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Throat wear with 210g 30 cal bullets.


blaser308

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what amount of throat wear is the norm for .308 cal with say 1000-1500 rounds of 210g weight bullets and varget & n550 with a ftr rifle and 32in heavy palma profile barrel, what increase to lands range could one expect.

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Blaser308.

 

My set up is wrong for the 210 but I have used the 185g Bergers for four years and experienced 27ths wear after I switched from N150 (single base) to N550. The wear was over two seasons F Class but only shooting five comps per year and club comps. Average b/w 1000 and 1200. Awful and I know of two others having the same problem with N540. I went back to N150 and slower fps.

 

New rifle this year and switched to RS52 and Palma brass. Increased FPS (2870) and no pressure signs. Too early for any signs of excessive wear. Having accepted the fact that the metal will wear I have ordered a new Bartlein as a spare just in case.

 

I would be interested to know what the lads are suffering with the 155.5g Bergers and 3100+ fps.

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Hi Spiker, "I would be interested to know what the lads are suffering with the 155.5g Bergers and 3100+ fps." would imagine there would be faster rate of throat wear with the 155.5 and 3100+ fps over the 2650-2700 fps and 210 bt Lr loading, How Temp sensitive have you found the RS52 propellent in comparisson to Varget or n150? Have you tried Lapuas new 220g scenar L bullet fir FTR ifso how have they performed in comparisson to the berger +200 grain heavies.

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The 210gn / 2,700 fps loading produces 3,400 ft/lb ME. It takes nearly 3,140 fps to produce the same energy with a 155.5gn bullet. In energy output, therefore energy input the two loads are identical. Having said that, if equal propellant characteristics are involved, the 210gn bullet will generate substantially greater and faster throat wear than the lighter bullet. (Greater inertia = slower movement = throat subjected to maximum pressure / heat for a longer duration.) Propellant characteristics are unlikely to be equal, but nevertheless, I'd reckon on the 210 wearing the barrel out first.

 

Before I used RS52 in the Scottish Long-Range at Blair in late June, I had a worry about its temperature sensitivity, so I left a box of handloads using small primer Lapua 'Palma' brass sitting in the front seat of the car in full sunlight for three hours before shooting a couple of test groups on a warm (>20-deg C) day at Diggle. Despite the MTM box being warm to the touch on retrieval, there were no signs of increased pressures on a full-pressure loading and groups remained small. I didn't chronograph them, so MVs may have risen. VarGet and N150 are both very temperature insensitive, and it's unlikely a 'high-energy' propellant with its NG content will be as good, but I doubt if you'd see your cartridges get any warmer than mine were that day in the UK. Run at pressures already past the red-line though, and half a dozen extra degrees ambient temperature plus letting your ammo sit in the open in full sun may be the straw that breaks the camel's back, not to mention your rifle action.

 

The 220gn Scenar is a low-BC bullet for the weight with a massively long bearing surface for its overall length. It is in no way a competitor to the 210gn and heavier Bergers as an L-R match bullet. I can't envisage what application the Lapua designer had in mind for it.

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Thanks for info Laurie, My FTR rifle supposed to be throated for the berger 210g BT LR bullet & seated 0.010 off the lands there seems to be a very small portion of bullet above boat tail junction seated into case neck, seated measurement 0.130in from top of boat tail to top of case mouth overall loaded round length from case base to bullet tip 3163in, Could there be any accuracy issues with small amount of bullet seated into neck? i understand i will also have to increase overall length as throat wears, does this small amount of bullet seating seem correct.

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Hmmmmm! That's definitely 'throated long'. You should be fine with 0.130" bullet shank in the neck.

 

Are you sure that IS the COAL though? If you use a Stoney-Point / Hornady OAL gauge and modified case in a good match chamber, you usually get a wildly incorrect reading in my experience. I've found on several occasions that I apparently needed very shallow seating / long COAL, but try an inert round at the setting and it won't chamber. I presume the problem is the modified case not suiting a 'minimum SAAMI' chamber and hence not chambering fully when taking the reading.

 

Anyway ... assuming the reading is correct, you have some options. First, the 210gn Berger LRBT is very jump tolerant indeed. Seat it a little deeper to give around 0.2" shank in the neck if you're worried (half bullet calibre = 0.15" is usually more than enough though). Secondly don't worry about throat erosion for at least 1,000 rounds - this bullet really will take jump, but check your velocities every few hundred rounds as they'll likely drop off a bit and you may need to refine the powder charge eventually.

 

Second, look at other Berger bullets. If you really have this amount of freebore, you'll be ideally set up for the 200 / 215gn Hybrids, maybe the 208 and 225gn Hornady bullets too. It'll likely still be on the short side for the 230gn Berger Hybrid, but that IS an acquired taste anyway.

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Laurie, In process of getting hold of stoney point gauge so measurements for now from case base to bullet tip, With my chamber and with the berger 210g BT LR shank seated half way in Lapua palma case neck the jump to Lands is 0.050 with oal from case base to bullet tip 3140 in, Will have to play with seating depth and see how well it shoots in comparison with 0.015in off lands load, As for the Berger 215g Hybird i would be interested to see how well this bullet shoots in rifle however not sure if Varget would be best powder for this bullet for ftr in 308, I have also heard that the 215g hybrid can throw up unexplained vertical issues and not as jump tolerant as the 210 bt lr have you any other info/views you could share with the 215g hybrid, Thank again for sharing info with previous posts.

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I've only used the lighter Hybrids, the 168 in particular with great success. They are not as jump tolerant as the LR BT true-tangent designs in my experience - in some cases they actually seem to like being treated as VLDs and seated into the lands. That's an experience based on one chamber-form in two makes of barrel, so is not exactly a wide sample. Certainly, so far as 155s go, most people won't move from the outstanding 155.5gn BT Fullbore to the Hybrid despite the latter offering a bit higher BC.

 

There are a number of people at the top of the GB-FCA FTR league placings who either use the heavier Hybrids or have done so with some success. Many of them also use the 210gn BT, and some have switched back to it. This has possibly more to do with availability and price than dissatisfaction with the 200 / 215 / 230 Hybrids. Also, more than a few people have compromise chambers that will take the 155.5 Berger seated out alongside the 210 BT seated maybe a little deep and get very good results with both. They select the load combination on likely match weather conditions. The 155s will nearly always outshoot the 210s and heavier simply because it's easier to get them to group well and handle the rifle consistently over 15 or 20 score shots. The heavies usually produce larger elevations, but that 'swing' is overmatched by the 'roundabout' of reduced windage effect IF the weather is rough.

 

So far as any heavies go, 210gn and up, nearly all successful L-R users load them in Lapua 'Palma' small primer brass with a Magnum or BR primer and a slow-burning 'high-energy' powder, Re17 / Elcho 17 and Viht N550 the usual pair with the emphasis on the latter. Standard large primer cases and VarGet will reduce your potential MVs, potentially considerably, and you may well find that case-life isn't great with primer pockets soon loosening at what don't seem unduly heavy loads or high MVs. That's not to say these bullets won't shoot well at lower MVs, but the whole object of the game is to obtain a significant reduction of lateral movement in a wind change. If the 210 and 155.5 aren't too far apart in this respect, you risk losing out by shooting a heavier bullet thanks to its various downsides. FWIW, QuickLOAD says that you won't better 2,650 fps in a 30-inch barrel with your set-up without exceeding 60,000 psi. The equivalent MV for the 155.5gn bullet based on the 210's ME (3,275 ft/lb) is 3,079 fps. Alongside each other, this pair see 7.3-inches movement with the 210 and 8.8-inches movement for the 155.5gn per 1 mph change of a 90-deg crosswind at 1,000 yards. That saving of 1.5-3 inches (most shot to shot wind changes on Bisley, Diggle, and Blair are in the 1-2 mph at 90-deg category because true crosswinds are relatively rare at these locations) assuming you miss the change completely may or may not make a difference to scores. That 'saving' also assumes both combinations produce identical 'precision'. A move from 0.3-MOA grouping to 0.5-MOA sees a 2.1-inch increase in shot dispersion at this distance which may wipe the wind benefits out. This is accentuated if the heavier bullet causes a deterioration in elevation consistency as the five-ring becomes 'narrower' the further one moves vertically from the elevation centreline (or 'watershed' as wind coaches call it). Rise or fall a half-MOA and your wind call needs to be near perfect to just get the 'five' at 12 or 6 o'clock. Some people, 'Big Steve' [Donaldson] in particular, seem to manage good elevations, most say they notice a deterioration compared to the lighter bullets.

 

As so often, there are no clear-cut, easy choices. Try the 210s and see how you do. If you're not happy, you can always have the barrel set-back and rechambered with a shorter throat at the price of a couple of inches of barrel length. I sold all my heavies and don't exceed 185gn these days, in fact rarely exceed 168gn and shoot a lot better for it, but that's personal to me.

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Laurie, I will indeed try the 210 and 215 hybrid, the 185 juggernauts shoot reasonably well even with Large jump and light seating,

What peak accuracy round count range could one expect With N550 and 210-215g weight bullets also would there be much difference using varget and lighter 185g bullets, 500 rounds or so maybe.

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