300-RUM-Whats up with this barrel

[barry206]

Someone explain please this barrel to me,am I lucky or headed for diseaster some day?
A little over a year ago I purchased a rem700 police model in 300rum.The velocities coincided with the loading data pretty close.The problem was I could only get 3/4 in-groups after trying almost everything.[bullet.powder combo]I decided to rebarrel it with a Shilen SS and true it up.30in blank faced at each end with a muzzel brake.I broke it in properly using some old 180 pro hunter sierra's at min. load.I noticed that the bolt was hard to open sometimes but I figured it was just a close headspace.Since then I broke out the chrony and the velocities vs powder charge are unreal to me.By the way,this is only my second match barrel so Im kinda green.Heres a few results.
200gr SMK-86.0 gr H-1000/3115 ave.The max load is 93.5 at 3050.
200gr SMK-95gr H-870/3290 TO 3315.Slight signs of pressure on primers.
165gr Swift scirocco/84gr H-4831sc/3640 ave.Bolt a little hard to open.
A couple of grains above any of these and I have to tap the bolt open and knock out the brass since I dont want to break the rem extractor.I have checked other rifles with this chrony and velocities were in the norm.Could the muzzle brake effect the chrony or is this barrel a fluke?Chrony 8ft away.Just thought I'd ask you guys since I cant sleep at night.By the way,with the H-1000 load 200SMK I shot a 8.25 5 shot group at 1000 on a no-wind day.Thats good for me.Any explanations or advice would be greatly appreciated.Im kinda new to this.

 

[Fiftydriver]

Barry,

I guess I am not sur ewhat problem you are worried about? Do you think the velocity is to high, to low?

Sounds like to me your just pushing the pressure a bit and need to back down until there is no bolt lift resistence at all.

I am relatively new to extreme range shooting but not to match and high performance hand loading. A case with the head diameter of the RUM case exerts alot of bolt thrust to the bolt locking lugs. If you are getting a sticky bolt, you are surely stressing the action.

Match barrels generally have tighter bores then factory barrels, also your chamber was probably cut to min specs to aid in accuracy. This will result in higher pressures with a lower powder charge but will generally increase accuracy potential.

Basically, we just need to know exactly what you are worried about with this barrel. It sounds like you just need to take the loads down a notch or two until bolt function is normal and as long as your groups and velocities are tight, your long range shooting will be fine.

8.25" five shot groups at 1000 yards is pretty good if you ask me. Sounds like she wants to shoot.

I also have a 300 RUM in the M700 but it is built on a classic sporter with a 26" barrel. I load the 180 gr Ballistic Silvertip to 3375 fps and early on it averaged in the 3/4" range from the pencil weight barrel. This barrel is ready to be replaced as the throat is burned pretty bad. During load testing I drove that same bullet to 3440 fps with only slight pressure signd and no bolt lift problems.

Let us know what your concerns are exactly.

Good Shooting!!!

50

 

[JustC]

My 30" PacNor with a vais screwed on only gave ~2950 with a 200gr SMK and 88gr of H-1000. Sounds like you got a fast barrel,...or a bad scale. Mine will not show the optimum velocities however,..until it has had a few fouler shots run through it. She needs a little powder fouling to really get her going.

 

[MAX]

I'm wondering if your case necks are too thick and need to be turned. Necks too thick in a tight chamber can create very high pressures and an unsafe situation. There is no free lunch here. The sticky bolt lift is telling you something is wrong.

Mic a loaded round at the neck, then a fired one, same place(before it is sized). The chamber(neck area) of any firearm must be slightly larger than the loaded case neck diameter to allow bullet release. If your measurements do not indicate a larger number for the fired case, you must turn your necks to facilitate bullet release. I hesitate to specify a specific number but .002" is commonly accepted. BR shooters use smaller dimensions but they are using much milder cartridges in the main.