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Post by ballistic on Nov 28, 2022 20:48:19 GMT -5
This has likely been talked about before - but I just wanted to add and get comments from others. This is a copied heading from a research article I recently revisited.
“When metal is subjected to a change in temperature, it responds by changing size, known as thermal expansion and contraction. An increase in temperature makes the member bigger and a decrease in temperature makes the member smaller.”
How does this apply to a smokeless muzzleloader ?
Several experienced shooters will agree that temperature has it’s affects on center fire rifles -but how does this affect the outcome of speeds with a muzzleloader ? It takes pressure (several thousands)to make speed. A known way to increase pressure and speed is to size a bullet bigger. If you have to hammer a round down the barrel -the speed will increase buy a large amount. If the round easily slides down the barrel with the weight of a ramrod alone -there’s a good chance your speeds will drop by a large margin.
Here’s an example of a .416 muzzy (full formed) that also applies to a smooth sized .402 or .452 bullet. The die is set (2 fingers load pressure) and the rounds are fired at 70 degrees. The speed was 2900 fps (350 grain bullet) and held single digit deviation. H4350 powder used.
The same combo as described was then fired on a 95 degree day. The loading pressure went up significantly and it took both hands on a solid ramrod and a few breaks in between to get the rounds to seat. Speed went up to 3050 fps and the zero rose 1.5”.
The same combo as above was then fired on a 25 degree day. If you guessed that the ramrod alone seated the bullet you are correct. If you guessed that speeds dropped to 2700-2750 fps and that the zero dropped almost 2” then you are also correct.
This has happened on several muzzies of mine with smooth formed bullets as well. So what happened ? My extreme extruded holy grail H4350 - not a chance - well likely some could be blamed……..
I’m going to go out on a limb and blame the issue on the thermal expansion of the different metals - specifically the barrel and the bullets. Alll metals expand and contract with temperatures but at different rates. Your favorite stainless or chrome moly barrel expand and somewhat similar rates. Look up copper and you will see that it expands at close to 1.5 times the rate of your barrel. And then look up lead - a staggering 2.5 - 3 times what stainless is doing. This can actually be measured with a set of .00001 five digit calipers by sizing a bullet at 70 degrees and then deep freezing it and measuring it again. The changes are actually pretty small - but unlock the reasons behind loose to tight fitting rounds and the zeros and speeds associated with them.
Ok - so how do we deal with the above and who has 5 digit calipers ?
My answer is to try and find a good balance on how you size your rounds and mark them. You might have to tighten the die a notch in the summers heat and loosen it a notch in the cold. Or buy a few dies for the temp extremes. Or just a least know what’s going to happen in your conditions and adjust for it. I’ve been playing this game for many many years and have never found the perfect combo where 1 size fits all and speeds and zeros remain perfect. Some claim to have found it - my hats off to you that have.
Just wanted to open the door for discussion. And maybe the above might benefit some new and also some experienced muzzy shooters.
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Post by sew on Nov 28, 2022 21:19:55 GMT -5
At the 35-40K PSI range (well below your load), only N110 was found to be virtually temp insensitive. This waswith both saboted 45s and 50s. A temp difference of 80 degrees F (10F and 90 F) caused less than 50’/sec in velocity when the 50cal was 2450 and the 45 was 2575 (250 and 200 SST / 45 and 38g). Vv120 at 2700 was between 100 and 200. The 50 cal duplex of 10/60 110/120/250g bullet when going from 70-80 F to 0 F went from 2700-1900.This was noticed/experienced by a lot of 50cal shooters in the same season of 2002.
Sabots likely won’t exhibit thesame characteristics as bore or land sized bullets. Is the much colder bullet significantly harder to obturate? If so, it will move further down the barrel before making a seal, which will lower the pressure and velocity.
What’s the optimal pressure for H4350? I bet it is well below the what most of us shoot in out smokeless MLers. And a whole lotowssthan the 140g load in the Bad Bull 50.😳
Obturation characteristics of the extremely cold bullet and powder temp sensitivity, including the “Extreme” powdersare more factors to consider.
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Post by nick50471 on Nov 28, 2022 22:15:37 GMT -5
An increase in temperature affects the powder far more than the barrel or bullet. This is why you saw a fps increase.
Bullet sizing doesn’t affect fps as much as you think. Certainly not over 100fps.
An increase in temperature will cause the metal to expand. Expansion of the barrel would theoretically decrease pressure and velocity. Expansion of the bullet would cause an increase in pressure and velocity. Your example has the speed going up with temp(again this actually due to powder temp). If…I’ll play along…if the bullet increased in size due to temperature the barrel would likely be subjected to an equal temperature and increase accordingly.
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Post by ballistic on Nov 28, 2022 23:09:23 GMT -5
An increase in temperature affects the powder far more than the barrel or bullet. This is why you saw a fps increase. Bullet sizing doesn’t affect fps as much as you think. Certainly not over 100fps. An increase in temperature will cause the metal to expand. Expansion of the barrel would theoretically decrease pressure and velocity. Expansion of the bullet would cause an increase in pressure and velocity. Your example has the speed going up with temp(again this actually due to powder temp). If…I’ll play along…if the bullet increased in size due to temperature the barrel would likely be subjected to an equal temperature and increase accordingly. I like your thought process and can agree mostly with what you are saying. Try pounding a bullet down the barrel with a big hammer (oversize it purposely) and (keep everything for the test at the same temp) watch the speeds rise. It’s easy with a slow burning powder like H4350 to get 150 fps increase in the speeds. Again this is with a slower burning powder and my tests have confirmed this still happens with faster burning powders but at a lower rate. Another argument that neither supports or disagrees is an issue that is known with (some) rifle cartridge shooters. In super cold temps -primers have been blown and speeds have increased. This is contrary to powder producing less fps and also contrary to the proven shrink rate of copper and lead (both should have shrunk more than the barrels metal). Muzzleloaders are different but also share many of the variables that are experienced with rifles. Hodgden claims of temp insensitive powders have had reviews that support and others that don’t support those claims. I don’t think the resistance of the bullet to the bore can be denied as a major factor to pressure and speed. With rifles bullets are forced into the riflings. With muzzleloaders we are trying to get a round down the barrel with just the right amount of tension to make loading easy and keep the bullet on the powder. If it’s too easy speeds will drop -too hard and they raise. I still believe it’s a combination of both the powders temp and the friction of the bullet. If you can slow a round down a millisecond in the barrel- more pressure will result in higher velocities. It could be the powder in one case and could be the friction/resistance in another case. It’s really a simple statement “how does the powder and metal work together from low temps to high” Its a simple statement with complex answers. I like your thought process on the powder. |
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Post by joelmoney on Nov 29, 2022 2:33:35 GMT -5
Could we even hammer down a bullet that has full obturation?
I believe a full form bullet obtuates quicker than a smooth formed.
Is a hammer down smooth form now acting like a full form?
If it’s simply thermal dynamics and barrel shrinks with lower temperatures wouldn’t my velocity climb when gun is loaded in summer and then shot in the late fall. I have not seen this with Reloader 16. I shoot my hunting shots on a fouled crusty barrel an have not seen that change my point of impact. This year when I unloaded my gun at end of season it impacted within an eight of an inch of where I was shooting this summer when it was over 50 degrees warmer.
I think Scat actually found an increase in velocity with cooler temperatures with RL-16
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Post by nick50471 on Nov 29, 2022 9:39:18 GMT -5
H4350 is a great powder when used as it’s intended. Make no mistake it is not intended to be used pushing a 350gr bullet out of a 40cal.
The velocity shift you are seeing is a direct affect of temperature on the powder.
I personally and several others have tested bullet load force to death. We all have seen the same results. SML’s load force affect on accuracy and velocity is minimal.
Note: one thing to consider especially when we talking about large powder columns. Which I assume is your case with H4350 and 350gr bullet.
During ignition the powder is intended to burn from breach to muzzle. Our SML ignition creates a flame torch that penetrates into the column. With powders like H4350 in a large dose the moment of ignition pushes the powder column away. This powder is not designed for that application and will be inconsistent. H1000, Retumbo and RL33 are far better choices.
Please I understand to you I’m just some guy on a forum. Everything I post comes from actual data from thousands of rounds and working in the industry with the manufacturers. I would be happy to explain more if you want. Call me anytime.
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Post by hillbill on Nov 29, 2022 13:32:11 GMT -5
My findings with temp change and bullet sizing:
Smooth form:
Bullets do size differently with a change in temp.
I’m not talking just a few degrees but say 20 or greater
I size bullets in my garage, temps can vary greatly depending on the season, with die, bullets and gun all sitting in the same temp change yes it can make a sizable difference in the way a bullet loads
Full form:
Even a greater difference can be found here, why? Only speculation but I know for sure it exists.
Recently with the full form rig I call rehab I sized some hard core bullets and then three days later sized more on the same die setting, they wouldn’t even start down the barrel.
I had to tighten the die down some to get the bullets to the same feel as the ones already sized
the only difference? 30 degree temperature.
Was it because of the steel shrinkage? Didn’t seem to be, the other bullets previously sized still fit fine?
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Post by Richard on Nov 29, 2022 14:57:53 GMT -5
My experience with tight vs. loos bullets (regardless of thermal expansion)is that velocity effects are very little. Yes, I am talking about hammering bullets down the bore (smooth sized with with a solid brass rod) It took so much force with a 16 oz. framing hammer, that my two shooting partners left the room we shoot out of! In fact, the velocity was only around 10 fps faster than produced by a normal two handed seat.
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Post by ballistic on Nov 29, 2022 17:52:04 GMT -5
My experience with tight vs. loos bullets (regardless of thermal expansion)is that velocity effects are very little. Yes, I am talking about hammering bullets down the bore (smooth sized with with a solid brass rod) It took so much force with a 16 oz. framing hammer, that my two shooting partners left the room we shoot out of! In fact, the velocity was only around 10 fps faster than produced by a normal two handed seat. Richard Was this with a .45 cal muzzy using a fast powder like 4198 ? Thanks |
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Post by yoderjac on Nov 29, 2022 18:53:34 GMT -5
My experience with tight vs. loos bullets (regardless of thermal expansion)is that velocity effects are very little. Yes, I am talking about hammering bullets down the bore (smooth sized with with a solid brass rod) It took so much force with a 16 oz. framing hammer, that my two shooting partners left the room we shoot out of! In fact, the velocity was only around 10 fps faster than produced by a normal two handed seat. Does that point the finger at powder? |
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mitch
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Post by mitch on Dec 18, 2022 12:41:11 GMT -5
This post was top of mind for me today. Shot my 7mm Rem Mag on paper to try to figure out how I missed my whitetail buck at the end of the season. Temperature was -27C that day with windchill down to -37C, and I clean missed my buck around 130yd, from prone off my bipod (I don’t miss that shot, ever…). So today was similar conditions (-21C with windchill down to -32C). On paper at 130yd with the same shooting setup, my first shot landed 3” to the left, second one landed 3.5” high and 1.5” right, and the next 5 shots steadily worked their way down until the last three were sub-MOA and about an inch high and right.
At these low temperatures the gun is wildly off of zero and imprecise, but comes back to normal as it warms up.
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Post by ballistic on Dec 18, 2022 15:41:53 GMT -5
This post was top of mind for me today. Shot my 7mm Rem Mag on paper to try to figure out how I missed my whitetail buck at the end of the season. Temperature was -27C that day with windchill down to -37C, and I clean missed my buck around 130yd, from prone off my bipod (I don’t miss that shot, ever…). So today was similar conditions (-21C with windchill down to -32C). On paper at 130yd with the same shooting setup, my first shot landed 3” to the left, second one landed 3.5” high and 1.5” right, and the next 5 shots steadily worked their way down until the last three were sub-MOA and about an inch high and right. At these low temperatures the gun is wildly off of zero and imprecise, but comes back to normal as it warms up. If you get a chance - try and get speeds on your combo. It could be shooting faster? Or slower ? The problem will be the electronics in the chrony and labradar. They don’t like temps that cold. Make sure your barrel and ammo is cold and then bring out the electronics prior to shooting. The affects are real - it’s not just one item (but could be) it’s all of them working together or against. Thanks for sharing. Not sure if you’re using a (7mm calls for them but I know guys that use large rifle) magnum primer -but that’s why they were originally made for -the super cold. It’s likely not the primer. If you get a chance to test for speeds in the same cccccold temps - please update us with your results. Thanks |
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mitch
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Post by mitch on Dec 18, 2022 16:34:12 GMT -5
Will do.
Oh I forgot perhaps the most important part: shooting solid copper bullets (Barnes 145 LRX)
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mitch
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Post by mitch on Jan 6, 2023 19:04:59 GMT -5
Pretty cool, MDT just released a video where they test a rifle and ammo cooled down by dry ice. Centerfire, not a smokeless muzzleloader, of course.
Other than one overpressure issue (hypothesized due to frosting rather than metal contraction), I’d say the difference is actually pretty underwhelming.
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Post by ballistic on Jan 6, 2023 20:15:51 GMT -5
Mitch
Good video.
Do you know if the barrel was full steel or a carbon fiber ? The author did not give any data on the speed of the round with the cold barrel/cold ammo other than it blew the primer. Normally a blown primer results in higher speeds but sometimes the speeds drop from the blown primer. That would have been great info to share. His results were a good test for that combo. I’ve seen and tested centerfire combos that shoot close to 200 fps fast and zeros shift several inches in super cold. Combos that had tape or balloons over the muzzle - but if humidity was trapped in the bore ice crystals could still form ? Every combo can be different that’s for sure. I have a 260 Remington that temp hardly has any affects on speed and the zero. I have another 260 match comp rifle that spikes in speed when really cold but the zero drops (sucks when the pencil barreled gun isn’t affected and the match is) -my luck I guess -lol.
It will be interesting to see what happens to your combo if you get a chance to test it in the cold. Please update your results when you get a chance. And keep sharing videos like the above. That was crazy to see how frozen that setup was.
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mitch
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Post by mitch on Jan 6, 2023 20:29:44 GMT -5
Everything I can see it appears to be a conventional (all steel) barrel. It has a pretty heavy contour on it, which I assume helped to minimize the POI shift but your pencil vs match barrel experience shows that may not exactly be the case, haha.
It was really unfortunate that they had such bad frosting issues during this testing as that added a huge uncertain variable, not just testing temperature effects at that point. But we aren’t paying them to be scientists for us so I can understand why they didn’t go super hard trying to work around that, haha.
I did some more testing the other weekend in the cold (but not extreme cold) and my 7mm RM is just inconsistent as all getout. Some one group is massive, next is sub-MOA (at a different POI), next is 1.5MOA at yet a different POI. I shot the groups identically (2min between shots) and about 30min between groups to return to a full cold-bore condition. So at this point it appears that purely thermal affects are not the root-cause of my issue. My leading hypotheses at this point are:
1) barrel is worn out (bought it used, I’ve sent 800 down the barrel, and it’s a 7RM so, fair enough). New barrel is on order
2) issues are from the stock and variation I’m seeing is from inconsistently handling the stock. It’s just the cheap Savage factory plastic stock. I have some tweaking and testing planned to investigate that further too.
But at this point my conclusion is my 7RM issues aren’t from thermal affects so no longer on-topic for this thread :-(
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Post by Sideshow on Jan 7, 2023 3:29:53 GMT -5
Balistic i dont shoot anything close to the loads you do but ive noticed the bullet fit changes alot from temps in a muzzleloader .
But this post also got me thinking about a issue that Browning had with A-bolts that were SS sporters actually peeling back like bananas in extreme cold when shot !!! You tube even had some hunts filmed where it happened on camera . Chrome moly barrels not 1 was ever reported to do that .
At that time i was barrel shopping and so i asked several manufacters about this . Nearly ALL told me chrome moly is far more stable and reccomended in extreme cold .
Thought youd like to know.....
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Post by flattopusa on Jan 8, 2023 11:11:03 GMT -5
ballistic: I have read this post with great interest and the situation you talk about (higher pressures at higher temps/lower pressures at lower temps) can be explained in part by expansion and contraction of dissimilar metals. It can also be explained in part by the powder charge that is used, and the burn rate of that powder that is used can come into play as well.
If the powder charge used is the same at high temps and the same at low temps the pressure developed by the charge and the velocities will be different. I ran a test with one of my modified cartridges a number of years ago and found that it required 4.5 grains of powder more to develop the same or near same velocities at 10 F, as it did at 100 F. Because the testing required that a safety standard for the cartridge be determined, I was working with max loads, and the "African" load required the aforementioned 4.5 grains less to acquire the same velocities, and therefor pressures, as the "Arctic" load. For changes in temp the load must change as well to maintain the same pressures and velocities.
That test was performed in a cartridge gun, but, if I would have loaded the "Arctic" load and shot it on a 100 F day...well I might not have fared so well!
Then back to the original question you posed. If a powder charge fired at high temp with a mild temp load and the "bullet/barrel, etc, has expanded due to those high temps", that would also increase the pressures/velocities, and vise versa if the load was shot below the mild temp which would decrease the pressures/velocities.
There were a few times when I competed in Benchrest that I had to reduce my load to maintain accuracy....cool in the morning and scorching hot in the afternoon.
I do nothing but hunt anymore and I dont carry different or multiple temp developed loads, differently sized bullets, and a thermometer with me in the field with my SML. I work up my hunting loads to a median temp that is consistent with the temps I hunt under which is 35 to 40 degrees and that gives me roughly a 40 degree temp average where the gun performs well.
In other words If the bullet and the barrel, and the powder and the primers are all shot at the median temp I can expect reasonably consistent performance from my gun for the average temps I hunt under.
Now the BIG question...How does this affect the SML? My median temp process seems to work well with cartridge guns and my SML and I will continue to go that route, but, if somebody knows something that I dont know I would sure like to hear about it...always learning.
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Post by Sideshow on Jan 10, 2023 1:43:43 GMT -5
Pretty cool, MDT just released a video where they test a rifle and ammo cooled down by dry ice. Centerfire, not a smokeless muzzleloader, of course. Other than one overpressure issue (hypothesized due to frosting rather than metal contraction), I’d say the difference is actually pretty underwhelming. Figured id add another tid bit of info on this dry ice thing from mitch that long range/target guys May find usefull . Theres a process used to freeze steels to very very low temps in labs that stress relieves the parts fairly effectively . I dont know if anybody has done this with barrels yet but it does work . Vibratory destressing is also used successfully . Just a fyi if there would be interest . Probably in cf this would show alot more due to faster rates of fire . A button rifled barrel would no doubt also have greater benefit . |
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Post by jims on Jan 10, 2023 9:59:48 GMT -5
I have had several barrels cyro frozen or whatever it is called. Can't recall from memory. Maybe it helped but I cannot really say I saw a difference although it makes some sense to me that it could have some benefits.
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