Accurate PC 350 Yds part 1

[Bama]

I started with with bore riders and to date have found them to be more accurate than other designs at higher velocities. With the bore rider it is already past the throat and in the bore almost half its length before primer ignition. Depending on alloy and pressures a portion of the bullet will be deformed. At the higher velocities bullets recovered from the most accurate rounds show swagging or "nose slump" to about 3/16" from the nose. I believe the initial pressure spike actually does the swagging. The portion of the bullet that is already closely fitted in the bore is swagged in one movement to fit the rifling, the portion in the throat is expanded to the throat and then into the rifling. This is why a loose fitting bore rider is seldom accurate because of the axial alignment. I believe it is also what makes a bore rider more accurate at high velocities ( when neck of bullet is swagged into rifling). Powder coating provides the barrier between the alloy and the barrel. This is one reason that the lubed bullets run into problems because on the heavier bullets as much as two thirds of the bullet went down the bore before the first grease groove. These are just my theories trying to explain what I have found so far.

Is sizing required--I have found very few bullets perfectly round and when PC is added it is not perfectly uniform. Also when I slugged my barrel the best I could measure it was .300, now I am sizing the nose portion to .301 or .302 (depending on barrel) and they slid in easily, Before I started neck sizing I could not shoot heavy bullets because they would not fit in bore. The sequence I follow is cast, set gas check, size to .310, PC, resize .310, and then size neck. There are extra steps but I believe the accuracy gained is more than worth the effort. This experiment has opened my eyes to the potential of cast bullets. I do not believe we are close to the limit yet.

[runfiverun]

so how do you think a pre-slumped design supported by the steel would work versus one that slumps possibly unevenly from it trying to twist in the rifling as it moves forward?

[Dragonheart]

I believe Bama is right or at least my thinking is the same.

A properly powder coated jacket is tough enough to withstand the pressure of spinup, protecting the alloy core, while providing superior lubrication for full power rifle loads with absolutely no leading; this I am sure of.

The problem with casting is and has always been making consistently uniform bullets, when we start out with so many variables. I personally do not think I can acheive full power accuracy at 100+ yards with a cast bullet design that is a long bullet that only contacts the rifling with a small band at the base. Unfortunately, this is the mold design for the majority of rifle bullets. The problem is I have been unable to make that design type bullet concentric. A total swaged PC bullet might be the answer, but paying a grand for swaging dies that might not work or buying multiple dies to boot is something I cannot justify. If the bullet is not concentric I can get fair accuracy at 50 yards, but not at 100+. It would appear Bama has found a solution that works and I do not think it is too much work to acheive an accurate bullet you can make at home.

[Bama]

in "pre-slumped" if you are referring to the old slug guns in which the bullet was forced into the rifling and driven down the barrel the end result is similar. Sizing the forward portion to the correct size to firmly ride the top of the rifling insures better axial alignment and reduces the chances of a non uniform slump. Since I have been playing with this I have not found any indication of any slipping or trying to strip in rifling. I am still trying to fully define or how to control the alloy to get velocity wanted, slump to fill out full rifling in forward portion of bullet for accuracy, and with enough copper to hold bullet together at the velocity. The parameters are not too tight but the engineer in me makes me want to find out what they are. The nose sizing is almost as fast as the push through sizer for driving bands and is sure worth the trouble.

[Bama]

I know this post may be controversial but I want explain something I have found concerning PC buildup in barrels especially for anyone running in high ends of velocity. I normally shoot at least 200 rounds per week. I have used powder from two sources and temperature is checked with thermocouple so I do not believe it is a problem with material or methods. Coating or “buildup” is not easily seen with the necked eye but the effects show up in shooting and in cleaning if certain cleaners are used. We shoot off stable benches usually at 350 yds at peel off dots on AR500 plate. Guns have aluminum bedding blocks in stocks for stability and typically 6 to 25 scopes so changes stand out. If a box of 50 rounds are shot without cleaning and stopping after each 5 shots to let barrel cool the point of impact will rise almost 6 inches (2500+ fps start velocity) and groups start opening up. If barrel is cleaned point of impact drops back to initial point. I had noticed that during cleaning patches were almost black. I initially thought that carbon from the powder was the issue. Several of the brushes put away without a complete wipe down has what looked like black varnish on the base when dry some so thick that I could not screw back into the cleaning rod. I tried all the normal solvents other than my normal cleaner from paint thinner, lacquer thinner, gas, even PVC pipe cleaner and Kano oil and none would touch it. As a trial I cleaned it using the cleaner previously used until patches were clean and then run a wet patch of Bore Tech Eliminator and it came out black. It took two brush scrubbing s and 8 more patches to get a clean patch. I have not seen any major indications of excess pressure in the rifle brass. Primers are flattened about the same as factory jacked round. I have also had this same condition on a 45 acp barrel. No indications could be seen looking down barrel from either end but still took 2 wet brush scrubbing s and about 8 patches to get a clean patch. I’m not sure if the coating only builds up to a certain depth and stops or continues to build. It does affect accuracy, is harder to remove, and only certain cleaners will touch it.

[popper]

Bama, your results and mine are the same. I use Smokes and HF powder and it's the same - both abrade going down the barrel. I only have a place for 100 yd shooting so the POI doesn't show, I also don't clean the barrel often. I did have that black gunk clog the gas key in the ARs and it's mostly NOT lead. Acetone pretty well cleans up the PC from glazed tile I cook on, going to try MEK next.
R5R - I was reading some Army docs a few years back, they did tests on Mil ammo and found the core was swaged into the throat/bore/rifling, not 'cut'. For 'long' throats, it does get swaged to throat, then 'cut' on forward motion. I was surprised by the radial vs axial pressures they measured in the tests, IIRC, 1/3 at ignition. Test were by 'drop hammer the base', not fired bullets. IIRC they used a charge behind a slug that then impacted the base in a closed 'container' with many pressure gauges.

[Hickok]

Dog gone it, I knew there had to be some glitch to PCing boolits!

Now I have to clean black melted plastic from my guns. Tell me it ain't so!!!

[Spector]

I tore the lenses out of some old cheap compact binoculars. They work great to provide magnification for viewing the chamber and interior of my pistol barrels.

I have removed the 45 ACP barrels at the range and held them to a clear sky and they've looked spotless only to check with magnification later at home and discover streaks or smears. At first I was upset, but discovered that a bronze phosphor brush makes short work of cleaning if I wrap it with a patch and use KG carbon cutter. When I am done, under magnification, they look spotless.

The magnification may show irregularities in your barrels though and in the beginning that may be upsetting if you've always thought your barrels looked perfect....at least to the naked eye and using a good light source.

Aluminum PB gas checks seem to keep the deposits to a minimum as well.

I haven't tried PC on my 300 grain 45 Colt lead boolits yet in my Bisley, but I am pretty sure the Hornady gas checks will keep it clean.

My grandson just bought an HK in 7.62x39 and I have a old SKS I sportered years ago so either those or my 6.5x55 sporter will be my first PC rifle rounds. I sure hope buildup at rifle velocities is no major issue. My old Vetterli only hits 1365 fps. I run Hornady checks on the Lee 310 grain through that one. I have a hollow base group buy mold I am wanting to try thru it using PC.

I am really wanting to send two Springfield barrels and my Bisley cylinder to Doug for work before i shoot much more. I haven't really checked the inside of my KKM barrel for a Glock 41 to see if it needs Doug's help or not.

I am a terrible procrastinator. grin

Mike

[HABCAN]

Just sayin', but is there any possibility that the mentioned PC 'goopy black fouling' resulted from un- or partially-cured coatings??? I have not encountered such with mine...............so far.

[Bama]

I bake at a little over 410'F and check with therm o-couple. Timer usually set for just over 25 minutes from a cold start to allow warm up to temp. I could not see in barrel of bolt guns or even in barrels of 45 other than being darker if looked in from side but it shows up when cleaning with the Bore Tech and shows up as a supper hard black varnish on brushes if not wiped off while wet. We are checking pure acetone tomorrow at range to see if it will cut it.

[popper]

I checked the BCG that mostly shoots jacketed or some PC GC boolits, no buildup in the gas key. The fouled ones are usually shot PB boolits, no scraping action there. When I get to shoot again, I'll try some lubed PCd PB and see if lube cuts down on the fouling from PC. @100 yds I haven't sen any accuracy problems. The PC is cured properly.

[Bama]

We are checking pure acetone tomorrow at range to see if it will cut it.[/QUOTE]

Checked two separate guns with two separate PC caster/coaters. Acetone looked like it might work but after getting clean patches from both, tried with BoreTech and got 4+ patches that were covered in dark brown/black. Not much harder to remove than copper in a new barrel but have to have right cleaner and may take a couple of additional patches. Still saw the elevation changes.

[popper]

MEK evaporates slower than acetone. Acetone will dissolve cured PC, don't know if it does much to 'burned' PC. super hard black varnish Had that problem when cleaning dark green HiTek out of 30/30. There was a ring of back gunk at the muzzle, had to pound a jag through to remove it. Next time I recycle some PCd I will save the 'burned' stuff and see what dissolves it.

[Dragonheart]

I would suggest trying the old way of removing lead and copper fouling from a barrel. Plug the chamber and fill the bore to the crown with Kroil Oil and let it set overnight or longer. The Kroil will get under the fouling and it can be easily brushed away. This is an old method I learned years ago and I would assume this method will work for polymer also?
I think there are a lot of questions still unanswered before we throw out the baby. Like powder composition, velocity, etc. etc. I am going to start by checking my handguns.

[HABCAN]

Another thought...........if one PC coat allows us to increase velocities, why not two to be a 'stronger jacket' (?) and let us increase velocities even more? Thoughts??

I haven't been able to chrono any yet (it's WINTER up here!) but I double-coat anyway just for cosmetics.

[popper]

Just another area of coatings we haven't investigated fully. What solvent to remove fouling.. I use Ed's red and #9 also have kroil but haven't tried it. Been using coatings for several years without problems but always willing to learn to get better.

[Bama]

I tried Kroil and it did not soften or even dirty a patch. I'm not suggesting to throw the baby out with the bath water, far from it. It is a beautiful baby! Any buildup is easily removed if the right cleaning agent is used. The effect on accuracy is like the 25 shot without cleaning on a new barrel that only had a hundred or so rounds shot through it. So far I have only found the Bore Tech that would remove it.
The question on double coating--I shake and bake and seem to get about .004 buildup and complete coverage. As far as velocities, the alloy is the limiting factor. Adding copper allows the bullet to be driven substantially faster and with a fitted bore rider accuracy often improves. I don't believe we have even scratched the surface yet.

[popper]

Appears that 'burned' PC turns to hydrocarbons so brake cleaner & other stuff should remove it.

[Dragonheart]

I tried Kroil and it did not soften or even dirty a patch. I'm not suggesting to throw the baby out with the bath water, far from it. It is a beautiful baby! Any buildup is easily removed if the right cleaning agent is used. The effect on accuracy is like the 25 shot without cleaning on a new barrel that only had a hundred or so rounds shot through it. So far I have only found the Bore Tech that would remove it.
The question on double coating--I shake and bake and seem to get about .004 buildup and complete coverage. As far as velocities, the alloy is the limiting factor. Adding copper allows the bullet to be driven substantially faster and with a fitted bore rider accuracy often improves. I don't believe we have even scratched the surface yet.

Did you try an overnight soak with Kroil Oil? It takes time for the penetrating oil to work it's way into the the metal and under the fouling.

No way am I going to throw out the baby, there are too many benefits and this is not a major set back, at least not for me. I agree there is so much that we do not know, starting with the types of polymer. So far Prismatic Powder is the only site where you can find out the type of polymer the powder happens to be. We possibly should be looking for powders with more abrasion resistance for higher velocities.

[popper]

Kroil won't cut it, it is a pentrating OIL. We need a solvent that soaks into the hydrocarbon. Carb cleaner (Berrymans B-12) or the like that breaks the mechanical bonds of the hydrocarbon build up. I remember pounding that ring of HiTek from my 30/30 barrel - had to place the muzzle on a pad and hammer the 1 piece cleaning rod with a tight patch to get it out. Chore boy wouldn't even touch it. Poly or epoxy PC turns to various hydrocarbons - called char - when burned, some where ~ 750F. Nylon based stuff is even nastier to disolve.