Accurate PC 350 Yds part 1

[Wreck-n-Crew]

Thermoset is sort of a misnomer for PC. HF red will reflow before deteriorating, as will Smokes gloss black. Hitek is closer to thermosetting, shrinks a bit then deteriorates.

I've noticed the same. Not sure if the word their term thermoset only applies to less than a few hundred degrees more than the baking temp. Either way misnomer applies in my definition of the term thermoset too.

Right now it seems we are reaching the limits of the current PC's being used. Maybe something comes along to reset the course. Ill have a chance to figure somethings out and maybe get a little testing in here soon. We'll see what happens and I hope I have something worth sharing.

[Phantom30]

Great stuff, but each answer generates three questions. Still this is real progress. As for cleaning, I have found that at the range if you periodically run some Standard FMJ through the gun to cuts back on most fouling build up and makes testing measurements more consistent. Besides shooting is more fun than cleaning. Think Bama has certainly done good work on HV bolt gun alignment. But the mag eaters still appear to be in flux as how to get longer range accuracy. And bore riders designs don't appear in the future for ARs. I am still looking forward to not using a GC for HV bolt guns.

[Bama]

Do not pass up trying a bore rider in an AR. If the bore rider portion is sized they function without a problem. They are very accurate in AR 10 and run like a champ in a Scar. The only problem I have had is when using old FAL inch series metal mags the will sometimes scratch coating on chambered but not fired bullets. It doesn't seem to affect operation but do not like it. Plastic Mags do not have that problem. Have used 170,180 and even 200 gr at max load in Lyman AR load manual.

[Wreck-n-Crew]

I've been doing some research on powder coats to possibly find a better powder. In my last post I referred to a powder type that had a higher AAMA rating. After speaking to several people and a few at Tiger Drylac it turns out the ratings can be misleading as to the inherent qualities of the powder coat.

Their highest AAMA rated powder is actually a softer powder that seems to not far well under pressure or temperatures but does well in acid rain and sunlight. not good for bullets from what I gather and it's also not made available to anyone without the proper training and is only sold to business as well as the other 3 makers of coating in that class.

So that's a no go so I took the time to ask questions while on the phone and got some suggestions as to what to use and type. I will soon have a powder from at least one company to try and possibly 2 more types to follow.

It's not easy getting anyone to reduce to sample sizes for testing purposes and purchasing 50lbs of an unknown powder to just try out can be cost prohibitive. So I've revised my search to finding those particular powders from distributers who deal in a smaller volume. Once I've acquired them ill be glad to share with someone who wants to test on their own. It seems that having different tests using different guns and calibers might be a better way to insure that success is not a fluke to caliber or gun.

Let me know if your willing to try some and when it comes in ill send enough for testing and we can see what happens?

[Phantom30]

So Bama, if I take your experience and apply it to my 300WM this is what I get. The 212gr boolit on the left and the chamber fit on the right. The alignment bore rider only make static fit contact over 0.125" of rifling in the bore. Plus I had to exceed the COAL standard slightly to do it. Next I'll take this design of to my 300 BLK chamber and see if it will static fit and then look into dynamic fit. Would really like to dump the GC and go with a BT rear end, probably bring it up to 220gr. (Atlanta House Plants wilted in the end)

[Phantom30]

Did a little quick static and dynamic fit analysis for the previous 300WM bore rider in a 300 BLK chamber using either Magpul or USGI magazines. The insert shows that the ogive will hit the feed lips and ride the edges forward. This creates a slightly increased pitch angle then a 223. if you have a weak follower spring it can induce bolt run over and jam. The Magazines clearly are going to be a problem. The front casing guide on the inside of the magazine is too large for these fat front nose boolits. It will cause toe in and misalignment of the rounds in the stack and can also cause miss feeds. The boolit design will need to have the cannalure removed and replaced with a taper to clear the throat. There is more COAL room to move the round forward about 0.020 increasing the static bore rider length from 0.120 to 0.140. And the GC should be replace with the BT because this is not HV only about 1700fps or less depending on barrel length.

[Phantom30]

Well in for a dime in for whatever. So I also back checked the 308Win SAAMI for a bolt gun. And it looks best of all here with the trimmed up design that should support 300WM, 300 BLK, and 308WIN. But then 308Win is where Bama started so it should be good. Hope this is helpful. And to all agoodnight

[Phantom30]

well good morning and guess what somebody has already been working a core like this. Found this one this morning looking to see if Arsenal could do RN noses Accurate can't,

[OS OK]

So the Idea is to build up that nose and have minimum Pb movement when sizing to .300" or so?
Do you think the nose will actually cast fatter than .298"? I like the PB design but would rather, I think, have a boat tail for going out further than 500 yards.

[Phantom30]

Exactly so this is the design I'd use to leverage off Bama's work for bore rider alignment in achieving down range accuracy. The PC would bring it up to .309 in the drive bands and .3005 on the bore rider. So you would have to have a Bama like nose sizer to get the polished effect. Concentricity, well it is what it is. The metallurgy is still TBD to get to hold together with a 1:10 twist HV long range or faster for ARs. The loads and harmonics still needs work and all that for each gun used. Still there is the peen effect on the base of the BT when Loading HV without a GC, which is what I want to do if it works. Arsenal Molds can make this in 4 cavity for about $90.

[sparky45]

Wow!! Good stuff. I have a 6.5 Creedmoor I'd like to cast for, but my 300 BO is already using Lead candy coated and I like it like that. Presently running with NOE's 247 grain. $90 for a 4 cavity is a good price.

[OS OK]

That looks like a good candidate for my 'long throat' 700 Varmiter. I have the 1:12 so it would be the upper weight limit on that twist, not sure. It would be easier on the torque-up though.
This rifle hasn't seen any cast rounds yet...my 168 grain match BTHP's are .130" from engagement with the lands when they are seated fully in the neck cause they are so short because of that skinny taper in front to the point but they shoot pretty well...

Attachment 187382

[popper]

I can see bore rider in 308 but not BO AR. Due to the larger case size, less damage to the nose in 308. Consider a bore rider as a boolit with large and small drive bands. The nose is whatever small ogive you want. I'm using a PB 170 RD style in BO, PC & size to bore. It goes into the throat ~ .2" but doesn't hit the lands. More testing to do on that one, I've shot it in the 10" pistol but not the 18" carbine, yet. IMO you will have to add Cu and a modified base to go PB. With a 145gr I'm pushing 45kpsi PB in the BO with accuracy, prob. mid 40k with the 170gr. I did shoot a few GC 185 of the RD that did better. The RD style with a RN should work pretty good. Mine drops 313, sizing to 308 gives me a long 'semi' bore rider with a nose that still feeds. You want the longer boolit (heavier) for better BC and distance, not sure the BT will actually do any good. If subs, your down in the 30k psi range, still takes a tough alloy for the BT.

[OS OK]

Pewter has copper in it...would it make the hardness and malleability we need?
When I was making HP blends I noticed it jumped the hardness higher by a 2.5 points when I was figuring just the Sn content. I hadn't used pewter before.

[popper]

pewter does have Cu but way too much tin. Basically use it to add tin.

[Phantom30]

I can see bore rider in 308 but not BO AR. Due to the larger case size, less damage to the nose in 308. Consider a bore rider as a boolit with large and small drive bands. The nose is whatever small ogive you want.
.

I was trying to show that a single bore rider design can exploit Bama’s technology for 300WM, 308W and 300 BLK. I have been working with Accurate Molds 31-215E, F, G and 31-240A. All these are PC core designs. The F and G designs have a reduced ogive and smaller tip to elevate AR feed issues. You need a tip about 0.18 or less to reduce jamming. The magazine problem with the internal guide ridge is common to all fat nose rounds. The solution in a Magpul is simply file it down so it doesn’t interfere. USGI magazines are not fixable, but still very useful for 458 SOCOM. The feed issue is a dynamic fit issue, it take $10,000 add on software to 3D CAD to be able to simulate the problems.

Your double drive band characterization is correct and it takes double sizing to get it right. Maybe there is a cheap way to use a sizing die to make two step nose sizer.

[Phantom30]

Bama is the only one with leftover boolits that he could load in 300 BLK casing and to dry fire cycle test to see what damage is done to the boolit PC and where feed issues occur if any.

Another observation: This last design only needs to be nose sized down to 0.700 from the base to accommodate all three calibers with 0.030 to spare to insure good transition. How does this impact the nose sizing tool.

[Phantom30]

Since we are at it and have special dies for sizing etc., Why not have a special die for making your own GC for BT or as I call it a BTGC bucket. If this keeps up we are converging on making full jacketed OTM

[popper]

The def. of a 'bore-rider IMO is where the nose actually rides the lands, not the throat. As the SAAMI BO dwg shows the lands start 0.3" (approx) from the case mouth, and boolit length restriction of the mag is 0.85, nose has to be <0.300 after the 0.3" point. A 1.2" long boolit will just have the base below the shoulder. Nose will need to be RN at min. I still see no need for the GC. IMHO, I'd run the base dia to just below the lands with a taper to bore-ride dia. IIRC that is what Bama does. I have noticed a little scuffing at the front edge of my 145gr from the throat - case isn't in far enough for perfect alignment.

[Dragonheart]

Since we are at it and have special dies for sizing etc., Why not have a special die for making your own GC for BT or as I call it a BTGC bucket. If this keeps up we are converging on making full jacketed OTM

If you contact Charlie Darnall at FreeChex he might be willing to take a look at your design, but according to Charlie a PC bullet does what a gas check does.