Plastic Coating and Bullet Size

I would also try .225.

Glad that is the consensus. I really didn't want to wait on mail order doodads.

I really do appreciate all you guys' suggestions. I was really wandering in the desert before now.

I am reminded of exactly this as I melt down all these reject bullets today

Judging by the roughness of the throat slugs I wonder how rough the throat surface is. Could be dirty or heat cracked. If you haven't already, give the whole bore a really good cleaning and decoppering this week while you wait for range time.

As a last resort you can drive a smooth, tapered punch into the throat to swage open the throat entrance a little bit.

From your pic, you are trying to judge throat size by pounding a bullet into the bore. Try something different. Load an unchecked bullet backwards into a case and try the plunk test, different sized bullets. You can roll size soft alloy by rolling between 2 hard surfaces. Cheap pin gauge test. Now you have approx. throat size. Seat (normal) to let the taper just protrude from the mouth. Vary depth so that the taper doesn't hit the bore, chance of jamming if it does and extracting a loaded round may pull the bullet. You want the bore riding nose to 'Ride' the bore, NOT engrave. About the best you can do. Fire a few and watch for the lead ring at the throat and leading near the chamber. If it appears, size a tad smaller til it goes away.
Notice the alloy doesn't tear in the groove when PCd? PC helps.
I have same problem with the SS BO I just got. Bore is correct but throat is huge. I took a case fired in it, loaded a 311 and dropped into the chamber. Fits. 309 shoots almost good, try 310 and 311 to see where it works. I KNOW that BLL coated leaves trash in the barrel for 309. BO pistil needs the same test, only used 309 in it.
Don't waste the GCs by melting until you find what works.
Hope that helps.

Bullets are cooking right now. I will try the plunk test and do some measurements with the Hornady guague (Stoney point OAL).

While I am sitting here thinking about things and planning out loads (danger danger!)... I have something I want to run by the group here...

I'm the type of fella that will err on the side of elimination of variables while I do my tests, where applicable and appropriate. With that frame of mind, I'm thinking of loading up these tests at around 1800 to 1900fps. With something like Blue Dot or 2400. The variable that I would be eliminating is high velocity that we know will introduce it's own set of oddities in group size. My reason for asking however is due to the fact that I know that initial pressure at high velocities will have different effects on the bullet. My guess is those effects will mostly be negative to accuracy. So is it worth going slow at first to see how the fit works out?

Probably worth mentioning that my goal over all here is not a super fast load. Just a load that is 2moa or less at 100 yards, that will cycle a 16" mid gas system. I do have some parts on hand to tweak my gas system to cycle at lower pressures (buffers, buffer springs, BCG), so most likely velocities do not need to be more than 2400fps. And with some powders I can get away with 2200-2300fps. Cycling has never been an issue with this project. Only group size has been. This will be used for 100 yard CMP high power leagues at my local gun club.

So my thought is slow at first, find the fit that works, then head up to the powder that cycles the action.

Suit yourself but I would crack open the loading manual, find a starting load for a jacketed bullet of equivalent weight to your cast ones using a powder you have on hand, and get to loading.

H322, H335, WW748, IMR 3031, 4895, Ramshot TAC, etc. will all be good choices. H335 at a near maximum jacketed load produced the groups I posted earlier on this thread and should have been cooking along between 3K and 3100 fps.

I normally use Quickload to find the powder that gives me the best fill/burn ratio along with the pressure requirements. I have noted, at least in my testing, if I find the pressure value at 8.5" down the barrel at 13.5k psi or higher it will cycle my bolt reliably. This is with a standard power spring, buffer without weights, and a low mass BCG.

I think I will go with the lower velocity test for now and make sure I get good results or at least results that I can work with to improve. Then I will crank it up with full power loads. Some using a little bit faster powders, like Rx7. And another one using a slower powder like Shooter's World Match Rifle. The latter is a ball powder a touch slower than H4895. The SW match rifle load will need to be near full power as it leaves an awfully lot of unburnt powder/carbon residue in the bore when using it for less than 85% full case loads. No dacron fillers for me, until I am out of other options.

Unfortunately, I was not able to stock up on the powders in the 3031/H335/Benchmark/Tac up to H4895 range before the powder hoarding began. I have less than a pound of benchmark left, and maybe 1.5lbs of H4895. I'm going to need to make up probably 1500 of what ever load I end up finding works well. Maybe even more since I will be shooting about 150 rounds a week during the CMP leagues. H4895 is my absolute favorite powder, and I would love to be able to restock that one.

I too use QL to work port pressure around for various ARs and other gas rifles in normal or strange chamberings. Very handy. I also use the program to find the powder giving me the desired velocity, port pressure, and lowest muzzle pressure to reduce wear and tear on my silencers.

Use whatever, but experimenting with 13-14 grains of RX7 for 2K fps did a little worse for me than full power loads with ball powder. This is with 13-14 bhn wheelweight bullets.

15 of 2400 or 20 of Rx7 should do good. 13 Rx7 did great in BO with a heavier bullet.

checking the leading in the bore 'variable'

What is this darker gray stuff? I notice just a tiny bit of leading, the brighter silver spots.

Probably antimony wash . Leave it alone until becomes a problem .

antimony looks like a flat grey dust coating the bore.

just M.O. but that looks like streaks of lead or Tin sticking to copper wash.

Antimony wash. Lordy get that copper out of there before you shoot anymore cast bullets through it.

If you don’t use it all the time (really abrasive) I like JB bore compound for a good thorough cleaning. Let the bore soak with Kroil for 45 min or so prior to use. This will remove all fouling down to bare metal in short order. The Parker Hale type jags work really well with the JB paste.

I use Iosso paste to very good effect as well. For copper I use either a Foul Out III or a mild ammonia-based solvent and work at it twice a day until the copper is completely gone. Bore paste will smooth a barrel to a certain extent after getting it completely clean. Polishing where the copper sticks is always a good idea.

I was not impressed with the Tubbs bore laps because they only touch half the barrel's surface, but cast bullet laps have done wonders for me.

TM Solution is decent on copper. Won’t hurt the bore, ever.

I find shooting cast thru a copper coated bore is a good way to remove the copper. The antimony wash sticks to the copper really well and when brushed out the copper goes with it.

Brad said:

TM Solution is decent on copper. Won’t hurt the bore, ever.

I find shooting cast thru a copper coated bore is a good way to remove the copper. The antimony wash sticks to the copper really well and when brushed out the copper goes with it.

Click to expand...

I did not know this...

I like the Boar Tech cleaning solvents. Eco and skin friendly with no harsh smell. Make sure you use a nylon brush so you don't get a false positive.

I don't think that is actually that much copper in the bore. I cleaned out as back before starting this, unless gas checks can cause copper fouling.

Sometimes I think a borescope visually shows things that are not necessarily as big of an issue. It may look bad up close in a big pic, but not while shooting. I try to use the patches that I see while cleaning as the final judge. I have had good luck so far with the pro shot copper solvent IV. It always shows me blue patches when there is copper in there. And for sure, always use a nylon brush when working it. Regardless, I will see what a patch shows me tomorrow when I give it another run through with the solvent.

@fiver. yeah those bright spots had me worried too. I'll let some kroil soak over night and give it a bronze brush treatment.

You're a hi-power shooter, I'm a cast bullet shooter. What seems like a little to you is a lot to me. You've seen my groups such as they are and there is NO copper in my barrels.