Omark Bolt Problems.

littlebang556 · Post by **littlebang556** » Thu Oct 02, 2008 2:01 pm

I recently needed to change boltheads on my Omarks to allow sharing of ammo at the Queens after 1st rifle went belly up.
The bolthead that was on there has various craters that cause detrimental effects on my brass so will not be going back on.
Trouble is, the bolt fits perfectly until firing pin is released then the caming action required to open the bolt is excessive...is there a way I can fix this?...I was thinking of precision grinding a thou or two off the rear of the bolthead lugs. As it is, I have had a few cases that needed persuasion to be removed.

I also need to reduce the length of the FP by a few thou or swap with other one...how do you pull the suckers apart? Some sort of a working diagram or detailed instruction would be handy.

Cheers

Rob Alman

Post by **AlanF** » Thu Oct 02, 2008 4:31 pm

In the eastern states we have these fellas called gunsmiths who do that sort of thing for you

.

Alan

littlebang556 · Post by **littlebang556** » Thu Oct 02, 2008 5:08 pm

In the West we are too poor and most of them are called blacksmiths.

Seriously Alan, with a little guidance anyone with half a brain could do a better job than what was done with my last rifle and I have already remedied several stuff ups.

Even thinking of getting my own lathe/mill and the like and doing the required paperwork.

Cheers

Rob Alman

KHGS · Post by **KHGS** » Thu Oct 02, 2008 8:38 pm

Hmmm maybe whoever did your last rifle started out because of blacksmiths too. Seriously, what you are proposing to fiddle with could adversely affect the safety of your rifle & is something you should have experience with before attempting. I analyse rifle blow ups for the NRAA & most are caused by lack of, or improper maintenance & modifications. As we say in the trade, having a lathe, milling machine & tooling, a gunsmith does not make.
Keith H.

littlebang556 · Post by **littlebang556** » Thu Oct 02, 2008 9:03 pm

Point taken guys, what I have done is swapped a few bolt parts and have measured the headspace and all is good.
Sear and cocking piece operating properly and FP is striking nicely, just need to FL some new shells to fit and I will be in business.
I will be sure to have my next rifle engineered by other than a forge and hammer.
It is a pity that some smiths are allowed to do such a bodge job in the 1st place. I am positive that any work I have done has made the firearm safer than it was delivered, even replaced bolthead locking pin.

Otherwise, are there any suggestions for Smiths in WA with experience with Omarks.

Cheers

Rob Alman

Quick · Post by **Quick** » Fri Oct 03, 2008 11:48 am

I have heard that Roy Alexander in Maylands is a decent smith. They have been around for a while. You could try them.

littlebang556 · Post by **littlebang556** » Wed Oct 08, 2008 9:54 am

Changing various parts of my bolts has worked wonders and apart from having a low bull group (due to the fact that I forgot my home range was not yards???? all 600 of them) scored 50.1 followed by a 50.7. Then without cleaning fired 20 straight for 100.something through the chrony.
Just need to fire form all my cases now as effective chamber is a couple of thou longer...I so wish it was the other way around so I could just bump the shoulders...but life wasn't meant to be easy was it!!!

The interesting thing I discovered was the massive drop in velocity that my 28" has over my 30." I expected about 60 to 100 fps drop max, not a shade under 150 fps. They are still flogging down the range at 2980 using 25.4 of 2208 (same load as other rifle). Even same ammo for other rifle with no modifications at all.

Rob Alman

Chopper · Post by **Chopper** » Wed Oct 08, 2008 2:47 pm

G,day Rob , just for interest sake what velocity was you getting out of youre 30", chop.

littlebang556 · Post by **littlebang556** » Wed Oct 08, 2008 3:14 pm

Hi Chop,

3127fps +/- single figure ES (and that was before I took possesion of my U Beaut RCBS Combo).....fairly wizzing down the track....in winchester brass that showed no signs of failure.....only ever had one case failure and I think it was a dodgy case to begin with...it split from shoulder to base.
Remember twist on it is 7.7 and not 8.
The new rifle is eating the brass though as the primer pockets die after just a few reloads...different batch or something???????
The ideal twist rate for a 223 with 80 Sierra pills is 7.5 and from memory Bartlein Barrels in the US do whatever twist you like....check them out....might even get my next from there to try it. If you do, tell them I sent you please.

Barrel is a different story though, after 2500 groups started opening up and was just competitive out to 3500 rounds....now fired 4800 and is totally shagged for the 1st 1". I may rechamber it one day to see if I can bring some life back into it for another 1500 or so.

Chopper · Post by **Chopper** » Wed Oct 08, 2008 9:10 pm

Rob, why dont you back off the loads to around 2950 and save youre brass and youre barrel, i dont think there is any advantage in running them that hard ,it may save you a lot of extraction problems and youre head as well, Rob if you are fire forming cases for that chamber it sounds like the change of bolt head has lost you some headspace , be carefull, is the brass youre fire forming new ? if so it sounds like you need to have it headspaced , i hope you dont think ime sticking my nose in but it just all sounds a bit sus to me, just trying to help, Chop.

littlebang556 · Post by **littlebang556** » Wed Oct 08, 2008 9:59 pm

Have tried backing loads off Chop but accuracy at the longs suffers and I am too lazy to have different loads for different ranges.
As for saving brass, my previous rifle with 30" and 3127 fps is onto reload 16, which is why I am thinking this batch may be a tad softer???????
Barrel life is only a case of dollars and a barrel every 2 years is only about $8 per week with Smith fees included.
As for extraction problems, there are none now that I have changed boltheads and extractor claw, they fly into my hand as the bolt slides back as they did in my old rifle.
The bolthead is actually locking on the lugs better than what the blacksmith did and it is the forward end of the case that is too short now by 13 thou...once they are fired they fill the chamber nicely and I will adjust my dies accordingly.
You only have to have a gander at the job the blacksmith did and one could see that it just would not perform, it was a real dogs breakfast.
Being a 2 piece bolt I am regular with my checks of the bolthead retaining pin and am aware that there is only so much I can do without the assistance of a proper smith.
I will let you know how things progress though and thank you for your just concern. I have all the measuring tools required to make informed decisions and have a background in engineering/architectural drawing, not just some jack.
The majority of shells I am using ave been fired in another rifle but some have been fired in this one with other bolt configurations.
There are only very minor adjustments left to make and all have to do with the reloading and none with the rifle.

Chopper · Post by **Chopper** » Wed Oct 08, 2008 10:21 pm

Well Rob i must say ive never heard of anyone getting that sort of life out of 223 brass and barrel running at 3100+ , 16 loads is incredable, one bloke i know ran his at 3100 and was tossing them after 2 shots, hows youre chrony,Chop.

littlebang556 · Post by **littlebang556** » Wed Oct 08, 2008 11:54 pm

Chrony used for 3127fps was a CED but this was only after using a Pro Chrono (and advice from another lister) and thinking that it was going ballistic for want of a better word.
The readings we for all intensive purposes identical and same ES & SD.

Not sure what the chrony used on the weekend was but an average of 2980 I would not think is out of the ball park but there were 2 real fliers at 3003 & 3012.

littlebang556 · Post by **littlebang556** » Thu Oct 09, 2008 8:29 am

Chopper wrote:Well Rob i must say ive never heard of anyone getting that sort of life out of 223 brass and barrel running at 3100+ , 16 loads is incredable.

What, not even that over priced Lapua stuff?????

I have a batch of ADI brass that was used in my 26" 10T for a total of 14K rounds with 69 sierra's running with 25.5 of 2206 & Federal 205M primers....now that poor little thing was hot hot hot. The ADI's are still sitting on my shelf because there is nothing wrong with them.

littlebang556 · Post by **littlebang556** » Sun Oct 12, 2008 4:44 pm

Blacksmith work performed OK today.

Shagged the 1st 2 applications by putting 3 over the top (4.9's on electronic targets but still 4's) for 97.8 then shot 20 strailght for VVVVVVVVV55VVVVV5VVV.
Then fired 10 more 55VVVV5VVV then another 10 for VVV5V5VV5V.
All at 700m. The hotter the barrel got the better it shot but I had to keep dragging the elevation down as the barrel fowled more.

Conditions were good, about 25 degrees with a changing frontal swinging around to the right...final shot had just 1.25 right wind.

Now I am not sure if I will bother resetting my die to the full chamber dimensions, might size them short.

All shots were fired without any cleaning and only had 3 shells that didn't want to come out easily (no cleaning rod required) and that was after about 50 rounds.

All in all, not too shabby for an old Omark...but I just love that Walnut fully adjustable Jerricho stock.