Educate Badger: what to do with .243

[WelshShooter]

Thanks for the detailed response Laurie. I have shot a 6mmBR rifle which was single feed, and it definitely felt like it would struggle to feed from a mag due to the shape of it. In fairness, I sometimes struggle to feed my 6.5x47 Lapua from a magazine when using Hornady A-Max (no problem with Scenar's) so I know what it's like.

What is the typical difference in barrel lifetime of the .243 versus the 6mmBR? Is the slight lack of performance in the 6mmBR outweighed by a big increase in barrel length compared with the .243? Or is it only the .243AI that "burns barrels" per se?

Is the 6mm Creedmoor just a necked down 6.5mm Creedmoor, much like the 6x47 and 6.5x47 Lapua?

[Laurie]

Barrel life is as long or short as a piece of string depending on:

Type of powder (primarily specific energy)
weight of powder charge
weight of bullet (heavy = more wear than light all other things equal)
Peak chamber pressure


There is a calculator based solely on heat the charge generates - no account of bullet weight.

http://bulletin.accurateshooter.com/?s= ... mit=Search

If you were loading the 243 with 45gn of a cool burning powder such as Viht N165 (Spec energy = 3,500 KJ / Kg) to 60,000 psi and shooting slowly, the calculator says 2,127 rounds

If loading 47gn of a higher energy powder - say Re or RS at 3,990 KJ / Kg - to 62,000 psi and shooting two shots a minute, life drops to 678 rounds.

6mm BR using 30gn H. VarGet (4050 KJ /Kg) 60,000 psi very slow shooting, 2,324 rounds life.

IME 6mm BR with 105s and moderate pressure loads, but a lot of string shooting and some benchrest (very high rates of fire for 5-shot strings), group sizes start to increase somewhere around 1,300-1,500 rounds, although the barrel will remain NRA target / varmint capable to somewhere between 2,500 and 3,000 rounds.

243 Win with factory ammo (57,000-58,000 psi) in normal sporting use (cold barrels, lots of single shots, few strings exceeding 3 rounds) was traditionally said to have a life of 2,000 rounds. But of course that begs the question of definition of 'life' as 'shot-out' is very different for a BR shooter v someone to whom 'Minute of deer' is adequate. In general range use I would guesstimate 1,000-1,500 rounds if strings are kept short and the barrel is allowed to cool between them, high energy powders such as the Viht N500 series and Reload Swiss RS60 / 70 are avoided, and loads are kept well under 60,000 psi.

[meles meles]

Our DTA barrel is rifled 1 in 7, so we expects it's good for some fairly 'efty bullets out to 600, maybe even 1000 mards...

Maybe someone can suggest a decent starting point for us to play at with 600 mards range and 2000 rounds barrel life being an objective?

Or maybe we mollycoddle it with some of Dromia's favoured boolits and a grain or two of snuff to see if we can get 100 mards and 20,000 rounds through it?

[dromia]

This Eagan style works well in my 6mm Musgrave and 0.244" Remington out to 300 yards with the occasional 600 yard foray.


http://noebulletmolds.com/NV/index.php?cPath=25_107

[Laurie]

Badger,

your 7-twist will let you do whatever you want and 1,000 yard loads are easily feasible. The main issue now is how much freebore you have - these very long heavy 6mm match bullets need a lot especially if you fancy trying the 115s such as the Tubb DTAC in its various forms. (Personally, I'm not a fan of the 115s and prefer 105 to 108gn.)

If you are looking to put dedicated L-R rounds together, the bullets I'd recommend are:

the 105gn Berger VLD seated mildly (10-15 thou') into the lands. Still very popular amongst 6mm L-R shooters in this country
108gn Berger BT - a little lower BC than the VLD but easy to tune and a superb performer. Often used by US mid and long-range BR shooters
107gn Sierra MK - now in improved factory-pointed guise and like all SMKs, made very well indeed and much more consistently than in the not so distant past. (Cheaper than Bergers too.)
105gn Berger Hybrid. Very, very highly regarded in the USA, but I've no experience of feedback from anybody I'd trust in this country. Questions over whether it works fully in the usual 8-twist, but not an issue for you. Availability here? Price?

Powder wise, H4831, H1000, IMR-7977, IMR-7828ssc, Viht N165. I'd recommend N165 for availability, lot to lot consistency, stability, good manners, and most important of all less barrel wear and tear as it is a low-energy cool burning propellant. There are others that give higher MVs, but will wreck the throat much faster than this powder. H1000 is another cool burner, but is harder to get hold of and more expensive.

1,000 yard capability with this bullet weight category and even the coolest burning powder isn't consistent with a 2,000 round barrel life. I reckon you'd be lucky to exceed half that. So for more general range use, I'd recommend use of a lighter bullet loaded to modest MVs. That could be 87/90gn match bullets or now that we can again load sporting bullets, one of the dual-purpose varmint / light deer bullets in the 85/87gn category. I used to use the 87gn Hornady HPBT for this purpose pre-Dunblane with very good results, and the other bullet manufacturers all have equivalents. The 85gn Sierra HPBT is a fine bullet and is much cheaper than equivalent match models. (£31 / 100 from Henry Krank and in stock again I see on their website.)

H/IMR-4350, IMR-4451, Reload Swiss RS62, Viht N160 will give this bullet MVs in the high 2,900s maybe just breaking 3,000 fps from a 24-inch barrel and at just under 50,000 psi. Ramshot Hunter adds another 100 fps MV at the same pressures but may be hotter burning. All mild loads to preserve barrel life. Avoid 'high-energy' numbers like the plague - N550/560, RS60 etc - they will give startling MVs but in full-throttle loads and with barrel-killing heat and pressure.

[meles meles]

Thanks Laurie for those excellent suggestions. Our DTA is the short barrelled 'Covert' model - ie about 16" barrel length so that will play a prominent part in what we do. It's probably unrealistic for us to expect high velocity, 1,000 mard performance with out at least singeing the barrel if not burning it...

An 85 gn Sierra HPBT with a single base powder sounds like a good starting point for a 600 mard load. We'll go peek in our copy of Lymans 49 and see if there are any suitable recipes for N165 at that weight. Might a slow burning magnum style powder be worth considering, or does the short barrel length rule those out?

For those not familiar with the DTA, there is a good review in Another Place - http://ukvarminting.com/forums/topic/12996-the-dta-srs/

[Laurie]

In this barrel length, Reload Swiss RS62 may well be best powder choice. QuickLOAD computes 2,700 fps for the 85gn Sierra HPBT at a barrel life saving 55,000 psi, 98% charge burn in the barrel and it is a good internal ballistics match to the cartridge / bullet weight.

Note that's the single-based 62 version, not the hot burning 'high-energy' RS60 AKA Elcho-17 and Alliant Re17. RS62 was originally developed by Nitrochemie for the 270 Winchester and is an excellent all-round powder for applications needing a propellant in the '4350s bracket'.

Viht N150 will likely work too, but give lower MVs.