OK, maybe this is a bit off the wall.

I have a new rifle going to proof next week. Got me thinking about proof loads and excessive pressures in hand loads - never good.

We all know that the classic signs of an over charged hand-load is a sticky bolt lift, flattened, if not blown primers etc.

I understand proof loads for rifles are 30-40% above normal operating pressures, so a proof load for a 60K PSI cartridge is going to generate 80-90K PSI pressure in my nice new rifle.

I asked the smith about this the other day, he was a bit vague, but stated he had seen rifles with perfectly normal bolt lift on firing proof loads.

Does the proof house have some sort of special load they use, or do they have to batter the bolt handle open with a mallet? Are our normal indicators of pressure, actually indicators of really excessive pressure well beyond that generated in proof loads?

Discuss.

Not really...but in rifle loads the cartridge is "oiled" on the outside. As you would lubricate a case before full-length sizing it. This increases both the pressure AND (more importantly) the thrust backward that bears on the bolt lugs.

Brian, your Sauer(s?) will already have been proofed - if not others of your guns. They probably survived.

- mike

I recently had a rebarreled rifle proofed by St. Etienne, french facility; the gunsmith said to me that they make/reload cartridges purposely over the max. loads, to achieve the proof. As I recall, they shoot 2 proof rounds.

Mike, this is not one of my existing guns. I have basically bought an action, a barrel and a stock. A gunsmith is screwing them together this week. This is a S/S wet weather gun.

The smith will have to submit it to the UK proof house next week.

This in turn got my stir crazy mind thinking about stiff bolt lifts, excess pressure etc.

Really just got me wondering about how the proof house go about this and if there is anything for a hand loader to learn from this.

I have no doubt the new rifle will pass without incident.

enfieldspares is right on with this.

In G.B. the proofhouse will be more interested not that the proof load will generate excess pressure but their looking at excess bolt thrust. My understanding of the early British proof houses measured not pressure in PSI but copper units. This was a better measure of bolt thrust wich is the culprit in most gun explotions.

If the cases are not oiled then it can be that high pressure can reduce bolt thrust. It depends on the shape of the case. A long case with a gentle taper will generate greater bolt thrust at a given P.s.i. A case with less tapper will at high pressue grip the sidwalls of the chamber and prevent the case from pushing back against the bolt reduceing bolt thrust.

I visited the proof house in Munich with a gun maker friend of mine. He was haveing a couple guns proofed as they were near completion.

At that proof house the proof loads were Norma factory proof loads. they come with a green mark on the case and the box denotes that they are proof loads.

The gentlemen at the proof house went over the rifles taking measurements with go and no go gages. they slightly recut one of the chambers because it was ever so slightly out of spec. then fired the proof loads. I don't belive they oiled the cases but I might have missed that. I don't think they do that in Germany. The fired cases did have all the signs of pressure and the primers were both blown completly out. (they did fire twice)

I wish I knew more about the British proof houses. I must admit that the info that I'm sharing here about the british proofing is based on what I've heard from people I consider knowledgable. I could be wrong but it all dose make since to me. Also I think EU has forced proof houses to the same standard possibly changing the way guns are proofed in G.B.

As far as bolt thrust P.O. Ackely studied it and made experiments. He found that pressure dose significantly reduce bolt thrust in some cases.

Interesting points guys particularly relating to the lubricating of the case for proof. I can see the logic, this certainly reinforces the need to completely clean your brass after resizing.

I can also see the logic in a straight walled case having less rearward thrust than a heavily tapered case. No doubt why H&H spec'd the 300 and 375 magnums for relatively low operating pressures, particularly given the likelyhood that these rounds would be used in places were the temperature is much higher than in northern Europe.

Brian,

I think the London proof house blew up two brand new Purdey sidelocks last year because they used the wrong proof loads....

Just thought I'd throw that one in for you mate...

K

Glad the rifle has worked itself out mate.

Any chance of a few pictures?

Regards,

A

quote:

Originally posted by Fallow Buck:
Brian,

I think the London proof house blew up two brand new Purdey sidelocks last year because they used the wrong proof loads....

Just thought I'd throw that one in for you mate...

K

Kiri, please tell me you are joking about the Purdey's?

Better blow up my "kit gun" than a Purdey.

quote:

Originally posted by Ghubert:
Glad the rifle has worked itself out mate.

Any chance of a few pictures?

Regards,

A

It didn't so much work itself out, as I bullied all concerned to get what I wanted.

I haven't any photo's yet. I don't want to tempt fate any further. When I get the damn thing in my hands, annd when I have done a bit of load development and can see that it shoots straight, I will post the full report including the sorry details.

Hopefully all will end well.


Next project is a 9.3x62 barrel for the Sauer, if the local polis will license such a beast.

Here you will find some videos about the proof of guns :

CIP

enjoy.

Cheers

quote:

Originally posted by Claret_Dabbler:

Next project is a 9.3x62 barrel for the Sauer, if the local polis will license such a beast.

Don't worry about the local peelers Brian; Tomo puts together a brilliant letter explaining the safety benefits of the 9.3 round for wild boar. Armed with your boar deposit confirmation and a supporting letter from Roger Pollen BASC N Ire they have no choice but to accept that "need" has been proved.

Still looking for my 9.3x74R barrels for the Finn Classic/Valmet, the 308 set are a bit marginal

Alan, I have already had the conversation with Lisnasharragh. They said to do exactly that.

I will be on to Tommo in the next few days.

I had the 260rem variation approved a few weeks ago. They seem to have basically removed all the restrictions on the FAC.

How did you manage that Brian???

quote:

Originally posted by 308mate:
How did you manage that Brian???

Aaron, no idea. Maybe I have a friend I don't know about? The conditions basically say I can use any of the rifles anywhere I think it is safe. Period.

Also, to upset our UK friends, the FAC allows me 1,000 rounds of each calibre on ticket.

Brian,

No joke on the Purdeys. Dig has the details on it but it caused quite a stir as you can imagine.

With regard to your 9.3 on the Sauer. I was looking at a barrel specifically ordered by Rick for driven boar a while back. It was a bit shorter and set up to shoot with open sights or low power scope. Big High vis sights and handled much like a shotgun, which was a plus to me!!

Let me know if you want me to get you the details of that as an alternative to the regular barrel.

Rgds,
K

Kiri, was looking at the Sauer website for 9.3 barrels yesterday. I see the one you mean.

Londonhunter's Mauser had a 9.3 barrel of this type. About 20" long, but heavier in profile, handled very well.

I suspect this barrel might not fit in the forend channel on my rifle.