Shot the 308 Corsair today

[melloroadman]

Finished up some accuracy testing with the rifle . The rifle has been tethered and regulated to 2700 psi Bullets were casted in 12 and 15 bhn lead . Sized to .30775. At 875 -906 fps at a target at 50 yards . All bullets would group a 5 shoot string at 1/2 inch or better . Weight of bullets was 88 -105 grains . Might try lower bhn levels at another time . All rifles are some what different but these mold numbers might help someone if they are thinking of buying a mold to cast their own bullets . 88 grains Ideal313249 , 96 grains Lyman 311227, 100 grains Lee 311-100-2R , 100 grains RCBS 32-98-WC .

[melloroadman]

Had two bullets that did not make the accuracy test yesterday . A 45 and a 81 grain bullet . FPS were 1076 and 926 . Tried 5 and 12 bhn lead . Were good at 30 yards but failed at 50 yards .
  Barrel was cleaned before test . Last night I inspected the barrel with a bore scope before cleaning it . The barrel had leading in the first 1 1/2 inches of the bore and it was on the thrust side of the rifling . Looks like the bullets were being striped as they entered the bore from the lead . The rest of the barrel was clean .
  These are light short bullets that are setting in the lead and travel around 3/4 of a inch before hitting the end of the lead and entering the bore . At several hundred fps. ,several thousand G's, and the start of several thousand RPM's . Might play with them at a later date .Marvin

[rsterne]

Did a few quick calculations for you.... Made a few assupmtions, but for the 45 gr. bullet jumping about 3/4" before engaging the rifling I got about 250 fps after 3/4" of travel.... Thought that info might be helpful....

I wonder how FX get away with their "smooth twist" barrels where only a few inches at the muzzle are rifled.... and the pellet (almost pure lead) has reached nearly full velocity before it begins to rotate?.... They certainly don't seem to have an accuracy problem.... As usual, more questions than answers....

Bob

[melloroadman]

Thanks . And yes I agree with what you have said . That is why I might play with this later on . But I want to enjoy what works for a while . Marvin

[melloroadman]

Well I converted the fps to mph . 170.45 mph . Marvin

[Bryan Heimann]

Did a few quick calculations for you.... Made a few assupmtions, but for the 45 gr. bullet jumping about 3/4" before engaging the rifling I got about 250 fps after 3/4" of travel.... Thought that info might be helpful....

I wonder how FX get away with their "smooth twist" barrels where only a few inches at the muzzle are rifled.... and the pellet (almost pure lead) has reached nearly full velocity before it begins to rotate?.... They certainly don't seem to have an accuracy problem.... As usual, more questions than answers....

Bob

i think it might work in part because the smooth twist concept is like a rifled choke.  grooves are larger than the bore, but the smooth twist creates something more like ridges that are tighter than the bore and smoother that grooves, plus i think it creates a tapered effect.  the "ridges" may grow taller or more pronounced as the pellet gets closer to the muzzle.  just hypothesizing

[rsterne]

I have no idea how the "smooth twist" barrels are made.... but it would make no sense for the rifling grooves to be larger than the preceeding bore as the pellet would then have to expand to engage them after having slid for maybe 20" through a parallel tube.... I'm guessing that the rifling lands must protrude into the bore, likely by a hammer forging process....

My point was that the "smooth twist" barrel was in some ways similar to the idea of a bullet having to jump from the smooth, groove sized, lead into the rifled portion of the barrel as melloroadman was describing.... It is possible that FX's rifling isn't just a sudden change from no rifling to an 1 in XX twist, but that the lands first protrude into the bore parallel (or nearly so) to the bore and then progressively twist.... I would think that would be pretty difficult to achieve in just a few inches, but who knows....

Bob

[melloroadman]

Tethered & regulated at 2700 psi, bi pod , on table , target 50 yards . 117 grain 15 bhn bullets out of the Lyman 311359 mold . Was able to get MOA 5 shot string 3 times out of 120 bullets that were sized to .30775 , sorted , and weighed. Would easily group 1 inch or better . Have yet to chrony any of these bullets that were accurate but will on a rainy day and then check out there BC  as well .Here is a picture of the bullets .

And here are the other mold numbers that have worked for me .Marvin
88 grains Ideal313249 , 96 grains Lyman 311227, 100 grains Lee 311-100-2R , 100 grains RCBS 32-98-WC .

[melloroadman]

Well I seated the 45 and 81 grain bullets in as far as they would go and it made no difference at all . What ever it is it is . I have 5 good bullets for this rifle now and these two might work out in one of my other two 32 caliber rifles . When the weather gets bad again I will chrony the five and run them on the BC calculator .Marvin

[melloroadman]

At the coffee table at the range . I was asked if I had tried to load  any of these bullets as well as the .357 bullets that had not worked  backwards { would give me a big melplate} ? I think I will give it a try .Marvin

[melloroadman]

Tethered and regulated to 2200 psi. Bullets 15 bhn sized to .30775 . At shot 4 I turned the tank valve off and shot the fifth shot and then read the pressure gauge . It looks as if it is using 100 psi per shot on all the bullets or so close to it that it really will not make any difference to me . This was done indoors because of the weather so the two inaccurate bullets were not tested for accuracy shot back wards . But I did chrony them in case they do work out latter . I will run the numbers on the BC  chart latter as well  .Marvin

[realpolitik]

I would be interested to know the results of the backwards projectiles.

[melloroadman]

Me too . But it is rainy and cold out side . The first day I get a little sun to keep me warm in the 40-50 degree weather I will give them a try in one of the Corsairs .Marvin