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New 6 ARC questions

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rcflyerarc

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I have a friend that recently got me interested in the new 6 ARC. I was previously shooting a Ruger 556MPR and decided to retain the upper configuration in the 556 and go with a new upper in the 6 ARC. I purchased a complete upper from Grendel Hunter with a 20 in barrel and 6.5 Grendel NiB BCG. The MPR lower is what I term a loose tight fit. There is some play, but not a lot.

My question:

First, I plan to load factory Hornady cases down to a min of 65g and max 87g Vmax or Sierra Game King bullets. The max cartridge OAL is listed as 2.260, and that is what Hornady's factory ELD match ammo is loaded to. However, if one looks at their reload data for the 6 ARC, particularly for the 87g Vmax, it indicates a max OAL of 2.140. I only have about 50 rounds fired through the barrel. and have gotten a few malfunctions using the factory ammo. My question is this: when I chamber a fresh round out of the magazine, if I then try to unload/remove the round from the chamber without firing, it takes both hands on the charge lever to extract the round, and appears that the bullet is hitting the rifling and becoming stuck, or that it is an extremely tight chamber and the base of the bullet is getting jammed into it.

I have a set of small base dies on the way to check the cases, but does this sound right to you? Also, once the bolt chambers the round, and I get it unstuck, if I then load it, it is WAY easier to remove it.

I have been loading bolt hunting ammo for many years, but this is my first attempt with this 6 ARC. Any help will be appreciated.
 
Thanks. That app is what I am using to reload the cases I have fired. It's not the load data I was asking about. Where my problem lies is when I chamber a round using the mag, and then try to unload the round, I have a really hard time getting the round out of the chamber. I think it's a factor of the factory rounds being so long (2.260" OAL) that the nose of the bullet is getting stuck in the barrel, or it is that the head of the case needs a small base resizing so it doesn't stick in the chamber.

I was just wondering if anyone else has seen this on their 6 ARC.
 
rcflyerarc said:
Thanks. That app is what I am using to reload the cases I have fired. It's not the load data I was asking about. Where my problem lies is when I chamber a round using the mag, and then try to unload the round, I have a really hard time getting the round out of the chamber. I think it's a factor of the factory rounds being so long (2.260" OAL) that the nose of the bullet is getting stuck in the barrel, or it is that the head of the case needs a small base resizing so it doesn't stick in the chamber.

I was just wondering if anyone else has seen this on their 6 ARC.
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It happens on other cases. So it's a loaded round (unfired round) or just fired? If it's an unfired round the bolt is closing and yes the ogive of the bullet can stick in the lands. I have a 243win (AR10) that does this with factory ammo due too the throat being very short. Have you run any factory ammo in it? The 243win was with factory ammo and would show marks on the bullet of land contract. Not every chamber is cut the same unfortunately. Make a dummy round (case and bullet only) to manual specs. Chamber it by hand loaoding into the chamber and slowly engage the bolt. If you have a forward assist you can use it if the bolt doesn't close all the way. Either you might need to get the throat cut or shorten the coal? Was this a factory gun or your build? If you have shot 100 rounds or more in that gun check the factory ammo. More info I guess!
 
Sometimes the brass on the case head is too soft and the extractor won't get a hold even with it just getting into the lands (stuck).
 
It was all factory ammo that I shot. I have a Hornady OAL setup gauge, and when I used it on this rifle, with the loads that I did, I found that when I inserted the modified case w/bullet into the chamber and then slowly pushed it until it met resistance, the OAL was right in accordance with what Hornady's load data specified. I went back and seated the rounds that I had previously loaded to the length that the manual and the Hornady gauge said they ought to be, and still get the round very tight when the spring closes and loads the round off the mag. It takes two hands on the charge lever to get the round out of the chamber (they are FL sized, but not with a small base die).

I am waiting to receive my small based dies from RCBS and if they still get stuck after resizing with them, I guess I will have to get back with Grendel and or Saturn barrels. It was shooting acceptable groups 5 rounds touching same hole.

Could the NiB BCG maybe be the issue? I was told that the upper was headspaced with the original Nitride BCG, but the NiB one was a replacement that was just sent to me.
 
rcflyerarc said:
It was all factory ammo that I shot. I have a Hornady OAL setup gauge, and when I used it on this rifle, with the loads that I did, I found that when I inserted the modified case w/bullet into the chamber and then slowly pushed it until it met resistance, the OAL was right in accordance with what Hornady's load data specified. I went back and seated the rounds that I had previously loaded to the length that the manual and the Hornady gauge said they ought to be, and still get the round very tight when the spring closes and loads the round off the mag. It takes two hands on the charge lever to get the round out of the chamber (they are FL sized, but not with a small base die).

I am waiting to receive my small based dies from RCBS and if they still get stuck after resizing with them, I guess I will have to get back with Grendel and or Saturn barrels. It was shooting acceptable groups 5 rounds touching same hole.

Could the NiB BCG maybe be the issue? I was told that the upper was headspaced with the original Nitride BCG, but the NiB one was a replacement that was just sent to me.
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The cartridge headspaces off the shoulder, not the head. Do you have the nitride bolt? If so just change the bolt on the bcg and recheck. If the headspace is too tight it doesn't affect if/when bullet contacting lands. The reamer used for chambering could be out of spec? If you were having the same issues with both bolts, it isn't the bolt unless both are cut incorrectly! If you have a depth gauge check the bolt. You should be able too use your caliper. You state you have a modified case for checking coal? Don't check what manual states, check what maximum coal is against the chamber. Another thing you could try is make sure die touches the shellholder on 1 case, then seat a bullet(bullet and case only) to manual specs and recheck chambering.
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I have the one on the left, the straight one. I have already done the check with the gauge. What I measured was within .002 of the value for the OAL that was shown for that 87g Vmax bullet, 2.140. The factory loads are 2.260 +/- a couple of thou.

I do not have the original nitride BCG. It was returned for credit when I received the NiB one. I can't see it being headspace causing the unfired round to be hard to extract. It has to be the bullet getting stuck in the lands or the head of the case being tight in the chamber. All of the rounds I have loaded have been with a standard FL Hornady die with a slight cam over on the rock chucker press. That's why I have ordered the small base die set to see if that helps. If not, I guess it is gonna need to go back to have the chamber checked. I have no way to check chamber pressures, but I am having the exact same issues with the factory hornady loads as I am with my handloads.

If I simply insert a round into the chamber and release the slide but do not let it slam forward, then I cannot get the bolt to close all the way, even using the forward assist lever. The only way I get it to completely close is with the action cycling using the springs. To me it has to be either the headspace is really putting a lot of force on the locking lugs, or the chamber is so tight on the base of the case it doesn't let the round go forward enough to close the locking lugs.
 
So with the modified case and bullet it's at 2.140"? If factory is at 2.260", then the throat is short. Load the bullet nose 1st into the case where the base is just showing in the mouth. Then chamber it. If it still sticks, then something is wrong with the chamber dimensions! By putting the bullet backwards in the case and chambering I keeps the mouth from deforming/shrinking. Again do this with just case and bullet (no primer or powder).
 
Just a comment in general, this thread is what makes a site like this valuable to some of us...
 
I hope my thread does help. I can't imagine that I am the only one who has these issues and questions. Thanks for the positive comment.

I did some more experimenting last night and I talked with both Andy from Grendel Hunter and with TEXASforLIFE, and I now believe that some of what I initially posted was incorrect, or at least some of my assumptions were.

I did some more experimenting with some of my resized cases, and found that the shoulder datum point had stretched about .009" when they were originally fired. Per a couple of videos on youtube, when I resized them, I only bumped the datum point back about .002 which, in my case, was apparently not enough and caused the binding I was having.

I reset my FL sizing die and ran another couple of the fired cases through it, and this time brought the shoulder back to its original, unfired length. That solved all of my chambering and extraction issues. Now the BCG can be locked on the head just by pushing on the back of it with my thumb, just like I don't have a case inserted.
 
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