TWIST in Ishapore .308

[Ray1946]

Don't mean to beat a dead horse, but in an earlier posting I asked if anyone knew the twist in the Ishapore .308, along with a few other questions about the rifle in general. Didn't mean to start a reloaders feud. Sorry for the confusion, but does anyone know the TWIST in the Ishapore .308? Thanks and have a good one,.................Ray

[dualsport]

I just measured mine, it's 1/12".

[Ray1946]

Dualsport; thanks so much for the info! I was hoping it would have been faster, but thats the way it is. I have been pipe-dreaming again about 600yds. with a cast bullet, kind of thinking I will stay with the .303. Have a good one,........Ray

[dualsport]

The 12" twist can be a real asset for what you have in mind. Try a good fitting heavy for caliber cb with some slow powder. The twist thing isn't quite the same when launching long heavy cbs as it is for jacketed. I'm no expert, so maybe one who can explain it will jump in.

[Multigunner]

Dualsport; thanks so much for the info! I was hoping it would have been faster, but thats the way it is. I have been pipe-dreaming again about 600yds. with a cast bullet, kind of thinking I will stay with the .303. Have a good one,........Ray

From what I hear the .303 SMLE is just coming into its own at 600 yards due to the compensation factor reducing vertical dispersion.

I haven't done any serious paper punching with the .303 beyond 300 yards yet, the owner of the land I'd been shooting on died unexpectedly and the heirs haven't settled the estate yet.
I can only go by the published material and it all seems to agree that accuracy can be better at 600-800 yards than performance at closer ranges would suggest, due to slower bullets leaving on the upwards stroke of barrel vibration so being given a touch more elevation.

I would have thought the 2A might have a 1:10 twist, but they seem to have used the 1:12 to best suit the NATO Ball of 150 gr or less. They say its a right hand twist as well, which might offset any leftwards bullet throw from action body flex.

[Mk42gunner]

I didn't measure the twist, but my 2A1 dated 1968 is definately right hand twist.


Robert

[303Guy]

From what I hear the .303 SMLE is just coming into its own at 600 yards ....Apparently it's due to the nature of the MkVII bullet and the mechanics of the SMLE that causes the bullet to travel in a spiral path which either dampens down or does not open up so that groups become 'tighter' at longer ranges, i.e. the groups don't open up with range in a linear fashion. The SMLE had a long and thin barrel. The barrel had to be "properly packed with cork" for this to be evident (which the target rifles were), or so I was told by my WWII armourer uncle. Not sure that the same applies to cast boolits or other models of Lee Enfield.

... maybe one who can explain it will jump in.It's because a cast boolit is denser and has a 'squatter' shape. It's heavier for the same length J-word and it's mass is shifted toward its circumference, making it more stable.

However, I would have thought that at cast boolit velocities, a heavier boolit that requires the 1 in 10 twist would be more suited to long ranges. Mind you, my 303 Brit seems to stabilize 245gr boolits just fine (I haven't tried them at long range).

[Ray1946]

303guy; Thanks so much for the input. I have 2 designs I am planning to play with. 1 bullet is 1.100 long and is a spitzer with a flat point, and should weigh about 180 grs. The other bullet is1.280 long and should weigh hopefully 215-220 grs. I am planning to use the 180gr. bullet for 200+300 yds. The big one I am hoping to fly to 600 yds. As you may have guessed by now, these are both nose-pour molds of my own design made for me by Colorado Shooters Supply. They really make a beautiful mold!......................Ray

[Multigunner]

Apparently it's due to the nature of the MkVII bullet and the mechanics of the SMLE that causes the bullet to travel in a spiral path which either dampens down or does not open up so that groups become 'tighter' at longer ranges, i.e. the groups don't open up with range in a linear fashion. The SMLE had a long and thin barrel. The barrel had to be "properly packed with cork" for this to be evident (which the target rifles were), or so I was told by my WWII armourer uncle. Not sure that the same applies to cast boolits or other models of Lee Enfield.

They say the post WW2 UK target shooters prefered the P-14 and No.4 for the shorter ranges and the SMLE for the longer range matches due to is compensation factor. Horizontal dispersion was usually less for the P-14 and No.4 with their stiffer actions.

The MkVII bullet used a lightweight filler in the nose, aluminum at first, then wood pulp, and even compressed paper.
This was a development of the "Velopex" express bullet, which allowed a long enough bullet for good bearing surface and a aerodynamic nose when a light weight but large caliber bullet was used for highest velocity.

I've fired a Benchrest Underhammer rifle that used duplex paper patched swaged bullets. The nose was of a harder lead alloy than the body to better hold up to hitting the air at max velocity, while the softer body upset more easily to fill the grooves.
I'm wondering if a similar process would allow a very light zinc alloy nose on a softer but more dense lead alloy body, either smooth paper patched or with grooves?

The long for its weight MkVII had excellent long range performance, outranging most every flat base bullet in its class.

Funny thing though, its volley fire range exceeded its effective range. At extreme ranges they found many bullets in the target zone that barely penetrated a cardoard target backing, and would have barely left a bruise.
Even then bullets faling like spring rain would have a disquieting effect on the enemy.

[303Guy]

Very interesting input, Multigunner.
Horizontal dispersion was usually less for the P-14 and No.4 with their stiffer actions.Was that not due to the stiffer barrels? The No.4 shouldn't be much stiffer than the No.I, if at all (I would think).


The MkVII bullet used a lightweight filler in the nose, aluminum at first, then wood pulp, and even compressed paper.
This was a development of the "Velopex" express bullet, which allowed a long enough bullet for good bearing surface and a aerodynamic nose when a light weight but large caliber bullet was used for highest velocity.It has been said and proclaimed that the lightweight filler in the nose of the MkVII bullet was to make the bullet unstable on impact, thus creating severe wounding ..... ? I have never believed that was the intent but it certainly seems to be the result. I think the design was to convert a 215gr round nose cartridge into a 174gr spitzer cartridge that suited the same rifle and had long range capability. So shoot me down if I'm wrong! (Of course, that's not to say the cunning Brits didn't have a hidden agenda in that design!)[smilie=1:

[Multigunner]

Very interesting input, Multigunner.Was that not due to the stiffer barrels? The No.4 shouldn't be much stiffer than the No.I, if at all (I would think).

It has been said and proclaimed that the lightweight filler in the nose of the MkVII bullet was to make the bullet unstable on impact, thus creating severe wounding ..... ? I have never believed that was the intent but it certainly seems to be the result. I think the design was to convert a 215gr round nose cartridge into a 174gr spitzer cartridge that suited the same rifle and had long range capability. So shoot me down if I'm wrong! (Of course, that's not to say the cunning Brits didn't have a hidden agenda in that design!)[smilie=1:

Considering previous British .303 service ammunition included hollowpoints and the FMJ MkVI ammunition was criticized for lack of wounding effect, I suspect that the added expense of manufacture of MkVII bullets would have prevented its adoption if not for its greatly increased lethality.
Still its much the same situation as the US open point sniper bullets decried as being hollow points, the tiny open point being there to increase range and accuracy rather than increase wounding effect, and the miniscule opening doing little or nothing to promote expansion anyway.

The British countered claims by the Germans by pointing out that high velocity spitzers also tumbled on impact.
The situation did lead to at least one mass execution of British riflemen captured by the Germans in WW2.

Italy also used a similar bullet in the 7.35 MM rifles in WW2.

PS
The No.4 barrels are usually stiffer, though a friend has an unusual No.4 with a barrel as slim as the SMLE barrel ( could have been a early trials barrel but the action body doesn't have a cut off).
The main difference in bullet throw and horizontal dispersion comes from the high thick left sidewall damping the action body flex.

[Pirate69]

If I have the data correct, this may help you on the minimum velocities to stabilize your bullets.




Don Miller's Twist Rule


Caliber 0.311 Inches
Bullet Weight 180 Grains
Bullet Length 1.1 Inches
Barrel Twist 12 Inches/turn
muzzle velocity 500 fps
Temperature 68 degrees Fahrenheit (59 is standard)
Pressure 29.92 inches of mercury (29.92 is standard)

Sg = 1.45

Sg shouldn't be less than 1.4. If Sg is greater than about 2.0, you may
gain some accuracy by going to a slower twist barrel.



Caliber 0.311 Inches
Bullet Weight 220 Grains
Bullet Length 1.28 Inches
Barrel Twist 12 Inches/turn
muzzle velocity 1000 fps
Temperature 68 degrees Fahrenheit (59 is standard)
Pressure 29.92 inches of mercury (29.92 is standard)

Sg = 1.44

Sg shouldn't be less than 1.4. If Sg is greater than about 2.0, you may
gain some accuracy by going to a slower twist barrel.

[mooman76]

It's not hard to figure out your twist rate. A cleaning jag and a good tight patch. Mark the cleaning rod and push it in and measur how far it goes to make a turn.

[303Guy]

I wonder how close 'Don Miller's Twist Rule' is? I use JBM Calculations and that comes up a little different. It works on the assumption (fact?) that the faster the bullet/boolit the higher the required spin is. The end result is thst a boolit at transonic velocity requires more spin than one a little slower and even less when supersonic - up to a point - then spin requirement falls off a little.

It seems that a 1-in-10 twist 303 Brit will stabilize a 245gr boolit and a 215gr bullet. I would expect a 1-in12 twist would stabilize a 200gr boolit.

[Multigunner]

I wonder how close 'Don Miller's Twist Rule' is? I use JBM Calculations and that comes up a little different. It works on the assumption (fact?) that the faster the bullet/boolit the higher the required spin is. The end result is thst a boolit at transonic velocity requires more spin than one a little slower and even less when supersonic - up to a point - then spin requirement falls off a little.

It seems that a 1-in-10 twist 303 Brit will stabilize a 245gr boolit and a 215gr bullet. I would expect a 1-in12 twist would stabilize a 200gr boolit.

In the days when relatively small bore high velocity bullets were the new kid on the block this is how they figured it



The spin of a rifle-bullet is more rapid as the twists of the rifling are shorter and the velocity of translation greater. In the Minie rifle the length of the twist was said to be 78 inches, meaning that the grooves made one complete turn in 78 inches of the barrel; in the Martini-Henry it is 1 in 22 inches, and in the Lee-Metford 1 in 10 inches. The twist of rifling may also be expressed " in calibres"— one complete turn in so many lengths of the barrel measured in calibres; and this is really the more accurate method. The proper rate of twist for any given rifle can be determined theoretically, but practically this is always arrived at by experiment. The greater the length of a bullet the greater must be its velocity of rotation, and therefore the shorter must be the spiral of the rifling in the barrel to obtain the greatest accuracy of shooting. The velocity of rotation depends on the muzzle velocity of the bullet and on the rate of twist of the rifling; as the velocity of bullets has been increased, so it has been found necessary to make the twist of the rifling more rapid.

The velocity of the motion of translation of a bullet varies with the distance from the firing-point, chiefly owing to the resistance of the air: the velocity of rotation follows the accelerations and retardations of the former, and changes with it according to the distance. It therefore follows that the translation and rotation movements cease together when the former ceases by expenditure of energy. But when the motion of translation is suddenly and completely interrupted by contact with an obstacle, then the motion of rotation continues until its energy is expended.


http://books.google.com/books?id=66a-s15TZggC&pg=PA20&lpg=PA20&dq=rate+of+twist+Lee+metford&source=bl&ots=IKniCETi0N&sig=wQzu0HYeMhXiaRQZZ4k0j2h5liw&hl=en&ei=2M3TS9rZKpGu9gTW6ui5Dw&sa=X&oi=book_result&ct=result&resnum=4&ved=0CBAQ6AEwAw
So the length of the bullet is a factor, the 174 grain MkVII requiring the same twist as the heavier 215 gr MkVI of the same length and with higher rotational speed due to higher velocity.

The shorter 144-155 gr 7.62 Ball of the 2A bullet at a higher muzzle velocity would still require less twist to obtain the same level of stability. A 1:10 twist can work with a 150 gr .303 bullet, my favorite load uses the 150 Hornady at a hair under 2600 FPS, but a slightly slower twist is better suited to the Nato Ball.

PS
According to pre WW2 literature before the MkVII bullet was adopted testing indicated that a 150 grain bullet at 2600 FPS was the optimal infantry rifle load. The US .30-06 with 150 gr bullet at 2700 FPS fell right into that category.

[35 Whelen]

I would expect a 1-in12 twist would stabilize a 200gr boolit.

I'm in the process of building a .308 with which to shoot High power out to 600 yds. I've learned that a 1-12" twist will NOT stabilize a 200 gr. bullet in fact it will only marginally stabilize the long 175 gr. match hollowpoints.
There's really no voodoo to calculating what twist will stabilize what bullet. The Greenhill Formula has been used for decades: http://www.z-hat.com/twistrate.htm or http://www.loadammo.com/Topics/July01.htm

According to the Greenhill Formula the 1.28" bullet will require a minimum 1-11.11" twist, while the shorter 1.1" bullet would require only about a 1-13" twist.

I've yet to shoot cast at 600 yds., but I believe the real issue will be transition to subsonic. It's my understanding that this is quite detrimental to accuracy. To avoid this transition, a cast bullet with a half decent ballisitc coefficient would have to have a muzzle velocity well in excess of 2000 fps.
Hopefully within a couple of weeks I'll be shooting cast at 600 yds. here at the house. All I need to do is finish this little puppy!:

Good luck,
35W

[Ray1946]

35 Whelen; Thanks so much for the info! I was on the Greenhill site the other night and got about the same results. I'm really not too concerned about the 180 gr. bullet, as I have used bullets of this weight before and shot in the low 190's at 300 yds. The 600 yd. target is the BIG deal! Using the online Greenhill site I gave the bullet a B.C. of .560. This is about the same as Lyman gives for there big 8mm bullet, I think its 323471. According to the data results, if I can get 1900 at the muzzle, I'm still good for 1200+ at 500 yds. Hopefully this would just barely dip into the subsonic at the 600 yd. mark.
The big problem as I see it would be to shoot the 88 rds. in the hot summer weather and not lead the barrel! A lot of people talk about high velocity with the latest lubes, but a lot of this falls short when you shoot this many rds. in hot summer weather.
I've got to make some bullets when I get back home. Hopefully I can send some pictures of them............................Ray

[Larry Gibson]

The .308W with 12" twist will stabilise a 200 gr RN bullet just fine. It will not, however, stabilize the 200 gr match bullets as 35 whelen points out.

The .308W with 12" twist also shoots the 175 gr MK very accurately to 1000 yards and beyond. NMC shooters were shooting the M118 (174 gr bullets of whichthe 175 MK is almost a direct copy) very well at 1000 yards with 12" twist NM M14s. I still shoot 1000 yards very well (Master level) with the 175 gr MK outof my 12" twist M1A. Granted, the 12" twist is not sufficient for the longer VLD 175 gr match bullets. An 1" twist is minimal for them.

Back to cast bullets. I also shoot a lot of 311299/314299s out of my 12" twist .308W/7.62s. At 1800 - 2200 fps they do shoot very well and unless you are at sea level or shooting in 80% humidity they hold sonic to 600 yards when shot at 2100+ fps muzzle velocity.

The 12" twist was found to be optimal for bullet stabilization under all expected conditions (arctic to desert) for the 7.62 NATO cartridge with various bullet weights (Match, Ball, AP, API, Tracer, etc.) to the considered maximum effective range of 1100 meters. The Palma Match, when restarted in the '50s, was around the current service cartridge, the 7.62 NATO. Originaly service rifles with service amunition were used and provided by the host country. Then the rule changed to allow the countries to bring their own rifles (this began the equipment race with match type rifles, originally service rifles but ten with special built rifles) but were to use the host country's issued M80 equivilent ammunition. This is why we find Palma Barrels in .308W with 13 and 14" twist as it is optimal for the 145 - 155 gr (the NATO spec for M80 bullets) bullets used in M80 type ball ammuntion.

Thus a 12" twist has been considered the "standard" twist for the 7.62 NATO/.308W cartridge since it's adption by NATO and introduction by Winchester. Several companies made commercial sporting rifles with 10" twists in .308W merely to simplify production as they were already making 10" twist .30 cal barrels. The 10" twist whilenot optimal for the .308W is adequate for most sporting applications. However, notice that even Remington, which was the first big producer of10" twist .308Ws, is now producing 12" twist .308Ws. I believe Savage is produing them also along with a 14" twist Palma barrel.

The 12" twist was standard for the FN/FAL which was the rifle the British adopted in 7.62 NATO and is no doubt why the twist of the Indian Ishapore is a 12" twst also.

Larry Gibson

[Pirate69]

Hi 303Guy,
This link has some information that may answer your question.

http://www.jbmballistics.com/bibliography/articles/miller_stability_2.pdf


I just hit a 100 posts!!!!:drinks:

[Multigunner]

Very asute observations Larry.
I'd read long ago that the standard 1:10 twist of the 1903 was not optimal for the 150 gr flat base .30-06 ball but accurate enough and the high rotational rate contributed to increased wounding effect, so much so that WW1 era ball was often prefered by hunters of the post war years over conventional sporting soft nose bullets of a heavier weight.

[303Guy]

Very informative and interesting post, Larry, thanks.

Thanks, Pirate69. I'm trying to connect but it's taking forever!:killingpc But it'll get there.:mrgreen:

[Multigunner]

I had wondered why the 1903 had a 1:10 twist when the 06 Ball was a 150 gr bullet, and only now realize it was because the 1903 version of .30 Government used a 220 gr bullet at a lower velocity.

It now seems more clear why the 06 and the German 7.92 154 gr spitzer were such mankillers. Both were relatively light high velocity bullets fired in bores with rifling originally optimized for a heavier and lower velocity bullet.
It also explains why both rifles handled heavier bullet long range , AP, and match loads so well. The rifling was already just fine for the heavy bullets.
7.62 Nato seems to limit AP loads to the same weight range as the Ball 144-150 with some extra high velocity AP going as low as 125 gr.
I suspect this is due to the expected select fire use of the M-14 and FAL type battle rifles, a heavier bullet making control more difficult.
Heavier bullet 7.62 NATO loads seem geared towards GPMG and Sniper use.

[adrians]

yep ,,,my 2a1 (i just did the cleaning rod measurement ) confirms mine to be 1-12,.
so for paper punching up to 200yds what do yall recommend?
i have the 311291 and the 31141(older) molds, i,m thinking try both huh!!!:twisted:[smilie=w::evil:

[Larry Gibson]

Try both of those bullets but I find the 311299 to be an excellent bullet in either 10 or 12" twist .308Ws.

Larry Gibson

[adrians]

watch out -- 311299 -- i,m coming for ya!.:evil::coffee::twisted:.
THX Larry