6x40mm

[gunmutt]

How hard would it be to do a 6x40mm? It would give more room to run the heavier bullets. I do understand that powder would be reduced to a certain degree but overall I believe this could update this wildcat towards todays heavier rounds. In some instances the powder charge might increase in that bullets would not have to be set as deep compared to the 6x45mm.

[GLSHOOTER]

Nov 29, 2012 7:55:00 GMT -8 gunmutt said:

How hard would it be to do a 6x40mm? It would give more room to run the heavier bullets. I do understand that powder would be reduced to a certain degree but overall I believe this could update this wildcat towards todays heavier rounds. In some instances the powder charge might increase in that bullets would not have to be set as deep compared to the 6x45mm.

Oh my!!

The cocept is sound but in reality the "heavy" bullets you can use are not going to gain you much. When you shorten the case you lose capacity. You have to get pressure somewhere and the fallacy of cranking it up in the smaller case is somewhat quetionable for longevity and safety.

If you want the easy route for your desires go with the 6X68 and don't look back. Shorter fatter case, longer/heavier bullet friendly, available realtively CHEAP non-custom dies and super quality 10+ loading brass.

Greg

PS: Did I mention you can get going with a 6X68 from BHW in less than 90 days and maybe less than half that? Oh AND factory ammo ala Tactical Ammunition.

[gunmutt]

I know I know. I just want to push to fat daddy 100+ grainers out of an 18" tube. You know kinda like a 6mm Blackout

[GLSHOOTER]

Nov 29, 2012 14:50:43 GMT -8 gunmutt said:

I know I know. I just want to push to fat daddy 100+ grainers out of an 18" tube. You know kinda like a 6mm Blackout

So how fast do you want to go?

I've loaded a FEW short MAG length heavies but mostly long single shot stuff. I could give you an opinion at least. ( I always have one of those!)

Greg

[40rod]

I load my 16" 6x45 to 2700fps w/ 80gr Barnes ttsx. Since it is copper the ttsx is as long as many 100g jacketed bullets. Sure they are seated deep so what? you should see how deep the military seats the current tracer round. It is a great 200m game load. If you need it for deer out past 300m you need a bigger case. Just like NASCAR there is no substitute for cubic inches. But for a 200m gun I like the 6x45.

[aspp]

I think you would have better luck with a 243LBC or 6x6.8. The smaller case will limit powder volume, and increase pressures. Yes the smaller case head will handle higher pressures, but if you step up the volume you can run a slower powder and get the same or better velocities out of a case that will not be worked as hard. There is a balance to all of that, and I would think that a 6x40 would push too far to one side.

Dont let me stop you, I would be very interested if you prove me wrong! If your serious about it, see if you can find a gunsmith who will run a 6x45 reamer in to 40mm and then make up some ammo to try. As far as new wildcats go, it would be one of the cheapest to build.

Looking around on ammoguide.com it doesnt look like anyone has tried it before, or they havent posted it. Good luck if you decide to go for it!

[gunmutt]

I probably going to experiment with the 6x6.8 first. Its a newer idea and seems to be more of what I am looking for. That case would be better to shorten a hair to pop the longer pills and stay within mag length

[GLSHOOTER]

Nov 29, 2012 20:08:39 GMT -8 gunmutt said:

I probably going to experiment with the 6x6.8 first. Its a newer idea and seems to be more of what I am looking for. That case would be better to shorten a hair to pop the longer pills and stay within mag length

You could trim the neck just a tad and lower the amount of bullet shank covered by the neck backing off the ogive. It won't hurt you a bit to trim a MM or so off the necks if you want to try that.

If you start moving shoulders back you will increase the cost exponentially for little gain IMHO.

Greg

[Deleted]

Nov 29, 2012 20:08:39 GMT -8 gunmutt said:

I probably going to experiment with the 6x6.8 first. Its a newer idea and seems to be more of what I am looking for. That case would be better to shorten a hair to pop the longer pills and stay within mag length

Shortening the case will not give you any difference in length. The maximum COAL will still be the same. The bullet will sit in exactly the same spot. The only thing trimming the case will do is remove the neck material that hangs over the ogive of the bullet. The same amount of space will be taken up with the heal of the bullet in seated in the case.
The only way to solve this problem would be using it in a platform with a longer magazine. A long throated reamer would get you the space.
Another way to accomplish this would be to use a short fat case like the Grendel or the BR. Either would give you the capacity to push the Long for caliber bullets.

[GLSHOOTER]

Nov 30, 2012 18:36:16 GMT -8 @rjohnson said:

Nov 29, 2012 20:08:39 GMT -8 gunmutt said:

I probably going to experiment with the 6x6.8 first. Its a newer idea and seems to be more of what I am looking for. That case would be better to shorten a hair to pop the longer pills and stay within mag length

Shortening the case will not give you any difference in length. The maximum COAL will still be the same. The bullet will sit in exactly the same spot. The only thing trimming the case will do is remove the neck material that hangs over the ogive of the bullet. The same amount of space will be taken up with the heal of the bullet in seated in the case.
The only way to solve this problem would be using it in a platform with a longer magazine. A long throated reamer would get you the space.
Another way to accomplish this would be to use a short fat case like the Grendel or the BR. Either would give you the capacity to push the Long for caliber bullets.

One other thing you can do to cheat is to cut the front out of the magazine. I HEARD it was good for 2.340 for four or five rounds. I have not done it but you now I have some ratty old ones up on a shelf that might have to be sacrificed!!

Greg

PS: There are directions all over the net on how this is done. Google/Dogpile is your friend!!

[GLSHOOTER]

I finally got some time to add to this though I collected my data a few days ago.

First off is a picture of the 6X68 as issued at 43 MM, next to it is one I trimmed back to 41 MM and the one on the far right has been trimmed back to 40 MM. This is 105 grain Hornady that is seated to STANDARD MAGAZINE LENGTH of 2.258.



This is the same ammo but suddenly a window appears in the regular 43 6X68 cartridge. Note how much boiler room is taken up by this big honker bullet. It may or not stabilize in some guns. It is hard to push them fast enough but it can be done if you want to abuse the brass. Realistically I would stick with nothing over 95 or MAYBE 100.



If you look at the rounds it makes no difference how long the case neck is as all it does is cover or uncover more of the bullet shank. Usable case capacity is not impacted by a short neck once you pass the neck/shoulder juncture. If you choose to set the shoulders back you start loosing case capacity at a rapid rate. Far better to stick the bulet down in there than to try and back off.

The next up is a 95 grain Nosler BT. It is a god bullet for deer and you can get enough steam with it to do the nicely. COL is once again 2.258 on this one. You can see where it is not quite as deep but still takes up some space.





The last set up shows the 58 grain VMAX. Truly the darling of the ufr hunter set. No boiler room is stolen from using it seated to 2.258. It can be driven HARD and will reach out way past the range that most of us would be comfortable with on a non-paper target.



Just to see what a load of Benchmark would see if it had a window to let the light in.



I just wanted to show you what it looks like when you start with the big bullets. A certain amount of case neck is required to adequately hold the bullet in concentric alignment. It is possible to crimp the snot out of them and hold the projectile in place but with so little bearing surface actually on the bullet the likelihood of the bullet becoming less than straight during feeding is quite high.

All of these were seated for a standard magazine at 2.258. The ASC's and the PRI's routinely handle 2.300 and that is a help. You can go in and cut a window in the front of the magazine and approach 2.340, so I am told, but that is only god for a 4-5 round capacity.

Just a little exercise in visual aids. I have another series on the 243 LBC that might be informative so I'll start a thread on that. I hope it was informative to all as I know I learned a bunch in doing it.

Greg

[gunmutt]

I understand where you coming from on this. Shortening the will lower its capacity thus making the round a much slower round in the velocity it has originally. The only thing that is gained by shortening is deceiving the ability to seat a heavier grain bullet at the correct depth. And yes moving the shoulder back would need to be done as well. I know it will make for a slower round thus create disadvantages to the original cartridge you created. Both of these would have a place. Your being great for long range, varmints, and taking advantage of the lighter faster bullets in the .243 class. The shorter round would be similar to the 6x45mm only with a wider case thus have a few grains of capacity all the while being able to run the heavier bullets. Again I have no argument towards the 6x6.8.

[GLSHOOTER]

Dec 5, 2012 16:47:06 GMT -8 gunmutt said:

I understand where you coming from on this. Shortening the will lower its capacity thus making the round a much slower round in the velocity it has originally. The only thing that is gained by shortening is deceiving the ability to seat a heavier grain bullet at the correct depth. And yes moving the shoulder back would need to be done as well. I know it will make for a slower round thus create disadvantages to the original cartridge you created. Both of these would have a place. Your being great for long range, varmints, and taking advantage of the lighter faster bullets in the .243 class. The shorter round would be similar to the 6x45mm only with a wider case thus have a few grains of capacity all the while being able to run the heavier bullets. Again I have no argument towards the 6x6.8.

Well lets look at what I consider the answer that is already in our armory and has a proven track record for killing deer etc.

here you go. Same bullets seated to their working lengths that can be increased somewhat depending on the throat of the chamber. I shoot my big boys longer than these are loaded too. The 95's out to 2.307 and some 105's out to 2.342. They were for single shot match usage but they can sure be puled back to 2.258 or 2.298 depending on your magazine.

Hornady 105's.



Nosler 95 BT



58 VMAX



The fat case adds quite a bit to the volume quickly. I shot some 105 grinrs in 243 LBC cases that had the shoulder blown forward 0.017 and the velocities for a load THREE GRAINS HEAVIER were about 80 feet LESS than the short case PLUS the original tall case had the bullets seated 0.080 DEEPER.

The 243 LBC is the only way to fly if you want to fudge factor in the long bullets IMHO. Plus it performs better with the big boys in my experience.

Greg

[gunmutt]

I know the 243 LBC throws the bigger pills but what does it gain over the original cartridge the 6.5 LBC. Here you get the 120-140 grainers and good BC.

[GLSHOOTER]

Dec 5, 2012 18:08:22 GMT -8 gunmutt said:

I know the 243 LBC throws the bigger pills but what does it gain over the original cartridge the 6.5 LBC. Here you get the 120-140 grainers and good BC.

Bullet choice. It really shines with the mid-weights and can be pressed into service with the bigger bullets. It makes an ideal predator round that won't tear up the furs if that is what you are into and will deliver good 6 MM bullets for big game usage.

The 6.5 is going to give you much better big bullet usage at longer ranges but is short on the small end in that few 6.5's are around that won't tear up smaller animals.

Greg

PS: One other thing is that bread and butter is good but a bit of spice like wildcatting adds a kick to it all.