85lc
.400 member
Reged: 19/01/18
Posts: 1146
Loc: Georgia, USA
|
|
Sharps,
You have provided very good comments and experience. I like your load for the 500 BPE. I may try that when reloadfing for my 500 BPE.
My comment on the strength of doubles was based upon comments by people with geater knwledge than me and was that double rifles are not as strong as bolt action or drop block rifles. I agree that new doubles are chambered in higher pressure cartridges like 30/06.
--------------------
RB
|
3DogMike
.400 member
Reged: 29/01/15
Posts: 1484
Loc: Western Slope, Colorado USA
|
|
Quote:
Sharps,
You have provided very good comments and experience. I like your load for the 500 BPE. I may try that when reloadfing for my 500 BPE.
My comment on the strength of doubles was based upon comments by people with geater knwledge than me and was that double rifles are not as strong as bolt action or drop block rifles. I agree that new doubles are chambered in higher pressure cartridges like 30/06.
Adding to thread drift….sorry!
One thing to keep in mind about the relative strength of double rifles (or any break open type action).
1) There is the strength of the barrels/chambers (maybe called hoop strength?) which would be comparable to any similar barrel on a single shot or bolt action rifle. Given good strong modern barrel steel this is not the limiting factor.
2) Then there is the strength of the actual action lockup. this is impacted by the (for lack of a better description) "bolt thrust" of the fired cartridge against the action face which acts on the locking surfaces and attempts to flex the action at the ~90º point between the breech face and action flats.
#2 is the weak point, and forces upon firing (call it bolt thrust) depend on the cartridge interior head dimensions and pressure.
this is (partly) why such higher pressure cartridges such as .30-06, 8mm's, etc. can be used in double rifles. Smaller diameter but higher pressure cartridges = less sq"/sq mm of area = relatively equal thrust on the action when compared to larger head diameter but lower pressure rounds like the .450's, .500's, etc.
All of this is of course resisted by the strength of the action lockup and quality/quantity of the steel in the action body.
Please forgive my layman's attempted explanation, I am not an engineer or physicist.
Suffice to say, I'm typically very careful to degrease the cartridges and chambers on my doubles which allows the cartridge cases to grip the sides of the chambers (the relatively strongest part of the rifle?) on firing and reduces or eliminates back thrust on the action face and thereby the stress on the action itself.
You can read about this phenomenon, that was published by PO Ackley, where he removed the locking lugs on a Winchester .30-30 lever action and then fired the rifle with degreased chambers & rounds with no ill effect. There was no thrust on the bolt , the entire pressure was contained by the cartridge case and chamber walls..
This of course was NOT using high pressure rimless rounds a la the .30-06 and similar.
- Mike
--------------------
"Will Rogers never met a fighter pilot"
- Anon
“Always carry a flask of whiskey in case of snakebite, and furthermore always carry a small snake."
-- W. C. Fields
|
eagle27
.400 member
Reged: 24/01/09
Posts: 1197
Loc: Rolleston, Christchurch, New Z...
|
|
Agree with 3DM, Jeffery took back thrust considerations into account when developing the 404 Jeffery cartridge for the opened up standard length Mauser actions coming up with a rimless case shorter than the rimmed 450/400 case and a bullet larger in diameter than the 450/400 the ballistics of which he was wanting to duplicate while reducing back thrust for use in the opened up Mausers.
The issue of cartridge grip in the chamber perhaps calls into question the common practice of cleaning cases/cartridges to have nice shiny ammunition (to which I am guilty of) and also the development of nickel plated cases in factory ammunition and of course subsequent reloads based on these cases. One of the advantages promoted by ammunition manufacturers in respect of nickel plating is the inherent slipperyness of nickel plating aids feeding and extraction. While this slippery plating may help the general movement of cartridges and cases in the journey from the magazine and into the chamber, the definition of easing extraction presumably means easing grip on the chamber walls too.
|
DarylS
.700 member
Reged: 10/08/05
Posts: 27484
Loc: Beautiful British Columbia, Ca...
|
|
Incidentally, when P.O. Ackley did that test with the .30/30, it was with quite a bit higher pressures than a standard .30/30, as he was demonstrating the sick-to-the-chamber walls phenomenon of the Ackley Improved case design with blown out sides and only .020 taper overall, only .010 per side.
A grossly tapered case will still produce lots of bolt thrust, but a dry case and dry chamber is so much better than oiled ones.
--------------------
Daryl
"a gun without hammers is like a Spaniel without ears" King George V
|
3DogMike
.400 member
Reged: 29/01/15
Posts: 1484
Loc: Western Slope, Colorado USA
|
|
Thanks Daryl,
I had neglected to add the expanded explanation re: PO Ackley experiments. I have forgotten the approximate number now, but modern solid head cartridge brass also will hold the pressure and not stretch at the web up to something like 45,000psi. “Most” of the early rifle rounds did not exceed these pressures.
As well, “most” of the early Double Rifle and Single Shot rimmed cartridges had/have straight walls with minimal taper so they will, if not greasy or oily, stick to the chamber walls rather well.
Side note: British proof was done with oiled cases in order to give the worst case breech face pressure.
You can see or feel this phenomenon in checking the primer after firing…..it will be just pushed out from flush with the case head where the cartridge gripped and didn’t get pushed back tight against the breech face.
- Mike
--------------------
"Will Rogers never met a fighter pilot"
- Anon
“Always carry a flask of whiskey in case of snakebite, and furthermore always carry a small snake."
-- W. C. Fields
|
DarylS
.700 member
Reged: 10/08/05
Posts: 27484
Loc: Beautiful British Columbia, Ca...
|
|
Exactly correct.
--------------------
Daryl
"a gun without hammers is like a Spaniel without ears" King George V
|
sharps4590
.333 member
Reged: 09/03/16
Posts: 285
Loc: Missouri Ozarks
|
|
Well stated by all of you!!
--------------------
Jesus said, "I am the way the truth and the life. No one comes to the Father but through me." John14:6
|
Previous
Index
Next
Threaded
Edit
Reply
Quote
