770 grain full-bore thumper

[oldandslow]

Hi Folks, 7/16/12

After an eight month delay I finally was able to get my hands on a 5# keg of Blue Dot powder and start load development for my Accurate Molds 770 grain full bore 12 gauge slug. I slugged the barrel and ordered 0.001" oversize from Tom.

I tried four different combinations of slugs in my smoothbore Remington Marine Magnum shotgun, including the BPI Shuttlecock (1.03 oz.), BPI Foster slug (0.86 oz.), Gualandi full-bore slug with attached wad (1.125 oz.) and the Lyman 525grain cast slug. Despite multiple attempts to get consistent accuracy at 25 and 50 yards using all the tricks I've read about here and at SGW the results were disappointing (2-8" groups). I tried multiple wads, shot cards, cutting petals half way and all the way off wads, roll and fold crimps and filling the rear cavity with epoxy resin, all with a clean barrel. The Gualandi slug gave great results with 1.25" groups at 25 yards and 3" groups at 50 yards but I hate to have to depend on these Italian imported slugs making it 12,000 miles to my home.

While some posters have good results with the above slugs many more at SGW and here seem to prefer full-bore slugs. When I was finally able to acquire some powder which others had recommended (Blue Dot) I changed the barrel to a Savage 24" rifled barrel made to fit the Remington 870 and started load development. Using the powder loads graciously provided by some helpful posters I started with 30 grains and experimented with different wads (BPI #18, Federal 12S4, Remington 12L's and an assortment of cut down wads, 12 gauge shot cards and gas seals in a 2.75" BPI unprimed hull (I can't get primed hulls shipped to me by any carrier).

Final results- velocities in the 950-960 feet/second range, accuracy of 1-1.25" consistently at 25 yards (mainly to be used on pigs from 10-50 yds) with all the tested loads (except I did not load the Rem. wads as they seemed too lose a fit in the hull). Scope used was a Leupold VX-3, 2-8 power mounted to the receiver. No leading at all and just a touch of unburned powder in the barrel. I tried moving up to 32 grains but the recoil and unburned powder increased moderately for a minimal change in velocity (1008 f/sec).

I want to thank all the people who chimed in with load data and encouragement here and at SGW, including but not limited to Longbow, Turbo, Hubel, Greg, Tommygirl, Ajay and the rest.

best wishes- oldandslow

[Al in Mi]

how did you fit up a Savage barrel for a 870?

[oldandslow]

Al, 7/22/12

When looking for rifled barrels for my 12 Gauge Remington Marine Magnum shotgun there seemed to be two sources for barrels. First is the Remington factory barrel which cost a bit over $300, then there is a Savage barrel made for the Rem 870 which is a drop in fit and costs about $200. I'm always a little leery of "drop-in" parts because many times they don't drop in but in this case the Savage barrel fit great. No free movement once the barrel nut is tightened up and the groups I get are similar over repeated outings to the range. I've done some internet searching looking for feedback on the Savage rifled barrels and it seems most everyone is happy with them. I'm just sorry that I didn't get the rifled barrel sooner as I spent a lot of wasted time and money on trying to make the saboted slugs work (but I guess then I wouldn't have known whether they worked or not with my gun). Hope this helps.

best wishes- oldandslow

[longbow]

Good to hear things are working out well for you.

I am still working with my smoothbores and making progress but not as easy or as good results as I had hoped.

I originally thought full bore slugs were the way to go but after shooting hundreds of slugs in a variety of designs, my results showed that a slug loaded into a standard shotcup tended to be more accurate. Having said that, to 50 yards my round ball loads shoot as well or better than most slugs I have tried.

A couple of exceptions have been some factory Foster loads, Gualandi DGS slugs and AQ slugs.

For rifled barrel I think I would go full bore because it just makes sense to me and eliminates the variable of a wad/sabot.

I think the main attraction to shotgun slug shooting for me is that giant "boolit" heading downrange!

I took a look at the Accurate website and am guessing your "boolit" is the 73-770S. Nice looking slug. Tom does nice work on his moulds doesn't he?

When I started out I followed Lyman recipes which used typical shotshell powders like Unique and PB under the Lyman Foster slug. In the end I gave up on the Lyman Foster slug and found that Blue Dot gave me very good results in most of my loads so I have stuck with it.

So far, I am quite happy with Blue Dot even in cold weather where Blue Dot has a bad reputation for poor ignition at times. I have shot in sub freezing temperatures several times with no problems that I noticed.

Blue Dot does seem to need a good gas seal and seems to favour heavy slugs though I got some great results using Blue Dot and 0.662" round balls (1 oz.) as well.

With a full bore flat based slug like yours, gas seal should not be an issue but with under bore balls/slugs in shotcups a solid wad column is needed to keep the gas seal from distorting and failing ~ especially under round balls.

It looks like you have made a good choice and are getting the results you were looking for. I just may have to break down and get me a rifled barrel/gun!

Good work!

Longbow