Head space... yes and the term defines itself... from the head of the case to the face of the bolt..... jim
Hornady releases 6mm ARC
- Thread starter Winny94
- Start date
Head space... yes and the term defines itself... from the head of the case to the face of the bolt..... jim
Like he said SAMI defines head space from the datum line on the shoulder to the face of the bolt is checked with a go and no go gage. right ? ok Smart guy what do you use on a BR Imp ??? A 6br go gage that seats against the shoulder at the neck. A 40 degree chamber checked with a 30 degree gage.... Now tell me about the datum line..... Heaven forbid you can't do that it isn't the way SAMI. says to do it. Nothing written in stone in terms like the new term of shoulder bump. for setting the head space on your case. ....jim
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HEAD CLEARANCE
The distance between the head of a fully seated cartridge or shell and the face of the breech bolt when the action is in the closed position. Commonly confused with headspace.
HEADSPACE
The distance from the face of the closed breech of a firearm to the surface in the chamber on which the cartridge case seats.
The distance between the head of a fully seated cartridge or shell and the face of the breech bolt when the action is in the closed position. Commonly confused with headspace.
HEADSPACE
The distance from the face of the closed breech of a firearm to the surface in the chamber on which the cartridge case seats.
Neither, all it tells you is if you have enough or not.
Yuo should seek professional help.
You are already being lead down a road of despair and disappointments.
morpheus
Gold $$ Contributor
Could you please elaborate a bit more? I am very interested in real-world experiences with this cartridge before I consider going this direction.
I've built & shot AR15 match rifles in both 6 HAGAR & 6 RAT (an improved 6mmAR, sort of like a miniature 6 Dasher). Never had any problems with the HAGAR using a C-158 bolt, nor with the RAT, but used a LMT Enhanced Grendel bolt made of 9310 steel in the RAT. I pretty much refused to do an AR bbl chambered for the 6 RAT unless the owner already had a quality 9310 bolt, or bought a J-P 9310 enhanced bolt from me.
I've chronographed a ton of HAGAR & RAT loads; the RAT in both AR15s & a couple of bolt rifles, and never got over 2800fps with any 105gr bullet, plus found best accuracy in both my 28" & 24" AR bbls at around 2740fps. So now we have the mention of someone getting 2880+fps out of a 6 ARC; that's faster than any of the 105gr loads I used to run in a 6BR tubegun built on a Pierce TG action in an Eliseo R5 tubegun with a 28" bbl.... Seems unlikely to me that even with powders like Superformance you could get this sort of velocity out of a 105 in the 6 ARC without exceeding the SAAMI spec max pressure of 52.000PSI. Also consider that the 6 RAT has more case capacity than the ARC, and reduced case body taper & a 40* shoulder; even with those advantages over the ARC, you won't catch me trying to get 2880fps out of any 105gr bullet in a RAT built on a strong Howa Mini action, let alone in an AR15.
So at least at this point, I can easily understand John Holliger's decision to be very hesitant to doing 6 ARC AR15 bbls for customers. Info on the internet is bound to push some guys to try to match or exceed reported velocities for a new cartridge, and in some cases, no amount of logical arguments will convince those shooters not to try pushing the envelope where pressures are concerned.
I've chronographed a ton of HAGAR & RAT loads; the RAT in both AR15s & a couple of bolt rifles, and never got over 2800fps with any 105gr bullet, plus found best accuracy in both my 28" & 24" AR bbls at around 2740fps. So now we have the mention of someone getting 2880+fps out of a 6 ARC; that's faster than any of the 105gr loads I used to run in a 6BR tubegun built on a Pierce TG action in an Eliseo R5 tubegun with a 28" bbl.... Seems unlikely to me that even with powders like Superformance you could get this sort of velocity out of a 105 in the 6 ARC without exceeding the SAAMI spec max pressure of 52.000PSI. Also consider that the 6 RAT has more case capacity than the ARC, and reduced case body taper & a 40* shoulder; even with those advantages over the ARC, you won't catch me trying to get 2880fps out of any 105gr bullet in a RAT built on a strong Howa Mini action, let alone in an AR15.
So at least at this point, I can easily understand John Holliger's decision to be very hesitant to doing 6 ARC AR15 bbls for customers. Info on the internet is bound to push some guys to try to match or exceed reported velocities for a new cartridge, and in some cases, no amount of logical arguments will convince those shooters not to try pushing the envelope where pressures are concerned.
I went with the 243lbc chamber in a 24" bbl, I'm getting average 2849fps with 105gr Hornady hpbt...have no pressure signs, 4-5 reloads so far on Lapua brass and still have tight primer pockets. I am using an adjustable gas block, and the accuracy is great out to 500 meters. I have a friend that has 2 barrels (6 arc) on order since May.....can't get even a guesstimate on shipping of either one ! I know times are different, but to roll out a new cartridge that can't be shot is like a new car , but the engines are backordered....The arc is really going to have to be something for me to consider spending money on...rsbhunter
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