New 6mm Advanced Rifle Cartridge

[newageroman]

Shipment of Winchester 748 came in just now, of course this being my hot rifle right now I'm wondering if anyone has loaded 105s with Winchester 748?
The burn rate chart looks like it should be decent around Varget/CFE223 and Leverloution.
The local shop also had Barnes 105 Match burners in stock, Has any one tried them?
I was about to order more brass but Starline is not even taking backorders now. Whoa! I'm hoarding all my cases now. Glad to have what I got when I got it.

 

[raptor99]

It is a crap shoot on what your rifle will like........

 

[Goldtriggerfinger]

Um, because they developed and tested it and it fit their needs for their mission set? You're assuming that this was all decided in theory and that the end user doesn't have a champagne budget and got the year and vintage they wanted after trying out a lot of bottles.

Keep in mind over on the FB 6mm ARC page people involved in this on the manufacturing side are sharing pictures of MVs. 11.5" barrels are pushing the 108s at 2324fps. Slow, but it's still hitting with 981ft-lbs at 200yds at sea level. My last tour in Afghanistan, the valley floor was 6600' above sea level. They wanted a good all around cartridge that would work from bad breath to 500-600m. Dropping the weight by 25% from an SR25 means less fatigue, guys can move further or get on an objective faster.

 

[Goldtriggerfinger]

I’ve had issues with both brands of magazines.
Basically I’ve had to test / prove out a magazine in lower(s) used for the 6 / 6.5 Grendel upper.
Magazines are the weak link for me with the Grendel based cartridges.
Once you find mags that work, GTG. Just keep them market and with correct lower. YMMV.

Cproducts(Duramags) I even use 6.5Grendel mags for my 762×39 ARs.
No fte,ftf or stovepipes.....ever. I even use them in my vz58 stanag conversion and bren2 stanag conversion. All 11/12 inch barrels,all 762×39. Buy the Duramags.

 

[Goldtriggerfinger]

Grendel 2 bolt. And yes unmodified grendel mags. Elander and ASC have been good so far

Please guys, we already went through the oddball mag routine with 762×39.
Cproducts(Duramag) is the way to go.
They have the right "curve" radius and the back of the mag gets wider, then narrows again towards the bottom.
These guys did the research and testing so you don't have to! Grendel 20rnd.mags work for my 762×39 ARs as well!

 

[Yondering]

Please guys, we already went through the oddball mag routine with 762×39.
Cproducts(Duramag) is the way to go.
They have the right "curve" radius and the back of the mag gets wider, then narrows again towards the bottom.
These guys did the research and testing so you don't have to! Grendel 20rnd.mags work for my 762×39 ARs as well!

LOL. Look at a Grendel case and tell us why a Grendel mag "needs" that curve and taper, and other straight wall cartridges don't? And how do all the other brands get away with straight mags if that curve is needed? (It isn't.)

It's pretty obvious Duramag re-purposed a bunch of x39 mags that weren't selling. The cases are very different shapes, never mind the same size case head. Cool if/that they work, but don't bs the rest of us saying that's what's needed for a straight wall case; the AR platform has way too much successful history with (mostly) straight mags for straight wall cartridges.

 

[Sutherlandsd]

So far ASC grendel mags have worked for me..

 

[Shifty6BR]

Asc 6.8 spc mags have been running flawless from the leftovers of a former .224V. Even better so than my asc 6.5 grendel mags, with a few hiccups here and there..in fairness they are brand new unbroken in.

 

[Yondering]

Asc 6.8 spc mags have been running flawless from the leftovers of a former .224V. Even better so than my asc 6.5 grendel mags, with a few hiccups here and there..in fairness they are brand new unbroken in.

Same for me, I use 6.8 and Grendel mags interchangeably from a few different brands with no issues at all. I'm currently at 7 different rifles in various 6.8 and Grendel cartridges all using the same magazines, mostly ASC, ELander, and PRI but a couple other brands as well.

I think at least some of the magazine issues (and maybe a large portion of them) people have stem from poor gas system tuning, with bcg speed too high or sometimes too low. Of course there are other legitimate issues as well, but it's interesting to me that some people have a lot of "magazine problems" with their rifles and many others have no issues at all with the same magazines.

 

[Goldtriggerfinger]

Yondering , Smallest to largest are :20rnd Grendel ,28rnd 762×39,30rnd 762×39. Without including caliper pictures, the 762×39mags are wider. You can see how the spine is tack welded with a gap instead of overlapping. The smallest(Grendal) mag also has a thinner center support rib(because of the straight Grendel case) I think the curve helps the case rims "space"a little better. Remember; the 5.56 case has a smaller rim and a longer body. Stanag mags were designed for ONE cartridge with ONE spec. My point is both Cproducts mags work for both cartridges (granted, it is easier to load the mags with their proper cartridges).That being said: Don't be such a jackass. Obviously,I have a lot of experiece with these mags. The other obvious thing is ;you don't. You can believe you are God's gift to Grendel and this forum but I am 53 years to old to be BS' ing anyone. Semi auto/military type rifles are my hobby. I have several AR uppers and lowers and many parts as well. I also enjoy VZ 58s,CZ bren2, Sig MCX, and all the old school U.S. military(Garand,M1carbine,mini14, mini30, etc.) My opinion is based on experience and intellect. I am not some blowhard newbie that just BOUGHT his first gun....and yes I reload: CFE BLK for 762×39 and Grendel....so I am efficient as well.
Suck it Yondering,
Robert Adams

 

[newageroman]

Well that escalated rather slowly...
Dev loads yesterday. Groupings/targets/chronos will be updated shortly, but overall I was getting ~2550-2600 yesterday with LeverLoution/Berger 105 Boat Tail Targets and VLD Targets. I still have a ladderload of 105s and 748 but the shadows were creeping up on me, so next time.

I had some spotting and zeroing difficulties(again) that kept me from getting hits long range, but wrapped those targets up with the 6.5 CM.

The CZ raceguns also ran, it was a great day.

There was a dude next to me shooting a brand new 28" bartlin barrel 6ARC - he was complaining about finding brass as well. I wanted to check his velocity numbers but when I got back down to the short range the guys there said he ran out of ammo and left LOL!

I'm glad I jumped on this train early - I had people telling me "just shoot factory and reload it" I trusted instinct. Its working out. I'm ditching my D650 223 setup for the ARC, I don't shoot much ARs anyway, have plenty loaded 223, so I put it all up and I'm checking on shipping today.

 

[jbailey]

overall I was getting ~2550-2600 yesterday with LeverLoution/Berger 105 Boat Tail Targets and VLD Targets.

There was a dude next to me shooting a brand new 28" bartlin barrel 6ARC - he was complaining about finding brass as well. I wanted to check his velocity numbers but when I got back down to the short range the guys there said he ran out of ammo and left LOL!

what is your barrel length?

And the dude w/ the 28" Bartlein ... was that a bolt or gasser? @Ledzep is running 28" bolt (I believe) and getting v impressive MV in mid 2900s. That is serious performance for under 30grs of powder.

 

[Ledzep]

My 28" is a bolt gun. 2880-2940fps with CFE 223 and LVR with 108-110gr bullets. Factory 108's at 52ksi usually run 2810-2830 which is still no slouch. I get 2775 or so with Varget and 110's.

 

[Yondering]

Yondering , Smallest to largest are :20rnd Grendel ,28rnd 762×39,30rnd 762×39. Without including caliper pictures, the 762×39mags are wider. You can see how the spine is tack welded with a gap instead of overlapping. The smallest(Grendal) mag also has a thinner center support rib(because of the straight Grendel case) I think the curve helps the case rims "space"a little better. Remember; the 5.56 case has a smaller rim and a longer body. Stanag mags were designed for ONE cartridge with ONE spec. My point is both Cproducts mags work for both cartridges (granted, it is easier to load the mags with their proper cartridges).That being said: Don't be such a jackass. Obviously,I have a lot of experiece with these mags. The other obvious thing is ;you don't. You can believe you are God's gift to Grendel and this forum but I am 53 years to old to be BS' ing anyone. Semi auto/military type rifles are my hobby. I have several AR uppers and lowers and many parts as well. I also enjoy VZ 58s,CZ bren2, Sig MCX, and all the old school U.S. military(Garand,M1carbine,mini14, mini30, etc.) My opinion is based on experience and intellect. I am not some blowhard newbie that just BOUGHT his first gun....and yes I reload: CFE BLK for 762×39 and Grendel....so I am efficient as well.
Suck it Yondering,
Robert Adams

View attachment 7576143View attachment 7576145View attachment 7576148

Careful, you might accidentally hurt someone’s feelings if you keep up that tough talk.

A tip though - if you’re trying to prove your credibility and intellect, telling us you load the Grendel with CFE BLK is probably not the way to do it.

I stand by my original statement- there are a number of good magazine choices. Your choice is one way, but don’t bs us that your choice is THE way.

 

[raptor99]

Well that escalated rather slowly...
Dev loads yesterday. Groupings/targets/chronos will be updated shortly, but overall I was getting ~2550-2600 yesterday with LeverLoution/Berger 105 Boat Tail Targets and VLD Targets. I still have a ladderload of 105s and 748 but the shadows were creeping up on me, so next time.

I had some spotting and zeroing difficulties(again) that kept me from getting hits long range, but wrapped those targets up with the 6.5 CM.

The CZ raceguns also ran, it was a great day.

There was a dude next to me shooting a brand new 28" bartlin barrel 6ARC - he was complaining about finding brass as well. I wanted to check his velocity numbers but when I got back down to the short range the guys there said he ran out of ammo and left LOL!

I'm glad I jumped on this train early - I had people telling me "just shoot factory and reload it" I trusted instinct. Its working out. I'm ditching my D650 223 setup for the ARC, I don't shoot much ARs anyway, have plenty loaded 223, so I put it all up and I'm checking on shipping today.

What was your load of LVR with the 105?? Were you seeing any brass marking on the case heads??

 

[TonyTheTiger]

Groupings/targets/chronos will be updated shortly, but overall I was getting ~2550-2600 yesterday with LeverLoution/Berger 105 Boat Tail Targets and VLD Targets.

I can't take it any longer. It's LeverEVOLUTION.

 

[newageroman]

I drove to meet a friend and traded a can of SW4530 for LeverLoution today!
Here is my range blog for the day:

6ARC, ATN scope, CZ racegun testing

Chrono Results are listed HERE! Where the radio runs out, in the hills of TN, there is a cove tucked in the woods that lets you shoot up to 1250 with live large Screen Impact monitors. It's ...

brassbucket.net

What was your load of LVR with the 105?? Were you seeing any brass marking on the case heads??

Just go back a couple pages and all my load dev is there. I have pics of case heads ect...

 

[Sutherlandsd]

I drove to meet a friend and traded a can of SW4530 for LeverLoution today!
Here is my range blog for the day:

6ARC, ATN scope, CZ racegun testing

Chrono Results are listed HERE! Where the radio runs out, in the hills of TN, there is a cove tucked in the woods that lets you shoot up to 1250 with live large Screen Impact monitors. It's ...

brassbucket.net

Just go back a couple pages and all my load dev is there. I have pics of case heads ect...

Where in TN is this range I’m not familiar with it?

 

[jbailey]

What was your load of LVR with the 105?? Were you seeing any brass marking on the case heads??

mine, based on a load from @Yondering, is 29.3gr of LVR, a CCI #41 primer and a 105gr Berger Hybrid. No pressure signs in 40-50*F but we will see as the temps heat up if this changes.

 

[Dino11]

mine, based on a load from @Yondering, is 29.3gr of LVR, a CCI #41 primer and a 105gr Berger Hybrid. No pressure signs in 40-50*F but we will see as the temps heat up if this changes.

29.4 gr. of lever behind a Nosler 105 RDF did not show any signs of pressure last summer in my rifle. I have gone all the way to 29.9 with out any problems. Hornady's bolt gun load data for max load is 30.8 gr. And their load data is on the conservative side. 29.4 works great in all my DI ARC rifles, I even use it for 108's and 100 gr. bullets.

 

[Tx_Aggie]

mine, based on a load from @Yondering, is 29.3gr of LVR, a CCI #41 primer and a 105gr Berger Hybrid. No pressure signs in 40-50*F but we will see as the temps heat up if this changes.

29.4 gr. of lever behind a Nosler 105 RDF did not show any signs of pressure last summer in my rifle. I have gone all the way to 29.9 with out any problems. Hornady's bolt gun load data for max load is 30.8 gr. And their load data is on the conservative side. 29.4 works great in all my DI ARC rifles, I even use it for 108's and 100 gr. bullets.

Correct me if I'm wrong, but the working pressure in a DI gun for the ARC, as with the Grendel, is based on the affect of increased bolt thrust on the life cycle of the bolt, not on what the brass can safely handle.

Based on Gordon's Reloading Tool, both of these loads are above 70k psi, while the safe working pressure for an Alexander Grendel bolt is stated as 50k psi. So while you may not be seeing pressure signs on the brass, you are probably beating the snot out of your bolt using those loads in a gas gun (jbailey, I'm not sure if you are using that load in a gasser or not, so excuse me if not).

I think at least for DI rifles, guys need to understand that just looking at your brass may not give you an idea of where you are in relation to the gun's intended working pressure.

 

[SWFShooter]

Correct me if I'm wrong, but the working pressure in a DI gun for the ARC, as with the Grendel, is based on the affect of increased bolt thrust on the life cycle of the bolt, not on what the brass can safely handle.

Based on Gordon's Reloading Tool, both of these loads are above 70k psi, while the safe working pressure for an Alexander Grendel bolt is stated as 50k psi. So while you may not be seeing pressure signs on the brass, you are probably beating the snot out of your bolt using those loads in a gas gun (jbailey, I'm not sure if you are using that load in a gasser or not, so excuse me if not).

I think at least for DI rifles, guys need to understand that just looking at your brass may not give you an idea of where you are in relation to the gun's intended working pressure.

I had 30.8 grains of LVR with a 105 at 67K+ in Quickload. The 29.3 load is around 56K, still over the SAAMI 52K. High bolt thrust on a weak bolt design. The thing with a Grendel bolt is they are fine until they aren't fine. Been there, done that, broken bolts, even a broken barrel extension (funny how precision machining, or rather lack of, causes stresses on lugs), case head separation on brand new Lapua brass (that one surprised me, and it killed a brand new elander mag), and a pile of brass turned into scrap. I decided to back off to normal pressures before I ended up a pirate, or learned the nickname "lefty".

 

[Dino11]

Honady's max load is 29.5gr. behind a 105gr. bullet. The problem with these ballistic calculators is they are not very accurate predicting the 6mm ARC round, I have seen this on more than one of them. You have to tweek them to get the match between what you are shooting and what they say is correct. I got Quick load very close to what it should be.

This is a screen shot of Hornay's gas gun page.

 

[Ledzep]

29.4 gr. of lever behind a Nosler 105 RDF did not show any signs of pressure last summer in my rifle. I have gone all the way to 29.9 with out any problems. Hornady's bolt gun load data for max load is 30.8 gr. And their load data is on the conservative side. 29.4 works great in all my DI ARC rifles, I even use it for 108's and 100 gr. bullets.

Bad call. The load data is done in a properly corrected SAAMI pressure test barrel and is up to the full 52,000 PSI that is recommended in Grendel/7.62x39 bolts.

I believe the RDF has less bearing surface than the Hornady 105 BTHP, and the max book charge is 29.5gr so you're probably fine at 29.4. Not arguing that.

I continue to see this trend of people thinking that book data is "lawer loaded" or conservative and it's not. I've seen the process and it's just not lol. The "lawyer" part is in the front of the book where they tell you they're not responsible for you blowing your stuff up. Obviously component changes can change pressures (more dramatically in some cases than a guy might think), but for the most part pressures signs that you can see on the case head start showing up in the low 70ksi range (semi-autos can be much lower-- in the 50's, depending on gas system arrangement from bolt unlocking/timing issues). There's lots of knobs to turn but the point I'm getting at is that when the pressure limitation is there for the bolt lugs, not the brass necessarily, the standard "pressure signs" aren't going to show up before you're in the red zone and all you really have to go off of is published load data, and the published load data is not "lawyer loaded".

With a properly tuned gas system, a guy could run 60-62ksi all day without visible pressure signs and fatigue load your bolt in short order. Equal pressure in a Grendel/PPC bolt face is putting ~30-40% more thrust on the bolt than 5.56/.223 sized cartridges. Cuts into fatigue life pretty quickly.

 

[Dino11]

Hornady tells me that at 29.4 gr. the pressure is 51,800, psi, with the 105 gr. bullet. That is within the 52,000 psi limit of the bolt. And their is a buffer margine calculated into it. Hornady is not going to publish unsafe data on any round, let alone one of their rounds on a platform that they developed.

What I was replying to is that their is no way that load was coming close to 70,000 psi, and I believe that the ballistic calculator spit those numbers out. As I had stated... I have yet to see accurate information from any of them. You have to tweek the input numbers to get a more accurate output. And I would not put my life on the line from any data from them, they are simply just a guesstimates. At least with 6mm ARC. I would never determine my load from any information from one.

I have tried different powders than those listed as safe to use. One of those was BL-C2, then right after I tested it a load was released for it and the numbers were spot on with what I was seeing with my load development. Folks told me that that powder would never work, but it was one of the more accurate ones I have loaded, even though the velocity was down some from Lever and CFE223. And now that I have a bolt gun with a longer barrel I have plans to revisit some of the other powders to see if their is something else that will work. Their is not much info out yet on the bolt action loads yet.

 

[jbailey]

yeah, I don't have much to add outside of the belief 29.3gr of LV isn't anywhere close to 70kpsi at the temps I was operating in. See the data book page @Dino11 posted, plus a bunch of the load development notes in the prior 10k pages (this thread is getting difficult to handle). I tried loads up to 30.0gr with seeing any pressure signs - only nice round primers. I know that brass signs aren't reliable on gas guns, but this was with the gas system turned off (I was having cycling issues that I covered 5k pages ago). As temps heat up, I will monitor the situation.

I am not a high volume shooter, so this gun isn't going to get 1000 rds on it in 5 years. Does that help with an over-pressured gun? Maybe if it is just a tad over-pressured. I agree that if I'm over 60k, I need to come down, but if I'm at 55k, vs the 52k max, maybe that is OK ???

 

[Ledzep]

Shot-to-shot variance is on the order of 1000-2000psi on good loads, often worse. 51,800 effectively is the same as 52,000. You're talking less than a tenth of a grain to average 200psi difference over a large enough sample size to matter. While I agree they're not going to publish anything very much over 52,000 psi on the nose (in their gun, with their brass, and their bullet, with their cleaning regimen-- which is not the same as yours necessarily), that doesn't mean there's a ton of leeway.

And again, I'm not arguing that you're not safe at 29.4. The RDF is probably going to have lower pressure for the same charge as the Hdy BTHP because it has a shorter bearing surface. However, I maintain that while you may have some success guessing what's safe, without a pressure barrel you don't know and there may be a window of performance that exceeds safe pressure but doesn't show you anything. That doesn't mean it's kosher. It just means you can't see it. Recognizing that is an important part of trying untested or unpublished loads, especially in this situation where the brass won't show anything until significantly higher pressure than what the gun should be fed.

Realistically, odds are that if you ran hot for a long enough time you'd break a lug off and have a bad range day, but then again, there's always the inner dialogue of "what if it's worse than that" in regards to you and others around at the time, etc... Anyway, banking on 'soft' max charges in published reloading data isn't a great habit IMO. From what I've seen they're right up to the SAAMI MAP. And that's in a temp controlled lab in relatively clean barrels.

 

[SWFShooter]

Hornady tells me that at 29.4 gr. the pressure is 51,800, psi, with the 105 gr. bullet. That is within the 52,000 psi limit of the bolt. And their is a buffer margine calculated into it. Hornady is not going to publish unsafe data on any round, let alone one of their rounds on a platform that they developed.

What I was replying to is that their is no way that load was coming close to 70,000 psi, and I believe that the ballistic calculator spit those numbers out. As I had stated... I have yet to see accurate information from any of them. You have to tweek the input numbers to get a more accurate output. And I would not put my life on the line from any data from them, they are simply just a guesstimates. At least with 6mm ARC. I would never determine my load from any information from one.

I have tried different powders than those listed as safe to use. One of those was BL-C2, then right after I tested it a load was released for it and the numbers were spot on with what I was seeing with my load development. Folks told me that that powder would never work, but it was one of the more accurate ones I have loaded, even though the velocity was down some from Lever and CFE223. And now that I have a bolt gun with a longer barrel I have plans to revisit some of the other powders to see if their is something else that will work. Their is not much info out yet on the bolt action loads yet.

I never said your 29.4 load was 70K, I stated the 30.8 load, with cartridge length to fit in an AR mag is around 67K. That uses default inputs for temp, so assuming load development was in cooler conditions, you should expect higher velocities and higher pressures when summer rolls around. Shoot whatever you want, I just figured a little info might be handy.

 

[Yondering]

I never said your 29.4 load was 70K, I stated the 30.8 load, with cartridge length to fit in an AR mag is around 67K. That uses default inputs for temp, so assuming load development was in cooler conditions, you should expect higher velocities and higher pressures when summer rolls around. Shoot whatever you want, I just figured a little info might be handy.

That's the trouble with QL or any other calculator though - if you haven't trued the results for your barrel and components, the margin of error is so large that the results are pretty much useless.

From personal experience over a lot of rounds I seriously doubt that 30.8 load is at 67 ksi. That would do noticeable damage to Grendel brass (specifically the "belted magnum" appearance) whether it's in a bolt action or an AR. I'll trust Hodgdon's data way before anything some calculator spits out; real world results always trump theory.

If you start off by truing your calculator to match several different loads from published data, then you've got something capable of putting out reasonable results as a starting point. Then true it further to match your rifle (i.e. if velocity is different than predicted, then the pressure curve is probably different too.).

 

[newageroman]

Where in TN is this range I’m not familiar with it?

Gun Range

Strategic Edge Gun Range stands as the pinnacle of shooting facilities in the Southeast, serving both government/corporate clients and private members. Our range is meticulously designed for utmost safety and offers a comprehensive shooting experience. Key Features: Long-Range Excellence:

www.strategicedge.us

they have a 600 yd match open to the public every month and this weekend.
Get on the wait list. Took me 2 years, worth it.

 

[SWFShooter]

That's the trouble with QL or any other calculator though - if you haven't trued the results for your barrel and components, the margin of error is so large that the results are pretty much useless.

From personal experience over a lot of rounds I seriously doubt that 30.8 load is at 67 ksi. That would do noticeable damage to Grendel brass (specifically the "belted magnum" appearance) whether it's in a bolt action or an AR. I'll trust Hodgdon's data way before anything some calculator spits out; real world results always trump theory.

If you start off by truing your calculator to match several different loads from published data, then you've got something capable of putting out reasonable results as a starting point. Then true it further to match your rifle (i.e. if velocity is different than predicted, then the pressure curve is probably different too.).

Way too many people jump on Quickload and expect some magic without understanding the program's strengths and limitations. As with any computer program "garbage in, garbage out" is a major reason for inaccuracies. After years of working with the program and verifying results with field data over thousands of loads, and verifying the estimated pressure calculations with real lab results, I have a pretty good idea of the program and it's capabilities. In response to the Grendel brass "belted magnum", I did a research project using numerous manufacturers of Grendel brass, the case bulging/base swelling is more prominent with certain manufacturers, and is influenced by the barrel chamber and 0.136 bolt as well.

 

[GONE BAD]

I've recently put together a 6 ARC but haven't been able to get out to see how it goes. That being said, when I got the parts ordered I started to feel byers remorse.

First off: Never really wanted anything related to the bolts used in this type of platform.

Second: The barrel and bolt are (by some on here) substandard.
Faxon barrel, Faxon BCG. But with things being the way they are, it was what was available.

Third: The lack of factory ammo and/or components to load with.

Anyway I'm head down the rabbit hole and now once again I'm seeing conversations regarding 'high pressures and possible bolt failure '.

I've got everything to make-up my own loads EXCEPT for powder!

So now I've taken to just examining what I have and the possibilities.
The rifle is all built. Pretty much threw it together, with exception of barrel and bolt, from parts I had.

I was able to buy factory ammo, dies, and some 105g Scenars.

Reading all of this thread, I've look a few things now.
I pulled one of the cartridges apart to do two things. One: establish powder charge and check what COAL could be with the 108 ELDM and the 105
Scenars.

The powder charge was 30.9
The max COAL with the 108's turned out to be 2.344" jambed into lands.
The Hornady factory ammo COAL is 2.250". So I'm looking at probably .084 jump if I took .010 off for being in the lands.

With the Scenar 105 I started the bullet and seated the bullet using the bolt.
COAL on them was 2.303 jambed. So taking .010 off for in the lands I end up with a COAL pretty close to 2.293.
Also my mags max length is 2.318 and 2.300 depending on brand.

So it seems rounds loaded to mag length with the 108 would have a .034 jump at mag length and the 105 scenar would be loaded to 2.293? If my numbers are right.

Also if this factory ammo 'IS' loaded with Leverevolution then it would seem to be over book by a full grain.
Maybe they are taking in the fact that its Virginia brass and the COAL is 2.250?
Idk.

Hope to get out soon to test.....and then find some powder

 

[SWFShooter]

I've recently put together a 6 ARC but haven't been able to get out to see how it goes. That being said, when I got the parts ordered I started to feel byers remorse.

First off: Never really wanted anything related to the bolts used in this type of platform.

Second: The barrel and bolt are (by some on here) substandard.
Faxon barrel, Faxon BCG. But with things being the way they are, it was what was available.

Third: The lack of factory ammo and/or components to load with.

Anyway I'm head down the rabbit hole and now once again I'm seeing conversations regarding 'high pressures and possible bolt failure '.

I've got everything to make-up my own loads EXCEPT for powder!

So now I've taken to just examining what I have and the possibilities.
The rifle is all built. Pretty much threw it together, with exception of barrel and bolt, from parts I had.

I was able to buy factory ammo, dies, and some 105g Scenars.

Reading all of this thread, I've look a few things now.
I pulled one of the cartridges apart to do two things. One: establish powder charge and check what COAL could be with the 108 ELDM and the 105
Scenars.

The powder charge was 30.9
The max COAL with the 108's turned out to be 2.344" jambed into lands.
The Hornady factory ammo COAL is 2.250". So I'm looking at probably .084 jump if I took .010 off for being in the lands.

With the Scenar 105 I started the bullet and seated the bullet using the bolt.
COAL on them was 2.303 jambed. So taking .010 off for in the lands I end up with a COAL pretty close to 2.293.
Also my mags max length is 2.318 and 2.300 depending on brand.

So it seems rounds loaded to mag length with the 108 would have a .034 jump at mag length and the 105 scenar would be loaded to 2.293? If my numbers are right.

Also if this factory ammo 'IS' loaded with Leverevolution then it would seem to be over book by a full grain.
Maybe they are taking in the fact that its Virginia brass and the COAL is 2.250?
Idk.

Hope to get out soon to test.....and then find some powder

Just FYI- the factory ammo is NOT loaded with Leverevolution, it is a non-cannister powder.

 

[GONE BAD]

Just like Superformance?

 

[SWFShooter]

Just like Superformance?

There is Superformance the Hodgdon powder and Superformance line of ammo, which does not use Hodgdon Superformance powder, so yes.

 

[Yondering]

After years of working with the program and verifying results with field data over thousands of loads, and verifying the estimated pressure calculations with real lab results, I have a pretty good idea of the program and it's capabilities.

And yet you are claiming that a load directly out of Hodgdon's actual tested data is making 67 ksi based on your QL prediction. Their real world results are far more credible than your QL predictions. You'd do much better to tweak your QL model to match their data, and work from there.

 

[Yondering]

I've recently put together a 6 ARC but haven't been able to get out to see how it goes. That being said, when I got the parts ordered I started to feel byers remorse.

First off: Never really wanted anything related to the bolts used in this type of platform.

Second: The barrel and bolt are (by some on here) substandard.
Faxon barrel, Faxon BCG. But with things being the way they are, it was what was available.

Third: The lack of factory ammo and/or components to load with.

Anyway I'm head down the rabbit hole and now once again I'm seeing conversations regarding 'high pressures and possible bolt failure '.

I've got everything to make-up my own loads EXCEPT for powder!

So now I've taken to just examining what I have and the possibilities.
The rifle is all built. Pretty much threw it together, with exception of barrel and bolt, from parts I had.

I was able to buy factory ammo, dies, and some 105g Scenars.

Reading all of this thread, I've look a few things now.
I pulled one of the cartridges apart to do two things. One: establish powder charge and check what COAL could be with the 108 ELDM and the 105
Scenars.

The powder charge was 30.9
The max COAL with the 108's turned out to be 2.344" jambed into lands.
The Hornady factory ammo COAL is 2.250". So I'm looking at probably .084 jump if I took .010 off for being in the lands.

With the Scenar 105 I started the bullet and seated the bullet using the bolt.
COAL on them was 2.303 jambed. So taking .010 off for in the lands I end up with a COAL pretty close to 2.293.
Also my mags max length is 2.318 and 2.300 depending on brand.

So it seems rounds loaded to mag length with the 108 would have a .034 jump at mag length and the 105 scenar would be loaded to 2.293? If my numbers are right.

Also if this factory ammo 'IS' loaded with Leverevolution then it would seem to be over book by a full grain.
Maybe they are taking in the fact that its Virginia brass and the COAL is 2.250?
Idk.

Hope to get out soon to test.....and then find some powder

Don't let the doom and gloom about bolt failures scare you off. It can happen of course, but isn't nearly as common as some online make it out to be.

With that said, the two most important things you can do to ensure the longest possible bolt life are:

1 - True your receiver (and/or shim or thermofit) to promote uniform bolt lug contact. Uneven lug engagement does more to raise stress on bolt lugs than anything else, and in the context of these broken bolt discussions, most rifles are assembled without this preventive measure.

2 - Tune the gas system so the bolt isn't trying to unlock under pressure. Early unlocking adds to the stresses on bolt lugs.

If it makes you feel any better, I've been loading 31.0gr of Lever under the 105 BTHP as my standard load in my 243 LBC rifles (granted, slightly more capacity but not enough to matter that much) for a few years now in 3 different rifles. Two were built on BCM uppers, the thermo-fit tight bore pretty much guarantees barrel extension alignment with the receiver, and the other was trued and shimmed so all of them have very uniform lug engagement. The only issue I've had was a broken extractor on the first 24" rifle after ~600 rounds running a bit over-gassed with a .125 bolt (the extractors are a little weaker and early extraction adds a lot of stress). That load is certainly hotter than Hodgdon's data recommends for an AR, although the numbers correlate very well with their 24" bolt gun velocity for the same load. Load at your own risk and respect the potential for danger, but don't be scared of it; if you follow their AR15 data you're not exactly pushing the ragged edge of safety or anything close to it.

 

[SWFShooter]

And yet you are claiming that a load directly out of Hodgdon's actual tested data is making 67 ksi based on your QL prediction. Their real world results are far more credible than your QL predictions. You'd do much better to tweak your QL model to match their data, and work from

No, I said the load listed above which was a 105 Hybrid, at AR mag length with 30.8 grains would be 67K. The Hornady bolt gun data is stated to be at 62K, and I was pointing out that the data should not be used in an AR, hence the bolt discussion.

 

[Yondering]

No, I said the load listed above which was a 105 Hybrid, at AR mag length with 30.8 grains would be 67K. The Hornady bolt gun data is stated to be at 62K, and I was pointing out that the data should not be used in an AR, hence the bolt discussion.

So are you implying that if you change the bullet in your model to the 105 BTHP your prediction will match Hornady's 62K data? Because if it doesn't, your prediction is wrong. That's my point. If it does, maybe you should have said so to start with.

If you have a solid starting point like that (closer the better), then the prediction might have some value. But the more variables that change from that correlated starting point, the less useful the prediction is.

 

[SWFShooter]

So are you implying that if you change the bullet in your model to the 105 BTHP your prediction will match Hornady's 62K data? Because if it doesn't, your prediction is wrong. That's my point. If it does, maybe you should have said so to start with.

If you have a solid starting point like that (closer the better), then the prediction might have some value. But the more variables that change from that correlated starting point, the less useful the prediction is.

I can't tell you why Hornady's data is the way it is. I know if I use Hodgdon's data the QL estimate is lower pressure than they tested, and Hodgdon actually ran pressure testing. The Hodgdon max charge weight is 28.2 for a 107 (51,800psi), and 28.5 for a 103 (51,100psi), both well below Hornady's 29.5 for a 105 (52K AR15 data). Assuming the Hodgdon data is accurate, calibrating to their tested pressure, 30.8 grains estimates at 66,000psi. Without calibrating to the actual measurements of a specific rifle and components, and then performing the actual pressure testing, we won't know actual numbers, and I am not getting out the pressure equipment just to test a Hornady 105BTHP. So the same powder, different bullet, Hornady states the pressure is 52,000 max, and Hodgdon posts the tested pressure number with the load. So either Hornady has a test AR barrel with a longer throat chamber, or they tested that unstable ball powder in cold temps, or some odd conditions exists. In any case, I still would not recommend using the Hornady BOLT GUN data as justification to exceed their stated max AR15 data in an AR15. Have a good one.

 

[raptor99]

That's the trouble with QL or any other calculator though - if you haven't trued the results for your barrel and components, the margin of error is so large that the results are pretty much useless.

From personal experience over a lot of rounds I seriously doubt that 30.8 load is at 67 ksi. That would do noticeable damage to Grendel brass (specifically the "belted magnum" appearance) whether it's in a bolt action or an AR. I'll trust Hodgdon's data way before anything some calculator spits out; real world results always trump theory.

If you start off by truing your calculator to match several different loads from published data, then you've got something capable of putting out reasonable results as a starting point. Then true it further to match your rifle (i.e. if velocity is different than predicted, then the pressure curve is probably different too.).

What do you mean by your brass looking like a "Belted Magnum" appearance?? Is this right at the base of the case?? I have seen this on some of my cases but I thought it was because I had "Oversized" my case when I sized it down more than I should have. I had bought some "Once fired" Grendel brass and it wasn't chambering like it should. I thought it was because it had been fired in another chamber and I probably needed a small base die. I actually cranked my die down until I got a slight "Cam over" and I still had some issues with chambering. So I set them a side. This brass had been mixed in with my new brass during the process of making 6ARC brass. So I don't know if it was from sizing or happened during load development. I had never seen it before until I started with the ARC.......

 

[Dino11]

Belted brass...

The lower part of the case is used to headspace the cartridge.

 

[SWFShooter]

What do you mean by your brass looking like a "Belted Magnum" appearance?? Is this right at the base of the case?? I have seen this on some of my cases but I thought it was because I had "Oversized" my case when I sized it down more than I should have. I had bought some "Once fired" Grendel brass and it wasn't chambering like it should. I thought it was because it had been fired in another chamber and I probably needed a small base die. I actually cranked my die down until I got a slight "Cam over" and I still had some issues with chambering. So I set them a side. This brass had been mixed in with my new brass during the process of making 6ARC brass. So I don't know if it was from sizing or happened during load development. I had never seen it before until I started with the ARC.......

This is an extreme case in a Grendel, "Lapua Grendel belted magnum".

 

[Ledzep]

I can't tell you why Hornady's data is the way it is. I know if I use Hodgdon's data the QL estimate is lower pressure than they tested, and Hodgdon actually ran pressure testing. The Hodgdon max charge weight is 28.2 for a 107 (51,800psi), and 28.5 for a 103 (51,100psi), both well below Hornady's 29.5 for a 105 (52K AR15 data). Assuming the Hodgdon data is accurate, calibrating to their tested pressure, 30.8 grains estimates at 66,000psi. Without calibrating to the actual measurements of a specific rifle and components, and then performing the actual pressure testing, we won't know actual numbers, and I am not getting out the pressure equipment just to test a Hornady 105BTHP. So the same powder, different bullet, Hornady states the pressure is 52,000 max, and Hodgdon posts the tested pressure number with the load. So either Hornady has a test AR barrel with a longer throat chamber, or they tested that unstable ball powder in cold temps, or some odd conditions exists. In any case, I still would not recommend using the Hornady BOLT GUN data as justification to exceed their stated max AR15 data in an AR15. Have a good one.

Variation.... Not everyone's SAAMI chamber is the same, not everyone's bore is in the same condition, not everyone's bore is in the same state of cleanliness, not everyone calibrates the same lot of cases, not everyone uses the same primers, the same bullets, etc.. etc... Ball powders vary lot to lot more than H4350 or Varget...

ETA: Hornady has hundreds of pressure test barrels, often multiples for every cartridge they produce. Seen it once.

What do you mean by your brass looking like a "Belted Magnum" appearance?? Is this right at the base of the case?? I have seen this on some of my cases but I thought it was because I had "Oversized" my case when I sized it down more than I should have. I had bought some "Once fired" Grendel brass and it wasn't chambering like it should. I thought it was because it had been fired in another chamber and I probably needed a small base die. I actually cranked my die down until I got a slight "Cam over" and I still had some issues with chambering. So I set them a side. This brass had been mixed in with my new brass during the process of making 6ARC brass. So I don't know if it was from sizing or happened during load development. I had never seen it before until I started with the ARC.......

As pictured above if you get a little sloppy on how deep your chamber chamfer is, or how big a radius you use on the corner break, you can leave unsupported case body that will expand and fill the 'void'. I've drawn this up in CAD before and you gotta goof it IMO on the machining side to create the situation. The deeper grendel bolt face means you have less wiggle room but you still gotta get a little zealous on the material removal to make room for the belt that far forward on the case. Unfortunately the pictures exist (as far as I'm aware, happy to be corrected) with no context to who's bolt/barrel and what the actual measurements were that created that. It's become a defacto "grendel problem" whether warranted or not.

 

[Constructor]

Variation.... Not everyone's SAAMI chamber is the same, not everyone's bore is in the same condition, not everyone's bore is in the same state of cleanliness, not everyone calibrates the same lot of cases, not everyone uses the same primers, the same bullets, etc.. etc... Ball powders vary lot to lot more than H4350 or Varget...

ETA: Hornady has hundreds of pressure test barrels, often multiples for every cartridge they produce. Seen it once.



As pictured above if you get a little sloppy on how deep your chamber chamfer is, or how big a radius you use on the corner break, you can leave unsupported case body that will expand and fill the 'void'. I've drawn this up in CAD before and you gotta goof it IMO on the machining side to create the situation. The deeper grendel bolt face means you have less wiggle room but you still gotta get a little zealous on the material removal to make room for the belt that far forward on the case. Unfortunately the pictures exist (as far as I'm aware, happy to be corrected) with no context to who's bolt/barrel and what the actual measurements were that created that. It's become a defacto "grendel problem" whether warranted or not.

ALL AR barrels have a larger chamfer at the breech to aide feeding. Bolt guns do not need a huge chamfer.

 

[newageroman]

^^^HOLY CRAP - That would scare the piss out of me ^^^

 

[Dino11]

A short 1 minute video explaining belted cartridge, they were manufactured with the belt.

 

[Ledzep]

ALL AR barrels have a larger chamfer at the breech to aide feeding. Bolt guns do not need a huge chamfer.

We've had this discussion before. I've spun my own ARC and 556 AR barrels and drawn the ARC setup in CAD and there isn't unsupported case where those pictures show it unless you cut the chamfer *too* deep or make the radius *too* large.

 

[SWFShooter]

A short 1 minute video explaining belted cartridge, they were manufactured with the belt.

Grendel belted magnum is just a goof on the brass that swells after firing in the same location due to a weak point in the brass wall lining up with the bolt to barrel connection. The brass is trash after it happens.

 

[Ledzep]

May shed some light on the whole Pam Pan thing... 105 rdf at 2.245