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After all the BS the last few days I went to the shop to check the max loadable OALs in the barrels I have in stock right now...chambered with reamers ground last summer.
I check the OALs before the barrel extensions are installed, easier to get in and out of the chamber. I pulled a 10.5", 12.5 18" all from this year and a 3 year old barrel that had an eroded spot on it, one I am not selling. All 4 barrels were within .01". After the first round I just wrote down the number once. I have videos of the whole thing but I'll have to figure out where to post them. As you can see all of them can be loaded longer than mag length. 2.295 is about as long as we can go and still function out of the mag. So if all bullets are loaded to 2.295" most will have a .035" jump to the lands, that is pretty close to what we want and trying to make a chamber that works well with most bullets. As you can probably guess I am not changing anything.
ETA some bullets like more jump, The Hornady HPBT are known to be accurate at the factory loaded length. The Barnes TSX have always shot well at 2.295" but that is a .105" jump to the lands.
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The need for speed is great but when someone knows that the diameter of their bullets varies from lot to lot you would think they would drop down to the max load for the widest bullet . Using OAL for an indicator of when bullets hit the lands only works if the ogive is at the same place on every bullet . You can have bullets that have the same oal and because of different shapes hit the lands at different times and different diameter = different ogive . When you have loads that are already worked up to max with narrow / short ogive or whatever bullets then put a larger diameter bullet where the ogive has moved forward, in front of the charge ( especially if said bullet is wider than cone ) you have violated the basic rules of loading . If something changes back off and work up . I know this is all elementary and something we all know except it appears the people loading these bullets forgot or ignored the basics . When I was personally working up a load with these same bullets -S&B brass and 2200 A couple of years ago I experienced a few that were over pressure and even unstable ,in all three of my barrels 12.5 -16 -& 18" at .5 less than what was my max load . I contacted the company and sent pictures of targets showing key holes and was told that someone who had made bullets for him had made some at . 278 and he was no longer using them but that may have been the problem . I had made a rooky mistake and poured 4 boxes into one so I wasn't sure if the problem bullets were from the same or different boxes . I measured and weighed all of them and found a couple fatter and shorter and one half bullet that didn't have a nose . I have measured every bullet since and have not had any problems . It would seem that recently the company had some left over bullets from that careless machine shop that has gotten into the mix or they were getting bullets made for factory loads from a different source than loading component bullets . Maybe I should have posted the problem and my findings public back then but I decided since they knew about the problem and it had already been taken care of on their end and very few of the off bullets had gotten out to not cause negative publicity . I wish they had done the same and quietly made the nessesary changes without the drama and I believe hindsight being 20 / 20 they wish they would have also . I saw where they posted that the problem with the bullets has been taken care of and they will be more concistant from now on out . In that Post they claimed there wasn't a better combination than ARP barrels shooting cavity back bullets and I agree 100% .

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The need for speed is great but when someone knows that the diameter of their bullets varies from lot to lot you would think they would drop down to the max load for the widest bullet . Using OAL for an indicator of when bullets hit the lands only works if the ogive is at the same place on every bullet . You can have bullets that have the same oal and because of different shapes hit the lands at different times and different diameter = different ogive . When you have loads that are already worked up to max with narrow / short ogive or whatever bullets then put a larger diameter bullet where the ogive has moved forward, in front of the charge ( especially if said bullet is wider than cone ) you have violated the basic rules of loading . If something changes back off and work up . I know this is all elementary and something we all know except it appears the people loading these bullets forgot or ignored the basics . When I was personally working up a load with these same bullets -S&B brass and 2200 A couple of years ago I experienced a few that were over pressure and even unstable ,in all three of my barrels 12.5 -16 -& 18" at .5 less than what was my max load . I contacted the company and sent pictures of targets showing key holes and was told that someone who had made bullets for him had made some at . 278 and he was no longer using them but that may have been the problem . I had made a rooky mistake and poured 4 boxes into one so I wasn't sure if the problem bullets were from the same or different boxes . I measured and weighed all of them and found a couple fatter and shorter and one half bullet that didn't have a nose . I have measured every bullet since and have not had any problems . It would seem that recently the company had some left over bullets from that careless machine shop that has gotten into the mix or they were getting bullets made for factory loads from a different source than loading component bullets . Maybe I should have posted the problem and my findings public back then but I decided since they knew about the problem and it had already been taken care of on their end and very few of the off bullets had gotten out to not cause negative publicity . I wish they had done the same and quietly made the nessesary changes without the drama and I believe hindsight being 20 / 20 they wish they would have also . I saw where they posted that the problem with the bullets has been taken care of and they will be more concistant from now on out . In that Post they claimed there wasn't a better combination than ARP barrels shooting cavity back bullets and I agree 100% .

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I concur with everything you said. Save that the tapered freebore did caused the difficulty. The problem wasn't with the bullets, it was due to an under sized freebore.
Also worth noting is that loaded ammo with none of our other projectiles has ever had any issues or pressure signs. 5.56, 300 BO, 6.5 Grendel or 308. 7.62x 39 is currently in the works. David at Druid Hill does an excellent job. He primes every case by hand and sets each bullet in the case mouth by hand. Each round is inspected and checked in a gage. Each and every round.
Also that the limited amount of ammo that went out that showed pressure signs did not in any test barrels. Bison, ERShaw and even PSA. Now all 6.8 ammo will be tested in an ARP barrel with a tapered freebore. Had we known the freebore was tapered we would have done this from the beginning.
So many have said they wished SPC II ammo was available so we tried. SSA used to load ammo even out to 2.3 in their 140 VLD ammo. We tried loading to to 2.28 to get a bit more speed and mimic handloads. However what a handloader can do and production ammo are different animals. We will load as warn as we can in the ARP test barrel.
Posts here and elsewhere keep eluding to projectiles over .277 being out of spec. However they are not. Projectiles up to .278 are normal in any 270 based caliber. This is why the spec for a freebore is .2781 in all 270 based calibers. As well our bullets never exceeded .2778. Now as said before will not exceed .2772.
Any projectile up to .278 also does not cause pressure in the barrel. I retested that ammo in the aforementioned barrels and got the same speeds and no pressure signs. All current ammo has been run in an ARP barrel and shows no pressure signs.
Our copper is softer. Thats why it holds together instead of fracturing. It obtiurates into the barrel more easily than other copper bullets. It is harder to get and to machine. That's also another reason they copper foul less.
I love ARP barrels for their costs, speed and accuracy. Also I will personally continue to use them. I just wish we knew about the freebore in the beginning.
Any current or future bullet producers could also make bullets up to .278 or ammo that way and still be in spec. Gages are set to .278 when I get back home I will.post what SAAMI shows as spec for a .277 projectile. It is .275 to .278.
Funny thing is I only let my emotions get involved in the 6.8. It is my favorite caliber. I will attempt to control that more in the future.
 

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Hey so I don't have an ARP barrel, I have a LWRCi. Are you saying that those of us who enjoy the SPC II loadings wont be able to now because of what seems to be a very minor issue with one barrel brand? Lots of other types of barrel manufacturers too, so just wondering...I can't remember what was the end all be all of the convo.
 

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Hey so I don't have an ARP barrel, I have a LWRCi. Are you saying that those of us who enjoy the SPC II loadings wont be able to now because of what seems to be a very minor issue with one barrel brand? Lots of other types of barrel manufacturers too, so just wondering...I can't remember what was the end all be all of the convo.
You know you pose a good question. I'll talk to Druid Hill about it. For now though yes, all ammo will be good to go in any brand barrel.
It's up to Druid Hill if they will do a Tactial load like SSA did, in addition to the SPC loads.
Keep in mind though we only shortened the loads up to 2.26 and tamed them down as little as we could.
Game will never know the difference and accuracy is the same sub MOA in any barrel that will shoot sub MOA with factory loads.
 

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Discussion Starter · #7 · (Edited)
Hey so I don't have an ARP barrel, I have a LWRCi. Are you saying that those of us who enjoy the SPC II loadings wont be able to now because of what seems to be a very minor issue with one barrel brand? Lots of other types of barrel manufacturers too, so just wondering...I can't remember what was the end all be all of the convo.
NO that was just a bunch of BS, like I said in the other post I can take those barrels and load 200fps faster than factory Hornady ammo just like we have since 2009. In 40 years of reloading I have never seen a bullet measure larger than the bore diameter in any caliber unless it was lead. Don't load bullets that are .278" in diameter in front of a charge that was developed using bullets .277" in diameter. IF Robert wants to direct the company that loads his ammo not to use a charge that high then that is his deal.
ETA - SSA was the only company loading faster than normal(Hornady) when they made the "Combat" loads from 2006-2008, then they reduced them to the "tactical"black box ammo. Wilson tried for a while to load faster ammo but now they have reduced those and truthfully I don't know how much faster that ammo was. Robert was trying to load his faster but I don't know how much faster it was. There is no spec for SPCII ammo, SPCII refers to a chamber design.
 

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I find it strange that other commercial brands of ammunition have worked well thru out the years and continue to do so whereas some CBB loaded rounds may have a problem as reported by a few. I am going to have a problem believing it is the the taper that sometimes causes the problem in light of the above. It sounds more like a manufacturing QC problem to me. Maybe the specs are closer to the line than the loader or bullet manufacturer can hold to.
 

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I find it strange that other commercial brands of ammunition have worked well thru out the years and continue to do so whereas some CBB loaded rounds may have a problem as reported by a few. I am going to have a problem believing it is the the taper that sometimes causes the problem in light of the above. It sounds more like a manufacturing QC problem to me. Maybe the specs are closer to the line than the loader or bullet manufacturer can hold to.
They are not loading to SPCII. Only SSA did, and it blew primers in a few barrels too. It has nothing to do with loader or bullet maker. We stopped loading to SPCII now no issues.
Think of this. SPCII relaxed tolerances to allow more pressure.
If what you said was true how could we adjust the bullet and ammo to be fine in an ARP barrel, which we did. It's all fine in ARP now. Bullets always were. Only the ammo at SPCII showed pressure in a very few barrels. Like 4 or 5 out of all the ammo sold thus far. As well then only like 20 % of the rounds showed pressure. The original poster even said the current ammo works perfectly and is accurate in his ARP barrel.
ARP took a limited sample of random projectiles and made a call.
I like everything else he did to his chambers.
However tapering the freebore effectively shortens the freebore with any projectile over .2772
While SAAMI says 270 projectiles are to be made between .275 and .278.
The problem wasn't that we can't hold a tolerance below .2772. It was no one told us we need to in ARP barrels.
Could I load to SPCII now with all our projectiles below .2772 and be fine in ARP barrels. Yes, probably. But it's not worth the risk.
ARP had input when we designed CBB for the 6.8 and didnt ever mention the tapered freebore.
I know I'm banging my head against the wall here.
Disputing anything H says.
However look at SAAMI drawings. I'm right on this one.
 

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The other day, you were posting SAAMI drawings, but there is no SAAMI spec for SPC II or whatever we call it... I don't believe H has changed anything about his chambers in recent years (but I obviously cannot prove that statement) and he always mentioned when he made an adjustment. I have had no problems with the CBB bullets I have used and we have only had a small number of reports of some rounds showing a problem while other rounds in the same box showed zero problems to my knowledge.

That leads me to believe that a few rounds were to close to whatever limit the chamber provides....but not all, and perhaps not even a majority. I am glad you did whatever you did to insure that all perform properly. I'm just not sure why you put the blame on H's chamber unless you have solid evidence that he changed something. It makes no difference in the long term other than some bridges should go unburned :)
 

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The other day, you were posting SAAMI drawings, but there is no SAAMI spec for SPC II or whatever we call it... I don't believe H has changed anything about his chambers in recent years (but I obviously cannot prove that statement) and he always mentioned when he made an adjustment. I have had no problems with the CBB bullets I have used and we have only had a small number of reports of some rounds showing a problem while other rounds in the same box showed zero problems to my knowledge.

That leads me to believe that a few rounds were to close to whatever limit the chamber provides....but not all, and perhaps not even a majority. I am glad you did whatever you did to insure that all perform properly. I'm just not sure why you put the blame on H's chamber unless you have solid evidence that he changed something. It makes no difference in the long term other than some bridges should go unburned :)
The SAAMI chamber drawings show a freebore of .2781 with a maximum projectile diameter of .278.
This is so a projectile does not encounter resistance until it is moving before it enters the rifling. This spec is for all cartridges chambered in any .277 based caliber. All other calibers are the same way.
It does not matter if it's SPCI or SPCII or like you said whatever you call it.
When the freebore is more narrow than 2.781 a projectile that is within spec at .278 will act like it's jammed in the lands even though it's no where near them. Causing a pressure spike.
Why say something? Because any projectile for any .277 caliber is still within spec at .278. Our projectiles were being blamed for being out of spec. But they were not. Thats why there was no pressure issues in any other brand of barrel.
In the early days of CBB I did a lot of testing in an ARP 22in. I pushed them very hard, wrecked brass, pierced primers but don't remember actually popping one. I knew they were over pressure, I did it on purpose so I would know what happened if anyone else did. I could load to 2.42 in that ARP barrel.
These latest ARP barrels including my 12.5 will not load that long, even a .2775 diameter won't. Well within SAAMI spec. Why?
No other brand 6.8 barrel had an issue with a .2778 projectile. They shot fine, fast and accurate.
I adjusted all CBB bullets to now have no issues in ARP barrels. However that does not mean someone else's won't. There are new monolithic manufacturers that come out. How do they know about the tapered freebore?
Any freebore in any caliber that is more narrow than the SAAMI maximum projectile diameter is out of spec. It really has nothing to do with 6.8 SPC whatever.
If someone was blaming your product when it is not your products fault what would you do? You would say so im sure. The your machine shop sucks, your loader sucks type comments are all not true. That a .278 projectile is to big for a .277 bore, not true. That's. 0005 on each side. Anything but a solid steel projectile easily obtiurates into the bore.
It wasn't our fault. But we fixed it. Now no projectiles over .2772 We would have made sure had we known the ARP freebore was tapered.
Sorry for the long winded responses.
 

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Out of curiosity, I checked the SAAMI specs for various 6.8 and 270 cartridges. The spec for bullets is .278 - .275 for the 6.8 SPC, 6.8 Western, 27 Nosler, 270 Winchester, and 270WSM and 277 Fury. All of them have a freebore diameter of at least .278".
The only cartridge that is different is the 270 Weatherby Magnum, which has a freebore of .2774. It specs bullets from .2773 - .2743.

It is important to note that most bullets need to swage down to a smaller size to go down a rifle barrel. The lands of the rifling are a smaller diameter than the max diameter of the grooves, yet most bullets are the size of the grooves. The lands of typical ".277-inch" barrels make up 30 - 50% of the interior surface. The diameter of those lands is typically .270", yet bullets of .277" are pushed down the barrel.

Also, it is not uncommon for competition barrels to be undersized. Kreiger, for example list "30 Tight" barrels with .298" bore and as small as .3065 groove diameters as opposed to SAAMI .300 bore and .308 groove.
 

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Discussion Starter · #14 · (Edited)
Out of curiosity, I checked the SAAMI specs for various 6.8 and 270 cartridges. The spec for bullets is .278 - .275 for the 6.8 SPC, 6.8 Western, 27 Nosler, 270 Winchester, and 270WSM and 277 Fury. All of them have a freebore diameter of at least .278".
The only cartridge that is different is the 270 Weatherby Magnum, which has a freebore of .2774. It specs bullets from .2773 - .2743.

It is important to note that most bullets need to swage down to a smaller size to go down a rifle barrel. The lands of the rifling are a smaller diameter than the max diameter of the grooves, yet most bullets are the size of the grooves. The lands of typical ".277-inch" barrels make up 30 - 50% of the interior surface. The diameter of those lands is typically .270", yet bullets of .277" are pushed down the barrel.

Also, it is not uncommon for competition barrels to be undersized. Kreiger, for example list "30 Tight" barrels with .298" bore and as small as .3065 groove diameters as opposed to SAAMI .300 bore and .308 groove.
And? I mean I really really hope after posting here for 15 years most people know that, if they don't someone should have said something in 2007 when we were talking about designing chambers and rifling buttons to decrease pressure so we could increase the performance of the 6.8 in hopes the increase would be enough to prove the performance and the military would agree the performance increase over the 5.56 was enough to change cartridges.
 

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If a SOFT lead bullet is .278" in diameter, will that bullet conform under heat/pressure of firing to a barrel?

If a SOLID copper bullet is .278" in diameter, will THAT bullet conform under heat/pressure of firing to the same barrel (as easily)?

WHICH BULLET is going to be a little more malleable under the pressure of firing? Think on that for a spell. Which material is a better choice for a .278" diameter bullet?

I believe it was a GOOD choice to veer away from a .278" diameter in a SOLID copper bullet.
 

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Discussion Starter · #16 ·
If a SOFT lead bullet is .278" in diameter, will that bullet conform under heat/pressure of firing to a barrel?

If a SOLID copper bullet is .278" in diameter, will THAT bullet conform under heat/pressure of firing to the same barrel (as easily)?

WHICH BULLET is going to be a little more malleable under the pressure of firing? Think on that for a spell. Which material is a better choice for a .278" diameter bullet?

I believe it was a GOOD choice to veer away from a .278" diameter in a SOLID copper bullet.
Agree, we worked for years thinking of the 6.8 as a military cartridge trying to help convince everyone it was the best choice(at the time) for a new cartridge. By late 2009 we all knew it wasn't going to happen so we started to look at it a different way. When SSA stopped producing the faster ammo and no other company would even think about it I did what I could in the barrels to increase velocity with the same ammo. We were seeing an increase of 60-90fps over the common 4 groove 11 twist barrels 16" long. When I changed from my 5R design to the 3R design years later I thought we would lose quite a bit but as it turns out we only lost 15-20fps. We cut engraving force down which cut the peak pressure but other changes helped increase the area under the pressure curve so we didn't lose as much velocity.
Most companies are still using the SPCII chamber design which is still a military type chamber. Bison and myself are using chambers modified to increase accuracy.
 

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Reading RD's post made me recall that a few months ago when someone asked about velocity variation due to barrel length, I went out and shot my three ARP barrels (one being the first chrome lined offering) with some various bullets.

When I was digging thru my commercial ammo, I found a partial box of SSL TACTICAL rounds with the Barnes 95 gr load. On the end of the box, I had written "too hot?" and I recalled Art had put out a warning stating that these rounds might be too hot for some guns. I had quit shooting them even tho they worked in my chrome-lined barrel without any problems. I shot them in all three of my barrels just for the heck of it and they worked perfectly well without any signs of over pressure.

That was the original 16" chrome lined edition and the 18" (think it was a special order edition if I recall correctly) and the 12.5". One of the latter two is a Triad. I'm too lazy to dig thru my safe to find out which is which.

I have complete faith in my barrels/chambers.
 

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Discussion Starter · #18 ·
Reading RD's post made me recall that a few months ago when someone asked about velocity variation due to barrel length, I went out and shot my three ARP barrels (one being the first chrome lined offering) with some various bullets.

When I was digging thru my commercial ammo, I found a partial box of SSL TACTICAL rounds with the Barnes 95 gr load. On the end of the box, I had written "too hot?" and I recalled Art had put out a warning stating that these rounds might be too hot for some guns. I had quit shooting them even tho they worked in my chrome-lined barrel without any problems. I shot them in all three of my barrels just for the heck of it and they worked perfectly well without any signs of over pressure.

That was the original 16" chrome lined edition and the 18" (think it was a special order edition if I recall correctly) and the 12.5". One of the latter two is a Triad. I'm too lazy to dig thru my safe to find out which is which.

I have complete faith in my barrels/chambers.
The chromelined were the first 2 production runs that Tim W and I made to mil spec back when SSA was still testing pretty heavy. There was also a batch of Lothar Walther polygonal chromelined. You've been a round a long time if you have one of those.
 

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Out of curiosity, I checked the SAAMI specs for various 6.8 and 270 cartridges. The spec for bullets is .278 - .275 for the 6.8 SPC, 6.8 Western, 27 Nosler, 270 Winchester, and 270WSM and 277 Fury. All of them have a freebore diameter of at least .278".
The only cartridge that is different is the 270 Weatherby Magnum, which has a freebore of .2774. It specs bullets from .2773 - .2743.

It is important to note that most bullets need to swage down to a smaller size to go down a rifle barrel. The lands of the rifling are a smaller diameter than the max diameter of the grooves, yet most bullets are the size of the grooves. The lands of typical ".277-inch" barrels make up 30 - 50% of the interior surface. The diameter of those lands is typically .270", yet bullets of .277" are pushed down the barrel.

Also, it is not uncommon for competition barrels to be undersized. Kreiger, for example list "30 Tight" barrels with .298" bore and as small as .3065 groove diameters as opposed to SAAMI .300 bore and .308 groove.
Yay, we are getting somewhere.
If someone was going to create a barrel with a spec below the SAAMI freebore diameter. Would it not also be prudent to make and post a bullet spec.
Say it was a .277 or 6.8 tight freebore. To randomly sample some bullets and say oh I can tighten the free bore is respectfully reckless. When SAAMI bullet specs for that caliber is what any projectile designer is going to look at .275 to .278
Now let's address what ARP did share. That the freebore is longer than SAAMI. As well that the forcing cone is relaxed to 45 degrees. Also that the land to groove ratio was changed from 50/50 to 40/60 or 30/70. Further reducing pressure. Thightening the freebore does not reduce pressure. It potentially increases it. It wasn't done trying make the cartridge attractive to the military. It was done to try and make his barrel more accurate. Without considering the potential hazzard. He said he did it for accuracy..
Now let's address jacketed or monolithic bullets.
Both will obtiurate into a .277 bore with no problem. Even more so with a reduced land surface area. Even more so with a 5R or 3R rifling configuration. So why would anyone think an ARP barrel of all things would pose a problem? Its got the right freebore length, forcing cone angle and land groove ratio. All the things to lower pressure and engraving force. Even melonited to further reduce resistance.
Now comes the tapered freebore. Any projectile of any material that is .278 or under, still in spec right. That hits a freebore after a very short distance. Or actually sits again or jams into said freebore is going to cause a big pressure spike. Jacketed, monolithic or whatever. That gentlemen is the issue, well was now that we fixed it. The freebore is called just that. To allow free movement. A freebore that tapers to .277 does not allow free movement. Even at .2775 it's an issue. That is why that is one spec that should be adhered to.
The issue of a bullet larger than .277 and less than .278 has no relevance in the barrel itself and rifling. It's a non issue. SAAMI approved that for all barrels. Even the dreaded 50/50 4 groove. Which I'm sure they tested in a 50/50 4 groove PacNor barrel. The ammo was accurate with no pressure in all other brand barrels even with a .2778 bullet.
Also of note here is that our copper is softer than bullet jacket material. Also making it obtiurate more easily.
In summation. A freebore below .2781 with a bullet max diameter of .278 will and did cause a bore obstruction. The projectile was in spec, the freebore is not.
Our projectiles have a max diameter now of .2772. Not because they were screwed up. Because the freebore is.
 
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