Did he have to purchase a “special “ machine to accomplish this arduous task, have it ‘tuned’ by a self proclaimed expert, or did a clean swab do the trick?
Bolt thrust
- Thread starter TAJ45
- Start date
The word Measure “ appears nowhere in this response.
It actually is a perfect example of things to be aware of.
"An oiled case does slide backwards. This was the standard British Army method used in proof testing throughout the 0.303 Lee-Enfield period and carried on into the 60s at least with 7.62."
It would be interesting to know how much oversize a 303 chamber is reamed. As it was designed to feed reliably with dirt in the action.
The amount of taper on the cartridge body , paired with oversize chamber. Could that not be the cause ?
It would be interesting to know how much oversize a 303 chamber is reamed. As it was designed to feed reliably with dirt in the action.
The amount of taper on the cartridge body , paired with oversize chamber. Could that not be the cause ?
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Andy Work
Gold $$ Contributor
For $800.00 you can eliminate the guesswork on pressure.
PressureTrace II & Shooting Lab Software Bundle
PressureTrace II & Shooting Lab Software Bundle
Thauglor
Silver $$ Contributor
Is that code interpolating between known data or actually a first principles code (simulating the burn reaction and the physics as the powder is ignited)? If it is based on known data, that probably means you are now extrapolating the data it has, and that has significant error bars. All engineering level codes (which that one probably is) tell you that going past known data (ie extrapolating) is not to be trusted. I doubt that 161k psi answer is correct
I don't know.
Wouldn't the 161K PSI also assume that there was no material failure? If the brass ruptured at 100K, I would assume the peak pressure would impacted as well.
As I have always understood it, Bolt Thrust is a function of the surface area of the Head of the case. For instance, an H&R Handi Rifle cannot handle Magnum Chamberings because excessive bolt head surface area creates too much Bolt Thrust. Another example is the 338 EDGE in a Savage small shank action. It works fine, whereas the 338 Lapua Magnun is pushing the limits of a Savage action because of its much greater bolt thrust, because of the greater bolt head surface area.
I have understood that Pressure is, in this regard, a separate subject. Too much of, or the wrong kind of Powder, will cause excessive pressure in all directions, and REGARDLESS OF BOLT THRUST ???
I HAVE NO IDEA IF ANY OF THIS IS CORRECT
I have understood that Pressure is, in this regard, a separate subject. Too much of, or the wrong kind of Powder, will cause excessive pressure in all directions, and REGARDLESS OF BOLT THRUST ???
I HAVE NO IDEA IF ANY OF THIS IS CORRECT
Yes, mostly...but it's the internal case dimension, not the actual rim diameter. If that was the case, you could rebate rims and change bolt thrust. Read the link on the first page. Good info.As I have always understood it, Bolt Thrust is a function of the surface area of the Head of the case. For instance, an H&R Handi Rifle cannot handle Magnum Chamberings because excessive bolt head surface area creates too much Bolt Thrust. Another example is the 338 EDGE in a Savage small shank action. It works fine, whereas the 338 Lapua Magnun is pushing the limits of a Savage action because of its much greater bolt thrust, because of the greater bolt head surface area.
I have understood that Pressure is, in this regard, a separate subject. Too much of, or the wrong kind of Powder, will cause excessive pressure in all directions, and REGARDLESS OF BOLT THRUST ???
I HAVE NO IDEA IF ANY OF THIS IS CORRECT
Point well taken
Edit…So, the Bolt Thrust of a Belted Magnum would only be determined by the diameter of the inside of the case, and not the larger diameter of the Belted outside ??
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Force (bolt thrust in lbs.) is equal to pressure (in psi) multiplied by area (sq. in.)
It is true that the area inside of the case is the determining factor. It would be difficult to know what that area is. You could section a case and try to measure but that would be difficult too because of the radius between the flat portion parallel to the breach face and the case wall. It could be calculated but that would be pretty complex in itself.
When I was rebarelling Handis I simply used the outside case head diameter to make it easy. This also will provide a safety factor in that what you calculate for Force (bolt thrust) will be higher than actual. It is for sure an imprecise method but it is useful for comparisons. Of course as mentioned above, rebated rims don’t work in this scheme.
To be clear though, I was not trying to do engineering level determinations to see if I was exceeding the strength of an action, I was just attempting to see if I was within the limits of what the designers/engineers built in the first place.
If H&R never chambered one in 300 WinMag, I wouldn't either!
It is true that the area inside of the case is the determining factor. It would be difficult to know what that area is. You could section a case and try to measure but that would be difficult too because of the radius between the flat portion parallel to the breach face and the case wall. It could be calculated but that would be pretty complex in itself.
When I was rebarelling Handis I simply used the outside case head diameter to make it easy. This also will provide a safety factor in that what you calculate for Force (bolt thrust) will be higher than actual. It is for sure an imprecise method but it is useful for comparisons. Of course as mentioned above, rebated rims don’t work in this scheme.
To be clear though, I was not trying to do engineering level determinations to see if I was exceeding the strength of an action, I was just attempting to see if I was within the limits of what the designers/engineers built in the first place.
If H&R never chambered one in 300 WinMag, I wouldn't either!
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Correct. Here's the link previously posted. It explains bolt thrust in detail, along with how to calculate it, as well as examples of approximate case ID's of most cartridges, like 223, ppc, 308,magum, etc. It's by an engineer in the firearms industry...Dan Lilja. I'm sure most of us are familiar with him and his barrels.Point well taken
Edit…So, the Bolt Thrust of a Belted Magnum would only be determined by the diameter of the inside of the case, and not the larger diameter of the Belted outside ??
I encourage everyone, again, to look at it. Very good info on this very subject.
A Look at Bolt Lug Strength - Lilja
All action designers are concerned primarily with producing a safe and functional product. All other considerations such as weight, finish, eye appeal and other cosmetics are secondary. From a safety standpoint, the strength of the bolt lugs is of prime concern. Bolt lug shear strength depends...
BoydAllen
Gold $$ Contributor
He wraps a fresh patch around his chamber swab.
USMCDOC
Silver $$ Contributor
once had a barrel (new at that too) bulge and set the boltface back 10 thou according to Randy Gregory.. it was determined that it detonated. And the load was considered a "safe" load for that case and the bullet i was using. .
DaveTooley
Gold $$ Contributor
I'm not saying it didn't happen but yours will be the first detonation I've heard of in 40+ years.
Did it bulge the chamber and receiver?
USMCDOC
Silver $$ Contributor
dave, it did bulge the chamber, bout 9 thou i believe it was
divingin
Gold $$ Contributor
Quick question, if I may: How did the chamber expand by 9 thou and not affect the tenon area of the action? Was the barrel tenon thinned out?
I've recounted a few stories which are somewhat germane to the subject, so I won't bore everyone with them again. Bolt thrust is a fairly simple concept, yet there are some complexities to it as well.
I watched a You Tube video of a couple of guys who chambered a Lee Enfield to 300 Win Mag and fired some proof loads through it. It did finally fail, but it took much longer than I would have thought. They didn't report at all on how much the cases stretched; this is something I would have liked to have known. The bolt finally failed after shooting several lubricated rounds. It also appeared the bolt may have suffered some damage prior to this test and was beginning to fracture. Anyway, it is an interesting video. WH
I watched a You Tube video of a couple of guys who chambered a Lee Enfield to 300 Win Mag and fired some proof loads through it. It did finally fail, but it took much longer than I would have thought. They didn't report at all on how much the cases stretched; this is something I would have liked to have known. The bolt finally failed after shooting several lubricated rounds. It also appeared the bolt may have suffered some damage prior to this test and was beginning to fracture. Anyway, it is an interesting video. WH
Dusty Stevens
Shiner
Lot of slack in the threads to displace metal
jackieschmidt
Gold $$ Contributor
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