the shoulder.

Usually with such a small change in neck diameter you don't get that donut.

[Bama]

Barrel is 1 in 8 right or wrong it is all I have so I have to make do! RPM is up there--till I started adding copper I had a lot that would turn into a white dust cloud in 15' of muzzle. Now I have not been able to make one go to dust even at MAX loads listed for J- bullets of near same weight. At upper end of velocity, accuracy goes to ****! As to fit, they just touch the lands ( will fit to drive portion if stuck into barrel with almost no wiggle)

[vzerone]

Bama, I've never made a cast bullet go to dust at high velocity high rpm's from a number of fast twist rifles including other people I've seen shooting equally fast twist rifles at high velocity. It's very interesting that you have.

[Bama]

It is not a good thing. Most occurred with 30 cal in 308 when getting near the upper end of published j bullet data. Several of our group had same problem. Really not good when wind was blowing into face. Alloy was pure lead with a lot of pewter. Probably got my lifetime exposure limit the first couple of occurances.

[popper]

I recovered a shard of rifle boolit (Cu added) that hit steel @ 1750 or so. All surfaces have a wavy (like a fine arc weld bead under a 20x loope) surface. Not the normal sheared/crystal break. I'm assuming the alloy rippled/expanded enough to eventually fall off/break. Definitely different than normal Pb/Sb alloy, even heat treated. Target was a knock back so didn't fine any other boolits on the ground.

[vzerone]

It is not a good thing. Most occurred with 30 cal in 308 when getting near the upper end of published j bullet data. Several of our group had same problem. Really not good when wind was blowing into face. Alloy was pure lead with a lot of pewter. Probably got my lifetime exposure limit the first couple of occurances.

I did a test firing a pure lead bullet in a 7x57 Mauser. I was pushing it too. It didn't strip through the bore, it didn't lead the barrel, and the acccuracy wasn't any good. Me thinks your large doses of pewter in your alloy is the culprit.

[Bama]

If you are using taper crimp die to remove the flare it may cause difference in flare. Those cases may also have an internal 'donut' at the shoulder.

Popper, I do not flare my cases. A friend go me started using the old herters in line seaters which have the sliding collars. If I champher the inside of the neck initially the bullets go in without flaring the neck with no scraping of the PC. He got the seater off Evil -bay and reamed the small diameter to fit the bore rider sized diameter. He is a retired machinist and really knows his stuff in the tool and die area!

[Phantom30]

I am firing the same boolit out of the same Arsenal Mold using Bama's Alloy from my Ruger Precision Rifle in 6mm Creedmoor with a 1:7.75 twist. The bullet weight is 113gr with PC and GC. Muzzles demonstrated so far are 2859fps with 32.5gr of IMR 8208 XBR and 2826fps with 44.0gr of H-1000. Bullets loaded with neck tension only with GC at base of casing neck, COAL 2.70-2.71. Picture has the bullet in Hornady Creedmoor casing aside of 223 and 308W casings and the Hornady 108gr ELD Match bullet for comparison. The bore rider concept appears to work well.

[vzerone]

I am firing the same boolit out of the same Arsenal Mold using Bama's Alloy from my Ruger Precision Rifle in 6mm Creedmoor with a 1:7.75 twist. The bullet weight is 113gr with PC and GC. Muzzles demonstrated so far are 2859fps with 32.5gr of IMR 8208 XBR and 2826fps with 44.0gr of H-1000. Bullets loaded with neck tension only with GC at base of casing neck, COAL 2.70-2.71. Picture has the bullet in Hornady Creedmoor casing aside of 223 and 308W casings and the Hornady 108gr ELD Match bullet for comparison. The bore rider concept appears to work well.

Holy Batman, that's 265,610 rpm!!!!!!!!

[Phantom30]

That is the beauty of 'Bamalloy'. Sticks together and keeps on spinning. I am trying t get it up to 3100fps, we'll see