Modern powders and barrel harmonics in 303's

[CINDERS]

Just a question; can modern powders set up a different harmonics in the barrel V 's the old MK VII ammo.
I am just thinking as a load I am working on develops 3,000 psi less than the AR 2209 (Varget) even though it is projected at 2440 fps which is the standard fps for ball ammo.

I realise it is the same fps but if the burn time is faster between the strands verses powder if it gets to the 2440fps quicker does this alter the wave sequence I know the vibration will not get ahead of the projie.

I will explain it this way; say Ball ammo exits the muzzle in 2 mili seconds after ignition and the reloads even though going at the same terminal velocity due to the faster burn rate get to the muzzle in say 1.5 mili seconds will this alter the barrel harmonics and groups ?

Thanks in advance for your thoughts on this

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[Parashooter]

Can you say "butterfly wing"? Each shot is the end result of a chaotic system. Barrel time is just one variable - and that can vary more from shot to shot than as a result of changing powder. Note how the QuickLOAD barrel time predictions for a flock of very different suitable powders vary only by a maximum of ~0.14 millisecond.

Cartridge : .303 British
Bullet : .311, 174, Sierra HPBT MatchK 2315
Cartridge O.A.L. L6: 3.075 inch or 78.11 mm
Barrel Length : 25.0 inch or 635.0 mm

Predicted Data for Indicated Charges of the Following Powders.

Matching Muzzle Velocity: 2440 fps or 743 m/s

Powder type Filling/Loading Ratio Charge Charge Vel. Prop.Burnt P max P muzz B_Time
% Grains Gramm fps % psi psi ms
-----------------------------------------------------------------
Vihtavuori N150 98.1 42.2 2.74 2440 98.8 41000 7134 1.392
Hodgdon H4350 97.8 44.4 2.88 2440 91.5 38257 7901 1.405
Accurate 2700 96.4 45.4 2.94 2440 91.4 45130 7172 1.350
Vihtavuori N135 95.4 39.5 2.56 2440 100.0 41026 6637 1.397
Ramshot Hunter 95.2 46.3 3.00 2440 90.9 37879 8023 1.414
Accurate 4064 95.1 40.6 2.63 2440 99.6 38945 7284 1.458
Vihtavuori N550 94.6 44.1 2.86 2440 93.5 37391 7941 1.430
Ramshot BigGam 93.6 42.7 2.77 2440 95.5 37939 7680 1.417
Winchester 760 92.9 44.9 2.91 2440 90.0 38120 7917 1.413
IMR 4064 -- 92.7 40.0 2.59 2440 96.3 41755 7159 1.379
Hodgdon V-GET 91.8 40.6 2.63 2440 95.9 41534 7255 1.377
Vihtavuori N540 91.7 42.3 2.74 2440 97.1 42671 7240 1.376
Vihtavuori N140 91.3 40.1 2.60 2440 99.8 41795 6799 1.382
Hodgdon H4895 91.3 40.3 2.61 2440 98.7 40227 7090 1.387
Hodgdon H380 90.8 42.4 2.75 2440 94.1 40055 7583 1.409
IMR 4320 -- 90.8 40.8 2.64 2440 96.2 40093 7295 1.384
Vihtavuori N133 90.7 37.9 2.46 2440 100.0 45114 6169 1.344
Hodgdon H414 89.4 43.5 2.82 2440 91.6 39190 7769 1.414
IMR 4895 -- 88.7 39.2 2.54 2440 97.7 38856 7276 1.394
Accurate 2495 88.7 38.3 2.48 2440 100.0 39433 6947 1.458
Alliant Reloder-15 88.5 40.4 2.62 2440 95.6 39452 7499 1.414
IMR 3031 -- 87.4 37.3 2.42 2440 100.0 38193 6951 1.422
Accurate 2520 86.4 40.6 2.63 2440 99.0 39362 7232 1.427
Vihtavuori N130 85.8 36.6 2.37 2440 100.0 46164 6054 1.341
Hodgdon Benchmk 85.0 38.2 2.48 2440 98.9 43851 6768 1.360
Hodgdon BL-C2 83.7 41.7 2.70 2440 97.3 38650 7542 1.425
Accurate 2015 83.5 36.9 2.39 2440 100.0 43725 6318 1.379
Alliant Reloder-12 83.5 38.9 2.52 2440 100.0 42607 6652 1.371
Vihtavuori N120 83.0 34.6 2.24 2440 100.0 50192 5515 1.306
Vihtavuori N530 82.9 38.1 2.47 2440 98.1 41176 7097 1.390
Ramshot TAC 82.8 39.6 2.57 2440 98.0 40695 7187 1.395
Hodgdon H322 82.6 36.6 2.37 2440 99.9 41195 6721 1.383
IMR 4198 82.2 33.7 2.18 2440 100.0 46218 5840 1.323
Accurate 2460 81.9 40.1 2.60 2440 98.8 41674 7039 1.407
Alliant Reloder-10x 81.3 35.0 2.27 2440 100.0 43417 6280 1.377
Winchester 748 81.1 39.8 2.58 2440 98.3 38651 7290 1.412
Accurate 2230 80.8 39.5 2.56 2440 98.9 42310 6929 1.393
Hodgdon H4198 80.0 34.3 2.22 2440 100.0 46650 6096 1.320

[CINDERS]

Thanks para I have the same program do you know if they need up dating every now and then as we now have AR 8208 (ADI) and I am not that conversant with this program to go entering burn rates etc.
Thanks for the input, still do you think the variation would adversely affect groupings just going through the elimination process trying to sort out a rifle.

[Bindi2]

AR 2209 is not Varget 2208 is.The switch over from 2208 to 2209 is with 180+ gn projectiles. My work showed 2206 had higher pressure than 2208 for same velocity and 2209 did not achieve the same velocity stability until the heavier projectiles were used. Cinders do a ladder test and dont get hung up on the FPS having to be 2440. Your best group maybe somewhere else,use that and construct a range chart.Unless you have Mk7 projectiles 2440fps with your projectiles will not match the sights except at the shorts. If you are using peeps your chart with a 300 zero is all you need. Will just be a little harder with the open U. Build the load you cannot duplicate Ball and cordite.
Muff probably wont agree with me but that is tuff.

[muffett.2008]

You stuffed up there Bindii, I do agree..........either you finally got something right, or I'm coming down with something

[Rastis]

G'Day,
I'm using 42 grains of 2208 with a 174 grain boatail projectile. I use 650 yards on the sight for the 600m range, 550 for 500m and about 325 for 300m. 200 and closer is good enough for me. Couldn't tell you what size group it shoots at 100, but a fortnight ago prone unsupported at 600 it shot 10 shots for a 31.

Rastis.

[Bindi2]

Haha you must be coming down with something, you have been quite lately so thought it was time to rattle your tree

[CINDERS]

Varget is the name the USA gives to our 2208 I use 09 - 08 in the 303's along with some experimental loads which I hope will bear fruit for the forum but time will tell, I wanted to incorporate AR 8208 (not 2208) into the quick load program for the 308's we shoot as the ADI site only goes on 24"brls and we use 30" for the 308's but I do not know how to get the burn rates into the program etc. I have run a few things min-max different primers and crimping light-med and so on with the 303's.
The weapons like the Hornady 150's with 42 gns '08 about 1/16"cannular showing and light crimp with a FED 210 primer, will get down to the ladder tests just have a weapon that has a mind of its own

My original Q was the rates between original stick Mk VII ball ammo and the modern powders and barrel harmonics. Thanks for the input so far

[Bindi2]

Get a chronny a sheet of graph paper and load 3 cases at each powder weight. weights across the bottom and create the graph averageing each 3 and plot .Keep lowest FPS figure spread looking for the horozontal line of groups before it goes vertical. The node will be apparent. If the node is not a tight group change something and check again.

[Bruce_in_Oz]

Without a clone of the old Mk7 bullet you will NEVER match Mk7 ball for anything except a few distances per loading.

The primer alone can start the bullet moving (not very far, mind you).

The combustion of the propellant determines how the projectile enters the rifling. MOST of the "propellant" effect" will take place in the first micro-seconds. This is partly because of how that combustion makes the bullet enter the throat. A "fast" propellant (like Cordite) will cause the bullet to "hammer" into the rifling; ("hammer" being a comparative term).

Remember that, on a Mklll* SMLE, the ENTIRE bedding and sighting system was built to optimise performance with ONE cartridge; Mk7 BALL, complete with Cordite propellant and a 174gn, flat-based, composite-cored FMJ bullet. The changes to the rifle: sights, bedding etc. required with the change from round-nosed Mk6 to spitzer Mk7 are significant. Mind you, there was so much Mk6 ammo left over from WW1, that it was still being shot off into the 1930s.

Use of a modern, thin-jacketed, HP boat-tail over a measure of a slower-burning, coated, granular, nitro-cellulose propellant MAY duplicate the muzzle velocity, but is VERY unlikely to come anywhere near matching the vibration / wave patterns in the barrel.

Not only that, but the slinky boat-tail, even if a precise 174gn and launched at the precise MV of Mk7 ball, will have a seriously different trajectory down-range. It will certainly have a different MPI even at 100yds. due to the different barrel vibration modes. At 600 yds., your guess is as good as mine. Be prepared to develop your own custom range table.

Furthermore, as noted previously, a steady diet of Boat-tails in a "pre-loved" Lee-Enfield, is a recipe for accelerated throat erosion.

It appears the both the Russians AND the Yugoslavs make a .311", 174gn FLAT-BASED ball projectile. As far as I am aware, NEITHER has the aluminium "nose-filler" that is an essential feature in the Mk7 bullet. Users of 7.7mm Arisakas and 7.63mm Belgian / Argentine Mausers should also be interested in these bullets.