Sod Farmer
New member
I have a new RRA R3 Competition. In the process of working up a couple of loads, I used my Hornady Lock-N-Load OAL guage to determine a starting point for C.O.A.L.. I was surprised when I found how extremely short the throat was. I mean so short that I could not even come close to seating a 55gr Hornady SP on the cannelure. I did recall reading that RRA cuts their chambers so that the lands gradually engage the bullet as it starts down the barrel. To say it another way the lands don't have a sharp shoulder where they start, but instead ramp up to grab the bullet at the throat. I called RRA and confirmed that what I had read was correct. By design, the bullet engages the rifling as it is chambered. When I asked how to determine the appropriate COAL, I was told that they could not answer my question because of legal concerns. The chambers are cut this way to minimize the effect of COAL.
Here is part of the article that I read along with a link for the entire article:
"The .223 Wylde is popular because it combines the tight .224 throat of the .223 with a longer freebore and the shallower leade of the 5.56x45mm. We get our best accuracy when we have .0005 inches of clearance on each side of the bullet when it’s chambered. The area of the bore just forward of the cartridge case (when chambered) is called the throat, and it needs to be tight to prevent the bullet from yawing before it contacts the rifling. Next, we need enough freebore (smooth area between the case mouth and rifling) to let the cartridge chamber without the bullet getting pushed back into the case, creating dangerous pressure spikes. Last, there needs to be a bevel on the leading edge of the rifling to prevent another pressure spike that would occur if the bullet just slammed into rifling that is usually .004-inch high. A bevel on the rifling also helps keep the bullet centered in the bore, which is good for accuracy.
The .223 Wylde has that .0005-inch clearance, so it has a nice, tight throat and the gentle bevel on the lead edge of the rifling (the leade) of the 5.56 NATO. The tight throat helps keep things accurate, and the gentle leade controls pressure of even hotly loaded rounds. The .223 Wylde is one of my favorite chamberings for 5.56 guns."
http://www.gunsandammo.com/reviews/rock-river-arms-x-series-review/
Has anyone else run across this challenge with their RRA barrel? How did you decide on your COAL?
Here is part of the article that I read along with a link for the entire article:
"The .223 Wylde is popular because it combines the tight .224 throat of the .223 with a longer freebore and the shallower leade of the 5.56x45mm. We get our best accuracy when we have .0005 inches of clearance on each side of the bullet when it’s chambered. The area of the bore just forward of the cartridge case (when chambered) is called the throat, and it needs to be tight to prevent the bullet from yawing before it contacts the rifling. Next, we need enough freebore (smooth area between the case mouth and rifling) to let the cartridge chamber without the bullet getting pushed back into the case, creating dangerous pressure spikes. Last, there needs to be a bevel on the leading edge of the rifling to prevent another pressure spike that would occur if the bullet just slammed into rifling that is usually .004-inch high. A bevel on the rifling also helps keep the bullet centered in the bore, which is good for accuracy.
The .223 Wylde has that .0005-inch clearance, so it has a nice, tight throat and the gentle bevel on the lead edge of the rifling (the leade) of the 5.56 NATO. The tight throat helps keep things accurate, and the gentle leade controls pressure of even hotly loaded rounds. The .223 Wylde is one of my favorite chamberings for 5.56 guns."
http://www.gunsandammo.com/reviews/rock-river-arms-x-series-review/
Has anyone else run across this challenge with their RRA barrel? How did you decide on your COAL?
