6x45 load development and observations.

[AJC1]

Got the barrel in the mail yesterday and had it put together. Had 100 pieces of PMC standing by so I found the longest piece and went to finding chamber length. The brass was shot in a loose chamber so it grew another .005 before the die engaged the shoulder... starting at 1.462 and growing to 1.468 I dialed it in until the gun finally closed the bolt at 1.459+. I dialed the die down to 1.456 and installed the expander ball. In a complete change to my previous system and from what I gathered in the brushing thread, I put a light arount of reading sizing wax on a Redding nylon brush and made one pass in each neck while sizing. The process of sizing went much smoother and I observed less handle force needed than sizing 223 withdrawing the expander.... I will stick with this technique with this loading to determine if I like it or not. Trimmed chamfered and deburred the 100 pieces and decided on a load. Ran 10 each of 23.3-24.1 with the Sierra 70 hpfb bullet. Now to see if I can monkey with the adjustable gas block and get this tool on target. No big expectations this trip other than that....

 

[AJC1]

Got out today and got her up and running. Started with some pulled 85 gainers from dad's pile as getting the gun running didn't need to be done with premium stuff. I then shot vs junior a ladder test load. I'm out to gather target measurements but here's the crono data 22" barrel. These represent shots 26-75 through thus rig ever. Group one is junior for shots 26-50 and group two is me after 10 minutes of cool down shots 51-75.
75 grain Sierra hpfb @2.255 aa-2015br

23.3-(2699 fps 49es 19sd)2671 38es 15sd
23.5-(2724fps 50es 19sd) 2720 38es 14sd
23.7-(2744fps 28es 12sd) 2749 28es 12sd
23.9-(2769fps 46es 17sd) lost data
24.1-(2796fps 41es 16sd) 2795 58 23

The 85s during tuning were 23.3 grains ran 2582 but es was 80 and SD 27.

 

[AJC1]

The on paper. Group sizes provided...

 

[AJC1]

Forming another batch of brass. This project is using pmc brass and I plan to form and shoot a batch of 200 or so pieces. If I can hurry up and find some more I'm happy to make that batch bigger....

 

[DMW1116]

I am intrigued by this caliber. What is the advantage over heavy 5.56 projectiles? Looks like the same or slightly more velocity with a heavier projectile with a similar or slightly better ballistic coefficient?

 

[kaferhaus]

It's a fine cartridge which is useful on varmints and deer alike. Very mild recoil and you can use a wide variety of bullet weights/designs with. The primary reason it never "caught on" with the masses is not "sexy". No hyper speeds, not a lot of noise or mayhem created so it never really got out of the wildcat stage. I've built several over the years and invariably they ended up in the hands of a grandchild at some point.

I've taken dozens of yotes, fox and bobcat with them. At at least half a dozen white tail. No fuss, no muss it just works.

With high quality barrels and bullets I never had any issue turning any of them into half MOA rifles.

 

[Charlie98]

This project is using pmc brass

John, what kind of PMC brass? What headstamp?

 

[AJC1]

John, what kind of PMC brass? What headstamp?

Standard 223 pmc brass... I don't have a better description .

 

[AJC1]

Loaded the last of the 75 hpfb Sierra varmitors at 23.6. Split the difference between best group and best crono numbers. Just fire forming brass and breaking in the gun. It's a riot to shoot and I'll play a little more before trying to develop a decent load. I plan on 68 gainers being it's primary food.

 

[DMW1116]

Where did you end up finding a barrel?

 

[AJC1]

Where did you end up finding a barrel?

X-caliber. I dropped my order during the winter sale.

 

[DMW1116]

This kinda hits a sweet spot for me too. Bullet options, SRP, easy to find brass, relatively small powder charge, standard bolt face, faster velocity or heavier bullets than 223, and my first wild cat if I decide to try one. I'm contemplating rebarreling my AR10, so we'll see who wins that battle.

 

[Show Me]

Even though I have no interest your write up is good reading

 

[DMW1116]

Looking at some load data, I don't know if this is enough different to justify all the hassle. About 200 fps or less increase for the same weight bullets isn't as much incentive as I'd hoped. Still, if I was just itching for a wild cat for it's own sake, its the one to try.

 

[AJC1]

Looking at some load data, I don't know if this is enough different to justify all the hassle. About 200 fps or less increase for the same weight bullets isn't as much incentive as I'd hoped. Still, if I was just itching for a wild cat for it's own sake, its the one to try.

It was an opertunity for me to acomplish the following goals. 1. Build out my first AR, 2. Use easy to source and very available components, 3. Modify cases, 4. Have rifle parts that could easily be reverted to 223 if I hated the experience, 5. Use up 6mm bullets I had on hand. I have over 3k 6mm projectiles left from my dad shooting 243.

There was no need for higher energy or better terminal performance. I was very interested in the history of development as a competition loading. I also want to shoot a 222 but that would be in a bolt....

 

[kaferhaus]

I'll be building one as well. I've been contemplating it for several years now. Time to go ahead and do it. Mild recoil, larger surface area projectile and decent enough velocity. I had one in a Bolt action based on a Remington 722 many years ago and never should have let it go....

 

[DMW1116]

It definitely has it's advantages. To me the biggest is using the same bolt and not having to get something unusual or less proven like 6mm ARC/6.5 Grendel. An increase ballistically is an increase, in this case just under 10%. It probably does it's best in the weight range of the Amax bullets you're using - 75 to 90. I'll check into my AR10 first. That's just a barrel swap at this point. Definitely cheaper there, though the barrel itself will be comparable or slightly more expensive. Going 6x45 would involve a new upper to pin onto my current DMR. I'm a little skeptical of my current AR10 barrel, so would just swap them out.

 

[AJC1]

It definitely has it's advantages. To me the biggest is using the same bolt and not having to get something unusual or less proven like 6mm ARC/6.5 Grendel. An increase ballistically is an increase, in this case just under 10%. It probably does it's best in the weight range of the Amax bullets you're using - 75 to 90. I'll check into my AR10 first. That's just a barrel swap at this point. Definitely cheaper there, though the barrel itself will be comparable or slightly more expensive. Going 6x45 would involve a new upper to pin onto my current DMR. I'm a little skeptical of my current AR10 barrel, so would just swap them out.

It's AR 15 not 10, so that may make a difference. 223 bolt.

 

[DMW1116]

Right. My quandary is do I replace the barrel in my AR10 in 308 with a Criterion barrel or build a 6x45 upper for my DMR AR15. I can’t do both for a while.

 

[AJC1]

Right. My quandary is do I replace the barrel in my AR10 in 308 with a Criterion barrel or build a 6x45 upper for my DMR AR15. I can’t do both for a while.

If you have a functional need in 308 absolutely do that first.... this is a range toy to contine my learning. My next project will be 300 hammer because I'm not running subs and the 110 Barnes in 300 hammer is better balistacly than 300bo. If I wanted to go subsonic 45c is just a way better option.