New 6mm Advanced Rifle Cartridge

[Yondering]

LOL. I’m shooting the 90gr TGK at 3150 fps from my 24” with Lever, and the 90gr ELDX will do 3050 so I’m sure the 87gr Vmax should do better. It’s not a 243, but using Lever in this cartridge brings the performance up pretty close to what stick powders can do in the 243 or 6 Creed.

H4895 is sloooow in this cartridge. Varget gets a little closer to the top end if you feel you need a stick powder.

There’s no getting around it - this small case performs a lot better with ball powders, especially Lever, and doesn’t have the capacity to be as effective with stick powders like the bigger cartridges are. Trying to treat it like the larger cases with stick powders neuters this little cartridge by 150-200 fps minimum, and that’s if you push the stick powders right up to max pressure.

 

[LRRPF52]

Oh my... where to start.

1205 posts later (yes the entire thread), the better part of my day reading and googling all the terms used in this thread, and a registration here i am. Wanting to build an 6arc, and wanting to get into reloading. You guys are an expensive influence.

First and most pressing question, I have a 7.62x39 bcg, am I grasping at straws thinking a bolt change will alleviate the need for a whole new carrier?

I resisted doing any other googling, including searching and pricing parts on this build, until I finished all 25 pages. This thread seems to have all the info I need, mag choices, barrel manufacturers, bcg options, even some pretty good load data with relevant powders (as well as what to look for in terms of overpressure).

I did have another question, when reading the difference between COAL, and CBTO. I seem to remember some people having a hard time loading to match Hornady's claimed velocity numbers initially (this was like 15 pages back), but then a comment about the loads not seeming to be on the anemic side with regards to the 52ksi number. Anyone still sitting on a box from the first 2 batches willing to chrono a few hand loading the long cartridges and comparing this to one that's been seated at the correct depths? Curious as to the difference 45-50 thousandths makes on the boom from the same charge. May not be much of any, as Henry showed speeds all within the same SD with I think 15-20 thou across his range, but that may be powder specific, and I also saw in here Hornady pretty well filled the case with whatever powder they chose, so does getting to to the point where your compressing the powder ramp up the pressure quicker? (Remember, never reloaded a day in my life, so be easy please, its my first time ).

Lastly, how does this compare to a true .243 ar10? I like fast shooting rounds, I'd like to crack 3-3200k fps, 80-90gr bullet (87vmax maybe?), out of say a 20-22 inch arc gun. I know this was a purpose built long bullet short fat case flat flying long range cartridge,just thinking out loud what other possibilities there are in getting outside of the norm 103-108 projectile. You know, all of this before I own the barrel or my first pound of powder, back to lurking.

Yes, you can just replace the bolt with a Grendel bolt with the .136” face depth. After-market 7.62x39 bolts that overlooked Colt’s R&D on the 7.62x39 Sporter will eventually snap the lip off the extractor because there isn’t enough material, even on the LMT enhanced 7.62x39 bolts with the lobster tail extractor design with 2 springs.

I would love it if LMT made a 2.810” long enhanced 6.5 Grendel/6mm ARC bolt with .136” face depth and the lobster tail with an optimum metallurgy for the extractor (no nitriding, balanced hardness/ductile tool steel with controlled heat treat).

 

[Jefftopgun]

Lots of good info here, appreciate all the advice so far. One of the videos posted on YouTube, guy who is pushing the limits exceeding Hornady suggested loads, claims he will be going down all the way to the 58gr vmax. Maybe I'm missing something on hornadays website but those bullets seem incredibly short compared to the 103/108s. Anyone have experience with a shaw arc barrel? Their 22 inch seems quiet appealing to me. Will they do a rifle+2 gas system?

Lastly, my first AR was a springfeild saint victor. I've got my 7.62 upper (10.5 inch) coming for a pistol build, already got a pair of lowers as well(and a spare aero bcg), so I'm thinking I might swap the bolt and barrel on the saint (for 6mm arc with free float 15 inch mlok), and swap over to a 12-14 inch barrel 556 setup, and using my AIM NB BCG in the 762. This leaves me with 2 'pistols' 1 in 556 and 1 762, and a, what I would consider, mid level AR with at least a decent trigger (NB assembly) for precision with the arc, and a spare 556 bolt for 'shtf'.

 

[Yondering]

Lots of good info here, appreciate all the advice so far. One of the videos posted on YouTube, guy who is pushing the limits exceeding Hornady suggested loads, claims he will be going down all the way to the 58gr vmax. Maybe I'm missing something on hornadays website but those bullets seem incredibly short compared to the 103/108s. Anyone have experience with a shaw arc barrel? Their 22 inch seems quiet appealing to me. Will they do a rifle+2 gas system?

Lastly, my first AR was a springfeild saint victor. I've got my 7.62 upper (10.5 inch) coming for a pistol build, already got a pair of lowers as well(and a spare aero bcg), so I'm thinking I might swap the bolt and barrel on the saint (for 6mm arc with free float 15 inch mlok), and swap over to a 12-14 inch barrel 556 setup, and using my AIM NB BCG in the 762. This leaves me with 2 'pistols' 1 in 556 and 1 762, and a, what I would consider, mid level AR with at least a decent trigger (NB assembly) for precision with the arc, and a spare 556 bolt for 'shtf'.

Nothing wrong with trying the light varmint bullets if you want. They should shoot great, but expect POI to be a bit different than the heavies. FYI if you don't know - the light bullets benefit most from a longer barrel. Heavy bullets generally are more efficient in short barrels, comparing apples to apples. I mention that because some guys mix that up and go with light bullets to make up for velocity loss in shorter barrels, but you give up more that way than sticking with the heavy stuff.

Also - a 12.5" ARC and a 22"-24" ARC cover a lot of bases, with maybe a 16" 5.56 in the middle as a general purpose knocking around rifle. The 12.5" ARC can outperform even a 16" 5.56 by a significant margin and can definitely take advantage of a proper mil/mil scope with repeatable dialing capability for distance.

 

[Jefftopgun]

Nothing wrong with trying the light varmint bullets if you want. They should shoot great, but expect POI to be a bit different than the heavies. FYI if you don't know - the light bullets benefit most from a longer barrel. Heavy bullets generally are more efficient in short barrels, comparing apples to apples. I mention that because some guys mix that up and go with light bullets to make up for velocity loss in shorter barrels, but you give up more that way than sticking with the heavy stuff.

Also - a 12.5" ARC and a 22"-24" ARC cover a lot of bases, with maybe a 16" 5.56 in the middle as a general purpose knocking around rifle. The 12.5" ARC can outperform even a 16" 5.56 by a significant margin and can definitely take advantage of a proper mil/mil scope with repeatable dialing capability for distance.

I'm picking up what your putting down, and it makes the 300 blackout make sense given they're all heavy bullets, enter your above statement, heavy bullets, short barrel. As for the light bullets (58ish), it just looks like they're like half the legnth of the 103/108s, didn't think they would seat right.

I would totally go all in on the arc for multiple platforms (short barrel etc) if didn't already have what I consider an excessive stockpile of 556 and 762. Im not even a 556 guy, but I've come to believe the biggest threat to freedom may come within, therefore its a caliber placeholder.

Thanks again all. Time to find a barrel that won't take 3 months lol, I'm so impatient.

 

[ormandj]

I'm picking up what your putting down, and it makes the 300 blackout make sense given they're all heavy bullets, enter your above statement, heavy bullets, short barrel. As for the light bullets (58ish), it just looks like they're like half the legnth of the 103/108s, didn't think they would seat right.

I would totally go all in on the arc for multiple platforms (short barrel etc) if didn't already have what I consider an excessive stockpile of 556 and 762. Im not even a 556 guy, but I've come to believe the biggest threat to freedom may come within, therefore its a caliber placeholder.

Thanks again all. Time to find a barrel that won't take 3 months lol, I'm so impatient.

You adjust seating dies based on the bullet to get the proper base to ogive; seating isn’t done based on the tip of the bullet. The only thing COAL matters for is magazine fit and ability to chamber in the action length.

 

[Henryrifle]

Update on 107 Sierra MatchKing testing:

In the first test with the 107s, I used the same charge weight where I found success with the 108 ELD-Ms, 29 grains of CFE 223. All of my testing with the 108s had been in the 66 to 75 degree fahrenheit temperature range and the speed was a consistent 2675 +/- 10 FPS with an average group size of .7 MOA at 100 yards.

The first test with the 107 SMKs was at 63 degrees with an average velocity of 2650 and average MOA of 1.0. Yesterday the temperature was 52 and I increased the load by .3 grains. I was happy with the muzzle velocity of 2681 but the groups opened WAY up to an average of 1.4 MOA at 100. Primers were flattened with almost no radius left on the visible rim though there were no raised burrs on the case head. Some had a shiny ejector swipe but no flow. The best group was 1.1 MOA and the worst was 2 MOA. I have shot a lot of bolt gun rounds in competition and practice recently so, some of that poor group size could be me but not likely .5 MOA of badness was me.

Going to give the barrel a good cleaning and retest from 28.6 grains back up to 29.2 with the SMKs. I was hoping to find a bullet that shot well for hitting steel and save the 108s for hunting or until the current shortage has lessened. I started with 500 SMKs but am not going to waste a lot more components (primers) on this testing at this time.

Will report back with more findings...

Stay well,
Henryrifle

 

[trdjohn]

I recently ordered 107 nosler CCs, still waiting for them to ship, wondering how those will run, even if I had them in hand today, still not enough time to work them up

 

[Constructor]

Yes, you can just replace the bolt with a Grendel bolt with the .136” face depth. After-market 7.62x39 bolts that overlooked Colt’s R&D on the 7.62x39 Sporter will eventually snap the lip off the extractor because there isn’t enough material, even on the LMT enhanced 7.62x39 bolts with the lobster tail extractor design with 2 springs.

I would love it if LMT made a 2.810” long enhanced 6.5 Grendel/6mm ARC bolt with .136” face depth and the lobster tail with an optimum metallurgy for the extractor (no nitriding, balanced hardness/ductile tool steel with controlled heat treat).

You have been posting this for years to back up your statement that bolts with a .136 recess are stronger but the .136 recess bolts are weaker. There is less support on the back of the lugs, only 7-8% but still weaker not stronger. Take Maxim Firearm bolts as an example, all of his bolts(5.56, 6.8. Grendel. 7.62x39) like mine are made from the same material and go through the same heat treat process. The bolts with a .124 recess have stronger lugs. Now you say the extractors are stronger with this drawing. Depends on who designed the bolt. If making the bolts from scratch the simple thing is to move the extractor pivot pin forward .010" instead of moving the groove on the extractor forward.
You know the extractors AA used can be used on 7.62x39 bolts. Same size extractor hook, no less metal and same strength. R-Guns use to sell them, Black Rifle Arms in Fla still sells them. Instead of a thinner dished out area on each side of the stiffener lug they are flat and actually thicker to give more strength to the hook. BRA-extractor

 

[jbailey]

Update on 107 Sierra MatchKing testing:

The first test with the 107 SMKs was at 63 degrees with an average velocity of 2650 and average MOA of 1.0. Yesterday the temperature was 52 and I increased the load by .3 grains. I was happy with the muzzle velocity of 2681 but the groups opened WAY up to an average of 1.4 MOA at 100. Primers were flattened with almost no radius left on the visible rim though there were no raised burrs on the case head. Some had a shiny ejector swipe but no flow. The best group was 1.1 MOA and the worst was 2 MOA. I have shot a lot of bolt gun rounds in competition and practice recently so, some of that poor group size could be me but not likely .5 MOA of badness was me.

Thanks for this update.

Why aren't you trying the 105gr Berger Hybrids? Those pills are widely used in the competition setting and they have an outstanding repudiation for precision in a broad range of cartridges. They are offering very good precision in the limited testing I have done with them (I'm struggling with MV from extruded powders and some short stroking, but this is unrelated to the bullet).

 

[LRBuck]

Thanks for this update.

Why aren't you trying the 105gr Berger Hybrids? Those pills are widely used in the competition setting and they have an outstanding repudiation for precision in a broad range of cartridges. They are offering very good precision in the limited testing I have done with them (I'm struggling with MV from extruded powders and some short stroking, but this is unrelated to the bullet).

Or the 109 Berger long range hybrid?
Anyone try them yet?
I bought some to try. Last time I looked around the 105’s were not easily found so I went with the 109’s since I was inclined to the heavier grain anyway.

 

[LRRPF52]

You have been posting this for years to back up your statement that bolts with a .136 recess are stronger but the .136 recess bolts are weaker. There is less support on the back of the lugs, only 7-8% but still weaker not stronger. Take Maxim Firearm bolts as an example, all of his bolts(5.56, 6.8. Grendel. 7.62x39) like mine are made from the same material and go through the same heat treat process. The bolts with a .124 recess have stronger lugs. Now you say the extractors are stronger with this drawing. Depends on who designed the bolt. If making the bolts from scratch the simple thing is to move the extractor pivot pin forward .010" instead of moving the groove on the extractor forward.
You know the extractors AA used can be used on 7.62x39 bolts. Same size extractor hook, no less metal and same strength. R-Guns use to sell them, Black Rifle Arms in Fla still sells them. Instead of a thinner dished out area on each side of the stiffener lug they are flat and actually thicker to give more strength to the hook. BRA-extractor

I know you already know this but extractor strength is a totally different conversation than bolt strength. I have never made the argument that a deeper bolt face depth is stronger than a shallower bolt face depth, all approaches to the lug support being the same.

I’m really not sure how someone could confuse the 2 parts.

The strongest 7.62x39 bolt that I’m aware of is made from AerMet by LMT. They use a .125” face depth since so many companies went with that despite Colt’s work on the 7.62x39 Sporter.

Guess what happens even to those extractors?

I’ve also seen claims from someone who either worked for or was a dealer for BHW say how they never saw any problems with .125” bolt breaking extractors (based on limited customer feedback). The next day, a customer asked what to do about his broken extractor from one of those bolts.

Anyone that has shot 7.62x39 in compressed high volume from AR-15s will tell you that bolts and extractors are expendable items for them.

There are people who are experiencing extractor failure at 50, 90, and 200rds with 7.62x39 AR-15s within the past year.

There are very few companies who have done legitimate high-volume pyramid testing with 7.62x39 in AR-15s starting with 100,000rds across at least 10 rifles. Colt is the only one I’m aware of that did their due diligence with outside funding for the program decades ago.

Another thing I’m seeing is that a lot of companies are installing O rings around the extractor springs by default, not aware that this was a band-aid for M4A1s shooting suppressed (and the resulting excess cyclic rate-induced FTExtract malfunctions). The excess extractor tension adds stress to the extractor lip when going into battery, and contributes to reduced extractor life.

As a rule, I don’t let extractors near my bolts with those O rings in them. I prefer a relaxed extractor that only has enough tension to do its job in an optimum gas system configuration (correct port diameter for the length-unlike the MLGS .223 Wylde barrel you sold me with a .094” port that recoils so violently that it broke one of my LPVO ocular pieces loose). The Mil-Std spring and buffer insert have plenty of tension.

As to the bolt strength, there are minor radius changes that can be made to the inner circumference of the wall and bolt face, as well as the lugs to re-gain lug root strength. You already know all about that.

Given the sheer volume of steel case that has been flowing into the market over the past several years, we should be hearing about all kinds of 6.5 Grendel bolt failures. There have been extractor failures for sure though, when companies have allowed their extractor manufacturing process to get out-of-line. I also see people nitriding extractors, which encourages embrittlement.

A have a good friend who, along with his family and friends, seem to be breaking Grendel extractors at 1000rds shooting Wolf Steel case. Every one of those extractors had the O ring in them.

Another buddy of mine built a 12.5” Grendel, in addition to 16” and 20” rifles. He used JP bolts for all. Last time I caught up with him, he had over 8700 rounds through the 12.5” in his log book. It has had mostly 123gr ELD-M through it. All of it has been suppressed. No failures.

I’ve been shooting Grendel regularly for 11 years now across multiple rifles of varying gas system and barrel lengths, with all kinds of hand loads and factory ammo. I have yet to break anything. I think I even herniated a disc moving some of my moving boxes full of Grendel brass, so this isn’t one of those cases where some guy shoots a few hundred rounds, which grow into thousands in his mind.

To date, the only bolts I’ve ever broken in an AR-15 have been 5.56 bolts, and that was shooting really compressed high-volume in tortuous sessions, with CLGS 16” after 10,000rds.

For a production extractor to have enough lip material for a .125” face depth, you really need a wider extractor (what POF did on the Revolution .308 Win), which means different bolt and barrel extension design. Not even LMT (who has forgotten more about sound production and design related specifically to the AR-15), has been able to make a reliable .125” face depth .441” case head diameter bolt extractor.

 

[Henryrifle]

I should try the Berger's but was trying to find a bullet that matched the following prioritized list:

1. Inexpensive
2. Accurate
3. Available

This is an attempt to save the better bullets until components are more readily available. Have had reasonable to good success with the Hornady 108 ELD-M but can't get them right now.

Henryrifle

 

[skyrep]

6mm ARC question: Is anyone producing 12-12.5 inch barrels yet? And really reaching...a complete upper with that barrel length?

I got my 12" barrel from X-Caliber. broke it in and tested the 108 ELD-M (avg FPS: 2429). Have 70 rounds through it. Easiest Barrel to brake in and to clean.

 

[newageroman]

Catching up on the results here. Good reads. I have been loading the berg 105s exclusively (see profile pic). They are good, but I'm sure I can tune for better groups. I have dev loads ready to go when I can get to the range. I will be getting more of these if the local enabler has them in stock after payday. Big If... may have to bribe them with more Krispy Kremes...

I just called for status of my most recent order of Grendle Starline brass and they said ~4weeks from now (ordered 2 weeks ago) - I guess I got accustomed to the short lead time (~2weeks) of the first batch I ordered. I still wish I had got all this setup a few months earlier but hindsight and all..

May order some fancy lapua cases to play with in the meantime. I've never shot those, they look like works of art.

 

[verdugo60]

@eugevita: I think you are going to enjoy your new rifle. Would be interested to know how you plan to use it. As I relate some of my experiences, my goals were to put together a relatively light weight platform that I could use for deer hunting AND one also capable of hitting steel at 1000 yards. As such, I have stayed focused on the heavier bullets and, most specifically, the 108 ELD-Match. I think the BA barrel is a 7 twist barrel meaning you can try the heaviest 6mm projectiles available. My current barrel, a Wilson, is 21.75" long with a 7.7 twist so, I may be capable of 20-40 FPS more than your barrel.

I started with Varget and H4895 and ran into pressure and ruined primer pockets early on only getting to about 2575 FPS. I could have made this work, however, several posters on this forum turned me on to CFE 223. I am now shooting the 108 ELD at 2660 +/- 5 FPS with no pressure and great brass life. This load shoots in the .7s at 100 yards, knocks down, on the spot, small to medium-small deer at 300 yards and easily impacts 1.8 MOA steel at 1000 yards.

It sounds like LEVERevolution is another great powder choice for this cartridge that I intend to try. It is hard to switch powders when you have something that is working...

I have used CCI 450, CCI BR4s and CCI 400 primers. All have worked flawlessly. I did not measure any muzzle velocity difference between CCI 450s and BR4s and, oddly enough, the CCI 400s increase velocity consistently by about 10 FPS. I have settled on the 400s to save the others for competition shooting while this shortage persists.

I have been loading the 108s at 2.255" using Hornady Custom Grade dies and did add the micrometer top to the seating die. The set comes the correct seating stem for the 108 ELD-M and 103 ELD-X bullet.

There are others shooting lighter bullets for varmint-style shooting that I know will weigh in to your question.

Let us know your plans for the rifle...

Henryrifle

Do you mind sharing your load with CFE223?

Just got my first upper and have a whole bunch of that powder. Couldn’t find ELD-M’s so I’m trying 107 SMK’s after I shoot up the factory ammo I have.

 

[Constructor]

Paul, for years you use to say Grendel bolts(.136) were stronger. I'm sure if someone wanted to go to arfcom and look in the archives they could find 10000 of your posts saying so. As for the rest of the 1000 word and pictorial essay I didn't waste time reading, I don't care. Anyone that wants a stronger extractor can get one from BRA when they come back in stock.

 

[Henryrifle]

@verdugo60: I've been using 29.0 grains of CFE 223 in Hornady brass with the Hornady 108 ELD-Match bullet and any of the following CCI small rifle primers: BR4, 450 and 400. My OAL has been very close to max magazine length at 2.255". My powder charge is below the maximum value of 29.1 grains that Hornady has published. My barrel length is 21.75" and the average muzzle velocity of this load is 2665 +/- 10 FPS. That said anyone engaged in hand loading their own ammo is solely responsible for their results.

I have tried the same load with the 107s and got results in the 1.0 MOA range. Trying more powder produces bigger groups. Going to retest again between 28.4 gains and 29 to see what I can find. More details of my experience and data for the 107 SMKs are in a few posts up from here.

Henryrifle

 

[LRRPF52]

Paul, for years you use to say Grendel bolts(.136) were stronger. I'm sure if someone wanted to go to arfcom and look in the archives they could find 10000 of your posts saying so. As for the rest of the 1000 word and pictorial essay I didn't waste time reading, I don't care. Anyone that wants a stronger extractor can get one from BRA when they come back in stock.

Negative. I’ve always recognized that all things equal, a bolt with a more shallow face depth will have more lug root strength. You’ve built a straw man argument, then bought into it for years, thinking I’ve said things I never did, then formed erroneous conclusions based on those false premises. You can’t find a single post I’ve made anywhere that states that a .124/.125” depth bolt is weaker or that a .136” depth bolt is stronger. I’ve seen other people say that by transposing the statements about a stronger extractor, but I’ve never claimed that because it doesn’t follow the basic structural mechanics.

You can put a radius on the inner face-to-wall circumference and get back lug root strength there since all case rims have a chamfer, and also put small radii on the lug roots where they emerge from the bolt body.

Not sure why you’re trying to dig this up again.

 

[verdugo60]

@verdugo60: I've been using 29.0 grains of CFE 223 in Hornady brass with the Hornady 108 ELD-Match bullet and any of the following CCI small rifle primers: BR4, 450 and 400. My OAL has been very close to max magazine length at 2.255". My powder charge is below the maximum value of 29.1 grains that Hornady has published. My barrel length is 21.75" and the average muzzle velocity of this load is 2665 +/- 10 FPS. That said anyone engaged in hand loading their own ammo is solely responsible for their results.

I have tried the same load with the 107s and got results in the 1.0 MOA range. Trying more powder produces bigger groups. Going to retest again between 28.4 gains and 29 to see what I can find. More details of my experience and data for the 107 SMKs are in a few posts up from here.

Henryrifle

Thanks for the detailed info. I hope 107’s work a bit better for me than 1 moa. I have a 16” stainless proof barrel, I’ll probably start low around 28 grains and work up, especially with the lower tolerance for pressure with these bolts.

 

[Dino11]

My most recent outing I loaded up a ladder using BL-C2. It falls in between Lever and CFE223 on the burn rate burn chart.

Had some pretty impressive 10 shot groups, and the SD's were the best I have seen with this cartridge.

Using Nosler 105 RDF's I was getting single didget 10 shot groups and shooting about 1 MOA on a windy day, wind was around 20 to 25 MPH with my 18" Faxon barrel rifle.

Best group was 29.4 gr of powder
2.250 OAL
CCI 450 primer
approaching the 2800 FPS
SD 6.7

 

[Henryrifle]

@Dino11: No pressure signs? Is this in a gas gun? That is impressive speed!

Henryrifle

 

[Dino11]

very light swipe marks.

But I am starting to think this is the norm for these rifles, I get them on factory ammo as well. They are not deep, you can't even feel them with your nail. But if you look close in the right light you can see them. And this is on three different guns.

I'm going to have to double check those chrono numbers, I was going off memory. I use a tablet to log everything and is in my range bag, That 2800 might have been the 29.7 gr load, just not 100% sure

 

[Henryrifle]

I get the same light swipes from factory ammo as well--both the Black 105s and the Match 108s. The factory rounds have a MV out of my barrel of 2700 and 2720 respectively. My hand loads are 30 to 50 FPS slower and I don't usually get swipes.

Without doing any tuning to the program (case capacity, exact seating depth & etc.), Quickload says that the 29.4 grain load of BL-C2 out of 18" barrel would produce 58,790 PSI of chamber pressure however, it only reports a MV of 2720 FPS. Using the same parameters, 29.7 grains of BL-C2 has an indicated chamber pressure of 60,885 PSI with a MV of 2749.

 

[Dino11]

Those numbers can't be right, sounds like the load in the program needs tweeked.

I for sure would have had signs of pressure at those PSI. And the powder is right their with Lever and CFE223.

I will take some pictures of the brass, I have not yet processed it. yet been spending my time at the reloading bench loading .223

I bet in the past month I have loaded more than 5,000 rounds of it, and does not include the other stuff I have been loading.

Pistol stuff comes next and I have a butt load of .40 and .45 to load. I want to add a powder check to my press first before I crank out any volume of pistol.

 

[ormandj]

Those pressure levels are normal for 5.56 and don't generally show significant pressure signs. You can't use relative burn-rate tables to determine pressure; the pressure curves can be totally different for powders even if they fall amongst others that are fine. I don't know if the QL data is correct, but it also would not surprise me if it is true (running 58.8-60.9 kpsi), even though you do not see pressure signs - that's why I'm sticking to book load data until I have a pressure barrel in place (working on this). That said, those pressures aren't dangerous per-say, they will just potentially lead to early bolt failure. As always with reloading data, YMMV and it's your assumption of risk.

 

[Henryrifle]

Yeah, I didn't intent to imply that you were operating in the danger zone. I plugged in those numbers to see if it was something I should put on the list of powders to try. Quickload can output some crazy data if it is not set up properly. When I get a chance I'll take another look at it. Very possible in my haste to check I fumble fingered one or more entries.

I have a an unopened box of RDFs. Hate to introduce yet another projectile but might try if I can't improve the 107s.

Henryrifle

 

[Dino11]

I used Hodgen data for a 6 PPC, it is very close to the 6 ARC in case capacity, only about 1 gr difference.

And their data shows 48,700 at 28 gr of powder.

My numbers were off, the font on the tablet it is so small 6's and 8's are hard to distinguish with my old eyes. I was approaching 2700 fps. The average for that shot group was 2680 and the SD was 6.7.

 

[Henryrifle]

I am very familiar with fonts and old eyes. Thank the lord for multi-focal contacts! Some of those primers do look pierced. That could just be lighting. Your MV does bring that charge more in line with the Quickload data.

Happy Friday all!

Henryrifle

 

[Yondering]

Guys (Henry and Dino), swipes are not pressure signs, they are indication of an over gassed system. Turn your gas down and the swipes go away. You have to understand that if your rifle is adjusted to run on stick powders like H4895 or Varget, it will show usually swipes with top end ball powder loads, especially Lever because of the difference in the gas pressure curves.

Permanent case head impressions do indicate either pressure or excess headspace, but swipes only mean the bolt rotated while the case was still under pressure, not that it went over max pressure.

Im not saying you weren’t over max, because you shouldn’t see any pressure signs at all, but it’s worthwhile to learn what the different brass signs are telling you.

 

[LRRPF52]

Those pressure levels are normal for 5.56 and don't generally show significant pressure signs. You can't use relative burn-rate tables to determine pressure; the pressure curves can be totally different for powders even if they fall amongst others that are fine. I don't know if the QL data is correct, but it also would not surprise me if it is true (running 58.8-60.9 kpsi), even though you do not see pressure signs - that's why I'm sticking to book load data until I have a pressure barrel in place (working on this). That said, those pressures aren't dangerous per-say, they will just potentially lead to early bolt failure. As always with reloading data, YMMV and it's your assumption of risk.

With 6.5 Grendel, we found that the Quick Load engine was usually at least 10,000psi off on its predictions when measured against a calibrated pressure test breech. When I say "calibrated pressure test breech", I’m talking about one that was built and registered for 6 months by an aerospace engineer who worked at National Labs for decades, and took a lot of input from pillars in the industry who have been doing pressure test breeches for decades. We got better gauges than the factory gauges, placed the gauges dead-center over the powder column where peak pressure is at its highest, and had a reamer built to simulate middle-of-the road SAAMI reamer life vs a new or worn one.

So I wouldn’t trust QL numbers with these short, smaller capacity, relatively fat cases until you make your own QL model with pressure test equipment. Best to look at published data from Hornady right now.

 

[Yondering]

I’ve noticed that QL often does more harm than good when used as it commonly is on forums and in this thread. Without a corrected model it gives bad data, and frequently results in some pretty wacky powder choices.

 

[Dino11]

Guys (Henry and Dino), swipes are not pressure signs, they are indication of an over gassed system. Turn your gas down and the swipes go away. You have to understand that if your rifle is adjusted to run on stick powders like H4895 or Varget, it will show usually swipes with top end ball powder loads, especially Lever because of the difference in the gas pressure curves.

Permanent case head impressions do indicate either pressure or excess headspace, but swipes only mean the bolt rotated while the case was still under pressure, not that it went over max pressure.

Im not saying you weren’t over max, because you shouldn’t see any pressure signs at all, but it’s worthwhile to learn what the different brass signs are telling you.

The gas block is almost turned off on my Odin barreled rifle, it is an 18" barrel with rifle length +2 gas port. Recoil is pretty much non exhistant and the brass almost trickles out of the ejection port and lands on the ground about 3' from me. I can watch the hits through the scope, can rapid fire 10 shots out to the 300 yard steel and make 10 hits in under 10 seconds. I think that the ejector spring is just a little to stout on that one. The 18" Faxon barrel is mid length gas and the riffle is a little more snappy on recoil, but still no worse than a .223. If I turn the gas down any more on it the gun does not cycle and it short strokes. The ejector sping may also be the problem with it. The 20" faxon barrel doesn't even have 200 rounds down the pipe so it's hard to put an accurate assessment on it at this time. The swipes are barely visible you have to have the right lighting conditions to see them.
,
All three rifles have rifle buffers,action springs, and extension tubes. Had to modify the Odin gun, the gas block is almost to the end of the barrel to give it extra dwell time, Had to remove 4 of the steel weights in the buffer and replace them with aluminium weights to lighten it and use a 10% reduced pressure spring to get it to cycle right even with the gas block opened up all the way, and this barrel has a gas port size of .101, it is huge. But after the modified buffer and spring was able to close the gas block almost completely shut/ Smoothest AR I have ever shot, almost like a .22.

 

[Yondering]

The ejector spring doesn’t cause swipes. It only affects how the case is thrown off the bolt.

It’s entirely possible to have swipes and early unlocking but weak cycling, especially if the gas system and buffer/spring system aren’t matched well to the type of load you’re shooting.

Of course a burr or sharp edge in the ejector hole can contribute to swipes as well.

 

[Henryrifle]

@LRRPF52: Very interesting findings with the 6.5 Grendel and Quickload pressure. Understanding that when communicating in a forum such as this that you never know who you might be talking to, a 10 KPSI difference strikes me as unusually surprising. That sounds like it could be as much as 20% off. I am not doubting what you are saying--it's just unexpected. I don't hold myself out as anything other than a casual user of Quickload but, it has been a good addition to the other tools I use and helpful in reducing load development time especially when you have a good idea of what MV is necessary to achieve. Once I tune Quickload to the results I am getting in the real world, It usually tracks very linearly with to those results over a reasonably broad range of powder.


@Yondering: Thank you for the reminder about swipes and gas. Old habits/thoughts and all...

The next bit is a reaction to your following comment:

I’ve noticed that QL often does more harm than good when used as it commonly is on forums and in this thread.

I am not sure what you mean by that statement and have to admit that I am not smart enough in many instances to understand subtle. Most of the re-loaders I know are very conservative as they approach max loads or new powders/calibers/projectiles (I know one who isn't--at all). My frame of reference is F-Class competition and bolt guns. I get that this post is in a semi-auto forum. We don't want to discourage guys from posting Quickload data or any other kind of data. If it's wrong there are enough more experienced guys willing to jump in and help/teach them [me] something. So, it goes both ways. In many cases the data is good for the community and posterity and in some cases it's an opportunity to teach the data publisher. When posting Quickload data, most of the info I've seen, including mine, contains a caveat or two about the reliability of the data or the means used to generate it. Quickload also displays its own disclaimers.

There is plenty of room for healthy disagreement in this sport--it's what keeps the progress going.

Henryrifle

 

[LRRPF52]

I don’t ever use QL anymore. I take published start loads and work up in 1% increments with maybe 2 ladders of single loads to establish a trend line, analyze the trend in charge weight-to-velocity increase, notice any excursions, pick a velocity range to work with, and tweak other things there for accuracy.

For a long time, I hated shooting 5rd groups starting with start loads due to component consumption, but I don’t waste components anymore since 2 ladders will tell me what I need to know. It gets me into the load range I’m going to be using anyway, without ignoring working up from start loads.

 

[Dino11]

The ejector spring doesn’t cause swipes. It only affects how the case is thrown off the bolt.

It’s entirely possible to have swipes and early unlocking but weak cycling, especially if the gas system and buffer/spring system aren’t matched well to the type of load you’re shooting.

Of course a burr or sharp edge in the ejector hole can contribute to swipes as well.

Or if the ejector pin is being pushed hard against the case head. The springs in these bolts seem to be really stiff, more so than any of my other bolts. You can't push them in with your fingers like I can with others I have. I thought about radiusing the edge of the pin, but it's not really been that big of an issue. They are really not that bad, almost unnoticeable.

 

[LRRPF52]

You’ll want a radius/chamfer on the ejector in any PPC-based cartridge in the AR-15, like Grendel and 6mm ARC.

The reason is that when cartridges come from right hand presentation in the magazine, as they feed up and align with the chamber, the side of the rim can get caught on the side of the ejector and generate a weird FTFeed malf. I’ve never had it because I saw the tip from Accurate Shooter I think over a decade ago.

Whenever I do a build, if the ejector does not have the chamfer (most do nowadays that I’ve seen), I remove the ejector, chuck it in a drill, spin it against a file carefully without making too much of a chamfer, polish, Oxy-Blue it, then re-install. I use the Brownell’s bolt disassembly tool, but you can also use a cut-down case head and a vice.

 

[LRRPF52]

One idea about where ejector channel extrusion comes from is that since we’re shooting a gas gun, the bolt will often be rotating before enough residual chamber pressure or case obturation has been able to subside, so the brass is still in a relative state of plasticity.

Since brass is extremely soft, it flows into wherever the path of least resistance is, in this case into the ejector channel. It cares not about the ejector spring tension, which is meaningless compared to chamber pressure, but before it has a chance to rebound, the bolt starts rotating while the brass body is adhered to the chamber walls.

With the extruded brass that has flowed into the ejector channel, and the bolt rotating, the brass that is protruding from the case head is now being sheared in a rotational direction. This is often referred to as a “swipe”. You’ll notice that on one side of the extrusion, it has an area where brass has been shaved off by the sharp edge of the ejector channel in the bolt face corresponding to the rotational direction of the bolt unlocking. From a .308 AR:

It’s more of a sign of gas system out of timing much of the time, but will be exacerbated by excess pressure because the extrusion into the channel will be deeper than when at lower chamber pressures, so it should never be ignored. It’s more pronounced on softer brass as well, like PPU or Federal.

 

[Yondering]

Henry- I mean that QL seems to often steer people in the wrong direction on choosing powders and loads to start with, because they think it’s a good baseline even if it’s not correlated to their chamber. In reality, all the variables in QL, combined with older, estimated, or downright flawed burn rate & properties data can result in the actual best powders not even making the top 5 in QL. I’m not pointing to any particular data here, just something I’ve observed over the years.

As an example though, here’s a simple check for your QL model with the ARC - if it doesn’t show Lever as giving the highest velocity potential with 95+gr bullets, there’s a strong chance the model is badly flawed.

Getting your QL results to line up with published data is a good start, but that doesn’t cover all the bases either since your chamber, barrel, lot of powder, and other components can vary from the data.

 

[Yondering]

One idea about where ejector channel extrusion comes from is that since we’re shooting a gas gun, the bolt will often be rotating before enough residual chamber pressure or case obturation has been able to subside, so the brass is still in a relative state of plasticity.

Yes to all of that.

I’ll add one clarification though to the statement above - as you are describing it, the brass is in an elastic state (I.e. it will spring back when pressure subsides) rather than plastic. Swipes in this condition indicate bolt timing issues, usually from an over gassed action but not always.

Your pics of the 308 cases show plastic (i.e. permanent) deformation into the ejector hole, which is an indication of one of two things:
- pressure was too high for that brass (as you said some is softer than others)
- excessive headspace, which caused the case head to impact the bolt face resulting in plastic flow.
This situation almost always results in swipes, regardless of timing and gas control.

 

[Yondering]

Or if the ejector pin is being pushed hard against the case head. The springs in these bolts seem to be really stiff, more so than any of my other bolts. You can't push them in with your fingers like I can with others I have. I thought about radiusing the edge of the pin, but it's not really been that big of an issue. They are really not that bad, almost unnoticeable.

I don’t understand what you think is happening there. The pin doesn’t normally cause swipes, the edge of the hole does.

 

[Dino11]

I don’t understand what you think is happening there. The pin doesn’t normally cause swipes, the edge of the hole does.

seriously... it's not a huge problem the picture I provided in an earlier post you can not even see them. Very light swipes that do not catch your finger nail or are not even really visible are not that big a deal. Some shooters tell me it is normal. And I can't see the Odin barrel unlocking early their is almost no gas, and the gas system is so long it has extra dwell time. Gas is so non exhistant the gun barely gets dirty from a day at the range shooting anywhere from 250 to 400 rounds.

But the edge of a sharp pin and a spring that is pushing hard will, and my pins look like the one in the first picture in the above post. I will grind the sharp edge off and smooth it out when I service the bolt this winter.

 

[Yondering]

seriously... it's not a huge problem the picture I provided in an earlier post you can not even see them. Very light swipes that do not catch your finger nail or are not even really visible are not that big a deal. Some shooters tell me it is normal. And I can't see the Odin barrel unlocking early their is almost no gas, and the gas system is so long it has extra dwell time. Gas is so non exhistant the gun barely gets dirty from a day at the range shooting anywhere from 250 to 400 rounds.

But the edge of a sharp pin and a spring that is pushing hard will, and my pins look like the one in the first picture in the above post. I will grind the sharp edge off and smooth it out when I service the bolt this winter.

I’m not saying it’s a huge problem- I’m saying it’s NOT a pressure sign, because both you and Henry implied that it was in your posts.

If the swipe is from a rough pin it’ll do it on every single round, not just when gas increases.

 

[LRRPF52]

Yes to all of that.

I’ll add one clarification though to the statement above - as you are describing it, the brass is in an elastic state (I.e. it will spring back when pressure subsides) rather than plastic. Swipes in this condition indicate bolt timing issues, usually from an over gassed action but not always.

Your pics of the 308 cases show plastic (i.e. permanent) deformation into the ejector hole, which is an indication of one of two things:
- pressure was too high for that brass (as you said some is softer than others)
- excessive headspace, which caused the case head to impact the bolt face resulting in plastic flow.
This situation almost always results in swipes, regardless of timing and gas control.

Roger that. Good call on the headspace. Gas guns require slop for reliable functioning, so we’re always going to have more case growth with generous chambers.

This all contributes to my preference for Lapua brass.

 

[Yondering]

Roger that. Good call on the headspace. Gas guns require slop for reliable functioning, so we’re always going to have more case growth with generous chambers.

This all contributes to my preference for Lapua brass.

Yep Lapua ftw. And in the ARC, conversion from Grendel brass means bumping shoulders back only .012-.020” back and getting perfect headspace the first shot, rather than loose like most factory brass. Kinda cool.

 

[Henryrifle]

@Yondering & @LRRPF52: You are both very smart cookies. As have a lot of other guys, I've learned a lot from y'all and appreciate what you share--thank you!

At this time, Quickload doesn't have LEVERevolution listed as a powder. I am curious how you guys use or used to use Quickload in the past. I don't think I use it as I think you've described.

Thank you again,
Henryrifle

 

[ormandj]

QL is flawed, as are all internal ballistics programs, in that they are approximations/estimates that need guidance based on empirical data. The models get better as more inputs are provided from testing. Eventually you can true them against reality enough to have them output what really happens - but what have you really gained at that point? Stay within the confines of book data and then let the targets demonstrate the solutions. Herein lies the rub - new cartridges like this don't have a ton of data out there yet. We've got data from Hodgdon and Hornady now, and nothing else. So you're somewhat limited on powder/bullet combinations with pressure data to work from.

FWIW, I ditched QL a long time ago and now use GRT, at least with that tool I can contribute code/data/etc and help improve things upstream. It lacks user data for some powders/projectiles, but it gets better every day.

 

[SBRSarge]

Does anyone have experiences with the Ballistic Advantage barrels in 6ARC?

I’ve been waiting for months for a back ordered Odin 18” barrel. They say they are still awaiting the material to make them, with no estimate on timing.

I might have to start looking at the BA ones, if they are giving good performance.

 

[LRBuck]

I just got the Rock Creek barrel from Craddock Precision I ordered back in July. I went with a 22” with a .875 gas block. Installed it, zeroed scope and shot about 40 rounds of the 105 Hornady Black so far. Really really pleased with it.
I wasn’t trying for groups as I was tuning the gas block/doing break in and haven’t put any muzzle device on it yet, but I had a 6 shot group that was around .5-.6 MOA. Thought I saved the target but I didn’t and didn’t take a pic. It averaged 2690 on the Magneto. The last shots were over 2700. Shifted to the 500 yard range and had fun confirming dope and hitting head shots on the steel. Surprised how well it shot the Black factory ammo. Haven’t shot the 108 ELD-M’s yet. Will try for groups with them next time out and post.