Thread: Ultimate compact rifle & catrige - 6mmGT/22GT in howa mini action

If you managed to get a gt chambered in a Howa mini, you probably won’t be able to get the performances that you can get in a standard action, simply due to the higher pressure that this case needs to generate to perform. ( I have chambered a 6mmgt barrel and fitted it to a defiance).

However a 6mm or 22 grendel or Arc would work well in the mini.
Also , a GT into an ex 22-250 kimber might work as well, if it can feed properly.
The Remington 788 in 22-250 would be another candidate.
But then, if you had a 22-250 you probably would not need a gt.

Originally Posted by Pommy

The Mini comes in 450 Bushmaster. That's based off of the 284 Win case and has the same .473 head. So it'll have a 308 bolt face.

That said, the bushmater has a pressure limit of 38,000psi which will limit the bolt thrust. I suspect there's a good reason that the engineers at Howa haven't chambered the mini in any high pressure 308 bolt faced cartridges like 6BR (other than the mag length being an obvious limitation).

Very good point there Pommy. the sammi pressure for 6mmGT is 62000PSI. However, I think howa mini can handle it fine. The custom rifle the guy built used BAT bumblebee action, which is aluminium. I am pretty sure mini is stronger than that. I didn't know there is mini for 450bushmaster, looks the mini family are expending

Originally Posted by hey

Very good point there Pommy. the sammi pressure for 6mmGT is 62000PSI. However, I think howa mini can handle it fine. The custom rifle the guy built used BAT bumblebee action, which is aluminium. I am pretty sure mini is stronger than that. I didn't know there is mini for 450bushmaster, looks the mini family are expending

You need to get to grips with how bolt thrust works, there is a reason the mini action is smaller than a std 1500 ,. . . I also think the 6 GT would be a great cartridge for NZ, I currently run a 6.8 SPC (pretty much the same as the 6.5 Grendal) and something with a bit more snot but without the barrel burning habits of the 243 and 6 CM would be nice. I doubt you'll fine a gunsmith brave enough to do it in any of the mini actions, and if you do you'll find yourself in mag feeding hell, there is a big difference between the x39 based cartridges and the ex 308 ones.

Originally Posted by Tentman

You need to get to grips with how bolt thrust works, there is a reason the mini action is smaller than a std 1500 ,. . . I also think the 6 GT would be a great cartridge for NZ, I currently run a 6.8 SPC (pretty much the same as the 6.5 Grendal) and something with a bit more snot but without the barrel burning habits of the 243 and 6 CM would be nice. I doubt you'll fine a gunsmith brave enough to do it in any of the mini actions, and if you do you'll find yourself in mag feeding hell, there is a big difference between the x39 based cartridges and the ex 308 ones.

I am not sure the bolt thrust has much to do here. F(bolt)=P(max)xA(internal or external), so long the pressure is same and the case head is same then the bolt thrust is the same. So really it is the pressure we are talking about here. the 5.56 (nato version if 223) has sammi pressure of 62366 psi, and your 6.8 is not far behind. Both are used in AR, a platform known weaker than a bolt action. the mini certainly will be weaker than a standard action but by how much is anyone's guess. Again you have very good point there. As for magazine, if it can deal with 450 bushmaster then it should work on GT. I have a 3d printed mini magazine so it is not end of the world if the factory one doesn't work.

"I think it can handle it" probably isn't good enough in this instance.

Copy/paste from BAT's website: "Action body is made with a combination of Aircraft grade billet 7075-T6 Aluminum and hardened 4140 Chromoly Steel to gain the best combination of light weight and high strength". So the Bumblebee's body might be Al, but you can bet the important bits - like the bolt head and lugs - will be steel. The footprint is also Rem 700 so it's going to be beefier than a Mini action.

With 63% more pressure than a 450BM and a larger case head than a 223/5.56, Grendel or SPC, there's going to be a lot more bolt thrust with a 6GT. On par with a 308 or a Creedmoor. Rifle actions are probably over-engineered. So I doubt you'd be about to blow your face off. But unless you know the exact FoS, you'll have no idea just how close to the sun you're flying.

Originally Posted by hey

I am not sure the bolt thrust has much to do here. F(bolt)=P(max)xA(internal or external), so long the pressure is same and the case head is same then the bolt thrust is the same. So really it is the pressure we are talking about here. the 5.56 (nato version if 223) has sammi pressure of 62366 psi, and your 6.8 is not far behind. Both are used in AR, a platform known weaker than a bolt action. the mini certainly will be weaker than a standard action but by how much is anyone's guess. Again you have very good point there. As for magazine, if it can deal with 450 bushmaster then it should work on GT. I have a 3d printed mini magazine so it is not end of the world if the factory one doesn't work.

Nice i have been trying to find the STL for those for a while.

Originally Posted by Pommy

"I think it can handle it" probably isn't good enough in this instance.

Copy/paste from BAT's website: "Action body is made with a combination of Aircraft grade billet 7075-T6 Aluminum and hardened 4140 Chromoly Steel to gain the best combination of light weight and high strength". So the Bumblebee's body might be Al, but you can bet the important bits - like the bolt head and lugs - will be steel. The footprint is also Rem 700 so it's going to be beefier than a Mini action.

With 63% more pressure than a 450BM and a larger case head than a 223/5.56, Grendel or SPC, there's going to be a lot more bolt thrust with a 6GT. On par with a 308 or a Creedmoor. Rifle actions are probably over-engineered. So I doubt you'd be about to blow your face off. But unless you know the exact FoS, you'll have no idea just how close to the sun you're flying.

Don't think GT can be compared to 308 or creedmoor, 43gr VS 54gr water capacity. I agree the Bumblebee could be strong but doubt will be as strong as howa mini. steel is roughly 2.5 times stronger than AL, and I don't think bumblebee is twice as big.
good discussion though guys. have a good weekend

Not a chance. Howa engineered it and choose not to use high pressure cartridges in it. Aluminium sleeved actions have been with us for decades and are proven. Its not just the material. Its the complete design.

I suggest you represent yourself when you sue Howa.

Hmmm. I get the impression you still want to press ahead with your idea. It's a very bad idea. So don't say you weren't warned, if/when it goes horribly wrong.

Originally Posted by hey

Don't think GT can be compared to 308 or creedmoor, 43gr VS 54gr water capacity.

In terms of bolt thrust, yes it can. You looked up the formula for it - it's just force = pressure x area. Nowhere is case capacity a factor.

I agree the Bumblebee could be strong but doubt will be as strong as howa mini. steel is roughly 2.5 times stronger than AL, and I don't think bumblebee is twice as big.

I quoted BAT to specifically point out to you that their action is NOT 100% aluminium. It's just the outer body. The rest is 4140 Chromoly Steel. I don't know why you chose to overlook that. They reckon the thing is stronger/stiffer than a similar action made of Ti!!!

Originally Posted by hey

not sure about that claim. I have shot a fallow with 69smk at the range of 50M, hit in the lung, watch it bolted. Then spent quite lot time to track it down. It is dead about 50m away, but in the thick bush it is very difficult to track it, no blood trial at all. I've also watch a friend shot a red hind with is 223, again it hit the chest, same thing, bolted and that time we could not find it. I agree shot placement here is the key for 223. but more speed/energy can't go wrong

You lost me after "spent a lot of time to track it down"...I use a .308 with 100 grain hollowpoints for fallow...I squeeze the trigger.. deer falls over dead. Sorted.

If you want to run a 22 wildcat chambering ,then surely, the most obvious choice would be the .22 Grendel .


Just putting it out there .

Originally Posted by hey

Don't think GT can be compared to 308 or creedmoor, 43gr VS 54gr water capacity. I agree the Bumblebee could be strong but doubt will be as strong as howa mini. steel is roughly 2.5 times stronger than AL, and I don't think bumblebee is twice as big.
good discussion though guys. have a good weekend

Like I said before, you need to understand how bolt thrust works, and your comments show you clearly don't. It's a function of the internal base diameter of the cartridge (area) and pressure (thrust) and locking lug shear strength.

Wow! thanks guys. For worrying about firearm safety. I appreciate that.
But, before you go on think I am going to blow up my gun with this carriage, have you actually had a look of the Mini bolt? Say put it side to side to a Tikka bolt. You might notice the bolt face wall thickness is about the same (if not thicker), the lug thickness is also about the same. They didn't make those important things "mini".
There are discussions about if bolt thrust is the only main safety factor for a bolt gun. As I understand it, for a bolt action rifle the majority force of the bolt thrust goes into its lugs, where it happen to be the strongest part of the action (for a reason). To cause failure of the lug you need very high forces. here is the force required to cause 4140 steel to fail.
ROCKWELL ‘C’ HARDNESS 4140 YIELD STRENGTH PSI
20 83,500
22 87,000
30 135,000
34 148,750
37 159,000
42 178,000
46 195,000
49 211,000
Now to reach this kind force, I will be worried more about other things first. like the case will be ruptured or at minimum the primer will be blown off, so the hot gas will flow through the bolt and heading towards shooter. Here is where howa bolt shines. It has 4 vents to direct hot gas away from shooter, while Tikka has none. If gas still reaches the shroud, the howa has metal shroud, while Tikka has piece of plastic (ok the later model has metal one now). On top of that the Mini has M16 style extractor which is consider safer than Tikka/Sako. So I will trust more in howa in such scenario.
I do own one gun that has lug setback due to the bolt thrust (only 1 thou so not an issue), and it is Remington titanium 700, never happened to my steel actioned rifle. Hence my suspicion about other material. I have never owned a Aluminum actioned rifle so happy to hear other opinions.
Happy discussion

Originally Posted by Ranger 888

You lost me after "spent a lot of time to track it down"...I use a .308 with 100 grain hollowpoints for fallow...I squeeze the trigger.. deer falls over dead. Sorted.

Well, that was the time when AR was still around, was the last time I shot deer with 223

Originally Posted by hey

Very good point there Pommy. the sammi pressure for 6mmGT is 62000PSI. However, I think howa mini can handle it fine. The custom rifle the guy built used BAT bumblebee action, which is aluminium. I am pretty sure mini is stronger than that. I didn't know there is mini for 450bushmaster, looks the mini family are expending

Originally Posted by hey

I am not sure the bolt thrust has much to do here. F(bolt)=P(max)xA(internal or external), so long the pressure is same and the case head is same then the bolt thrust is the same. So really it is the pressure we are talking about here. the 5.56 (nato version if 223) has sammi pressure of 62366 psi, and your 6.8 is not far behind. Both are used in AR, a platform known weaker than a bolt action. the mini certainly will be weaker than a standard action but by how much is anyone's guess. Again you have very good point there. As for magazine, if it can deal with 450 bushmaster then it should work on GT. I have a 3d printed mini magazine so it is not end of the world if the factory one doesn't work.

Originally Posted by hey

Don't think GT can be compared to 308 or creedmoor, 43gr VS 54gr water capacity. I agree the Bumblebee could be strong but doubt will be as strong as howa mini. steel is roughly 2.5 times stronger than AL, and I don't think bumblebee is twice as big.
good discussion though guys. have a good weekend

I agree with tentman your in dangerous territory making engineering assumptions especially as you clearly dont grasp even half the concepts.

The BAT action uses a 4140 chromoly steel (around 655Mpa yield) portion at the front for the bolt lug recesses and the barrel threads. This is the area that takes almost all the load and is further supported by the 7075 heat treated aluminum sleeve (around 450Mpa yield). It is larger than the howa mini (made of some sort of stainless probably a 416r(around 650Mpa) by a significant portion and far stronger and takes magnum cartridges. You can see the aluminium is not much weaker and the 4140 yield i gave is as supplied it can be much stronger whereas the 416 has issues with impacts if hardened further. Also the lugs on the mini are tiny, a kimbers are noticeably larger to take 308 cases. The lugs of the remington 700s or BAT action are larger again.

Everything behind the ejection point can be almost any material i.e. how ar15s can be made with plastic upper receivers and the majority are aluminum as all the chamber forces are maintained with steel up front and the only serves assistive functions and only needs to cope with recoil forces. there are lots of aluminium actions nowadays, seekins, sauer, gunwerks, blaser to name a few

Bolt thrust increases significantly as bolt face cartridge diameter does. A 62kpsi case the diameter of a 223 and one the diameter of a 308 is not even close to the same when talking bolt thrust its 56% higher. Also case diameter is the main determining factor is bolt thrust not powder capacity. This can be seen in the 84M and 84L kimber action which share the same action design from the ejection port forward as the bolt face remains the same even though i can run a 280AI in one that holds equivalent powder to most short magnums.
Its even hypothesized that with minimal taper cases that the longer cases actually work better as they gain more grip with the sides of the case to help the brass hold some of the force reducing bolt thrust.

After all that I know Guys have built 6mmBR Howa minis and their wildcats but all are playing on the fine edge of things where an oily chamber cause cause a failure whereas normally it would just cause a sticky bolt as damaged brass. Most smiths wont do it in NZ.

Lastly why build a 6.5GT on a Howa action when its performance gains in short short barrels is minimal then its no longer compact and for less weight a 16 inch 6.5 creed in a kimber will outperform it easily without going custom.