6mm Arc Bushing size

[JonnyD91]

I am looking to pick up a set of RCBS Matchmaster dies for a 6mm arc.
Does anyone know the bushing size to start off with to reload their match ELD 108 heads?

I tried to calculate this off the saami spec but the OD of .274 seem wrong.

My dad has the caliper at his house but i forgot to give him a loaded round to measure.

 

[Team RCBS & Bushnell]

Without loaded ammo you're actually using and going off SAAMI, looks like .271" & .272" would be the ones to start off with.

Neck Bushings | RCBS

Self-centering, changeable neck bushings let reloaders precisely set the amount of tension on the bullet when using RCBS Gold Medal Match Series reloading dies.

www.rcbs.com

 

[FuhQ]

Just to update this old thread, I bought a .271 Short Action Customs $30 bushing based on this thread, and it's way too big for Hornady brass. I normally measure before ordering, but I didn't have any factory ammo to measure at the time, and this thread was the only info I could find about possible bushing sizes for 6 ARC.

You will need a .266 bushing for Hornady 6mm ARC brass. Now I'm having to order the correct $30 bushing after getting prepped to reload for it tonight, which I guess isn't happening now since the Nosler 115 RDF's slip right into the neck and fall into the case with zero effort...

Hope this helps someone else in the future, since it just wasted me $30... Can't send back a used bushing.

On a good note, I did discover that if you make your own case gauges for measuring distance to the lands using the Hornady tool, a .271 bushing is about perfect slip fit without any side-to-side play.

 

[Dogtown]

Oh man, yeah 0.271 is close but too big. I was in the same boat as you, not having any ammo to measure, but I also shoot 6mm C and already had some 0.264-0.268 bushings to play with and yep, 0.266 seems to be the sweet spot.

 

[FuhQ]

Oh man, yeah 0.271 is close but too big. I was in the same boat as you, not having any ammo to measure, but I also shoot 6mm C and already had some 0.264-0.268 bushings to play with and yep, 0.266 seems to be the sweet spot.

Yeah, I’ve never owned or loaded for any 6mm’s, so this was all new to me. I own just about everything else from .30 cal down to .17, but never owned any 6mm’s, and think .277 is pointless (I’m a 7mm guy)…But everything else, I got it covered.

After measuring the loaded factory Hornady Black 105 BTHP ammo that I NOW have on-hand (to get the brass), I just ordered a new SAC .266 bushing, which should give me about .0025-.0030 neck tension. Midway is pretty fast shipping, so hopefully it’ll make it by the weekend, so I don’t have to postpone load development for yet another week.

 

[FuhQ]

Midway came through for me, and the new bushing showed up today. Got them all resized (again), and loaded up my first round of load development for my 16" Christensen Arms MPR. I'm running 1x fired and FL sized Hornady brass, CFE-223, CCI 400's, and Nosler 115 RDF's. I'm running all the way up to 29.0gr in 0.5 grain increments (first round of data is pressure baseline and finding a rough node pattern). I'll report back my findings.

In case someone else reads this in the future, DO NOT use bolt-gun load data in a gas gun. Bolt guns can handle a lot more pressure.