6.5 creedmoor
- Thread starter Boarboy
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Hornady quote a twist rate of 1:7-1:8 so that suggests 1:8 is on the edge of stability. I read on a yank forum that that 1:8 is the optimum for the 208 gr ELD which explains why your 1:11 is struggling, most people find 1:10 is the limit it seems.
As for the .308, the post I was responding to was specifically talking about long range target DK, not long range hunting, very few hunters in the uk shoot live Quarry with deer calibre rifles at distances >500 yards. So for target shooting single loading is not an issue for most UK disciplines, in fact a lot of FTR rifles are single shot. In the context of the post I was replying to the 208 fired from an appropriate twist rate keeps up to 1400 yards on the range. I have seen a DTA .308 shooting 208 gr a-max keeping up with a a 6.5 SAUM shooting accubonds.
To paraphrase and slightly adjust your 6.5 CM.
The argument about .308s is a bit pointless. The essence of the .308 Winchester is that it is an inherently accurate round, extremely easy to load for and available in a vastly wide range of factory ammunition. With the benefit of cheap milsurp availability for plinking and practice!
At the end of the day both .308 and 6.5 with an appropriate rifle and bullet/load will work past most people's ability at long range to well in excess of 1200 yards and there are few places in the U.K. Where the public can shoot that far.
If it was for a stalking rifle at U.K. typical shooting ranges I'd personally go 6.5x55 which I have, and I have creedmoor and .308 for target. But at uk stalking ranges they will all work well!
Small primer, Remington Bench Rest 7 1/2 works for me
Top left, cold just cleaned barrel. Then a 3 shot grp. 100yds.
Top left, cold just cleaned barrel. Then a 3 shot grp. 100yds.
I should stop cleaning your barrel.
2 shot zero check with game kings at 100 yards, dirty barrel, off sticks, in the dark by torch light, raining and sub zero temperatures. Not technically a 'group' but I know the rifle groups and I know the first and second shot will go exactly where the rifle is zeroed
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Scapegoat
Well-Known Member
You can all give up now. This is three rounds at 200, standing on one leg, in the dark, in the fog, near a hole, with an owl. Whilst eating a bag of chips and under attack by seagulls.
(It's actually three rounds at 50 on a ladder test, but I just thought I'd join in......)
No it doesn't! Twaddle, as my Grandma would say. It doesn't suggest anything of the sort!
On this one mate, you'll be best placed to admit defeat early and move onto the next battle.
If you'll admit on th target range the 308 with 208 gr matches the 147 then yes I'll admit defeat on the twist and stability, I had wrongly guessed it would be a similar length to the 150 gr smk which requires 1:7.5 but it's 65 thou shorter it seems.
Out of interest have you physically measured the twist on your howa?
Mine was witnessed by a fellow SD shooter but he may have been distracted by the grunting of the rabid badgers I omitted to mention
@kennyc
Blindfolded 
The point is, it's clearly a very accurate round, that seems pretty easy to reload for !
The point is, it's clearly a very accurate round, that seems pretty easy to reload for !
Blindfolded
The point is, it's clearly a very accurate round, that seems pretty easy to reload for !
Blindfolded is good going . . . .
It is but so are 6.5x55 and .308 to be fair
Afraid not - your assumptions are incorrect.
On paper at any rate, comparative ballistic performance (wind drift + retained velocities) between designs is a straight combination of muzzle velocity and the bullet's BC in any given set of ambient environmental conditions. In this comparison, it's a very simple exercise as the two bullets have near identical average G7 BC values:
147gn 264 ELD-M ................ 0.338
208gn 308 ELD-M ................ 0.335
(Source: Ballistic Performance of Rifle Bullets 3rd edition, Bryan Litz)
So, the question is can a 308 Win rifle in match form achieve the same MVs (or better ones) with a 200-210gn bullet as 6.5X47L, 6.5X55, 260 Rem, or specifically in the context of this thread 6.5mm Creedmoor?
The 'in' FTR 308 bullet in 32-inch barrel custom match rifles is the Berger 200.20X 200gn HPBT model. 2,700 fps is achievable, even a bit more through abusing both barrel and the very strong Lapua 'Palma' small primer case. The cost (apart from bullets costing well over £75 / 100) is barrel life. 2,000 rounds accuracy life is good with such loads.
The Creedmoor with a 30-inch barrel, also using small primer brass (Lapua or Peterson) will produce 2,800 fps or a little more, and up to 2,900 if 'pushed' with very hot Reload Swiss 'EI' type powders. Barrel life is dreadful at the hotter end of that pressure range at 1,000 rounds or less. (ie 6.5-284 levels). I frequently partner a very competent F-Open shooter at Diggle where we shoot F matches over 300-1,000 yards and he used the 147 Creedmoor small primer brass ~2,900 fps MV combination at shorter distances last year winning enough matches to get the club's F-Open championship against very stiff competition and far more ballistically capable cartridges. (It shoots very well to 1,000 and no doubt well beyond, but at 800 and beyond the sevens - 284 / 284 Shehane / 7mm SAUM, 7mm WSM - and the 300 WSM or RUM rule so he uses his 284 Shehane at these distances.)
Most large primer Creedmoor brass such as Hornady's see a short life at anything much over 2,800 fps.
The barrel lasted a bit under a season, the cost of 2,900 fps with this bullet weight, but that's as noted virtually he norm at the top end of national competition FTR with 308 and heavy bullets.
In any event, there is a clear 100 fps MV advantage to the 6.5 cartridge over the 308 and a potential 150-200 fps one. With near identical average BCs, the 308 would need that advantage to be negated to give the same paper ballistics.
Twist wise, the 147 at 2,800 is around 1.58 Sg in a 1:8 pitch barrel; the 208 ELD-M 308 1.54 at 2,700 in a 1:10, so again no issue on paper. However, people are finding that not all of the long, pointy new-generation bullets seem to live up to their ballistic promise at long distances and some are trying faster twists giving higher Sg values to try to overcome what seems to be inherent stability and dynamic balance problems. I know the 264 147 ELD-M works at 1,000 having seen it do so on the very tight F-Class target; I've yet to hear of anyone having long-range success in a top-level match with the 208 thirty in FTR. The one top competitor I know who tried it in a Bisley GB F-Class Association league round was disappointed that excellent short to mid range consistency wasn't carried through to long range. (I had a frustrating time with its 208gn AMax predecessor in FTR use and gave up up on it eventually.)
Uncle Buck
Well-Known Member
So Litz's BC are short of hornady's, no surprise there, the funny thing is though the figures I came up with were from Litz's Ballistic AE app! This I compared directly to the figures posted for Creedmoor on the comparison chart above, which is at <2700 for the creedmoor with 147s.
Based on your post both sets of figures are wrong! 2900 is very hot for creedmoor though, I'm getting 2860 with a stout load of RS60 in lap brass and a 139 scenar at 10 thou off the lands and I couldn't push it any further
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Question....did you manage to finish your chips..?
Buck.
I figured the seagul may have caught the rest of the mag!!
I D E A L !!!
Laurie,
I'm finding the thread, and your information very interesting, but I guess it's made me a little concerned over the load I'm using, in regard to barrel life.
"On paper" / QL, everything looks safe, with regard to barrel pressures, burn rates, etc'. Generally, I do aim to get closer to a 100% fill as well, but this worked.
It appears to be well below Pmax, certainly no signs of pressure on the cases, but I assume I'm missing the effect of the RS60 ?
I'm finding the thread, and your information very interesting, but I guess it's made me a little concerned over the load I'm using, in regard to barrel life.
"On paper" / QL, everything looks safe, with regard to barrel pressures, burn rates, etc'. Generally, I do aim to get closer to a 100% fill as well, but this worked.
It appears to be well below Pmax, certainly no signs of pressure on the cases, but I assume I'm missing the effect of the RS60 ?
Yes, it IS hot, even in this barrel length. The Lapua Creedmoor brass appears to take it though even if it plays merry hell with the chamber throat and back end of the barrel. As a non iPhone user/owner, I can't comment on the Applied Ballistics app values. Bryan's book is generally regarded as a gold standard for such comparisons though. He regularly updates his tests between editions and all results are adjusted from whatever ambient conditions applied during the test shooting to the ballistic standard environment for temperature, atmospheric pressure and humidity so that results are comparable. At 0.338 average G7 BC, the 208 ELD-M is marginally ahead of the current world favourite Berger 200.20X which Litz gives as 0.328, but taking into account the Hornady model's extra 8gn weight, the Berger is the marginally more efficient / lower drag. It may be that Bryan has updated his methodologies between the app being created and the 3rd edition of the book being published, or it may be vice versa with the app value being more recent. (This book edition is dated 2017.)
In raw ballistics only terms the two heavier 0.264" ELD-Ms are outstanding performers with the 140gn version generating an i7 'form factor' value below 0.900 and the 147gn version barely above at 0.901. Only a handful, probably single figures, of bullets out of the 950 or so listed in the book manage to get below 0.900.
(The 'form factor' is drag related for those who wonder what I'm on about and compares the in-flight air-drag of a design against that of a 'reference projectile', the G7 model in this case which started out as a low drag long-range artillery shell design. The 'form factor' combines with the sectional density which is calibre/mass related and is therefore common to all bullets of a particular weight in a calibre to give us the BC. So, the 147 ELD-M at 0.901 generates almost 10% less drag than the very efficient G7 reference and the 140gn model at 0.892 nearly 11% less.)
A very interesting (difficult too!) issue.
Starting with QL, I generally trust it little with the smaller 6.5s (even with actual values input and not using defaults), and even less with some Reload Swiss powders, RS52 in particular. Can't comment on Elcho-17/Re19/RS60 as it's a powder that I rarely use since I shot my 6XC's barrel out. (As an aside on QL and 6.5s, Bill Alexander, the 6.5 Grendel's creator warns that QL must not be trusted on choosing loads for the baby in the calibre.)
RS itself has an RS60 load for the 143 ELD in its data where a max charge of 41.1gn is quoted as 3,856 bar PMax (that's 55,927 psi) for 2,680 fps - barrel length not quoted but 24 inches is the usual.
So at 42gn and 2,875 fps (?) that would appear to be a rather warmer load than you may have thought!
The RS 'EI' grades - RS40, 52, 60, and 70 in the more common rifle grades - provide exceptionally high MVs through two mechanisms. First, they (like the Viht N500 grades) are 'high-energy' types. That is they are manufactured as a 'single-based' nitrocellulose only recipe then have the much higher energy / hotter burning nitroglycerin high-explosive compound 'inserted' or infused using a patented chemical process. (Nitrochemie, the RS manufacturer, invented this process and sold or licensed it it some years ago to Vihtavuori Oy, but claims that today its current version is more advanced having had considerable further R&D input.)
Then, the 'EIs' use the Nitrochemie patented EI process to infuse the 'deterrents' that determine initial burning speed further into the powder kernels instead of surface coating as used by everybody else so they last longer into the intial part of the charge burn to extend the period of retarded burn and 'flattening' the pressure curve. That's why the Z1 line is so much further to the right on QLs' pressure / time / bullet travel / velocity graph compared to comparable powders from other manuacturers. Result: enhanced periods of both time and bullet travel at peak chamber pressures and a resulting MV boost.
Then add in a heavy-for-calibre bullet, 143gn in 6.5mm being such and 147 being even more so. The heavier bullet for any given calibre the greater the barrel 'wear' at any given PMax. This is simply because a heavy bullet has more inertia than a light one and accelerates more slowly under any given pressure on its base. The leade and throat are therefore subjected to a longer period of maximum heat and pressure and it is this that causes erosion of the steel alongside flame temperatures.
The other question - which I can't answer - is how does the use of a high-energy powder running at a lower PMax than that of a 'cooler' equivalent affect barrel life? Does such a powder producing say 55,000 psi PMax to get 2,800 fps MV produce more, less, or the same amount of wear as a conventional powder that needs to be loaded to 60,000 psi to get the same MV? What we do know is that where the extra performance on offer is fully utilised barrel wear can be heavy.
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