I Think I Found The Problem

[HollowPoint]

I recently reverted my rebarreled and rechambered K31 Swiss rifle back to it's native 7.5x55 Swiss cartridge. I still had the original barrel so it was a simple matter of putting it back on.

This rifle in its' original configuration was a tack driver as far as military surplus rifles go. I've posted photos of my two hundred yard targets here before. One target in particular showed a cluster of a little under an inch and a half. This was done with a scope mounted but my 100 yard groups were about the same using peep sights.

My problem was that after re-installing the factory barrel I was unable to get those groups I was once getting with the same loads. At the very least I expected to have to tweak them after reinstalling that factory barrel but I just couldn't get those groups to tighten any more than two and a half or three inches at a hundred yards; and this was using the same charge weights and bullets/components as before.

I've been using the same RCBS powder scale for years. This is what I used to load all of my guns with the exception of my occasional use of an old Lee Powder scale and a short time when I bought and started using one of those Lyman digital powder dispensers. I quit using it because the powder charges it was dropping never matched the weights that my RCBS scale was registering.

Out of frustration of not being able to tighten up my K31 groups I took that digital scale out of the storage closet and blew the dust off of it. I also had one of those cheap Harbor-Freight digital postal scales on hand as a cross reference. I was determined to figure out what was going on with my previously accurate loads no longer being accurate so, I used the calibrating weight that came with the Lyman digital scale and proceeded to test each of my scales. Lo-N-Behold, it was the RCBS analog scale that has been off all of these years. With the lighter charge weights it was off by a bit over .5 grains. The heavier the charge weight, the more it was off. And I couldn't have been luckier than to find this out before my next range session.

I had loaded up a batch of OCW test loads for my 6.5x55 Swede and I had planned on testing up to the maximum loads in the Nosler load book. My RCBS scale at the listed maximum load was off by a bit over 1.5 grains. That's over 1.5 grains over maximum. (KaaBoom)

There have been other time when I reloaded ammo that had been previously proven to be very accurate out of the same rifles and the accuracy just wasn't there. I had just chalked it up to me having a bad shooting day. In addition to the RCBS analog scale I had also use one of those cheap Lee analog powder scales from way back when I first started reloading . I see now that no powder scale can be completely trusted unless or until they've been cross referenced with other powder scales to confirm their accuracy.

I fiddled around with my RCBS analog powder scale until I finally got it calibrated with both my digital powder scales. It took some doing. I had to take some weight off of that little sliding thingy on the beam and then slowly add it back on until all three scales were able to mimic one another. I'll probably quit using the old Lee powder scale all together. So, I took apart all that previously loaded ammo and re-did it so that now it all falls in line.

Now I have to go back and take apart at least one of all of my previously loaded accuracy loads for my .223, .303, K31, .45, 9mm and my 380. Fortunately, I still have some of those loaded accuracy loads so that I can take one of each apart and just weigh the powder charges to at least get me close to the updated charge weights. I'm not to worried about the handgun loads, those were all loaded light; it's those rifle loads that I need to check.

Have any of you guys ever checked the weights that your go-to powder scales are giving you against any other powder scales to see if they are giving you accurate measurements? For me, it's been at least thirty years. All this time I had just assumed that because it was a brand name scale, it was giving me accurate readings.

HollowPoint

[Mike W1]

Back when John T. Amber was editor they did an article on scales and accuracy. The gist was they had some of the big name writers weigh some lab certified weights with their own scales and the results were amazing. I decided after that the only way to check a scale, analog or digital, was to use a good set of check weights. Comparing between various scales is akin to comparing apples to orange far as I'm concerned.

[frkelly74]

I have always thought my scale was "right". Now I will have to find a way to check it out.

[Der Gebirgsjager]

Perhaps a bit off the main subject, but what was your K-31 barreled for, and why did you change back?

[Houndog]

There are lots of things that can change the harmonics of your rifle such as the barrel torque mating the action and barrel, the action screw torque, the hand guard position and tightness, did your new barrel disrupt your rifle's bedding in some way? As you can see there's more to it than your scales being off!

[country gent]

A set of the lyman or RCBS check weights with a scales is as important as the standards with measuring tools. With out them you never know for sure. I use them like gage blocks and check the scales setting at the charge weight, This verifies the scales and the setting. IE For a 41.5 grn charge 2 20 grain weights, 1 1 grn weight, and a .5 grn weight = 41.5 grns. Its a good check and adds to the surety of the set up and equipment

[HollowPoint]

Perhaps a bit off the main subject, but what was your K-31 barreled for, and why did you change back?

A couple of years back I got a wild hair up my butt and decided to rebarrel and rechamber my K31 from the native 7.5x55 Swiss to the 6.5x55 Swedish Mauser. I did it mostly because when I did my initial internet inquiries as to how it was done or if it were possible for a home gunsmith to do it, all I got were negative replies warning me of the complexity of doing such a project. Even after I successfully completed that project I still got some negative replies to my writeups. Not here on the cast bullets forum but in some of the other forums I was frequenting at the time. Most of the readers of my write up of this project here in the cast Boolits forum were very supportive.

I got to liking that chambering so much that I bought a Tikka rifle chambered in the 6.5 Swedish. I didn't really need two rifles with the same chambering so I reverted my K31 back to its' factory chambering and started working up loads in my Tikka rifle. The 6.5 is a real mild recoiling cartridge compared to some of the other I've shot. Lately I've been thinking of rebarreling the Tikka to the 6.5x55 Ackley Improved but if it happens it won't be for a few months down the road.

HollowPoint

[HollowPoint]

A set of the lyman or RCBS check weights with a scales is as important as the standards with measuring tools. With out them you never know for sure. I use them like gage blocks and check the scales setting at the charge weight, This verifies the scales and the setting. IE For a 41.5 grn charge 2 20 grain weights, 1 1 grn weight, and a .5 grn weight = 41.5 grns. Its a good check and adds to the surety of the set up and equipment

I couldn't agree with you more. A couple of days ago I may not have agreed with you; mostly out of ignorance. Fortunately my Lyman digital powder measure came with just such a weight gauge so I was able to use that 20 gram weight to cross reference my other two powder scales. The results really surprised me. I fully expected the cheap Harbor Freight postal scale to be the one to churn out faulty weights. As it turns out it was dead-nuts spot-on with the Lyman scale. Not so with the RCBS analog scale.

HollowPoint

[psweigle]

A set of check weights, as stated, are a must for ANY scale. Its tbe only way to know if its right.

[Der Gebirgsjager]

I do remember that thread, went on for many pages. I was one of the avid readers, and was impressed with your willingness to tackle a difficult job and the good results. I thought you were the one who did it, but wasn't sure, and couldn't bring it up in an earlier search. I'm kind of surprised that you'd go back the other way, having accomplished what others thought impossible. I would have found another K-31 in 7.5 Swiss to shoot and kept the altered one for bragging rights!

You're right about the 6.5 Swede being a pleasant cartridge to shoot, and it has outstanding ballistic qualities, excellent for hunting.

[GhostHawk]

Check them against the calibration weights often. Adjust as needed.

With my old RCBS pan scale its simple, set all to zero and adjust the front screw base until it reads zero. Never had an issue with it. Digital scale left on too long I've seen cumulative errors add up until a 20 gr charge of 4895 was overflowing the case. Only took some 25 hand weighed charges to do it.

I dumped the whole works and started making dippers. Never yet seen a dipper that throws a weighed 20 gr charge of a given powder throw near 40 grains because its brain got scrambled.