12 Bore Schrifle project

[rookhawk]

Any insights are a welcome addition. I have a lot to learn about slug guns. I imagine you have quite a bit of knowledge as you build them and hunt exclusively with them in state.

I've only learned out of frustration. I don't like modern guns that go way down in value. And I don't like buying new guns where the actual gun "cost" was 15% of finished purchased price. (insurance, distribution, marketing, etc). So those are some of my frustrations I had to swallow my pride to accept. The other issues was quality slug availability. Historically, the most accurate slug ever made was a barnes slug (federal loading?) that was discontinued 4 years ago. Today, a box of 5 of those slugs sells for nearly $80. They were that good and everyone had their guns regulated to that extinct load.

On the open market today, in 90%+ of guns, the most accurate slug by several orders of magnitude was the 20 gauge Remington Accutip sabot slug 3". So instead of doing custom load development (which is illegal in many slug states...factory loads only) it began the "so what is the most accurate slug gun that can be made?".

Options:

-Best of the West slug gun built on a Savage 110 (MSRP is around $6000?)
-TarHunt built on the Savage 110 (MSRP is around $6000?)
-A New England Arms Ultra Slug Hunter. A $115 total piece of junk that now sells used for $700 and needs a LOT of work to be good.
-A new in the box savage 110 heavily customized to overcome SERIOUS defects. (Gun is $700 and you throw away most of the parts)


Things I learned along the way in my plight where handloads weren't an option (some of the insights may be of value on your journey)

-Glass bedding is CRITICAL CRITICAL. The recoil is so fierce, the wood compresses or the screws back out. Either way, accuracy is due to harmonic consistency. The only way to torque down the screws and have them stay put is to glass bed actions.

-Feed sucks on slug rifles. Glass bedding can help with feed as it makes sure the bottom metal/magazine stays put on the correct angles too.

-The most accurate guns use one-gauge down in barrels. Heavy barrels matter. The ultra slug hunter barrels (Verney Caron I believe makes Hastings for almost ALL shotguns?) were 10 gauge barrels with 12 gauge bores, or 12 gauge barrels with 20 gauge bores. That's how a $115 gun could shoot exceptionally well and its why people will drop $1000 on a new in box old stock one today when Walmart sold them for $115 four years ago.

-Good mounts and rings are essential...stuff moves under the recoil of these "bore rifles".

-3" shells have a 90% chance of shooting better than 2-3/4" shells across the board. Why? Its a freebore issue or a gas pass through issue. Bullets closer to the forcing cone / lands appears really important.

-Extraction can be an issue. Bolt slug rifles are important and useful.

-Cleaning regimens need to be similar to muzzleloaders. The fouling of lead, copper, and plastic is a mess and it builds in layers. A bore snake and done is not a good plan with a slug rifle.

In the end, 3"-5" five shot groups are possible at 300 yards, but I found it cost $2800 or more to get there, and in the end I own a laminate and plastic pile of crap that will be at a garage sale someday. Never have I spent more for less...$2800 can buy a hell of a fine vintage rifle that appreciates in value, whereas I was forced to buy tactic-cool junk due to legal restrictions in the midwest...still sour on that. (as I look at three of these custom rifles staring at me in the case)


For the sake of argument, have you tried the new barnes factory 12 gauge slug OR the Remingon Accutip 3" just for comparisons? I realize you're cutting your bullet weight in half if you do, but your KE and penetration are up. I would think something at 1750-1900fps at 500gr might be more effective than 1000gr at 1000fps for close work?

In the olden-days I think the 12 bore paradox rifle was shooting a 2-1/2" 12 bore load of cordite with a 730gr piece of lead at 1150fps and 4.3tpsi (*Westley Richards) . Another was 2-1/2" case with black powder and 750gr lead at 1000fps for 1.8 to 3.5tpsi (*proof house records). These were with fosberry bullets. <- This tells me that bullets being lighter might be necessary to safely get you the speed you want?

 

[Shootist43]

Chris, have you considered using Trail Boss as a powder for your project?

 

[Shootist43]

Rookhawk, I put a Hastings barrel on my 870 Remington and never looked back. The gun would cloverleaf at 75 yds. which is where I had it sighted in for. I used that gun for a couple of years when I hunted in or near a swamp and 100 yd. shots were possible but not probable.

 

[ChrisG]

Chris, have you considered using Trail Boss as a powder for your project?

Trail boss is so fast burning I wouldn't likely get much more than 500-600 fps before I hit max pressure. Plus there are no pressure signs for a shotgun when you are wayyy overpressure. You likely wouldn't get any pressure signs until you are 3-5 times max chamber pressure... if your gun didn't blow up first. So until it is tested you can only extrapolate from known data. Trail boss shouldn't be compressed at all and has a burn rate similar to bullseye. If I could find a way to fill the shell up and just set the bullet on top without touching the powder, perhaps I could make it work... at that point though I am in totally uncharted waters and I prefer to stay away from those.

 

[rookhawk]

3021 is the closest thing to cordite. Wouldnt' that be the path forward if you wanted to build based on known paradox / fosberry loads?

 

[ChrisG]

So I went to the range today and tested a few rounds out. All seemed to be fairly low pressure compared to the 3" turkey loads in terms of recoil and report. Those gas seals picked up about 100 fps without modifying charge weight at all.

35.0 grains
300 MP.
Chronograph didn't read but powder didn't burn completely and report and recoil weren't all that impressive.

The bullet skipped up the hill about 200 yards and was found lodged in the snow and ice after about 4 skips. Velocity couldn't have been more than 550 fps.

30.0 grains
Alliant Blue Dot
950fps.
Report and recoil were definitely "shotgun-like" and the bullet could be heard audibly passing through the air and the impact with the target board sounded like hitting two wooden baseball bats together.

20.0 grains
Unique
865 fps.
Similar to above but with less recoil.

 

[Hogpatrol]

Can you use two gas seals? Picking up that much velocity is pretty impressive and validates what I thought about gas leakage around the wads. I would surmise your next step would be with the powder charge or type or with the existing loads are you going to first have a pressure test?

 

[ChrisG]

Can you use two gas seals? Picking up that much velocity is pretty impressive and validates what I thought about gas leakage around the wads. I would surmise your next step would be with the powder charge or type or with the existing loads are you going to first have a pressure test?

I am going to abandon Unique and 300MP. They are simply not going to work for what I want. I'm going to stick with Blue Dot. I will try 31 and 32 grains of that next. A 1 7/8 oz. Shotload in this shell calls for 34 grains of blue dot(1,155 fps). Since that load doesn't have to be squeezed into rifling, I am going to stop at 32 grains until it is pressure tested. If those get me up to the velocity I am looking for, I am going to send those off to be pressure tested. I don't want to try two gas seals as they are not very compressible and I would need to remove the cushion wad. This could lead to dangerously high pressures. I found one of the gas seals downrange in the snow and it was in perfect shape, blackened a little and with rifling marks around the outer surface. So I would guess that it did it's job very well and didn't collapse or tear apart.

Here are the ballistics I calculated for this bullet with a muzzle velocity of 1050 fps and a sight in range of 85 yards. Totally viable as a 100 yard large game cartridge.

 

[rookhawk]

Question: will 1.5 ounces of soft lead, say at 1500 foot pounds and 900fps, have sufficient penetration?

I don’t know, that’s why I’m asking.

I say this because an all copper sabot 3” at 260gr going 1900fps is not an ethical deer killer past 300 yards....and that’s a lot smaller bullet of better tech traveling faster with a better BC. (500fpe @300yds)

 

[Hogpatrol]

I was thinking with two gas seals, one on top of the powder and one under the slug. That way you'd still have the cushion but have a secondary gas seal. It looks like you're on the right track.

 

[ChrisG]

Question: will 1.5 ounces of soft lead, say at 1500 foot pounds and 900fps, have sufficient penetration?

I don’t know, that’s why I’m asking.

I say this because an all copper sabot 3” at 437gr going 1900fps is not an ethical deer killer past 250 yards....and that’s a lot smaller bullet of better tech traveling faster with a better BC.

It isn't soft lead. I cast them of a mixture of 1lb wheel weight, 1oz. Antimonial lead (20% Antimony and far harder than linotype) and the rest is pure lead. They are dropped into a bucket of cold water and in about a week they have age hardened up so much that you can't scratch them at all with your fingernail. In .45 super, I've put that alloy through blocks of hardwood and boxes of sand and aside from the sharp edges being smoothed off, most of the bullets look like they could be reloaded. These are also not hollow at all (like a slug), but one solid piece of lead with a SD of .208. To put that in perspective, that's more SD than a .44 mag 260 grain bullet. I've seen deer killed with one of those (from a rifle) at over 100 yards and got a complete pass through. It was only carrying about 750 ft lbs AND didn't have a problem. It also is shaped like a wadcutter and punches .60" wound channels without any expansion. I am thinking it should penetrate stem to stern without too much trouble.

You can't see the bottom of my chart but my bullet is still carrying 981 fpe at 300 yards. I will never shoot it that far, but because of its weight, it carries it's energy a LONG ways

 

[ChrisG]

Thought this was interesting but proved my point that with regular shotgun loads, barrel length has very little effect on velocity until you go ridiculously short

 

[ChrisG]

So the bolt action 12 gauge is gone. I bought an H&R ultra slug to replace it. They are stoutly built with barrels the size of a 20mm cannon and an action that will handle the pressure of heavy slug loads for years to come. It got the same treatment :

So I loaded up some of those punkin' chuckin' rounds with 32 grains of blue dot. Average velocity with 2 x 1/2" veg fiber cushion wads, capped on each end by a nitro card and sealed with a gas seal was 1,008 fps. I don't know if I want to much beyond that. Even as the rifle sits, it weighs around 8.5 pounds and recoil is starting to get fierce. Calculated momentum puts this round up in about the same category as a .375 H&H loaded with 300 grain bullets. Even though energy is only just over 1,700 ft-lbs.

Still playing with it but I like that load, now I just need to sight it in.

 

[Hogpatrol]

Is that a rifled barrel? Are you shooting bare lead? Just curious because I tried it with a rifled 20 gauge slug gun and it took me two hours to peel the lead out of the rifling.

 

[ChrisG]

Yes it is rifled and it is an exposed lead bullet but I smear my own homemade soft bullet lube into the grooves. The lube is 25% carnauba wax, 50% petroleum jelly and 25% beeswax. The bullet is also not cast of pure lead but has about 3% antimony and 2% tin. It's hard enough that you can't scratch it with your fingernail. Zero leading issues. Here is a bullet I recovered from the snow fired a few weeks prior.

 

[Hogpatrol]

Yes it is rifled and it is an exposed lead bullet but I smear my own homemade soft bullet lube into the grooves. The lube is 25% carnauba wax, 50% petroleum jelly and 25% beeswax. The bullet is also not cast of pure lead but has about 3% antimony and 2% tin. It's hard enough that you can't scratch it with your fingernail. Zero leading issues. Here is a bullet I recovered from the snow fired a few weeks prior.
View attachment 277065

Looks good! Any acceptable accuracy?

 

[ChrisG]

Looks good! Any acceptable accuracy?

I don't know yet. Up to this point it has all been load development and chronographing. The next stretch is getting on the bench and seeing how I can do with it out to about 75 yards

 

[ChrisG]

So I left this thread hanging a bit... here was the result of shooting for a group at 75 yards with a red dot on the rifle. I could still work on it but it is probably a result more of recoil fatigue on my part than mechanical accuracy of the gun. I only had four to shoot that day after sight in and if you discount the last shot low left, 3 of them were within 2 inches... not bad for a bullet that is 3/4" in diameter!

Getting roughly 1050fps with this load. It is a blast to shoot off hand and the audible sound of the bullet moving through the air is an experience!

 

[ChrisG]

Here is the recovered bullet after passing through a hardwood pallet and 2 feet into the packed, dry, hard clay berm.

 

[DonT]

ChrisG,
Quick Question... That last shot that went low left, is it the way the target was photographed or did it actually start to keyhole on you??
DonT