omark rebarrel

[LoneRider]

gday,i am still looking into rebarreling the old omark for long range F open.
i was toying with a 7mm fluted heavy barrel.
any recommendations on which variant of 7mm and twist ?
this rifle is for 800,900 and 1000yrd primarily.
i have another in 308 for 700yrd and under fullbore.


regards

sean.

[Flash Gordon]

gday,i am still looking into rebarreling the old omark for long range F open.
i was toying with a 7mm fluted heavy barrel.
any recommendations on which variant of 7mm and twist ?
this rifle is for 800,900 and 1000yrd primarily.
i have another in 308 for 700yrd and under fullbore.


regards

sean.

Sean,
My advice is to forget the idea,leave the Omark for .308 or .223.You need a more solid action for F/Open.I don't shoot F/Open as I shoot FTR,but I have shot alongside a lot of Australia's best F/O shooters and they don't use Omarks.A good solid action may seem to be a lot of money,but it is a one off expense,barrel replacement and ammunition components are the same for either action.
Try and meet some F/Open shooters and see what they use.Looking from the side,I would suggest a .284 Winchester or the 280 Ackley.
Welcome to long range F/Class.
Mike.

[Rinso]

Any reason behind the 7mm?
308 will shoot the distance no problem, if you want to try something different then I would suggest re-barrel to a 6.5x47 Lapua, 260AI, 6 x 47 Lapua or 6mm Dasher or similar 6BR wildcat.
These all use the same bolt face you have, are all short action suitable and have far less recoil making them much more comfortable to shoot.
A little research will show that all those have been proven at the longs many times over and whilst 7mm's shoot they have always seemed to suffer more from a lack of good bullets.
If you really like 7mm then consider the 7-08 or 7-08AI
The Omark action is not ever going to be as good as a modern custom action but it will serve the purpose, they are under rated IMHO for the price you pay for them.
Good luck

[LoneRider]

i read somewhere that 7 was the best for long shots.[could be mistaken]
the guys up here have gone from omarks to savage and remington [?] rifles,off the shelf and accurate.

sooo,that kills that idea....

what twist and projectile weight is best for those distances ?

[albow]

the guys up here have gone from omarks to savage and remington [?] rifles,off the shelf and accurate.

sooo,that kills that idea....

Hey Lonerider not sure why the other guys buying the savages or remingtons kills your idea but i can tell you the omark definitely is not a custom action but set up properly will be perfectly fine for what you want to do.

I know because i have a LR rifle for 1000yd BR built on an omark that runs my 30 cal cartridge shooting 175 SMK pills which was pipped in setting the australian lightgun 6 match aggrgate records for score and group by one point and 1/2" respectively a couple of years back by TZ with his 6BR

As far as cartridge for f open in 7mm that you could use in the omark i think most are running 284 win or 284 shehane with the 280 ackley another option, 175 or 180 grain pills and 9 twist barrel.

Don't be discouraged with using the omark

[LoneRider]

sorry mate,i was referring to going the 7mm direction.

if i stay with the 308,what twist and pill weight for that ??

[Seddo]

Give a 7-08AI a go. A mate is getting the same velocity with his 32" 7-08AI as he was with his 28-29" 284 with less powder.

[Rinso]

i read somewhere that 7 was the best for long shots.[could be mistaken]

The 7mm is popular in NRAA circles for the longs based on high BC bullets and some shoot results internationally, there is no empirical evidence that it is THE calibre for long range. If you look at LR BR results you will see that everything between 6mm and 30 cal all work out to 1k.
As Albow mentioned TZ shot the BR light gun 6 match agg's with a 6BR, closely followed by himself with an Omark based rifle.
An Omark set up properly will out shoot most shooters ability to read wind at long range. Build the rifle set it up straight and tune it well, you will do fine.
Also you don't need big optics at those ranges a good 24x40 scope or similar will do well.
If you are set on a 7mm the 7-08AI is a good choice for the Omark IMHO. Although I would give serious consideration to the various 6mm chamberings with the 6.5x47 Lapua and 260AI close behind.
I seem to remember Matt Paroz being virtually unbeatable in F Open some years ago with a 6BR as well. I also remember reading something about the latest batches of 7mm match bullets being less than perfect, this has been the biggest issue with 7mm's over the years the bullet batches are so up and down, more so than any other calibre.

[LoneRider]

thanks rinso.....good info.

[Brad Y]

Most common accurate cals being used in the world at the moment at 1000yds would be 6 dasher and 300WSM. If you want to stick to an omark, do a 6 dasher as the boltface wont work with a magnum round. Remember any caliber will have bullets blown about. Its all up to the pilot to make it work or not.

[Seddo]

It's funny how f class is ruled by 7mm's and LRBR and FLY are 6 and 30.

[albow]

Seddo

My thoughts on that is that they are different types of competitions. BR is about shooting groups and fclass is shooting scores.

As rinso said the 6mm and 30 seem to group more consistently in aggregates than the 7mm but the 7mm with the better BC probably are more 'forgiving' when picking through an f class match.

Having said that though my new HG has the 7mm barrel out of my f open rifle screwed in so with it being a cross breed BR and F class gun will no doubt shoot super high scores and itty bitty groups

[Leeroy]

Seddo

My thoughts on that is that they are different types of competitions. BR is about shooting groups and fclass is shooting scores.

As rinso said the 6mm and 30 seem to group more consistently in aggregates than the 7mm but the 7mm with the better BC probably are more 'forgiving' when picking through an f class match.

Having said that though my new HG has the 7mm barrel out of my f open rifle screwed in so with it being a cross breed BR and F class gun will no doubt shoot super high scores and itty bitty groups

I think the main reason why the 7mm doesn't do so well at LRBR is really nothing to do with the cal or cartridges, but in the bullets. As many of you would know it's quite difficult to make a long slender high BC bullet accurately. The high BC Berger VLD's have so much forming and stretching of the jacket there's no way to keep the walls uniform. I and a few others have noted the waves in the jacket walls in the nose.
The high BC makes them good for relatively large x ring score matches but not up to scratch when shooting for tiny groups..

Cheers
Leeroy

[Brad Y]

Exactly. If you can keep 10 shots in a 10 inch circle at 1000yds you have a good score in f class. 10 shots in 10 inches in BR rarely cuts the mustard. I like shooting f class and while 7mm does rule the roost at long ranges and windy conditions they are often beaten by 6mm's and good drivers at short and mid ranges.

Back to the original topic, in an older action like an omark- which are starting to get hard to obtain parts for, I would stick with something mild. Loading and unloading a 284 in it will be annoying. Plenty of good 308 based cals that will just about match the 284 anyway. 260AI 7-08AI and then the smaller 6.5x47L and down to the dasher, BRX and straight 6BR/22BR.

Still havent seen any gun as sheer accurate as anything based on the BR here. Hopefully my rechambered dasher will be kicking butt shortly- we have our first 1000yd BR of the year next weekend.

[Rinso]

It is possible to shoot small groups with a 7mm.
Jacko Bending has done so many times at 1k and I recall young Alan Fuge shooting very well with a 7mmRemMag many years ago. The 7mm's will work but as I said earlier bullets have let the 7mm down for many years and those guys results are the exceptions rather than the rule. The variation batch to batch is a nightmare for LR BR..
I would suggest that because F Open as Albow points out is a score match the 7mm bullet variations are not noticed as much because of the constantly changing aim points which are the nature of score shooting. This changing aim point would combined with wind changes make detecting the subtle differences difficult for the shooter when viewing the finished target.
BR however requires a group and as such aim points and any adjustments are vital to the end result. To expand when shooting a group I can tell you the aim point and subsequently I can see when bullets have changed impact point on the target relative to there fellows. This shows the variation in bullets.
That is why bullet batching at the longs is so important, the slight variations are the ones that ruin your group and this is evident when shooting.
Now I am not suggesting that LR BR is more difficult or better than F Open but rather that they are different. I am sure that if more F Open shooters adopted 6mm's you would see a difference in results as well. 30 Cal is probably to much recoil for most in an F Open rifle but I do recall someone doing very well with a 300WSM not that long ago.
If I wanted to build a rifle for F Open I would narrow it down to 6 Dasher, 6BRX, 6x47 Lapua, 260AI or 6.5x47 Lapua I am sure there are plenty of other suitables but this would be the list I would look at.
Why
All are based on Lapua brass
6mm's can run 103 copperheads, 6.5's 123 Scenars or 130 Bergers
Easy to manage recoil
All offer solid barrel life
Most importantly all will cover the yardages 300 to 1000 without trouble and are proven accuracy winners
Just my opinions though