The Goal of this thread is to maintain folks in this great forum updated of a new AR project, The AimArms AR 6x45. This is intended for people interested on following up on progress with questions, suggestions and collaborative opinions.
This is not to compare, degrade or criticize this or other AR variants or systems. A simple case of dedication to some of the AR variants and share the objectives and results with you. I find this interesting for everyone who likes a super accurate system. At least that is my case.
Bullets: Any .243 up to 105gr. (plenty in stock)
Parent case: .223 Remington / 5.56x45 NATO. (plenty in stock. We will be using custom dies)
Barrel: AR LW50 - LotharWalter caliber .243x45 - 20" 1:9 twist of rate.
Billet: Sunju Industrial
Trigger: RRA 2 Stage National Match
1-Prove and test Functions with new bore.
2-Improved Ballistics - Include summary about hunting and tactical applications
Phase Two (long term):
3-Custom long stroke Piston - Enhancement with automated regulator with suppressed and cancel mode.
4-Eliminate The need for buffer tube.
5-Improve AR Charging handle.
3-Maintenance and reliability.
5-Battle Operations Advantages and Disadvantages
Planning diverse tests in most common scenarios. We will start from the bench and then move forward from there.
The ballistics goals are simple. We aim for a little range and terminal improvement of an already time tested, battle proved and extremely efficient round, the 5.56.
The numbers are confirmed confirmed between a 18% to 30% improvement over s.223 terminal ballistics. The renewed interest comes from several sides:
A) extremely accurate. It won world matches back in the 70's.
B) low cost and versatility with that increased in terminal ballistics.
C) Easy to implement.
the 6mmx45 (.243x45) or also known as the 6mmx.223Remington. I start with the baseline but we do not discard improvements over the case. I am also looking into serious powder work down the road. We start with a 20 inch barrel that we might be chopping off at some point but we have other things to resolve first.
We are not trying to reinvent anything. We are continuing where others left.
Everything starts and ends with the bullet, hopefully a good one.
The reason for the .243 caliber is very simple. The biggest assortment and some of the best bullet selections were considered in the following calibers:
.224 bullets are already very popular in several casing, obviously including the current .223 REM and 5.56NATO standard M-16 & AR-15. 1:8 twist of rate heavy barrels do an excellent job stabilizing the 75, 77 and 80gr bullets. 1:7 is desired for 80 and above but I found that at 80gr you are pretty much maxed out in terms of maximizing performance out of the .223 REM casing.
.308 bullets have a huge selections but no good ones can be shot out of the AR with a substantial gain. We might have a good round for short to mid range but then new mags, new bolts maybe carries, the whole nine yards. The WSSM variants that initially seemed a good idea are dedicated systems (hunting), suffer in accuracy and good high BC bullets cannot be run due to the max COAL. Great systems for what it is but this is not a research for the next great AR caliber. Rather is an exercise to improve on what we already know.
.25 and 6.8 were discarded due to bad bullet assortment and low ballistic performance. Sometimes the limitations, like also in the .308 is not the bullet assortment but OAL in the AR-15 magazine.
6.5 was also considered due to some extremely good bullets but for that we already have a nice grendel. Not MBR bound but a great special purpose system.
So, we are left with possibly the one of the best assortment of bullets in the .243 caliber. We can find good bullets in this section with .243 bullet of boat tail spitzer shape in 85gr that have a pretty good ballistic coefficient to make an excellent bullet at longer ranges than the current .224 ones and with the higher sectional density for a much better penetration.
These are some quick visual comparison of some good bullets many with high BCs. Hopefully the pictures will be ok to appreciate some of the details....
From left to right... In .224 caliber:
55gr GI, 62gr GI penetrator, 69gr SMK, 70gr Barnes TSX, 75gr Hornady Match, 77gr Berger VLD, then one match hand load with Federal Case and a Sierra MK 69gr. Now in the middle next to the .223 round we have a .243x45 handload with a 87gr. Hornday SP. and then continuing from left to right in .243 caliber... A sierra Game King 85gr.HP, Barnes 85gr TSX BT, and the Hornday 87gr SP. Finally a couple of cases once fired necked up to .243 one is a Federal Cartrige and the other a PMC Nato spec. Both necked up w/o any issues. I use canola oil for lube after resizing and trimming and wash the rounds before priming.
I took several pictures to start sharing with anyone interested in this project. I have to remind that I am not building a Grendel or a 6.8 or a BRX or a WSSM. I already have them so I want to do something new closer to mil spec but, again different.
These are the dies...
The initial goal would be to military standards of good performance up to 500 to 600 yards for a rifle/carbine.
The fact that the military abandoned this initiative doesn't mean anything and actually for me is an encouraging factor. After all they have made some pretty bad decisions many times before and it was up to individuals in the military and/or civilians to figure out a solution, sometimes later adopted and successfully implemented.
Another pic from above....
Some solid performers...
Also Amax, Vmax and Bergers area good performers with LC brass, VLD mags. I will post range results as time allows...
A nice reference chart...
A picture of one of the systems used for the tests....
We had some hiccups with the new parts for the gas piston so the piston development will have to wait but it was a nice day out and I couldn't resist putting my hands on the lothar walther barrel so I put the barrel in a delton receiver with a regular hand-guard (floating though) with other spare parts I had and headed for the range with some 70 hand loads.
I was not expecting much as these were the first shoots to break in the barrel so you know the drill shoot and clean, shoot and clean while I worked in zeroing the scope a 3-9x44 Nikon Monarch with BDC reticle that I had catching dust....
Started at 25 yards to zero in 2 shots and moved up to 50 yards.
At this point I am cleaning the barrel after every shot for the first 10 shoots.
Then every 2 or 3 shots and after a few strings and zero was confirmed I moved the targets to 100 and put 5 rounds...
I was adjusting the gas block and not paying too much effort into the actual accuracy.
But then after 40 shots I realized groups were starting to close up so I took a bit extra time.
At first I was shooting Hornady 87gr SP, that are cheap and great for brake in. I was doing 24gr of H4895 with once fired cheap FC cases and Fiocci primers.
Then I switch to the remaining of the loads, the last 20 loads that were loaded with 85gr Sierra Game King...
This is the first group at 100 yards. Obviously when you go to the range you have to forget something and as you can see I have to improvise some targets...
Wind was picking up but I was so pleased so far that in the last string I put my soul into it. Loaded the last 5 rounds and got a new target......
Wind 15mph heading 90
PMCx1 fired with Sierra Game King 85gr and 24.3gr of H4895 (in the targets I wrote SMK but I made a mistake they are SGK as I mentioned)
The main group no more than 1/4 of inch apart with one off 1/2 inch apart.
The way things are going this barrel and round combination is showing a lot of potential so I will continue to break in with other loads and post the results here.
I am also fabricating a center stack AR-15 magazine that will allow to seat the bullets further out so it will be interesting to see what we can get.
This week and after a long summer I was able to finalize both the new upper and lower and today prepared some loads and headed for the range with the new barrel.
This barrel is practically the same as the first one but with the 1:8 twist vs. the 1:9 twist and the main reason is so we can shoot the following bullets"
- Berger 95gr Hunting VLD
- Hornady Amax 105gr.
Both have superior Ballistic Coeficients of .486 and .500 respectively.
Just to give you an idea how good the above bullets are, a 168gr A-Max bullet that is a top choice is still behind these two above in terms of ballistic coefficient and sectional density in the 105.
The barrel is not fully broken in (around 50 shots) but it is already starting to show very good results.
I took some pictures of the new upper (and lower). The quality is not great since I could not find my good camera so I took them with the phone.
6x45 20" 1:8 twist. Adams piston. JP bolt. NM trigger. and Troy rails.
Other side view....
Matched billet. Very tight...
Troy TRX floating rails (I wished they made one just 12" long) for the piston.
These are some groups with 87gr SGKs and V-maxes. Today I didn't put a lot of time in the loads or the accuracy as I was running late and was doing things real quickly but so I was pleasantly surprised to see gruops below 1/2 MOA. one group here shot slowly gave .31 MOA. Other groups shot in rapid fire did stay nicely together.
This is the ballistic charts based on tests with the 1st barrel. It shows superior range and energy.
Great hunting system even at decent range. I had almost identical results with the Hornady Match HPBTs.
Although energy is nicely retained recoils is very mild. Obviously a little more
than the .223.
Here we can see how energy and speed is nicely held by the V-max.
It shows clearly 6x45 is a great 300 yards white-tail / pig rifle with close 1000ft/lb at 300 yards and
also a nice 500-600 yards coyote rifle for those that like the very long shots.
I am now back at work on the VLD magazines and will post the progress.