Re barrel Omark 44B

[leadlauncher]

G,day,

I want to replace the original barrel in my Omark44B which is 1:14 twist.

What is the general consensus. What brand, length, grooves, twist etc for F Standard with HBC 155 grain ?

Would it be better to set up for FTR, with say a faster twist ?

Generally speaking, would a rifle set up for FTR, and able to take advantage of using heavy bullets with better BC than the .462 of the HBC 155 grain, be a better or more accurate proposition at say 700, 800 & 900 yards?

Not expecting miracles, just want the best for the bucks. To me the most important things are (1) recoil at the lower end (2) accuracy at 900 yards. Any advice for this novice is well appreciated.

cheers

[williada]

Leadlauncher, you can really get those old Omarks performing well, but because they are not as robust as other actions and the older barrel’s chamber dimensions, particularly in the throat are not optimum in Omark barrels it would be a good idea to get an adapter so you can custom fit and chamber.

In fact the chrome moly Omark barrels in 44B dimension are fine barrels re-fitted to an adapter. I did of course slug and lap these and their steel and hardness were as good as anything on the market today. If you have access to older barrels, then I suggest that the Black Mountain (Lithgow) barrels are too tight for the HBC some of which had groove diameters down as low as .3060” and we designed for the slightly smaller diameter 7.62mm 144 grain projectile. On the other hand, the early Shultz and Larson barrels are great for HBC as their dimensions are larger and closer to a groove diameter of .308”. However Shultz and Larson changed hands and internal dimensions were brought in line with modern thinking and came out with barrels in .3074” groove for the new British projectile that was similar in shape to the old Sierra 155. But they changed their old profile which the latter Omark 44B barrels were closer to, making them a skinnier and there was not much on the reinforce to adapt them. These later Shultz barrels shot brilliantly for 200 rounds then fell apart because the steel was soft in the few I had. I got six of them form Peter Hallet and they all went the same way back in the day. But I did buy the last VRA stock of about six barrels of the Omark barrels made by MAB in chrome moly for experimental purposes and they were excellent quite a few years back. Percy Pavy gave me many 44B barrels which I adapted and rechambered and used in a large schools program when Bruce Blanchonet was VRA Secretary. We did this as a free service to get young people going.

Herb McRorie was making a few adapters out of old Omark barrel stubbs but if people go down that path then they need to certified by a mechanical engineer, hardness and crack tested. Herb gave the practice away because of risk. Nielson made some adapters and I know of the odd failure. So be careful in buying a second hand rifle with an adapter.

Assuming you can get a suitable adapter, then a longer 30” barrel is better than the older 27 ½” jobs to get a bit more velocity to be competitive in FTR. I feel the number of joints and short thread length into the action with an adapter will not support longer barrels as well. Given you want to shoot HBC’s to 900 yards, then I feel a barrel in 1.14 is not ideal and you would be better off with 1-13 or 1-12. Certainly a 1-12 if you want to extend yourself to 1000 yards. Of course if you get an old Musgrave they will support long barrels even though they have a short action thread because they have an internal lug to which you draw the rear face of the barrel onto as well as the shoulder. It can’t move, but if only the shoulder bears against the action face in a Musgrove it will move.

You want a minimum Gyroscopic Stability factor of 1.4

BULLET WEIGHT 155 IN GRAINS
BARREL TWIST RATE 14 IN INCHES PER TURN
BULLET DIAMETER 0.308 IN INCHES
BULLET LENGTH 1.225 IN INCHES
MUZZLE VELOCITY 3000 IN FEET PER SECOND
PRESSURE TEMPERATURE (CELCIUS)
(MBAR) 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36
1012 1.12 1.13 1.13 1.14 1.15 1.16 1.17 1.18 1.18 1.19 1.20 1.21 1.22 1.22 1.23 1.24 1.25 1.26 1.27
1014 1.12 1.12 1.13 1.14 1.15 1.16 1.17 1.17 1.18 1.19 1.20 1.21 1.21 1.22 1.23 1.24 1.25 1.25 1.26
1016 1.11 1.12 1.13 1.14 1.15 1.15 1.16 1.17 1.18 1.19 1.20 1.20 1.21 1.22 1.23 1.24 1.24 1.25 1.26
1018 1.11 1.12 1.13 1.14 1.14 1.15 1.16 1.17 1.18 1.18 1.19 1.20 1.21 1.22 1.23 1.23 1.24 1.25 1.26
1020 1.11 1.12 1.13 1.13 1.14 1.15 1.16 1.17 1.17 1.18 1.19 1.20 1.21 1.22 1.22 1.23 1.24 1.25 1.26
1022 1.11 1.12 1.12 1.13 1.14 1.15 1.16 1.16 1.17 1.18 1.19 1.20 1.20 1.21 1.22 1.23 1.24 1.25 1.25
1024 1.11 1.11 1.12 1.13 1.14 1.15 1.15 1.16 1.17 1.18 1.19 1.19 1.20 1.21 1.22 1.23 1.23 1.24 1.25

.
BULLET WEIGHT 155 IN GRAINS
BARREL TWIST RATE 13 IN INCHES PER TURN
BULLET DIAMETER 0.308 IN INCHES
BULLET LENGTH 1.225 IN INCHES
MUZZLE VELOCITY 3000 IN FEET PER SECOND
PRESSURE TEMPERATURE (CELCIUS)
(MBAR) 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36
1012 1.30 1.31 1.32 1.33 1.33 1.34 1.35 1.36 1.37 1.38 1.39 1.40 1.41 1.42 1.43 1.44 1.45 1.46 1.47
1014 1.29 1.30 1.31 1.32 1.33 1.34 1.35 1.36 1.37 1.38 1.39 1.40 1.41 1.42 1.43 1.44 1.45 1.46 1.46
1016 1.29 1.30 1.31 1.32 1.33 1.34 1.35 1.36 1.37 1.38 1.39 1.40 1.41 1.41 1.42 1.43 1.44 1.45 1.46
1018 1.29 1.30 1.31 1.32 1.33 1.34 1.35 1.36 1.36 1.37 1.38 1.39 1.40 1.41 1.42 1.43 1.44 1.45 1.46
1020 1.29 1.30 1.31 1.32 1.32 1.33 1.34 1.35 1.36 1.37 1.38 1.39 1.40 1.41 1.42 1.43 1.44 1.45 1.46
1022 1.28 1.29 1.30 1.31 1.32 1.33 1.34 1.35 1.36 1.37 1.38 1.39 1.40 1.41 1.42 1.43 1.43 1.44 1.45
1024 1.28 1.29 1.30 1.31 1.32 1.33 1.34 1.35 1.36 1.37 1.38 1.38 1.39 1.40 1.41 1.42 1.43 1.44 1.45

BULLET WEIGHT 155 IN GRAINS
BARREL TWIST RATE 12 IN INCHES PER TURN
BULLET DIAMETER 0.308 IN INCHES
BULLET LENGTH 1.225 IN INCHES
MUZZLE VELOCITY 3000 IN FEET PER SECOND
PRESSURE TEMPERATURE (CELCIUS)
(MBAR) 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36
1012 1.52 1.53 1.54 1.56 1.57 1.58 1.59 1.60 1.61 1.62 1.63 1.64 1.66 1.67 1.68 1.69 1.70 1.71 1.72
1014 1.52 1.53 1.54 1.55 1.56 1.57 1.59 1.60 1.61 1.62 1.63 1.64 1.65 1.66 1.67 1.69 1.70 1.71 1.72
1016 1.52 1.53 1.54 1.55 1.56 1.57 1.58 1.59 1.60 1.62 1.63 1.64 1.65 1.66 1.67 1.68 1.69 1.70 1.72
1018 1.51 1.52 1.54 1.55 1.56 1.57 1.58 1.59 1.60 1.61 1.62 1.64 1.65 1.66 1.67 1.68 1.69 1.70 1.71
1020 1.51 1.52 1.53 1.54 1.55 1.57 1.58 1.59 1.60 1.61 1.62 1.63 1.64 1.65 1.66 1.68 1.69 1.70 1.71
1022 1.51 1.52 1.53 1.54 1.55 1.56 1.57 1.58 1.60 1.61 1.62 1.63 1.64 1.65 1.66 1.67 1.68 1.69 1.71
1024 1.50 1.52 1.53 1.54 1.55 1.56 1.57 1.58 1.59 1.60 1.61 1.63 1.64 1.65 1.66 1.67 1.68 1.69 1.70


With regards to bore diameter for the HBC which has a larger bearing surface in the body it is better suited to .300/.308 dimensions but my wife’s .298/.3075 just loves the HBC.

In FTR you are competing against the heavier class of bullet which does offer some advantages at 1000 yards but the HBC is on par with the Berger 156 in terms of its BC. There are a few in Britain who have come back to the Berger 156 because bag handling and sheer accuracy of the bullet. But they are driving that pill very fast up to 3150 fps. I’m sure they are using the finest barrels and actions and worked up loads very carefully using longer throats to dampen pressure. This is specialist stuff and looks at gear that could handle 65,000 psi. So the above tables have stopped at 3000 fps just to give you an idea of suitable barrel twist only because the Omark action is not as robust and bearing in mind your 900 yard goal then a more suitable speed would be around 2975 fps depending where an accuracy node sits. The Omarks came out to handle pressures around the 55,000 psi mark. Shooting at 1000 yards is on the margin and to be realistic how many times do club shoots go there. You will get more pleasure from your Omark tricked up a bit at all other distances and its balance will be better with a shorter barrel not stretching for the extra fps.

Percy Pavy once commented to me, that a person o/seas commented that his rifle stock looked like a bit of deal. “Deal” being scrap wood. They didn’t know him and that the forend was quartersawn, not flashy to reveal a grain. They didn’t know that a quarter sawn timber has minimum shrinkage and was essential to Perce’s bedding of his .303 remaining intact. He was giving me a lesson as a young bloke over 40 years ago that knowledge was power and you certainly can’t judge a book by its cover. Leadlauncher, go and kick some shiny butt with your Omark.

[leadlauncher]

Thank you Williada, for your most informative reply to my post.

cheers

[bsouthernau]

Would it be better to set up for FTR, with say a faster twist ?

Only you can decide that but I can tell you I have an Omark with a 32" 1:10 and it shoots fine. As David said - just don't stoke it up TOO much.

Barry