6mm ARC - anyone ... anyone...

[tdogg]

Holy crap you aren't kidding you made some 6Arc brass.  How many steps to get it necked down?  I made mine from actual Grendel brass, I have only made 20 thus far!

I shot my first load work up on Friday:

Bullet   Bullet Weight (grain)   Primer   Powder   Charge (grain)   OAL (in)   Temp (F)   Wind (mph)   Distance (yd)   Quantity Shot   Average Velocity (Ft/s)   Velocity StDev (ft/s)   Range (ft/s)   Measured Spread (in)   Measured MOA   Notes:
Sierra Matchking   107   CCI450   Varget   25.0   2.23   66   0-5   50   4   2387.5   15.4   34         Used to zero scope, no data.  First Shots in new gun!
Sierra Matchking   107   CCI450   Varget   25.5   2.23   66   0-5   50   4   2389.3   13.8   30   0.213   0.407   Stellar Group!
Sierra Matchking   107   CCI450   Varget   26.0   2.23   66   0-5   50   4   2479.0   7.6   16   0.578   1.105   
Sierra Matchking   107   CCI450   Varget   26.5   2.23   66   0-5   50   4   2499.0   8.5   20   0.636   1.215   
Sierra Matchking   107   CCI450   Varget   27.0   2.23   66   0-5   50   4   2616.3   2.2   5   0.504   0.962   

The ES was getting better and better but I was approaching/past max load for a gas gun.  No signs of pressure on the brass but pushing the edge.  That group at 25.5 was excellent I'm wondering if it will repeat once the barrel is fully broke in.



I worked up a ladder with Barnes 95gr LRX and Varget and went out to shoot it after work today but ran out of light and the chrono quit on me so I stopped.  I will have to redo that rung on the ladder and try again.

Thus far mostly sub MOA capable and decent velocity.  The barrel has a very tight chamber and I can't load the longer 105 class bullets at mag length.  It may limit my velocity but I'm also able to load close to the lands so I will hold my judgement for now.

Cheers,
Toby

[newageroman]

Well it certainly shows promise! I've heard Varget is a little slow burning and prone to pressure spikes at the upper end.
I'm gonna do a writeup on the brass process. It's a lot of work though - I think it will be worth it. I would stick to converting Grendle if you can.
I've heard Hornady brass should be available this month, but I still can't find it anywhere(else) - I just checked starline and it is still on back order but the Grendle basic is not.
Keep posting results pls!

[tdogg]

Worked up a the Barnes LRX load this afternoon.  It was really windy and gusty (enough that it blew over my chrono).  Can't complain about the groups though given the conditions.

Equipment
Caliber:  6 Arc
Bullets:  Barnes LRX 95gr
Brass:    Starline
Powder:  Varget
Max Velocity:  ~2600 fps (20 inch Barrel)
Primer:  CCI450
OAL:  2.258 inch
Rifle:  AR
Qty:      4 rounds each, slow fired
Weather:  61F and partly overcast, 10-15 mph winds with gusts up to 30
Chrono:  Caldwell G1

Load      Avg Vel      SD      Elevation (in)      Group (MOA)
25.0      2588          49.5      0.32                0.92
25.5      2555          3.9        0.98                0.94
25.8      2583          25.7      1.13                0.85
26.0      2626          12.8      1.37                0.83
26.5      2680          12.2      1.68                1.06
27.0      2713          5.0        1.32                0.57

NOTES:
• Still breaking in the barrel and velocities may not be stable yet.
• Initial 25 and 25.5 grain loads had chrono issues, repeated the 25.5 and added the 25.8, then shot the rest.
• Groups may be slightly larger due to gusty strong winds.



Cheers,
Toby

[newageroman]

Man there is no denying those results of that last group. Is that on your top end of pressure? What's your case volume with the sticks? I'm able to pack 29 gns of ball powder in but haven't tried the sticks.

[tdogg]

I haven't tried to fill a case completely but these are slightly compressed loads at the top.   I can feel crunching during seating.  The charges are reaching into the shoulder area for sure.

It's tough to say exactly what the max charge is with this bullet.   I've reached out to Barnes for any load data but they haven't responded yet.  In my experience, the solid copper bullets tend to run at higher pressures for a given velocity (meaning they usually have a lower max charge vs a lead core bullet of same weight).

If you you look at hornady data I'm not at max yet.   If you look at hodgdon data I'm over max.  Looking at the cases I finally saw the faintest of mark's at the 27gr charge on one case.   I'm sure the 27gr is over pressure with this bullet (for a gas gun).

Cheers,
Toby

Sent from my SM-G950U using Tapatalk

[newageroman]

Are you worried about staying in that high pressure node during a hot summer day at the range? when you are at the top like that do you just keep letting them rip or more slowly evenly send 'em?

I got the footage for the ATN scope up. Please roast! I will say it is fun to get the gongs to dance under fast fire at distance.

https://youtu.be/zjgycnxhAAQ

[tdogg]

The Barnes LRX load development is for hunting.  I won't be shooting a bunch of that at the range ever really.  I'm OK with letting that be hot as long as the load shows promise.  Part of the problem with doing load development right now is that I won't be hunting in the mid 60's temperature.  It will be significantly cooler, so right now I just want to understand if the load is safe and do final load work up this fall when the weather changes.

In general during any load development, I'm shooting slow and trying to capture both velocity and accuracy.  Making sure the chrono is positioned aligned with the shot, making sure I don't shoot it, and following good shooting process (breathing, relaxed, good trigger control, etc...).  When the load approaches the top, I will focus more on signs of pressure, how did it feel when shot, what does the brass look like, did it cycle the action, how's the bolt lift, etc...

I'm not sure what to evaluate next?  I think I'm going to look at Staball 6.5 and then maybe RL15 or N133?  I will probably move back to either Sierra or try Bergers?

Cheers,
Toby

[newageroman]

Ahhh, that totally makes sense for a hunting round!
I use a similar method for load dev now.
Good luck with sta-ball - I have some but I'm saving for 6.5CM unless you lead the way there.
I've had good results with W748, Leverloution. I think the next one to try for me will be CFE223. Lots of talk on lever and CFE223.
There is some redneck in TN that makes 6mm bullets for a lot of bench guys there. sposed to come off a single die so consistency is king and price is same as other factory. I can't find him though - yet...

[tdogg]

Worked up a the Sierra Matchking 107gr over Staball 6.5.  Wind was better today but still gusty.  I still can't complain about the groups though given the conditions.

Equipment
Caliber:  6 Arc
Bullets:  Sierra Matchking 107gr
Brass:    Starline
Powder:  Staball 6.5
Max Velocity:  ~2450 fps (20 inch Barrel)
Primer:  CCI450
OAL:  2.225 inch
Rifle:  AR
Qty:      4 rounds each, slow fired
Weather:  54F and partly overcast, 5-10 mph winds with gusts up to 20
Chrono:  Caldwell G1

Load      Avg Vel      SD      Elevation (in)      Group (MOA)
28.0      2283          14.7      1.15                0.91
28.5      2321          8.2        1.01                0.88
29.0      2367          13.3      1.36                0.67
29.5      2437          10.8      1.41                0.65
30.0      2499          14.4      1.81                0.64

NOTES:
• Barrel seems pretty stable now with 68 rounds down the pipe.
• This powder lives up to its name and is very easy to work up.  Velocity is down over other options though.
• Groups may be slightly larger due to gusty strong winds.
• No signs of pressure with any of these loads
• I'm beginning to really like this barrel and cartridge...



Cheers,
Toby

[newageroman]

Would be great for a short range < 500 round given velocity. I can't wait to try it in 6.5CM.

[tdogg]

Worked up a the Sierra Matchking 107gr over CFE223.  I have to say I was expecting more velocity.

Equipment
Caliber:  6 Arc
Bullets:  Sierra Matchking 107gr
Brass:    Starline
Powder:  CFE223
Max Velocity:  ~2575 fps (20 inch Barrel)
Primer:  CCI450
OAL:  2.225 inch
Rifle:  AR
Qty:      4 rounds each, slow fired
Weather:  61F and partly overcast, 5-10 mph winds with gusts up to 20
Chrono:  Caldwell G1

Load      Avg Vel      SD      Elevation (in)      Group (MOA)
26.5      2442          11.3      -.34                1.07
27.0      2468          9.7        -.22                0.48
27.5      2513          12.7      -.19                0.79
28.0      2569          16.6      -.27                0.80
28.5      2603          9.9       -.22                 1.13

NOTES:
• Barrel seems pretty stable now with 88 rounds down the pipe.
• I adjusted the turrets to keep the groups on target at 100 yds.  May need to go up 0.5 MOA.
• Final ladder load was interupted by the wind as it blew over my target.  I don't believe the group is that large, it was me having to reset that opened it up.
• No signs of pressure with any of these loads.
• I have to say I am a little disappointed with the velocity of this powder, I expected more.



Cheers,
Toby

[newageroman]

Nice Data Toby - I am a bit surprised at the love velocity as well. I'll keep posting results when they come in.

Here is some good ballistics testing (not min, I just found interesting) with Berger 109s
https://www.youtube.com/watch?v=q8x5iC9haRI

[tdogg]

Worked up a the Sierra Matchking 107gr over Vihtavuori N550.  I know this powder is too slow and it showed as it was really dirty.  I have about a 1/4 pound left.

Equipment
Caliber:  6 Arc
Bullets:  Sierra Matchking 107gr
Brass:    Starline
Powder:  N550
Max Velocity:  ~2550 fps (20 inch Barrel)
Primer:  CCI450
OAL:  2.225 inch
Rifle:  AR
Qty:      5 rounds each, slow fired
Weather:  60F and partly overcast, 10-15 mph winds with gusts up to 25
Chrono:  Caldwell G1

Load      Avg Vel      SD      Elevation (in)      Group (MOA)
26.0      2330          35.1      -.67                1.31
26.5      2410          8.8        -.13                0.91
27.0      2476          12.5      0.18                0.82
27.5      2528          9.6       0.48                 0.96
28.0      2583          9.0       0.47                 1.59

NOTES:
• Overall this powder was really dirty in this cartridge
• 28 grains showed the slightest sign of an ejector swipe on the case head.
• I used these to fireform some newly processed Starline 6.5 Grendel Brass, it was new.



Cheers,
Toby

[newageroman]

I confirmed my fire forming process yesterday. With the bullets jammed into the lands - they all fired wile single feeding (too long for mag - intentional). Brass looks still looks good. Basically I wanted to see if the longer bullets at this COAL functioned and fire formed easily as part of the process. The next step is to take one of THOSE cases and load it 4 or 5 times at the range and see about how long until the necks or primer pockets start to go.  I'm hoping for 4+ on that.
After that will be the same test but with annealining between each firing to see how much annealing helps with brass life.

In the meantime, I'm gonna load all those cases(~200 or so up ready to fire form using the D650). And I still have another unopened box of 250 pieces to convert as well. Set for a while...
I shot the CZs of course and the ruger 22s as well. Caught up with a reloader friend and got to use labradar for the first time ever (Not mine).

Also the loads I'm running are a little slow @2563 but great ES and SD numbers and good accuracy - so I'm gonna spin 'em in.
More details/pics here..http://brassbucket.net/category/range-days/

[tdogg]

Well I can confirm that the converted Starline 6.5 Grendel brass is still going strong at 5 reloads.  I do anneal after every firing.  I probably get two firings before having to trim but I only trim to 1.490".  I don't see or feel any signs of case necking near the case head.

I think I'm going to stick with my Varget and Staball loads to develop further.

I also did do a slight neck turn on the cases as I noticed that there was quite a bit of bullet runout using my concentricity tester.  I was hoping it was my Hornady seating die but it's the brass.  The Starline brass has pretty horrible wall thickness variation at the neck.  It wasn't all the cases either, there was a large variation from some that had great wall thickness uniformity to some that were horrendous.

I had to order a new sizing bushing as I took about a 1.5 thousandths off the neck wall thickness and that didn't clean it up completely.  I'm not sure what neck diameter I have in my chamber so I didn't want to take too much off.  It's hard for me to use the bullet slip in a fired case trick as the necks always get dented upon extraction in my gasser.  I probably need to turn the gas down a bit now that it is broken in.  I probably need to take a mold of my chamber and measure it.  Or just borrow a gauge pin set from work.

By neck turning I've shrunk the bullet runout to a worst case of ~0.003" at the ogive.  I was running much more than that (~0.008) before neck turning the cases.  It will be interesting to see how accurate I can make this gasser as it has been stellar thus far!  I wasn't really expecting this level of accuracy from this gasser, to date my average is 0.9 MOA for all 133 shots fired!  That is ridiculous especially for an AR considering this is across all load development (4 powders, 3 bullets, and a wide range of velocities).

I'm curious what your wall thickness variation is on the formed basic brass?  I'm wondering if I just got a bad batch? 

Cheers,
Toby