Bob Kingsbury
New member
Is a 13" twist to fast for 68'S in .825 jackets. Can they be overstabilized
by a half inch more twist, and how is it seen on the tgt.?
by a half inch more twist, and how is it seen on the tgt.?
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Frank Green
- Thread starter Bob Kingsbury
- Start date
F
Frank Green
Guest
Bob, I don't think it would hurt at all. That half of an inch faster twist if anything would help not hurt. Going to slow a twist will hurt more than anything else.
Here is one extreme example. Years ago ( around 1990) I was starting to play with a Ar-15 for service rifle matches (I know it's not a bench gun so bear with me). It was just a rack Colt A2 model with a 1-7 twist barrel. Shooting 69gr. Sierra's the gun shot fine around 3/4" groups off the bench. One day I ran out of my handloads and had a couple of boxes of 55gr. ball ammo (yes the lowest form of ammo on earth!) and proceeded to shoot some thru the gun. I was getting 2 out of 5 rounds going thru the target sideways at a 100yds! I thought twist to fast? I knew it was way faster than what was needed with 55gr. bullets as we all know they will stabilize in a 14 twist.
Any ways went back to the range with more handloads and 69gr. bullets and also loaded up some 52gr. Hornady Match bullets and some more ball ammo and a clean gun. Shot the 69gr. Sierra's first. Gun shot fine like before. Shot some 55gr. ball ammo again and again the same results one or two rounds going thru the target sideways at a 100yds. Perfect keyholes. I then shot the handloads with 52gr. Hornady Match bullets. Guess what? No bullets going thru the target sideways and the gun was grouping right around 3/4" just like the 69gr. Sierra's.
The above paragraph is a real story and no B.S.! What was the difference? Quality of the ammo and above else the quality of the 52gr. Hornaday bullet vs. the crap ball ammo (and we send guys to war with this stuff!)
Do I think you can over stabilize the bullet? I don't think that is the correct terminology for it but I guess that is what we will call it for now.
I don't think the 55gr. bullets we're over stabilized but the real problem was the run out the factory loaded ammo had and the quality of the bullet (not to mention the $7 dollar Colt AR-15 barrel didn't help anything at all). The more run out your loaded ammo has/poor quality bullet the faster twist and in this case the crummy barrel/long throat/poor chamber was a receipe for how poorly it shot. The more run out the ammo has with the poor quality bullet as it makes the jump into the rifling of the barrel the more chance it has to enter the barrel not in a straight line of it's axis etc....This ends up putting a premature wobble on the bullet. In this case it actually caused the bullets to go thru the target sideways at times. In other cases it would cause your groups to get bigger as the bullets go down range.
Did that make sense?
Another example is guys shooting palma rifles. All palma guns have to be .308 style chambers. If you make the Palma team and you shoot in a palma match and every time the international palma matches are held by a different country and you travel to that host country you we're not allowed to bring your own ammo the host country supplied the ammo and usually it is 7.62 ball ammo (this might have changed but don't know for sure). A lot of guys shooting palma rifles shoot a 1-13 to a 1-14 twist barrel. With the most ball ammo running around 147-155gr. weight and of being poor quality the slower twist helped with accuracy vs. running a faster twist etc....This is why places like Sierra came out with the 155gr. palma bullet and you have Berger making 155's, Lapua etc...now. I shoot a 1-12 twist barrel on my palma gun. Why? Gives me a choice to shoot a broader range of bullet weights from the 155's up to 190's. If I we're to show you targets shot with the 155's and targets shot with the 175's you wouldn't be able to tell me which target is which. Accuracy is excellent.
The moral of this long winded story. Shooting a good quality bullet in a slightly faster twist isn't not going to hurt you but shooting a to slow of a twist will.
Talking to one of the bullet makers a couple of weeks ago we got deep into this subject and 6mm bench guns and came up to the same conclusion and agreed that even a 1-14 twist is on the ragged edge depending on what bullets you are shooting. Going to a 1-13.5 or even to a 1-13 wouldn't hurt in fact might help. Especially in different climate conditions and wind etc...
Give me a call. I can give more examples than space to keep writing a book. Sorry for going on and on and on.
Later, Frank
262-649-1574
Later, Frank
Here is one extreme example. Years ago ( around 1990) I was starting to play with a Ar-15 for service rifle matches (I know it's not a bench gun so bear with me). It was just a rack Colt A2 model with a 1-7 twist barrel. Shooting 69gr. Sierra's the gun shot fine around 3/4" groups off the bench. One day I ran out of my handloads and had a couple of boxes of 55gr. ball ammo (yes the lowest form of ammo on earth!) and proceeded to shoot some thru the gun. I was getting 2 out of 5 rounds going thru the target sideways at a 100yds! I thought twist to fast? I knew it was way faster than what was needed with 55gr. bullets as we all know they will stabilize in a 14 twist.
Any ways went back to the range with more handloads and 69gr. bullets and also loaded up some 52gr. Hornady Match bullets and some more ball ammo and a clean gun. Shot the 69gr. Sierra's first. Gun shot fine like before. Shot some 55gr. ball ammo again and again the same results one or two rounds going thru the target sideways at a 100yds. Perfect keyholes. I then shot the handloads with 52gr. Hornady Match bullets. Guess what? No bullets going thru the target sideways and the gun was grouping right around 3/4" just like the 69gr. Sierra's.
The above paragraph is a real story and no B.S.! What was the difference? Quality of the ammo and above else the quality of the 52gr. Hornaday bullet vs. the crap ball ammo (and we send guys to war with this stuff!)
Do I think you can over stabilize the bullet? I don't think that is the correct terminology for it but I guess that is what we will call it for now.
I don't think the 55gr. bullets we're over stabilized but the real problem was the run out the factory loaded ammo had and the quality of the bullet (not to mention the $7 dollar Colt AR-15 barrel didn't help anything at all). The more run out your loaded ammo has/poor quality bullet the faster twist and in this case the crummy barrel/long throat/poor chamber was a receipe for how poorly it shot. The more run out the ammo has with the poor quality bullet as it makes the jump into the rifling of the barrel the more chance it has to enter the barrel not in a straight line of it's axis etc....This ends up putting a premature wobble on the bullet. In this case it actually caused the bullets to go thru the target sideways at times. In other cases it would cause your groups to get bigger as the bullets go down range.
Did that make sense?
Another example is guys shooting palma rifles. All palma guns have to be .308 style chambers. If you make the Palma team and you shoot in a palma match and every time the international palma matches are held by a different country and you travel to that host country you we're not allowed to bring your own ammo the host country supplied the ammo and usually it is 7.62 ball ammo (this might have changed but don't know for sure). A lot of guys shooting palma rifles shoot a 1-13 to a 1-14 twist barrel. With the most ball ammo running around 147-155gr. weight and of being poor quality the slower twist helped with accuracy vs. running a faster twist etc....This is why places like Sierra came out with the 155gr. palma bullet and you have Berger making 155's, Lapua etc...now. I shoot a 1-12 twist barrel on my palma gun. Why? Gives me a choice to shoot a broader range of bullet weights from the 155's up to 190's. If I we're to show you targets shot with the 155's and targets shot with the 175's you wouldn't be able to tell me which target is which. Accuracy is excellent.
The moral of this long winded story. Shooting a good quality bullet in a slightly faster twist isn't not going to hurt you but shooting a to slow of a twist will.
Talking to one of the bullet makers a couple of weeks ago we got deep into this subject and 6mm bench guns and came up to the same conclusion and agreed that even a 1-14 twist is on the ragged edge depending on what bullets you are shooting. Going to a 1-13.5 or even to a 1-13 wouldn't hurt in fact might help. Especially in different climate conditions and wind etc...
Give me a call. I can give more examples than space to keep writing a book. Sorry for going on and on and on.
Later, Frank
262-649-1574
Later, Frank