I figured it was time to post some work I had been doing since last summer. I've had my Ithaca Mag10 for a few years, it is one of my favorites. Last year, about this time, I was walking through a gun store and happened to notice a rifle sighted barrel. It was an SP10 barrel, but I took a chance and bought it. Thankfully Remington did keep most of the dimensions from the Mag10. The SP10 barrel had the same diameter/length shank to fit the receiver, and the gas system was identical. Unfortunately the difference was the bolt notch cut was short by maybe .030". I tried all kinds of gunsmiths, all of them told me it was not possible to fit the barrel. Still, so many had done it before I knew it was possible. Finally I took maters in my own hands. I ground a flat file to the exact width of the bolt notch in the barrel, and made a simple guide to help keep the angle. I then spent a couple hours carefully filing. That barrel is extremely hard, it took about 2 hours to cut .030". To do this I needed to remove the bolt, and using a brand new shell for headpace, I cut until it would just close on the brand new shell.
After all that, I shot the first couple shots with a string. Success. I then glued a strain gage onto the barrel for pressure testing and went to work. The barrel came with a very tight turkey choke. The only source of 10 gauge remchokes I could find was Brileys. I bought an extended cylinder. The bore on Ithaca and Remington 10 gauges is .780" or thereabouts. This "cylinder" choke measures .770", so it's actually an improved cylinder. No response from Briely's about a replacement. The only other thing I did was replace the front sight with a blade, which I prefer.
The first thing I did was work up some bismuth shot loads. I was getting sick of paying 3x the price for the BPD-10 wad, and it's spotty availability was the final straw. I went with my old steel shot favorite, the SAM1. Using the Pressure trace II system, I found the following load to be ideal. *Warning, the following data was not professionally tested*
Remington 3 1/2" hull
Remington 209 primer
37 grains Bluedot
Sam1 10gauge wad + 20 gauge felt wad in bottom
2 ounces bismuth B shot
PSB buffer
overshot card
fold crimp
11,000 psi MAP
I don't have a record of the velocity, I seem to remember around 1275 fps from my 32" barrel
Note that this load is nearly identical to a load from the Lyman shotgun handbook. In that load, it used the BPD-10 wad with 36 grains Bluedot. The SAM1 wad patterns tighter too. With B shot, it is an honest 50-55 yard goose gun, and I've absolutely smoked some ducks with it too. Notice in the following pictures that the wad gas seals are in great shape. One nice feature of the SAM1 wad is that the gas seal ruptures if pressures are too high. I've never found a ruptured 10 gauge version, but have got ruptures in 12 gauge. They pretty consistently let go around 13,000-14,000 psi. Both the 3" and 3 1/2" 12 gauge versions do. Many 12 gauge 3 1/2" loads using these wads are inconsistent because they run up to the SAMMI maximum, and the ruptured seals ruin consistency.
After bismuth, I turned to some slug loads. The most obvious choice was a round ball. I also played with my custom Accurate 73-943CN, with improved hollow base, it came in at 1 3/4 oz. Using the latter slug, I couldn't quite get a good fit with wads. I turned to a creative solution that may prove useful for someone in the future. I cut sabot's from milk jugs! I first cut into strips the correct width for the bullet length. I then cut them to length to fully circle the slug, but no more. I finally cut those strips in half, creating two half shells. It's a PITA, but actually works well. In the following picture, you can see all recovered sabot's were in great shape. The problem in this case was the slug. Groups ranged about 2 feet at 50 yards. I don't know why the slug is bad, but it's bad. I get similar performance in 12 gauge, and only a rifled barrel 12 gauge brings those groups down to about 12" at 50 yards. It is a failed slug design. I was impressed with the mild jug sabot's though. The thickness was thinner than a wad, yet very tough, consistent, and economical. I have to think this could be used in other loads.
Turning to the round ball, I found instant success, as I always do. My first tests were with a .780" ball, and later went to a .784" ball. In my particular gun, the .784" works better for the .780" bore. Load data is easy, I used 1 5/8 oz data. Using the PT II system, I found pressures similar or lower than lead shot data. For example, one load I found was Remington hull, Rem 209 primer, 43.5 gr Bluedot, SP10 wad (plus a bunch of spacers), 1 5/8 oz lead shot, fold crimp. Instead I substituted with a stack of hard card wads, and a round ball. I recorded 8,000 psi. Bluedot works PHENOMENALLY well in 10 gauge. Even at this low pressure, the burn was incredibly clean. Over time I came up with the following load, which I was shooting the other day. *Warning, the following data was not professionally tested*
Remington 3 1/2" hull
Remington 209 primer
45 grains Bluedot
X10X gas seal + (6) 1/8" 10ga nitro cards
3.4 CC scoop PSB buffer
.784" round ball
fold crimp (an overshot card can be used to improve the crimp)
Guestimated velocity at 1350 fps.
It's not quite tack driver, but at around 4" at 50 yards, it is as accurate as any round ball in a smooth bore that I've tried. The following groups were shot on a windy day.
The first went 4" even, 5 shots at 50 yards.
I then adjusted the sights, and shot these five into 4.5". I also found a box of Federal 1 3/4 oz rifled slug factory ammo, which is the holes with cardboard. They went about 12" at 50 yards. So much for factory slugs being accurate.
At $12 a box, I didn't want to cut open a shell. My guess is that Federal uses a far too undersized slug. In cutting open 16 gauge slugs, I found federal uses a slug of only .635". That's practically a 20 gauge slug! The 12 and 20 gauge slugs are much more in line with reality, I don't know why they use such poor slugs for 16 and 10 gauge.
I haven't got any takers on deer hunting with this yet. Recoil is not that bad. A .780" cannonball at 1300+ fps is heavy, but most of the lighter 12 gauge guns are worse.
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Originally Posted by bikerbeans
