Throat erosion - a word of warning

[Tikka CTR yummie]

Straight-wall designs generally cause less erosion because they generally have a lower capacity / charge weight to bore area ratio, and most (not all) use lower pressures than modern bottlenecked types. Those that do use higher pressures such as .458 Win Magnum tend to see fewer shots fired in a year, and very few if any 20-round strings in competition. If you built a say .224 cal straight-wall running at 65,000 psi it would produce greater erosion than a same performance, same pressure well-designed bottlenecked design if you accept the TP (turbulence point) hypothesis.

TP theory says that the case shoulders direct the flow of partially burned powder kernels infused with superheated gas that forms at the case mouth and allied to neck length either retains this highly erosive mass inside the case-neck or pushes it outside into the leade where it wears the barrel out quicker. The simple test is to take a scale drawing of the case and extend the shoulder lines forward until they intersect - that's where the TP will form. If outside of the case-neck, bad; if inside, good.

A real-life example is to be found in the sixes - the early 50s design 243 Win with 20-degree shoulders and a short neck; the slightly later 6mm Rem with 26-deg shoulder angle and much longer neck with its TP inside the neck; the still later smaller capacity 6mm Tubb XC with 30-degrees shoulder and longer neck. All other things being equal (bullet weight, pressures, propellant flame temp / heat values, rate of fire / barrel heating) the XC and 6mm Rem should give longer barrel lives than the 243 Win, but they're not equal here as there are capacity / charge weight variations across the three.

There are however reformed, enhanced variants of the 243 that simply involve running a 243 case through the new version's die and/or a small amount of fireforming. The 6mm SLR (Super LR) simply grafts the XC's 30-degrees shoulders and long neck onto the front end of the 243 case, no other change, by pushing the shoulders back and reforming them. Ballistically you still have a 243 Win (6mm-08) with maybe 1gn less water capacity due to the reforming, but with a 'more efficient' front-end that moves the TP back inside the case.

Super LR

The 6mm Competition-Match is a similar modification with a 31-degree shoulder designed by Joe Hendricks and used now by his son Joe Hendricks Jr very successfully in US Hi-Power XTC.

Both cartridges claim to enhance barrel life over alternatives in the competition role, in some cases provide a doubling of barrel life. However, it turns out there is a degree of sleight of hand here. Yes, the front-end is far better than that of the 243, but few use that cartridge in serious competition and none in disciplines like PRS and XTC with high round-counts and rapid fire-strings, where the smaller 6XC is the obvious choice. Such users burn through two XC barrels in a season despite the efficient case-design. The SLR and C-M give enhanced life because having the larger 243 Win case capacity lets them use cooler burning propellants - Hodgdon H1000, and even more so Viht N165. So despite being more over bore-capacity, they reduce barrel life compared to the very well designed XC. (N165 has proven itself in this respect in several cartridges and this isn't a shooting / urban myth) So, there is nothing to stop you loading your 243 Win with this propellant and treating your barrel more gently. (Because of its burning rate, it's only really applicable for use with heavier bullets though, 100gn and above.)

Laurie, I have a Tikka CTR 6.5mm C As I understand, using single based powders is better than double for slowing down throat wear. If that's true, Vit N series are going to be the obvious way to go. Which powder do you recommend for 140gr bt bullet. N160 or N150. Have you tested any loads for the 6.5mm C. As we can't get H4350 anymore, are there any other powders you can suggest please.

 

[fizzbangwhallop]

Good post as usual Laurie .......very informative.

Taking this sideways a bit, as they maybe a bit more accessible to U.K. shooters(?)....how does the Ackley version match up against the SLR and XC cases?

 

[royr]

Good afternoon Gents,
When posting the 2 x BARREL LIFE formula, there are just too many variables to say the resulting calculations are in any way "DEFINITIVE". But, they are a useful guide in giving predictions on barrel life with different burn-rate, heat potential powders.
When developing a new load, I will now always choose a powder with a lower "Heat Potential" if I can achieve the ballistic requirements for that given rifle, calibre, and bullet.
A colleague wanted a fast longer range foxing round for his .243; below is what was developed.

.243 Recent Example :-
Winchester 700 with 24inch barrel, 1-10 twist, .243, 55gn Nosler CT BalSilverTip (51030). NB. I required 100% powder burnt within the 24inch barrel; i.e. No muzzle flash at night. For safety, the QL predicted PSI pressure loading is kept to around 10% below max SAAMI PSI - .243 @ 60,000psi Max. Starting loads always lower!

QuickLoad offered:-------------case fill------ weight-----------powder burnt---------------PSI------------Heat potential------barrel life prediction
IMR 3031-(Non REACH)--------94.5~%------42.22gn--------100%@22.1inches---------52667psi-------------3880----------------1669 rounds
Alliant AR-Comp *C *T ---------91.2%------- 42.1gn--------- 100%@14.4inches ------- 52667psi-------------3740----------------2017 rounds
Vihtavuori N135 *C ----------- -97.5%--------44.0gn--------- 100%@20.8inches--------52511psi-------------3590----------------2266 rounds
( have no idea why some of the text has changed to GREEN??)

The Vihtavuori N135 *C load was chosen, and with actual Chrono'd velocity of 4020fps, is a useful longer range Foxing round.
Zero'd at 250yards, bullet is approx 1" high at 200yds; 2" low at 300yds and 9" low at 400.

Have fun
Regards
RoyR

 

[Tikka CTR yummie]

Thanks RoyR. Blistering round. I have a Tikka CTR 6.5mm C As I understand, using single based powders is better than double for slowing down throat wear. If that's true, Vit N series are going to be the obvious way to go. Which powder do you recommend for 140gr bt bullet. N160 or N150. Have you tested any loads for the 6.5mm C. As we can't get H4350 anymore, are there any other powders you can suggest please. I would like to care for the barrel for as long as poss.

 

[Laurie]

Have you tested any loads for the 6.5mm C. As we can't get H4350 anymore, are there any other powders you can suggest please.

My testing in this cartridge was back in the early days and we've moved on a lot from there, so I claim little direct expertise. N150 and 160 are both 'quicker' in real life applications than burning rate charts suggest. That's why N150 is very widely used these days in competition loads for 308 Win, but the 4350s only rarely if ever. Some US F/TR competitors describe N150 as being very close to H. VarGet in the 308 in fact. Likewise, N160 is usually shown on the same line as IMR-4831 - look at actual loadings and it's much closer to the 4350s.

Some people use N150 happily in the 6.5 Creedmoor / 140gn with reported good results. I didn't do so well with it when I had a try some years back, and obtained better results with N160 with this bullet weight, as one does too with the slightly larger case capacity 260 Rem. N150 is well suited to 120-130gn bullets in this pair though. One thing to watch with both powders is that they turn nasty very quickly indeed in such applications over very small charge increments once near to full pressures are achieved. Viht has recently reformulated them and they are now claimed as 'temperature-stable', so there should be less risk of blowing primers or other nasties in a warm summer now. One final caveat with N160 alone - don't believe QuickLOAD results using the program's default values (unless they've been upgraded since my old V3.6). In 260 size cartridges, I use QL to advise an initial top load ~5,000 psi below where I want to be - ie if loading up to 58,000 psi (estimated) in this class of cartridge, the top loading I use in the initial 3-round pressure / MV range-tests will produce ~53,000 psi according to the program.

There is no doubt H4350 is the near ideal 6.5mm Creedmoor propellant. We now have a LOT of Reach-compliant alternatives:

IMR-4451*

Alliant Re16*

Norma 204*
Norma URP*

Lovex SO65
Lovex SO70

Ramshot Hunter*

Viht N150
Viht N550*
Viht N555* (to arrive shortly, due in the spring, some loads data already available)
Viht N160

Reload Swiss RS60* (aka Alliant Re17)
Reload Swiss RS62

* = double-based or 'high-energy', in either case containing a degree of nitroglycerin.

I plan to try many of these in 7mm-08 later this year as alternatives to the N160 / Lovex SO65 I currently run in a high-freebore match version barrel with the 160gn Sierra TMK using H4350 as the baseline / 'control'.

As a broad rule, single-based powders do give better barrel life than those containing nitroglycerin, but to look at this aspect alone over-simplifies things. First, nitroglycerin levels vary considerably in those powders containing them. Take Norma (made by Bofors) the only company I know which actually tells you the NC content by grade. NC weight percentages vary from 4% to 12-13%. (The only ones above 10% are the high performance grades - URP and MRP). I'm very relaxed about low NC content powders up to say 7.5% providing pressures / MVs are kept modest.

And that's the key thing - ANY powder will kill a barrel quickly if you it lets you load it to high enough performance. 308 Win F/TR shooters loading 200gn bullets over 'mild' N150 in small primer brass are killing stainless match barrels in 2,000 rounds, sometimes not even that. Run a 155 with N150 in large primer brass at less pressure in a very hard hammer-forged chrome-moly factory barrel and you'll get 6 or 7,000 rounds, maybe even 10,000 unless you're into shooting long strings really fast so the barrel becomes too hot to touch.

RS62 is a great powder in 6.5mm Creedmoor and can give very high MVs with 140s, but if you want a long barrel life the trick is to find a node below maximum that is nice and wide so it's not affected by minor condition changes on the day. What do I mean by a node below maximum? You'll constantly hear that "I get 2,850 fps or 2,875 fps with XX 140gn bullet in my 24-inch barrel Creedmoor", well that's likely OTT pressure-wise anyway. The top node that groups well is more likely to be a bit less say just below or just above 2,800 fps. Lower nodes (the points where groups pull in tighter) most likely fall at around loads that produce around 100 fps MV steps, maybe a bit larger. so the next node down will fall in the high 2,600s to low 2,700s. If you want a long and happy barrel life go there and give up 100-125 fps MV. If you look at most 140gn 0.264" match bullets' external ballistics you're still well above the speed of sound at 1,000 yards, in fact above trans-sonic speeds too. Look at Berger's online ballistic calculator, JBM etc and input the Berger 140gn LRBT a nice easy to tune tangent ogive design that really shoots well at long distance in most rifles but which is lower BC than top of the line Hybrids, ELDs and suchlike. A modest 2,650 fps MV sees 1,370 fps at 1,000 yards under standard conditions. ie 1.216 MACH.

I suspect the better choices here are RS62, N160, Norma 204, and an outfielder Lovex SO65, a much underrated powder - but NOT the same quickness as VarGet as shown in the Explosia burning rate chart that caused it to be sold as a replacement for that powder during one of the long VarGet droughts some years ago. This is a poor 308 Win powder, but an excellent one in the mid-size 6.5s and 7s up to and including 7X57mm and 7X64mm case sizes. For Creedmoor loads data ignore Lovex's maker Explosia's loads data and go to the American Shooters World and get the loads for 'SW Long Rifle' which is what this US distributor has renamed it. This is a plain-Jane long kernel tubular type, not great in traditional powder measures. On the face of it Lovex SO70 should be the alternative to IMR or H4350, but back in the days when this was AA-4350, it was the slowest of the bunch by a fair margin and in its applications sometimes fell closer to IMR-4831.

I also suspect that for higher-performance loadings, Norma URP, Alliant Re16, and the soon to arrive Viht N555 will be the ones to look at. Re16 is already gaining a reputation in the US as an ultra stable, high-performance H4350 replacement. If N555 doesn't work well in this application I'll eat my hat - Viht'd be mad not to produce this result. I find, N550 a tad too quick and finicky in 260 Rem with 140s - I imagine N555 will be a bit slower burning and more flexible here. RS62 loaded up higher joins this group too.

 

[Tikka CTR yummie]

My testing in this cartridge was back in the early days and we've moved on a lot from there, so I claim little direct expertise. N150 and 160 are both 'quicker' in real life applications than burning rate charts suggest. That's why N150 is very widely used these days in competition loads for 308 Win, but the 4350s only rarely if ever. Some US F/TR competitors describe N150 as being very close to H. VarGet in the 308 in fact. Likewise, N160 is usually shown on the same line as IMR-4831 - look at actual loadings and it's much closer to the 4350s.

Some people use N150 happily in the 6.5 Creedmoor / 140gn with reported good results. I didn't do so well with it when I had a try some years back, and obtained better results with N160 with this bullet weight, as one does too with the slightly larger case capacity 260 Rem. N150 is well suited to 120-130gn bullets in this pair though. One thing to watch with both powders is that they turn nasty very quickly indeed in such applications over very small charge increments once near to full pressures are achieved. Viht has recently reformulated them and they are now claimed as 'temperature-stable', so there should be less risk of blowing primers or other nasties in a warm summer now. One final caveat with N160 alone - don't believe QuickLOAD results using the program's default values (unless they've been upgraded since my old V3.6). In 260 size cartridges, I use QL to advise an initial top load ~5,000 psi below where I want to be - ie if loading up to 58,000 psi (estimated) in this class of cartridge, the top loading I use in the initial 3-round pressure / MV range-tests will produce ~53,000 psi according to the program.

There is no doubt H4350 is the near ideal 6.5mm Creedmoor propellant. We now have a LOT of Reach-compliant alternatives:

IMR-4451*

Alliant Re16*

Norma 204*
Norma URP*

Lovex SO65
Lovex SO70

Ramshot Hunter*

Viht N150
Viht N550*
Viht N555* (to arrive shortly, due in the spring, some loads data already available)
Viht N160

Reload Swiss RS60* (aka Alliant Re17)
Reload Swiss RS62

* = double-based or 'high-energy', in either case containing a degree of nitroglycerin.

I plan to try many of these in 7mm-08 later this year as alternatives to the N160 / Lovex SO65 I currently run in a high-freebore match version barrel with the 160gn Sierra TMK using H4350 as the baseline / 'control'.

As a broad rule, single-based powders do give better barrel life than those containing nitroglycerin, but to look at this aspect alone over-simplifies things. First, nitroglycerin levels vary considerably in those powders containing them. Take Norma (made by Bofors) the only company I know which actually tells you the NC content by grade. NC weight percentages vary from 4% to 12-13%. (The only ones above 10% are the high performance grades - URP and MRP). I'm very relaxed about low NC content powders up to say 7.5% providing pressures / MVs are kept modest.

And that's the key thing - ANY powder will kill a barrel quickly if you it lets you load it to high enough performance. 308 Win F/TR shooters loading 200gn bullets over 'mild' N150 in small primer brass are killing stainless match barrels in 2,000 rounds, sometimes not even that. Run a 155 with N150 in large primer brass at less pressure in a very hard hammer-forged chrome-moly factory barrel and you'll get 6 or 7,000 rounds, maybe even 10,000 unless you're into shooting long strings really fast so the barrel becomes too hot to touch.

RS62 is a great powder in 6.5mm Creedmoor and can give very high MVs with 140s, but if you want a long barrel life the trick is to find a node below maximum that is nice and wide so it's not affected by minor condition changes on the day. What do I mean by a node below maximum? You'll constantly hear that "I get 2,850 fps or 2,875 fps with XX 140gn bullet in my 24-inch barrel Creedmoor", well that's likely OTT pressure-wise anyway. The top node that groups well is more likely to be a bit less say just below or just above 2,800 fps. Lower nodes (the points where groups pull in tighter) most likely fall at around loads that produce around 100 fps MV steps, maybe a bit larger. so the next node down will fall in the high 2,600s to low 2,700s. If you want a long and happy barrel life go there and give up 100-125 fps MV. If you look at most 140gn 0.264" match bullets' external ballistics you're still well above the speed of sound at 1,000 yards, in fact above trans-sonic speeds too. Look at Berger's online ballistic calculator, JBM etc and input the Berger 140gn LRBT a nice easy to tune tangent ogive design that really shoots well at long distance in most rifles but which is lower BC than top of the line Hybrids, ELDs and suchlike. A modest 2,650 fps MV sees 1,370 fps at 1,000 yards under standard conditions. ie 1.216 MACH.

I suspect the better choices here are RS62, N160, Norma 204, and an outfielder Lovex SO65, a much underrated powder - but NOT the same quickness as VarGet as shown in the Explosia burning rate chart that caused it to be sold as a replacement for that powder during one of the long VarGet droughts some years ago. This is a poor 308 Win powder, but an excellent one in the mid-size 6.5s and 7s up to and including 7X57mm and 7X64mm case sizes. For Creedmoor loads data ignore Lovex's maker Explosia's loads data and go to the American Shooters World and get the loads for 'SW Long Rifle' which is what this US distributor has renamed it. This is a plain-Jane long kernel tubular type, not great in traditional powder measures. On the face of it Lovex SO70 should be the alternative to IMR or H4350, but back in the days when this was AA-4350, it was the slowest of the bunch by a fair margin and in its applications sometimes fell closer to IMR-4831.

I also suspect that for higher-performance loadings, Norma URP, Alliant Re16, and the soon to arrive Viht N555 will be the ones to look at. Re16 is already gaining a reputation in the US as an ultra stable, high-performance H4350 replacement. If N555 doesn't work well in this application I'll eat my hat - Viht'd be mad not to produce this result. I find, N550 a tad too quick and finicky in 260 Rem with 140s - I imagine N555 will be a bit slower burning and more flexible here. RS62 loaded up higher joins this group too.

Laurie, thanks a million for your reply and expertise. I will have to re-read a few times to take it in. Looks like RS62 will feed my CTR and some of my Military rifles. I take the point concerning N550. I have seen Utubers use R16 to great effect. I am loading to 2700fps for 800-1200, which is supersonic all the way with stock140, 142 Sierra MK and the Hornady 143eld. Once again thanks.

 

[Laurie]

Yes - 2,700 fps is a good place to be in that rifle / cartridge combination. I've no experience with the ELD, but have found the 142gn SMK an excellent all-distance match bullet. Their only downside was that if you go back a few years, their BTO dimensions were all over the place. Sierra's recently made MKs, those in the new label purple mountain boxes and factory-pointed are usually very, very consistent and can be used out of the box for most purposes.

 

[User00033]

@Laurie

I am curious to know if there has been any definitive pressure testing of small rifle primer brass. All I can find is hundreds of forum posts, rather than an article by a recognised authority.

Specifically, this issue of whether small primer brass masks high pressures, and if this poses a risk to the shooter other than accelerated throat erosion.

As you have stated many times, a lot of Creedmoor reloaders are pushing their Lapua SR brass beyond stated maximum pressures, SAAMI (62,000 psi) and CIP (63,091 psi), and some of them are going well beyond these pressure limits whilst reporting no ill effects. Peterson Brass Company goes as far as saying this about their SR primer brass:

If you plan to load above SAAMI max pressure and are concerned about primer-pocket leak, Peterson recommends you try their 6.5 Creedmoor Small Rifle Primer. While they do not suggest loading over SAAMI max pressures, Peterson's small primer pocket 6.5 Creedmoor have proven to hold up over SAAMI max pressures when tested in their universal receiver.

I load to the node just below CIP pMax for a measured MV of 2,756fps. Careful Quickload modelling and fine tuning to my Chronograph and drop tested trajectories gives me a chamber pressure of 63,077 psi. My interest in running "hot" is retained energy at range, as the rifle is used exclusively for medium range (300-600m+) pest control.

Dropping the load to a "safer" pressure of pMax-15% reduces terminal energy by 10% at 600m, and affects modelled windage by a similar margin. For my purposes at these ranges, I need that 10% working in my favour.

Some of the Lapua and Peterson Creedmoor H4350 loads I am privvy to, and particularly with RL16, are well above these levels with no obvious ill effects and continued good brass life. Certainly, the SR brass is lasting far, far longer than the Hornady LR brass. I don't think barrel life is a particular concern, as both myself and my shooting acquaintances are able to swap barrels out with ease (and at low cost).

Any comment or sources of further reading would be much appreciated.

 

[Tikka CTR yummie]

@Laurie

I am curious to know if there has been any definitive pressure testing of small rifle primer brass. All I can find is hundreds of forum posts, rather than an article by a recognised authority.

Specifically, this issue of whether small primer brass masks high pressures, and if this poses a risk to the shooter other than accelerated throat erosion.

As you have stated many times, a lot of Creedmoor reloaders are pushing their Lapua SR brass beyond stated maximum pressures, SAAMI (62,000 psi) and CIP (63,091 psi), and some of them are going well beyond these pressure limits whilst reporting no ill effects. Peterson Brass Company goes as far as saying this about their SR primer brass:

If you plan to load above SAAMI max pressure and are concerned about primer-pocket leak, Peterson recommends you try their 6.5 Creedmoor Small Rifle Primer. While they do not suggest loading over SAAMI max pressures, Peterson's small primer pocket 6.5 Creedmoor have proven to hold up over SAAMI max pressures when tested in their universal receiver.

I load to the node just below CIP pMax for a measured MV of 2,756fps. Careful Quickload modelling and fine tuning to my Chronograph and drop tested trajectories gives me a chamber pressure of 63,077 psi. My interest in running "hot" is retained energy at range, as the rifle is used exclusively for medium range (300-600m+) pest control.

Dropping the load to a "safer" pressure of pMax-15% reduces terminal energy by 10% at 600m, and affects modelled windage by a similar margin. For my purposes at these ranges, I need that 10% working in my favour.

Some of the Lapua and Peterson Creedmoor H4350 loads I am privvy to, and particularly with RL16, are well above these levels with no obvious ill effects and continued good brass life. Certainly, the SR brass is lasting far, far longer than the Hornady LR brass. I don't think barrel life is a particular concern, as both myself and my shooting acquaintances are able to swap barrels out with ease (and at low cost).

Any comment or sources of further reading would be much appreciated.

Hi, what calibre are you using?

 

[Laurie]

Some of the Lapua and Peterson Creedmoor H4350 loads I am privvy to, and particularly with RL16, are well above these levels with no obvious ill effects and continued good brass life. Certainly, the SR brass is lasting far, far longer than the Hornady LR brass. I don't think barrel life is a particular concern, as both myself and my shooting acquaintances are able to swap barrels out with ease (and at low cost).

I've never seen a pressure trace either for SP brass for larger cartridges We can say it DOES affect pressure and pressure build-up in that it normally requires a charge weight increase to attain the same MVs as obtained in LP brass (even where other factors such as make and internal fireform capacity are the same).

I've seen 10 years now of very heavy 308 Win loads in the original Lapua 'Palma' brass and there is no doubt that these cases, and by all accounts, more recent arrivals in other cartridges and from other makers, stand up to very much higher pressures than were ever possible with the best conventional LP types. I've no concerns there, nor have I heard of anybody damaging an action by running stiff SP brass loads. (That's not to say that ultimately stress related problems won't arrive after very significant number of rounds are fired with some makes/models.)

On barrels, there are simply no free lunches. You pay for the performance here one way or another and match quality stainless barrels are relatively 'soft' compared to factory hammer-forged chrome-moly types. Two examples: 308 Win will give at least 5 or 6,000 rounds through a stainless barrel using the NRA GGG contract ammo. Some users eke their barrels out to nearer 10,000 rounds. SP brass loads regularly used in F/TR see barrels 'gone' (not just producing a bit more in the way of long-range elevations, but 'gone' as in useless, clapped-out, totally f**ked) in 2,000. Now some of that is down to the use of heavier bullets compared to TR and GGG 155s, but most of it is simply pressure and performance related. I sold my F/TR rifle late last year with 2,850 rounds down its Broughton all 155.5s and 168s at what QuickLOAD says is a bit over SAAMI Max pressure wise, but running a full 100 fps MV below what most people do with these cases, and yet more below what some do There was five to six inches firecracking and although it still shot well (very well indeed), performance collapse could occur at any time with that degree of cracking. Personally, I'd have expected a few more hundred to obtain say 3,500 rounds. All slow-fire, and mostly single-based powders. (The rifle was priced and sold on the basis of the new owner rebarreling either right away or very shortly.) Around the same time I was in a well known northern gunsmith / riflebuilder's workshop and we discussed the 6.5X47L and the pressures some users run - a case with a classic ejector extrusion mark with heavily smeared brass from it all round the case-head that I'd picked up on a Diggle firing point after a tactical match prompted this. The gunsmith said that 6.5X47L tactical shooters were amongst his best customers for new barrels such are some of the loads being fired coupled to high round counts. It's not not that long ago that forums were full of happy 6.5X47 shooters saying ... I get quarter inch groups, fantastic MVs with these handloads and a barrel life of 4,000 rounds. Well, not everybody at least for the last claim now it turns out.

On Re16, a US shooter told me recently that its Re23 slower burning stablemate that uses the same TZ treatment technology was acquiring a reputation as a cool burner and barrel life is good despite it being a very able performer. It may be that Re16 shares this - it's been around in the US more than long enough for any horror barrel-burning type stories to appear, and if they have I've yet to pick up on any. So Alliant / Bofors may have come up with some jackpot winners here. Onhe can but hope.

 

[Blobby159]

Just for ultimate clarity here please Laurie, but are you saying that BOTH Rel16 and Rel23 are shaping up to be "good" propellant powders where, in hand loads, they have BOTH a good showing of reasonable to high velocities coupled with the ability to do this whilst NOT destroying barrel rifling at anything like the increased levels they were initially thought to possess ???

I should also like to Thank You Most Sincerely for your continued, high level of support and reasoned criticism of our collective knowledge (or erm... lack thereof) in this and other 'strings' where the answer assumes a technical knowledge many/most of us just will not have, yet you being that knowledge to the table giving those of us on here the benefit of said in a manner that makes it generally understandable!! ...... I salute you Sir!!

Sincerest Regards,
Blobby159


ATB ..... and shoot safely

 

[308tikka]

I will, but for the new build I want to change my ways and reduce the erosion I'm seeing with my current powder/load combination.

Erision is basically a factor of bore to case volume ratio. A 22-250 will ‘erode’ more quickly than a 222rem. More powder. Double base makes it quicker but might be more consistent (and accurate).
Everything is a trade off.
Also I had a pacnor barrel once. Rough as hell finish. I got it cheap so not overly fussed and it shot ok but wasnt match grade. Stick to known good barrel makers and you will enjoy shooting much more with much less worries.

 

[User00033]

Hi, what calibre are you using?

6.5 (Creedmoor) and 6mm (Creedmoor).

And a whole bunch of others but these are the two that I'm using the SR primer brass for. Lapua for the 6.5 and Lapua and Starline for the 6mm.

I know where the pressure signs start in both cartridges with H4350 (2209 here). Stiff bolt and primer observations are the normal indicators. But the Alliant powders have allowed us to go well past those muzzle velocities without the same pressure signs.

We use a clever setup to test for pressure with no risk to the shooter, with a chrono, so we'll go hunting for pressure then back off to the closest accuracy node. Velocity and hence trajectory and energy are important to us because of the application. Small primer brass is lasting far far longer compared to what first came out. I haven't lost a single case from the first hundred Lapua cases I bought in 6.5 Creedmoor, I'm up to their 7th reloading now and not a hint of a problem. When I say lost, I mean not lost to pressure damage. I haven't lost any in the grass either!

 

[Laurie]

Just for ultimate clarity here please Laurie, but are you saying that BOTH Rel16 and Rel23 are shaping up to be "good" propellant powders where, in hand loads, they have BOTH a good showing of reasonable to high velocities coupled with the ability to do this whilst NOT destroying barrel rifling at anything like the increased levels they were initially thought to possess ???

What I'm saying is that I have heard it said that Re23 is a relatively 'cool burner'. This may or may not be the case, but Americans now have a fair bit of experience with this grade and it is shaping up very well.

On Re16, it's a case of absence of bad reports (quite the reverse, all good to date) from users. These two powders were introduced in 2014, but didn't get into American gunshops in a big way until summer / autumn 2016. That's three years plus now and by all accounts they are selling very well. Both give excellent performance in suitable applications in their class (4350-'class' and 4831 respectively) and so far no horror stories have appeared of prematurely worn out barrels, or unduly rapid wear. They would appear to offer yet another incremental improvement in all-round performance with so far no reported downsides.

I recently bought a copy of Sierra's new and long-awaited reloading manual ('Edition VI). This really is an excellent publication and has turned out to be worth waiting for, As well as a large increase in the cartridges covered, it has managed to get many of the new IMR and Alliant powders in and added them to some data-sets for older cartridges. Re16 is very well represented now, Re23 less so. Sierra has also continued its practice of giving the 'accuracy load' and 'hunting load' at the foot of each table and in appropriate applications Re16 has picked up a very large number of the former accolades. As Sierra shows loads against stepped MVs, it also allows an appreciation of where a powder stands against others in the same class. Re16 nearly always provides the same top MV as H4350, occasionally hits the next MV step up. In charge weight terms, it is usually apparently slightly 'quicker' than H4350 attaining same MVs with 0.5-1.5gn lower charges, but there are exceptions where it uses the same or even a slightly higher charge. It is also marginally 'slower' in this respect than its Re17 stablemate in some applications. As before, if highest possible MV is the handloader's primary consideration, Re17 often achieves that within this tabular format.

 

[palo]

I'm having my sako trg rebarreled to 6.5x47 at the moment and I am planning to use 123 and 130 grain bullets.
What powder would be recommended for accuracy and barrel life. I'm not looking for max velocity.
I have some vit n140 and was hoping to use it.

 

[Laurie]

Try N140 - it'll probably work out fine. N150 is better with these bullet weights in some barrels. Other choices are Alliant Re15/Norma 203-B and Lovex SO62 for the 123; IMR-4451, Ramshot Big Game, and Alliant Re16 for 130s.