#solidcopperbullet

By late winter I had the concept in hand  (picture at top of page) and by early spring I had the first test batch in my possession for preliminary testing: 25 x boattail and 125 x flatbase. I kept the boattail and 25 of the flatbase, the rest were mailed out in 25 count boxes to testers who were experienced in shooting monolithics or who were experienced shooting sabotless with Blackhorn209. All were .458″ since all the testers primarily shoot Full-Form.

First run of the Monolithic B.O.M.B off the Swiss lathe:

The first thing I discovered was that these copper bullets were not the nightmare to size that I had heard from other shooters using other solid copper bullets. That meant the choice of copper already showed an advantage. On the flip side, I had to adjust my sizing die 8.75-ish notches tighter. The Hankins die does not have fine graduations like the Swinglock die so you have to estimate or scribe your die if you ever need something in between that you intend to reference again. The usual setting I use for the cup and core bullets was painted green so I knew where to return to. Without that sizing adjustment there was no prayer of those bullets going down the barrel. That is why you pull your plug and size bullets then test fit them at the house. If you don’t you get to the range and they might not load.

Flat Base and Boat-Tail versions of the Monolithic B.O.M.B. Full-Formed after test sizing:

Where I ran into an issue right up front was I had been shooting a bunch of IMR3031 along with jacketed bullets for the past year. I chose to clean the barrel prior to switching over to H4198 and the mono bullet. My test fit at the house was spot on for a clean barrel. After two foulers into the berm and a 3-shot group I found the next bullet had to be hammered down using a rubber mallet. I shot it and hammered down two more (seen below is the target with the first two groups shot with these bullets). If you reference the target it supports my claim that as seating pressure increases it is less controllable and precision suffers (not much in this case but happened nonetheless).

Boat-Tail at 100yds from my gun:

I jumped in the truck and sped away to the house where I again pulled the plug and tightened up the die until I had an appropriate fit for the dirty bore that allowed for one hand of seating pressure. I sized three more bullets, threw my charges, re-primed my modules and headed back to the range since I had an hour of light left. Since the M-BOMB had shot so well at 100yds I could not call it quits until I had shot them to 300yds. I got to the range with enough time to go paint a piece of steel and hammer out a group in the cold, windy evening as the light failed.

Boat-Tail at 300yds from my gun:

Having seen the night before that the boat-tail M-BOMB was stellar when Full-Formed I felt certain that the flat base would be too but Full-Forming the flat base had to wait. With a six week work trip coming up I had limited time so I decided to draw some down to .452″ and smooth size them since I hadn’t gotten .452″ bullets for testing. I chose the flat-base over the boat-tail because conventional wisdom is that you cannot shoot boat-tail bullets Smooth Form. Since I did not have a ton of the boat-tail nor did I have a surplus of time I took the safe bet. Maybe I’ll test that theory later.

I Smooth-Formed them and they tumbled when I shot them so I determined that as soft as these were compared to other copper bullets they were not soft enough for smooth form. It is possible also that running a .458 bullet through a .454 sizer, then a .452 sizer, and finally a Swinglock Smooth-Form die work hardened the bullet to a point where it was too hard for use as a land rider. I decided to anneal them and try again. Fifteen minutes on the electric stove, set to high, softened them up (but did not jettison the tip which annealing with a torch will do as one tester found out which supports the idea they work pneumatically) and quenching them in a cup of Apple Cider Vinegar cut the oxidation right off. Some guys do not bother cleaning them after annealing but I don’t like to put anything that looks like that through my dies or barrel. A quick spin in a piece of bronze wool and they looked brand new. Don’t worry, the .452 version will come pre-annealed using inert gas so you will have a soft and clean bullet for Smooth-Form without having to do any of the work.

A copper bullet will slightly shrink when you anneal it so it came out slightly undersized with my current setting on my Swinglock Smooth-Form die. I didn’t want to adjust the die since I only intended to Smooth Form a few so for the first (and probably only) time in my life I used a pair of files to knurl the annealed bullets up a touch in diameter until I had the proper fit. Some guys do this regularly and it works. I would caution  if you do this, ensure you use high quality files or you could end up with slivers of teeth from the file embedded in your bullets and that will ruin a barrel (happened to a couple of guys I know).

Flat-Base annealed, drawn down to .452, and shot Smooth-Form in my gun:

I Full-Form sized the remainder of the flat base bullets for testing precision and drops to confirm or deny what computer modeling had predicted for ballistic coefficient. They sat for the next eight weeks, unused while I was gone, and were shot when I got back. Apparently a copper bullet will spring back just a touch over time just like a cup and core bullet will. After two months they were just enough larger that they went from one hand loading to two hands. I recommend, regardless of bullet, that you size them only as you need them to fill your shooting needs. I did not bother resizing them because I could load them consistently enough to feel good about it and was getting pretty good precision.

Flat-Base at 100yds from my gun:

Flat-Base at 300yds from my gun:

My buddy Carlos did quite a bit of testing of the M-BOMB as well. Carlos is a long time SML shooter and does a lot of internet muzzle-loader business for Ed’s Gunshop in Vass, NC.  He used two separate rifles for the testing: one gun had a 1-18″ twist like my gun and the other gun was a 1-22″ which is more common for a .45 SML. In either case he met with great success using the M-BOMB and had results compiled for me as soon as I got home from my training.

Flat-Base at 100yds from Carlos’ Gun #1:

Flat Base at 100yds from Carlos’ Gun #2:

Flat Base at 300yds from Carlos’ gun:

With everything having panned out so far Carlos, Rob, and I hit the range to test some 415gn BOMB bullets and to test powder sensitivity with the new M-BOMB. The bore was freshly cleaned so Carlos shot a fouler then we started the test. Using 81gn, 85gn, and 90gn of IMR3031 with the M-BOMB showed very little change in the point of impact across the 150fps change suggesting that the bullet is fairly insensitive to changes in powder charges. This was mirrored in my gun also which showed very little POI shift between boat-tail and flat-base versions of the M-BOMB.

Powder Sensitivity Test: