TR and Palma Shooters:
- Thread starter Obtunded
- Start date
rnbra-shooter
CGN Ultra frequent flyer
- Location
- New Brunswick
For no particularly good reasons, other than it was standard practice at the time and known to work, all but one of my TR barrels have been MacLennan 1-14" twist, .299"x.307", four-groove buttoned barrels. Note that this originated from early-90s wisdom as to what was the right barrel, and this is what was found to best shoot sloppy issue ammunition (IVI and DA). When we went to good bullets (Sierra 155s etc), it was found that these barrels also worked well with good bullets too.
The most common barrel at that time other than .307" MacLennans, was the .3065"x.298" Krieger (1-13" twist IIRC). American Palma shooters really liked that barrel too. The wisdom was that the very short bearing surface of the Sierra 155 made it advantageous to use a particularly tight (.3065 Krieger, .307" MacLennan).
I think that an understanding has developed since then that with good bullets, it is not necessary to squash them down so much, so .3075" and .308" barrels are often spec'd these days.
If I were to be buying a new barrel today, for 155-only use I'd look for something like a 1:13"-1:14" twist, .3075" or .308" bore. But I would be sorely tempted to think about getting something that would also work with Berger 185 VLDs or 210s, in case I ever wanted to shoot US Palma (which has no bullet weight limit) or F/TR (also no bullet weight limit). A 1:13" twist might be just the right tradeoff, it gives a Miller stability factor of:
Berger 155.5 @ 3000fps, Sg = 1.29 - OK
Berger 185VLD @ 2850fps, Sg = 1.14 - likely fine
Berger 210 @ 2700fps, Sg=1.06 - likely too marginal
(edit - Tom's 1:12.5" Bartlein would probably shoot all of these bullets wonderfully - Sg=1.15 for the Berger 210)
The most common barrel at that time other than .307" MacLennans, was the .3065"x.298" Krieger (1-13" twist IIRC). American Palma shooters really liked that barrel too. The wisdom was that the very short bearing surface of the Sierra 155 made it advantageous to use a particularly tight (.3065 Krieger, .307" MacLennan).
I think that an understanding has developed since then that with good bullets, it is not necessary to squash them down so much, so .3075" and .308" barrels are often spec'd these days.
If I were to be buying a new barrel today, for 155-only use I'd look for something like a 1:13"-1:14" twist, .3075" or .308" bore. But I would be sorely tempted to think about getting something that would also work with Berger 185 VLDs or 210s, in case I ever wanted to shoot US Palma (which has no bullet weight limit) or F/TR (also no bullet weight limit). A 1:13" twist might be just the right tradeoff, it gives a Miller stability factor of:
Berger 155.5 @ 3000fps, Sg = 1.29 - OK
Berger 185VLD @ 2850fps, Sg = 1.14 - likely fine
Berger 210 @ 2700fps, Sg=1.06 - likely too marginal
(edit - Tom's 1:12.5" Bartlein would probably shoot all of these bullets wonderfully - Sg=1.15 for the Berger 210)
Brutus
CGN Ultra frequent flyer
On my Wichita IIRC, it carries presently a Krieger in 1 in 13 twist, 29.5 inch length.
I am too new to this sport to offer informed opinion, but the vendor I purchased it from stated this twist was 155 grain "friendly."
I do not know the land & groove diameter.
I launch 155 Lapua Scenars out of it, but I think I need more load development though. (2850 too slow?)
Will be tagging this thread for interest.
Cheers......
I am too new to this sport to offer informed opinion, but the vendor I purchased it from stated this twist was 155 grain "friendly."
I do not know the land & groove diameter.
I launch 155 Lapua Scenars out of it, but I think I need more load development though. (2850 too slow?)
Will be tagging this thread for interest.
Cheers......
FFIW, I'm shooting a 155.5 Bergers out of a 1-12" 5C Broughton (f/tr gun). That rilfe shoots very well. Russel Simmons won the F Class F/Tr division shooting the same 155.5 Berger out of a 1-14". (unsure of rifling config.) I think barrel pickiness has lessened as the days of issue ammo dissappear.
rnbra-shooter
CGN Ultra frequent flyer
- Location
- New Brunswick
FWIW, Matt's .308 is probably one of the better shooting .308 F/TR rifles in Canada. And the Russel Simmons that he mentions, won the F-Class World Championships F/TR division this July in Bisley (so his rifle is probably shooting fairly well too...!)
twist rate for 155gr VLDs
FWIW, I have had some problems at 1000 yds using a Stolle Panda with Krieger 14 twist 4 grooves .3075x.298 and Lapua Scenar 154gr bullets. It performs very well up to 900 yds but the groups open up more than expected at 1000 yds. No problems at all distances with a similar load and Sierra bullets.
My Musgrave has a Krieger 13 twist 4 grooves .3075x.298, no problems at all at any distance with any of the bullets.
My next barrel (used exclusively with 155gr bullets) will be a true 13 twist for the reasons mentionned above.
Gale Stewart
Quebec city, QC
Canada
FWIW, I have had some problems at 1000 yds using a Stolle Panda with Krieger 14 twist 4 grooves .3075x.298 and Lapua Scenar 154gr bullets. It performs very well up to 900 yds but the groups open up more than expected at 1000 yds. No problems at all distances with a similar load and Sierra bullets.
My Musgrave has a Krieger 13 twist 4 grooves .3075x.298, no problems at all at any distance with any of the bullets.
My next barrel (used exclusively with 155gr bullets) will be a true 13 twist for the reasons mentionned above.
Gale Stewart
Quebec city, QC
Canada
Thanks guys, One question though... I totally understand the rationale behind the tight bores when we were in an era where IVI et al, was issued at your matches, but with the advent of the triple nickels and the other superlative palma bullets, is the tight bore based on any real comparison of accuracy or is it merely a case of "don't fix what aint broke"?
I ask this because the Team Captain for Team Canada to Brisbane is watching with fervent interest. I'm an F-Open shooter and I go for the best ballistic coefficient I can shoot for a given calibre. I am just not able to provide any credible real-world experience, only a "market survey" of sorts...
I ask this because the Team Captain for Team Canada to Brisbane is watching with fervent interest. I'm an F-Open shooter and I go for the best ballistic coefficient I can shoot for a given calibre. I am just not able to provide any credible real-world experience, only a "market survey" of sorts...
Obtunded,
Here is a good read on the subject of barrel bore (and throat) size which is a safety concern. Although not dated it was instrumental in the making of the rule 150 at Bisley and also for us in Canada.
www.triplej.com.au/pdfpages/pressure_factors.pdf
Hope it helps,
Gale Stewart
Quebec city, QC
Canada
Here is a good read on the subject of barrel bore (and throat) size which is a safety concern. Although not dated it was instrumental in the making of the rule 150 at Bisley and also for us in Canada.
www.triplej.com.au/pdfpages/pressure_factors.pdf
Hope it helps,
Gale Stewart
Quebec city, QC
Canada
As one can see from the UK test, things like presure are easy to measure, and the paramaters are well known, and have been so for almost 100 years. Barrel diameter (too tight) has little effect on pressure. It can cause damage to the bullet because the lead core is less elestic than the jacket.
I specd .307 for the RATON McLennen palma barrels because it seemed like a reasonable compromise between the .308 needed for the Sierra bullets (.3084") and the IVI bullets (not round and a variety of diameters). If I was doing it today, I would probably choose .3075.
Part of the barrel dimension issue is the ratio of land and goove widths. This is what determines how much bullet metal gets displaced and the effect on pressure. A .3065 x .298 barrel (very tight) with wide grooves can displace less bullet metal than a bigger barrel with narrow grooves.
The bigger concern for pressure is throat length and diameter. In England they worry about this because the shooters use factory made ammo. They have to make barrels to match the ammo. here we do it the other way around. We make ammo to work well in our barrel. The throat length of our barrel does not matter because we always load our ammo to be, say, 20 thou off the rifling. For us, throat length determines bullet seating depth, which effects case capacity, which effects pressure if we have a long VLD bullet seated too deep.
Note that your throat position changes with wear. It typically moves forward 5 to 10 thou a year.
But the concern is accuracy. Some barrels are more accurate than others. The hole drilled through the bar of steel is not perfectly straight. On a match quality barrel it is almost perefect. I have seen many barrels where the bore was banana shaped, inside the barrel. Given 100 "identical" barrels, a few will be outstanding and a few won't shoot well. the rest are in between. The range of variation is less in top quality barrels, but they all have a range of accuracy.
Also, some "identical" barrels will shoot a particular bullet better than another. This is why it is so important to try several bullets, to see what your barrel "likes".
Twist is not an issue. If twist is inadequate, the short range grouping will be poor. A bullet gains stability as it slows down, so twist problems are not long range problems. I have yet to find a 155 VLD that will not work in a 1-14 at 2950 fps.
Most of my barrels are 1-13.
Long range problems are usully a time of flight problem. Some bullets start to do funny things at a certain point in time (think harmonics). If you drive the bullet a bit faster, that point in time is after 1000 yards.
At long range the bullet is coming down a bit point up and a bit yawed. That is when the wheels can come off. A faster twist will cause the bullet to be more point up. A slower twist bullet will have more yaw. No real advantage of one over the other. But a faster bullet will have leass of both at 1000 yards. A big advantage.
I use a 32" barrel and a compressed load of N150 to get over 3000fps with a 155.5.
I specd .307 for the RATON McLennen palma barrels because it seemed like a reasonable compromise between the .308 needed for the Sierra bullets (.3084") and the IVI bullets (not round and a variety of diameters). If I was doing it today, I would probably choose .3075.
Part of the barrel dimension issue is the ratio of land and goove widths. This is what determines how much bullet metal gets displaced and the effect on pressure. A .3065 x .298 barrel (very tight) with wide grooves can displace less bullet metal than a bigger barrel with narrow grooves.
The bigger concern for pressure is throat length and diameter. In England they worry about this because the shooters use factory made ammo. They have to make barrels to match the ammo. here we do it the other way around. We make ammo to work well in our barrel. The throat length of our barrel does not matter because we always load our ammo to be, say, 20 thou off the rifling. For us, throat length determines bullet seating depth, which effects case capacity, which effects pressure if we have a long VLD bullet seated too deep.
Note that your throat position changes with wear. It typically moves forward 5 to 10 thou a year.
But the concern is accuracy. Some barrels are more accurate than others. The hole drilled through the bar of steel is not perfectly straight. On a match quality barrel it is almost perefect. I have seen many barrels where the bore was banana shaped, inside the barrel. Given 100 "identical" barrels, a few will be outstanding and a few won't shoot well. the rest are in between. The range of variation is less in top quality barrels, but they all have a range of accuracy.
Also, some "identical" barrels will shoot a particular bullet better than another. This is why it is so important to try several bullets, to see what your barrel "likes".
Twist is not an issue. If twist is inadequate, the short range grouping will be poor. A bullet gains stability as it slows down, so twist problems are not long range problems. I have yet to find a 155 VLD that will not work in a 1-14 at 2950 fps.
Most of my barrels are 1-13.
Long range problems are usully a time of flight problem. Some bullets start to do funny things at a certain point in time (think harmonics). If you drive the bullet a bit faster, that point in time is after 1000 yards.
At long range the bullet is coming down a bit point up and a bit yawed. That is when the wheels can come off. A faster twist will cause the bullet to be more point up. A slower twist bullet will have more yaw. No real advantage of one over the other. But a faster bullet will have leass of both at 1000 yards. A big advantage.
I use a 32" barrel and a compressed load of N150 to get over 3000fps with a 155.5.
Last edited:
maple_leaf_eh
CGN Ultra frequent flyer
bulldog284
CGN Regular
- Location
- pigeon hill
my f/tr barrel is a krieger 307x298 shoots the bergers very well and the sierras,but for the life of me i cant get the lapuas to shoot at all. Darin
maple_leaf_eh
CGN Ultra frequent flyer
bulldog284
CGN Regular
- Location
- pigeon hill
no i did not try them with that much jump i belive the most i jumped them was 15 thou.
bulldog284
CGN Regular
- Location
- pigeon hill
ganderite
is this normal for the lapuas?i was thinking it might have been because of the tight bore that i had?the reason i say this is because i have a savage ftr and it loves the 155scenars and jamed into the lands a lot it will consistently shot half minute groups out to 600meters if i do my part.cant even come close to that with my custom rifle with a krieger.but a berger or a sierra and things change.. Darin
is this normal for the lapuas?i was thinking it might have been because of the tight bore that i had?the reason i say this is because i have a savage ftr and it loves the 155scenars and jamed into the lands a lot it will consistently shot half minute groups out to 600meters if i do my part.cant even come close to that with my custom rifle with a krieger.but a berger or a sierra and things change.. Darin
Lapua GB491's have shot as well as any bullet with a varity of OALs, from 40 thou. off to 20 thou into rifling. It doesn't mean that your rifle will shoot them at all, as this is the nature of shooting. I think, generally, that a more generous leade is better, i.e Rule 150 chamber, although many fine results are obtained with Obermeyer specs.
Regards,
Peter Dobson
Hirsch Precision Inc.
Lapua in Canada, officially
Regards,
Peter Dobson
Hirsch Precision Inc.
Lapua in Canada, officially
