"omarks" making them shoot

[mick l]

With the number of Omarks still in use,some thirty seven years after their relese to the market.
There must be a wealth of knowledge on making them shoot well,as many do.
Many things have been tryed and found to work,or not as the case may be.
Starting with a standard Mod.44,what would you do to improve it?
eg,adaptor for new barrel
truing action/adaptor/blueprinting
adding take down screws
trigger new or improve old
bolt/ new firing spring
turning firing pin/lighting or make tip smaller
inprove lock time
bedding/many ways which is best
primary extraction
sleeve action
Is the action better in .223 than.308

Just a few things to think about
What works,what does not

mick

[Barry R]

I think that the Omarks have surpassed the requirement of their time. They were there when military ammo was all that there was and those of us who quietly pulled that ammo apart and put 'similar' projectiles with 'exact' weights of powder into cases that weighed the same found that we didn't really change the world much. F4 wasn't too bad for what it offered to us - back then.
Now, where can you get a single shot target .308, in a stock, with a barrel that likely would'nt impress your friends - let alone a girlfriend - for about $100.00 - anywhere....?
Why ask?
Well, a new Chrome moly bbl fitted, a better trigger, an aluminium bedding block will cost about $700 on top of the $100.
Not that bad when you consider that any 'top' range target action, barrelled and bedded is going to cost about $3,700 approx.
Select .223 instead of .308 and the pic improves yet again.
Hate 'em....love 'em they were a really great design, that even today is not beyond a gripping challenge, anywhere, particularly in .223.
Buy a few - give them to your friends.

[littlebang556]

For those of us out there that do not have a bank up our A*#@ the Omark is truely a good starting point and as it would seem there is no need to go further than this 37 year old action.
My latest efforts have been as follows:
400y 50.4 & 50.10 = 100.14
500y 50.7 & 50.9 = 100.16
600y 50.10 & 50.10 = A really swollen head.
300.50 over the 3 ranges in full bore competition and would no doubt be even better with a scope and rests.
But I don't think there has ever been much doubt that the Omark in .223 is capable out to these distances and my local club stretches out to just 700y at the moment so is hard to test it much more but when I get the chance I will let all know how it copes.

Cheers 4 now

Rob A

[mick l]

Rob,
With shooting like that you deserve a big head.
Great shooting!
Please tell how you have set up the "omark"
It shoots very well,but the nut behind the butt must be doing something right as well.
regards
mick

[littlebang556]

No worries, I'll just take a deep breath.

Here goes,

Rifle is Omark with MAB adaptor supporting a 1:7.7T 30" S/S Krieger barrel. Unsure of reemer for chamber but katasen@wn.com.au (Esperance Trim & Canvas) will know.
A firing pin grind down to 1.6mm and a new spring.
Davies trigger @ 1.6kg.
All this is bedded "not glued" on an aluminium block that is glued in with ultra clear araldite.
Stock is 3 piece laminate of Tassy oak fixed with resorcinol glue has no adjustable check piece but a curved adjustable butt plate that I raise 3.35mm each 100 yards starting at 300y.
Sights are TMAC & variable front with .5 eagle eye. 100.20 with 2.9 ring front and 1.2 rear.
2 point sling.
Spotting scope is Nikko Stirling 20-60 angled on a $5.00 stand that I picked up at the salvage yard.
Winchester brass (not weighed) on 7th reload trimmed to 44.5mm and FL resized every time with no neck turning. Washed in petrol then dried in oven at 60 degrees C for 90 minutes then left to cool.
Primers are Rem 7 1/2 and are all put in at the same time and primed cases kept in a 500g plastic powder bottle until needed.
Powder is 25.4 of 2208 trickled by hand not trickler and weighed on lyman pro 500 scales.
Weighed 80.0gn SMK not moly coated seated 15 thou off with Lyman Die.
Seating depth found with sized case with 4 virtical cuts down to shoulder and projy loaded long and then loaded in rifle and measured with a vernier caliper, yeah I know...bit on the rough side.
Resizing die set by sizing case and trying in rifle with no FP spring, just the bolt body and head until no resistance to close then backed off just a smidgen. After 20 or so shots bolt becomes a tad harder to close but comes good after a good clean.
Clening is with Action Blaster on a cloth on the end of a piece of dowell with a slot to clean chamber. Then insert rod guide and run 2 patches of action blaster through and 3 dry ones. 1 patch of sweets straight through then a scrub with another sweets patch and another straight through...let soak 5 to 10 minutes...bronze brush with sweets for about 20 passes in each direction being carefull of the crown...let soak 3 to 5 minutes then 1 dry patch and spray 3 seconds with action blaster...4 dry patches followed by 2 wet patches of hoppes #9 powder solvent...remove rod guide and patch out chamber with dowell again cleaning lugs as you go with a action blaster patch and 3 to 4 more dry patches down the bore and the you are ready for the next dispatch. Then clean brushes and rod guide with action blaster and store in clean bottle or the like.
WOW. I'm all worn out now.
Did I say that I don't usually clean my rifle when I get home from the range...too lazy, pooor thing gets done on a friday night or saturday morning.
Hope this helps.
The rest is up the to gods but I wait for them to settle down more often than winding the knobs.

[mick l]

Rob,
You say a firing pin grind,
is it just the tip or have you bushed the bolthead
regards
mick

[littlebang556]

My gunsmith (Noel Blakely) katasen@wn.com.au did not sleeve/bush the bolthead but the hole was made smaller to accommodate the smaller FP of 1.6mm.
Otherwise I am not completely sure how he did it, but it works good.
You could give him a call on 0890717733.
He has a precission grinder that is set up for the FP job and I am sure it would not take him long to do it.
If you call him just let him know that you know me.

[Barry R]

Might this reduced tip be just for high intensity loads for longer ranges?
I suspect that most of what it achieves is the reduction of primer cratering as the powder loads go up while trying for extended projectile stability through higher velocity at longer range. Even with the strongest brass used for these high pressure loads the primer pockets will likely become 'middle aged' pretty fast I'd guess. Probably, at shorter ranges with lighter, standard 'out of the book' loads the operation of the finer firing pin tip would be no different from a normal diameter pin.

[littlebang556]

I was told by a couple of reliable sources that accuracy would improve once FP Reduction done so I did it, had nothing to lose and it paid off. In fact, I was also told that most .308's could do with the same FP reduction, all to do with lightening the total weight of the FP to reduce lock time.
Further more, I can't be bothered with lighter loads at shorter distances. I just dish up maximum punch (subject to ladder testing loads) at all ranges. Having said this, next time I get the chance, I wouldn't mind doing a ladder test at 1000 yards to see what is going on but I don't think I will be all that surprised.
As for the primer pockets getting a flogging, maybe you are right, but my Winchesters are into theie 7th reload with no signs of wear to date. If I can get a dozen reloads out of a batch of brass I will be happy but I anticipate they will last a bit longer.

[Barry R]

It's said by those more experienced than I that fast lock time is important for Full Bore (hand held) but not so much for F class or benchrest (rested). It would be interesting to know how much lighter that firing pin of yours is Rob because those scores show that you're equipment is doing as well as anything could be expected to do, hand held.

[littlebang556]

Although lightening of the FP tip will assist in lock time reduction, the amount taken off is almost negligable but further lightening would be possible. The main thing to do with the Omark is to replace the spring at regular intervals of about 1000 firings.
So my FP would be close to the weight of a standard Omark FP.
This topic was covered on fullbore list forum some time back by some very knowlegable listers so if you have acces to the list you may be able to pose the question again. My comp went belly up yesterday and I lost ALL the good stuff otherwise I would quote them...sorry.
The main thing is, it works and it works damn fine.

[Barry R]

Rob, have you tried the 25.4 of 2208 with the 80gn projectile close to or into the lands? There are those on this side of the island who find that 10 thou into the lands with about that powder load gives excellent results at all ranges. One works progressively up to 25.4gns of course. The advantage is created firstly by carefully F/L resizing the case, which results in the projectile sitting 'centred' by the bore before discharge - no matter where or how the rest of the case sits in the OMARK chamber.

It is a good thing to be seen in concentric circles - they say.

[Lynn Otto]

Barry

I have found that seating depth is very dependant on the particular rifle. My old 223 would not shoot unless it was seated in, 20thou from memory, my technical advisor is currently at work, but my new 223 will not shoot unless it is out of the lands and has a jump.

Lynn

[littlebang556]

Too true Lynn,

With no jump the poor old .223 has all sorts of trouble with pressure and the likes even more so with a hot load.
Mine are seated around 15 thou back to help prevent these problems and believe me, I have had plenty of them whilst trying to get the little bugga to shoot.

[littlebang556]

Yes Barry I have tried upto and into the lands but have always had enormous trouble extracting the fired cases whilst using: Winchester, Lapua, PMC, ADI92 and Remington brass.
I will say that, for my way of thinking if your car was resting on a curb and you tried to push it beyond the curb I am sure you would have to to use quite an effort/pressure but given just a short run up the effort required would no doubt be smaller and result in a more constant velocity.
I am getting less than or equall to 5 feet/sec variation in MV with my current setup and have had one batch that had ZERO deviation.
With the way you suggest my deviation was more like 30 to 50 feet/sec.
Having said this, it is also true that each rifle is different.
Even minor differences like twist rate Mine= 7.7 most others = 8.0
Barrel lengths from 26" to (30" mine).
Type of reamer.
Depth of throat.