I went to the range this weekend and had two new rifles to get going. I was putting one through the Final Finish process (50) rounds in ten shot strings, then cleaning before next ten-- really only three or four shots and then allowing barrel to cool-- and I had about four rounds have sticky bolt, one really firm to lift. Definately not acceptable in a hunting situation! The brass was second time reloaded WW nickel-plated in 300 WSM. The load was about five grains below minimum for the bullet weight, 60 instead of 65.5 grains of 4831sc. The sticky rounds were not in succession or even the same level of bullet within the final finish abrasive classes, (maybe 2 were) I didn't have this issue with the .270 WSM I was shooting for the first time--Same type brass etc. Is there anything to 'polishing the chamber' -How do you do that? I had a friend with the same 300 WSM and he had hard bolt lift with factory ammo and sent his rifle back to SAKO, (last year -- pre Beretta?) and when he got it back it functioned flawlessly, the work ticket on his rifle said check and polish chamber. The rifle is a Sako 75 Finnlight in the V Action, I have a new one in the SM action and haven't had the problem--yet??? Would appreciate your thoughts and advice. I made this same post on the reloading forum also--Thanks, Don.

Kinda hate to bring this up as it always causes some controversy on loading boards, but the "detonation" or "secondary explosion effect" has been reported with reduced loads of 4831 in large-for-bore cartridges like the .25-06. It's not what I'd choose for reduced loads, and going below the minmum load in the manual you're on your own.

Ricochet is correct on this one for sure...loading below recommended book minimum is a poor policy with 4831 or any other really slow powder.



Still, there are numerous other possibilities as well which can cause hard extraction, one of which IS indeed a rough chamber.



Others include...



- Cases not trimmed for length, resulting in a few which are overlong for the chamber and create excessive pressures when fired...

- Cases with oversized bases caused by not using a "small base die" for resizing cases originally fired in oversized chambers ...thus making the cases excessively tight when reloaded and putinto standard size chambers....

- Bullets seated sufficiently long that some (because of inherent variations in bullet shape) are thrust into the rifling while most just clear the rifiling...

- Possible powder mislabeling (if it has been removed from original containers). IMR 4350 looks exactly like 4831 and has exactly the same dimensions...the only difference is the amount of burning deterrant inherent in their composition...

- Mixing of some magnum primers with standard ones, if the primer box has ever been spilled on your bench where other primers might have been laying... (Could have happened at some time in distant past?)

- Flaw in extractor fit to bolt so that it is a bit loose and can be crammed into different positions relative to the cartridge case heads when the rifle bolt is closed on a loaded round...

- In SOME rebuilt military actions where the cocking cams have been polished (intentionally or not), the polishing may have compromised the hardened cam surface(s)...



There are, of course, others reasons for hard extraction too. Most are pretty unlikely, but all CAN occur and are worth checking.



In the meantime, as Ricochet says, MY first step would be to use only recommended mimimum book loads or higher when using slow-burning powders.



If you want to polish your chamber, it can be as simple as using a 1/4", or 5/16" soft wooden dowel and some approx 400 to 600 grit crocus cloth. Split the end of the wooden dowel. Put a strip of the crocus cloth through the dowel (in the split), and wrap it around the dowel. Chuck rod and cloth into an elecric drill or electric screwdriver. Insert in chamber. Turn on power and work back and forth, in and out.



Remember, the object is to polish, not to remove metal or re-shape the chamber. Do less than you think is necessary. Inspect frequently. Stop too soon. Take it to the range and try rifle again. Lifting the bolt and inspecting the exterior of the fired brass should let you know when you are where you want to be. DON'T try to get the chamber glass smooth. You want the brass to grab the chamber walls while the pressures are high, not to use all that pressure to thrust the cartridge case back agains the bolt face. Make haste slowly and you should be fine.



Good luck



Alberta Canuck

Thanks Canuck, I mentioned to Ricochet on the reloading forum that I wasn't aware of the issue with using 5 or so grains below min. and won't go there again. I do think that it is a chamber issue as the same load didn't cause an issue in my other Sako 300 WSM on the SM action, nor an equally light load in my 270 WSM. Also as I mentioned one of my friends had the same issue with factory ammo and Sako apparently polished his chamber and he hasn't had any issue since. I sure appreciate the feedback--
Regards, Don.