Fun and Games.....an old problem

Well here we go again, haven't had this one for awhile.

Young buck on the range with his new toy, a 1941 Lithgow, all shite and briny and a bucket of old Milsurp ammo.

He asked me if the ammo was okay, took a look at the headstamps...MF 57, if it goes bang it should be okay.
So off to the firing line and started banging away, problem is he was shooting about a foot to the left of target. Quick sight adjustment but not much improvement, good job there's a mountain back there, he needed it all for a backstop.

He finally approaches with a handful of cases and asks if they are okay, well no...
magic banana syndrome.

So I grab a texta and his bolt and begin to fill him in on why bolt lugs need to both have contact.(good job these old girls have a large lug on the right side, 'cause it was doing all the work)

As I had a few old clunkers with me, I grabbed a few bolts and found one that gave contact and gave it a go.....plinking in a foot to the right, so reset the blade back to it's original position and put in a bit of a group for him.

So here I am, sorting out another basic problem that we seem to forget about.....note no mention of that H word, we all know the real relevance for that.
I guess it's money in the bank though, got to keep someone happy, even if it's just the bank manager.
Note no mention of nosecap, normally this would push the bullet the other way, being anchored front and rear, but this one was sportered, so what you see is what you get.

Acouple of pic'sAttachment 102641both bananas on left, corrected bolt next and extreme right a good case.

Attachment 102640kissing bananas, with two corrected cases

Muffet.2008, if I understand correctly, the rifle with the bolt that had uneven bearings produced the distorted cases. And when you switched out the bolt for one with even bearings, the result was cases that were not distorted?

It was all the same ammunition used for all the samples in the pics?

Yep, same ammo. That's the quick field fix, there's a bit more to it than that though.
It's not just the bolt lugs that need checking, the bolt lug recess is just as important, you may get a wipe on the bolt lug when opening and closing, but the small lug recess may not be contacting in the fully closed position.

I use whiteout to check this contact point, it dries quick, leaves a good skin and is easy to remove afterwards.
One of the Target Shooting crowd came up with a neat spring loaded case that applied backward pressure to the boltface back in the '30's, maybe Central or Rawson, mine has nothing on it.....I rarely even use it, probably because it's never where I thought I left it, so an empty case and cleaning rod down the barrel gives me the same even centred pressure, which you won't get by just cranking and pulling back on the bolt.

Remember though that any change to the bolt requires a few other checks also, Headspace, bolthead clocking, firing pin protrusion just to rattle off a few.

I remember doing a post on the effects of altering various bearing points once before, barrel pressure...up, down, sideways, With and without nosecap, forewood etc. that rifle also had lug contact problems.
The draws have no effect on accuracy if the woodwork is intact, the only effect from the timber is when the timber is driven foreward against the sight when firing......that is assuming the barrel is not bedded along the barrel as most Range Rifles are.
It all comes down to the correct fitment of bolt to receiver and barrel condition.

That article was Bedding and Accuracy and was posted back in 2017, maybe some technosmart can attache it here.

…..and just to throw another curveball at you, there are a few things to check with the bolt also.

We check the lugs for contact, wear and cracks....Attachment 102658


this one is so bad, they just kept filing down the high spots...…Attachment 102657


Don't think there is a lot of meat around the lugs, 'cause there's not...Attachment 102656.

Very interesting post Muffett, thanks.

Muffet.
Thank you for taking the time to show us the effects of poor bolt contact. The photos of the bent cases are worth seeing.
Very interesting stuff!

Quick question on the use of whiteout - do you put it on the BOLT lugs or the relevant points on the receiver? Do you simply work the bolt with a Dummy round in place or without or do you have to fire the rifle to get the full picture?

Quote:

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Originally Posted by newcastle

Quick question on the use of whiteout - do you put it on the BOLT lugs or the relevant points on the receiver? Do you simply work the bolt with a Dummy round in place or without or do you have to fire the rifle to get the full picture?

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Fitting rifle bolts.
Posted By: Peter Laidler
Date: Tues 4 Dec 2007 12:07 pm
In Response To: Fitting rifle bolts. Any interest? (Peter Laidler)
First things first. Bolts could only be fitted at Field and Base workshops because they were the only ones that had a 'GAUGE, Inspectors, Bolt'. This is a brand new, calibrated bolt. Still in white metal and marked as such. If my memory serves me right, the slot in the long/top locking lug is machined right through to identify it. So that's the reason if you have ever seen one. This bolt is bare. Clean the locking lug surfaces of the rifle and put a smear of 'engineers blue' marking dye onto the corresponding locking surfaces of the inspectors bolt. Insert this bolt RIGHT FORWARD, rotate it closed, then draw it backwards and forwards a couple of times to mark the mating locking surfaces of the rifle. Push it forwards, unlock and remove.
Examine the locking surfaces of the rifle. The blue witness marks should be evident. This ensures that whatever wear that has taken place on the rifle locking surfaces has taken place equally. If its not, then I'm afraid that the rifle is unserviceable.

Thank you - Much appreciated!!

That's great info from PL, but when we don't have access to the correct gauge, we are not setting up a new bolt, and we are not part of a Field or Base workshop and it's not 1940 but 2019, than we do the best with what we have.

The Gauge, Inspectors bolt ensured that the rifle in question had even bearing on the lug recess and showed up damage to the small lug recess, in this instance we are checking a previously fitted bolt for contact on both lugs, even contact across the small lug recess and contact of the large lug and the size, length and condition of the corresponding lugs and mating surfaces of the bolt.

So whether the bolt being tested is the correct bolt for the rifle, or a used replacement, we can be sure that the spec's of the bolt we are playing with will have a percentage of wear, both lugs and body diameter will be different, that is why we try several bolts to get the best possible fit without the need for excess stoning(I'd prefer not to stone at all)


The reason I prefer to use the spring loaded case adaptor or a fired case and cleaning rod, is to reduce a false reading due to excess slop in the fit of bolt body to receiver
by letting the rifle barrel set down on a cleaning rod and case, we apply pressure directly to the rear, as opposed to holding back on the bolt handle which twists the bolt body to one side if excessive clearance in the bolt channel is present.

Just light finger pressure to open and close the bolt is sufficient and gives a better result than by pulling back and cranking the bolt.

Now back to the small lug recess....I use whiteout as opposed to bearing blue because I want to know how much of the small lug recess makes contact, the whiteout is thick enough to get a visable marking and where the lug pocket is not contacted due to wear or hammering, it will leave a measurable skin that can be removed and checked, so I know early if I am just wasting time on a stuffed receiver.

We are trying to keep these old clunkers going for as long as we can before they resort to wall hangers, but SAFETY is the overriding factor, wear, fatigue and our own stupidity are the things that determine how long we can keep this up.