I would measure fps if possible. And then back off a little.
Erratic pressure signs on previously safe load
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Frank in the Laurels
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Just back it off to 3500fps, I hardly think any animals vital area will notice the reduction, plus your brass will last much longer and that'll make your wallet happy ..
gohring3006
Well-Known Member
How old are the loads?
Did the bullet "weld" to the case neck on some?
Did the bullet "weld" to the case neck on some?
milo-2
Well-Known Member
If this is a new rifle, most likely your barrel broke in and sped up. You have not said if it was new or not, just the brass has been mentioned. If this is the case, your load was on the ragged edge before break in, now it is over pressure.
Your chrono will always be your best friend here, if something isn't right, chrono, deduce it back from there.
I think these guys nailed all the most probable causes. But if you are shooting pure copper at 3700 fps, I think I'd borescope my barrel.
I would not be surprised if you have some copper plating. Small temp diff with extra friction back press in the bbl. may just have you out on the final margin of pressure.
If you have copper get some Boretech CU 2+ give it a good cleanout, and see. Borescope will tell you.
I would not be surprised if you have some copper plating. Small temp diff with extra friction back press in the bbl. may just have you out on the final margin of pressure.
If you have copper get some Boretech CU 2+ give it a good cleanout, and see. Borescope will tell you.
Did you load up the first 30 and the second batch during the same reloading session?
Doodle
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I think you may have hit it. It is in fact a relatively new rifle…maybe 120 rounds through it.
Veteran:
I'm generally pretty good about decoppering if I'm shooting a lot of copper, but I don't usually send them this fast. I do need to buy a bore scope. Any recommendations?
I like my teslong. I only paid $65 dollars, it hooks to the computer, and uses the computer camera, and you get 2 or 3 extra lense attachments to go with it. Its long enough it goes through all my barrels, and its a rod tube design.
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You can shop around to see if Amazon or other places have any better prices. But the product works. Specially good for the cash.
Yes, I bet there's copper galore in that barrel. You are shredding those bullets at 3700 fps. There was one guy here doing 4000 fps with hammers here........Gotta be some copper in those tubes......Probably enough to make a few copper pennies of Abe Lincoln.
Hugnot
Well-Known Member
Stuff happens - pressures probably 65K psi or about
Check brass length & trim if needed, check out neck wall thickness of 1X brass & see if neck walls are thicker - these will probably be the same but check again. Bullets should easily slip fit into fired case necks.
The loads are at the edge of being excessive - the IMR 4064 density may have been affected by humidity drying/absorption meaning 64.5 grains the first load included extra weight and the 2nd 64.5 grain lot included less moisture - probably not but a consideration as the time between loading was short.
Powder charges may have varied in actual weight if scale not calibrated between lots. "only difference was the day they were loaded"
Don't see how fire-forming new brass in chamber with working loads would produce less pressure than with next or 1X fired loads - the chamber dimensions are the same, pressure is exerted in all directions, bore dimensions are same, same bullet, same primer. Don't think miniscule tiny brass expansion with new brass would work as some type of shock absorber to relieve chamber pressure. As noted - "So none of them were loaded on virgin brass" - new brass was not re-loaded.
Cold welding - I have noticed this with previously used brass - bullet get stuck real good. Should these bullets need to be pulled a tiny bit deeper seating breaks the cold weld - like POP upon exerting force on bullet. Using new brass this is not noticed. but "So none of them were loaded on virgin brass"
Seating depth the same or COAL equal? Pressures may change with seating depth variations. I do seating depth measurements on each ammo lot.
Copper fouling - kind of doubtful but worth checking - Hammer bullet expense probably would preclude lots of shooting.
My thinking is ammo reliability & safety is more important than 1% or 2% velocity increase or a small accuracy increase within a limited window.
Have to admit, a 124 gr. .30 solid copper/copper alloy bullet at 3700 looks like a real killer.
Check brass length & trim if needed, check out neck wall thickness of 1X brass & see if neck walls are thicker - these will probably be the same but check again. Bullets should easily slip fit into fired case necks.
The loads are at the edge of being excessive - the IMR 4064 density may have been affected by humidity drying/absorption meaning 64.5 grains the first load included extra weight and the 2nd 64.5 grain lot included less moisture - probably not but a consideration as the time between loading was short.
Powder charges may have varied in actual weight if scale not calibrated between lots. "only difference was the day they were loaded"
Don't see how fire-forming new brass in chamber with working loads would produce less pressure than with next or 1X fired loads - the chamber dimensions are the same, pressure is exerted in all directions, bore dimensions are same, same bullet, same primer. Don't think miniscule tiny brass expansion with new brass would work as some type of shock absorber to relieve chamber pressure. As noted - "So none of them were loaded on virgin brass" - new brass was not re-loaded.
Cold welding - I have noticed this with previously used brass - bullet get stuck real good. Should these bullets need to be pulled a tiny bit deeper seating breaks the cold weld - like POP upon exerting force on bullet. Using new brass this is not noticed. but "So none of them were loaded on virgin brass"
Seating depth the same or COAL equal? Pressures may change with seating depth variations. I do seating depth measurements on each ammo lot.
Copper fouling - kind of doubtful but worth checking - Hammer bullet expense probably would preclude lots of shooting.
My thinking is ammo reliability & safety is more important than 1% or 2% velocity increase or a small accuracy increase within a limited window.
Have to admit, a 124 gr. .30 solid copper/copper alloy bullet at 3700 looks like a real killer.
All rifles are different but I will have to say I have shot the IMR 4064 with the 124 in 300WSM in 26" 1:10 TW so comparable barrel specs. My barrel has 400+ through it.
I was showing pressure at 62.0 grains of IMR4064 at 3745 fps and 2.730 COAL crimped 1/8.. I truly believe you are over pressure and recommend resetting your load down a bit. 2.5 grains difference in a load in same barrel length is not likely going to have disparity in pressure this wide. Just a suggestion to consider.
I was showing pressure at 62.0 grains of IMR4064 at 3745 fps and 2.730 COAL crimped 1/8.. I truly believe you are over pressure and recommend resetting your load down a bit. 2.5 grains difference in a load in same barrel length is not likely going to have disparity in pressure this wide. Just a suggestion to consider.
milo-2
Well-Known Member
Given the fact that new brass grows in length by an average of .005", and in diameter by .003", your statement makes little sense.
Most people wont develop on new brass just because of these factors. Though firing brass made for that chamber really isn't considered fireforming.
Hugnot
Well-Known Member
Makes lots of sense to me seeing that OP did not load new or "virgin brass" The situation as I see it was 2 batches of 1X brass were loaded & the last batch was too hot. Assuming the brass "grows in length by an average of .005", and in diameter by .003" the same 1X brass was loaded in 2 sessions and pressure increases were noticed with the second batch. OP - "So none of them were loaded on virgin brass"
Did I not read - "So a load that was safe on virgin brass can show pressure on 1x fired brass because it isn't using as much energy to push the case out to chamber You should be seeing velocity that's higher as well."
I need a good reference as to how chamber pressures may be reduced upon firing new brass as apposed to 1x or fire formed brass (making brass conform to chamber) - anecdotal stuff is not enough. If anything, case capacity would be increased by fire forming and pressures would be reduced upon subsequent loadings.
milo-2
Well-Known Member
Whether he was firing once fired brass was never the question, you are the one who alluded to not seeing how firing new brass would result in any less pressure than with fired brass. He has changed nothing here.
Being I am willing to only provide "anecdotal stuff" that I am right, why don't you prove me wrong with science or whatever method you deem necessary. I wont be the only one waiting for this.
This is not the the op's problem.
