Introducing the THR10-51 aka 40-308

[BT Sniper]

Here are some pics of my new caliber. Well maybe not all mine but certainly a joint project with credit given to those that where gracious enough to help me.

I'm currently loading blanks for fire forming the brass so the post will be short for now but here are some pics to keep you all interested.

A lot more to come!

Till then let me introduce the

"THR10-51" or "400 THR Knockout" not quite sure of offical name yet. I like the looks of both.










Here is alook at all the ingrediants I used for the COW (cream of wheat) method of fire forming cases.

[DukeInFlorida]

Brian, looks suspiciously like 300 aac blackout, except oversized....

Nice work.

[BT Sniper]

It does does'nt it! I actually got some 300aac brass I'll have to compare next too.

Now that you mention the 300 aac blackout maybe I'll call this one the 400 THR Knockout!

BT

[b52fizzle]

What shoulder diameter did you go with, I thought of "copying" the 40/400 whelen but use the .400 bullet with .458 shoulder, like the idea of using the 308 with this shoulder and neck, shooting the heavy for caliber subsonic loads. How do I go about getting barrel chambered, dies made, proper procedure I guess you could say.

[BT Sniper]

Well I'm pretty simple minded about such things. This caliber shown above is nothing more then a standard 308 case necked up to 40 cal.

This cartridge has allready been proven by others and I expect I'll be shooting it a bit this weekend. Don't know what size piece of lead we could throw out the end off the barrel for subsonic loads but a 300 grain 40 cal at 1100 FPS should pack a pretty good wallop if in fact the 40-308 would throw it that fast?? I think the 338 spectra is shooting the 300 grain SMK bullet subsonic and I think it is nothing more then a 10mm case? Yep looked it up, teh 338 Spectra launces the 300 grain bullet at 1,000fps and the parent case is simply the 10mm! This 40-308 I would think has A LOT more case capasity. Bigger bullet??!!!!

As for barrels and chambers, you can pick up 40 cal barrel blanks from many of the custom barrel makers out there. Getting it chambered maybe the difficult part. I maybe looking into having a custom reamer made for the 40-308.

Range tests will come soon!

BT

[BT Sniper]

Fire formed 275 rounds of brass this morning. Now to inside neck ream and anneal again.

I had some duds in my fire forming. Probably 25% of my loads did not fully expand the neck. I could tell the ones that did not get a full burn charge. I think it was because I used the 22 cal cleaning patch rather then a 1/4 square of toliet paper for the wad filler on top of the powder. I might have got some of the COW mixed in with the powder or somthing? Rather then a BANG all I got was a poof.

I used the TP when I formed my 400 BTS mag cases with zero issues and the 22 cleaning patch with the 10-51. It was the only difference so it must have been the cullpret.

Ohwell, off to the shop.

BT

[BT Sniper]

Results from inside neck reaming 250 thick LC pieces of brass.



BT

[BT Sniper]

Sized, fire formed, annealed 2x, neck reamed, primer pocket reamed, primed, cleaned and tumbled and the resulting 250 40-308s ready to load.



BT

[BT Sniper]

Finally got a chance to get out and shoot the 40-308 this evening. More like late evening!

I was very happy with the results.

I'll have a full write up soon but at 75 yrds with 189 grain HP bullets made from 9mm brass, loaded with 42 grains of RL-7 powder I got a three shot group of .605 and the 45 grain load went 1.0"

It was getting to dark for the crony to measure FPS but I did get initial readings from my first few shots. Loaded with the same bullet and 44 grains of RL-7 I got an average of 2250FPS.

I loaded some 300 grain bullets I had made for me from comercial jackets and was testing those when it got to dark to measure FPS. The last reading I got was 1948 fps from the 300 grain bullet pushed by 41 grans of RL-7.

I was safely able to load and shoot the 300 grain pills with 44 grains of RL-7, no idea how fast I pushed it though.

I got enough brass now to send off to Hornady to have some custom dies made for me. Shooting a .6 group from the 40-308 was pretty good considering I was using 40S&W dies to load the bullets with

Also using the stock "tuperware" Savage fiberglass stock that they say is not good????

Well more to come! It was nice to get out and shoot a bit. Wind was blowing 30 kts all day long till 7pm when I left to go shooting then it finally calmed down.

BT

[Bigslug]

I think you may have just created the ultimate eastern deer cartridge. I really think you've got a winner there.

Now we just need it in a pump action. . .

[b52fizzle]

Not sure why this cartridge intrigues me so, but have been thinking constantly about it. Essentially you have a shortened 400 whelen, which can push a 300-350 gr to 2100-2400fps , comparatively speaking could probably get within 200-300 fps shy of this, with shortened case. Could probably go up to 450-500gr for subsonic use, throat depending.

338 spectre uses the longer 10mm magnum.

40 super can sling a 200gr upwards of 1300 fps, could go 300gr subsonic with this one.

I think I'm combining two threads about this but been following both.

[BT Sniper]

It has been a fun cartridge to shoot. Recoil is pleasent and so far I have been very pleased with the performance.

I took it out the other night shooting milk jugs full of water. With the 225 grain bullet pictured above it smashed threw 6 jugs in a row before coming to a rest. Recovered bullet was 200 grains with a nice mushroom. With the 190 grain HP I got explosive expansion and bullet was stoped in 3 jug. Recovered weight was only 80 grains. It was AWESOME! Just what you would need to make a BIG hole in bad critters.

I don't know how fast I could have pushed 300 grain bullets, I got 1948fps with 41 grains of RL-7 and loaded up to 44 grains. Maybe close to 2100-2200 FPS with the big 300 grain pill? I have a short 18" barrel too, not sure if a longer one would benifit in FPS with this case?

I have a 1-16 twist and not sure how slow and how heavy of bullet I could stabilize. I'm sure I got enough throat to shoot a +400 grain bullet. I bet I would have to load it down a little to keep it sub sonic. Your probably pretty close to my guess too with a 450-500 grain bullet sub sonic. Wonder how big the 458 socoms are shooting?

I'll have some more accuracy testing this summer I'm sure. For now .6" at 75 yrds with 190 grain pistol bullets made from 9mm brass is a pretty darn good shooter. That was my goal with this gun, to be able to shoot a lot of my favorite caliber bullets at increased FPS vs. the most powerful 40 cal pistol and still be able to enjoy shooting it a lot. If I want to go bigger, badder and faster, the 400 BTS MAG is always availble.

Good shooting and swage on!

BT

[BT Sniper]

I'll have to get a pic posted of the "full power" live fire formed brass. The shoulder is much more defined then in the previous pics.

BT

[b52fizzle]

Was wondering about the shoulder sharpness myself just last night, did you just use a 308 reamer then neck with 10mm reamer, then throat? 458 socoms believe run a 500-600gr on the heavy end, I saw a 600 gr bronze solid in one on here some where looked nice. Thought about this one myself, but I am looking for a heavy medium range that has easy to find brass, and a caliber nobody else has, plus if possible can use the same swage dies to make .400's for my 40 super when I get that built.

[BT Sniper]

I didn't cut the chamber, I had a more knowledgeable friend of mine do that. I do expect I may have a custom reamer made in future if intrest and demand deems it.

I'll get a pic of the good looking shoulder as soon as I can.

BT

[a.squibload]

Also using the stock "tuperware" Savage fiberglass stock that they say is not good????BT

Yeah, and it looks awful, you should sell it to me!

Would your knowledgeable friend be interested in reaming another barrel?
(He might get a few hits on that from here.)
Who else would cut a chamber?

What's a price range to look for on a 40 cal barrel?
I've never ordered one, would a specific cartridge designation be necessary
or advised?

You got me all fired up here.

PS: Fire-forming, long ago a friend would cast 7mm boolits to fireform 7mm TCU
cases in his TC, at low power of course. More work but maybe higher percentage
of good ones? I guess if they come out close with COW, the next firing with a
boolit in it would make 'em just right. OK never mind.

[BT Sniper]

Any of the barrel makers out there offer a 40 cal .(400) barrel. A lot under $200, jsut need it chambered. I bet if intrest was enough I could possibly have a custom reamer made for the 40-308. That would certainly make the job of cutting the chamber a lot easier. Then too if intrest permited I bet we could get a package rate from one of the suppliers. We could go as far as providing them with the reamer and they could cut the chamber.

Just a quick search turned up these guys. Of course there are severial other even better quality barrel makers out there. http://www.mcgowenbarrel.com/catalog7.htm

Savage actions are the way to go IMOP for ease of assembly without a gunsmith needed but a bit of common sence is a must. Not difficult and a lot of fun. Once you know how to rebarrel the savage action you all of a sudden find yourself with a safe full of extra barrels. I must have a half dozen or more all ready in varous calibers.

I'm sure we could make it happen for those that may be interested. After all anything is possible and the 40-308 is a good one in my book! Especially since I am shooting the same 40 cal bullets now in both my riffles and pistols.

BT

[a.squibload]

If looking for a Savage 110
I guess the bolt face (diameter, extractor) should be
for a 308 or very similar cartridge.
(Barrel will be replaced anyway.)
I'm no expert on rifle cartridge similarity,
what cartridges would use the same bolt face as 308?

Saw a couple used 110s in 308.
There seem to be quite a few 30-06s available used.

[BT Sniper]

.473 bolt face is comon. 243, 260, 308, 30-06, 270, 280, so on and so on. I'm sure a short action will work best for the 40-308 so look for a savage 10, 11, 12 model etc. The 110 or 111 or 112 etc. anything with a three digit sufix is a long action. The two digit models are short actions.

Use a donor rifle in a caliber you might want to shoot again some day or just what ever happens to be a good bargin. I used a 243 savage model and plan to use the 243 barrel for testing new bullets some day.

I drew a NE Oregon deer tag again this year. Guess what new gun I may be taking out after them this year.

BT

[a.squibload]

Uh, a flintlock pirate pistol? (AAAAAARH!)

Thanks, I had a feeling you would have mentioned that
if it was critical. I'm trying to make it harder than it
really is. As usual!