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Post by hillbill on Sept 10, 2023 9:59:30 GMT -5
So I’m doing some guns right now that are basically all clones .45 cal, # 6 profile @ 24”
[My thinking is this I’m doing one with a 72 grain chamber One with about a 50 grain chamber One with no chamber 72 and 50 are spun up No chamber in process
The load is Benchmark, likely in the 92 grain area with a 303 HC bullet What difference will I see in the 3??? I’m thinking the largest of the chambers will yield higher speeds? Been wrong before though I do know that this load shoots very well in guns with no chamber, been there. Advantages? Down side? I do know of one Small doses of powder can’t be used but most will never shoot a reduced load anyway.
Thoughts?
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Post by Kyle on Sept 10, 2023 16:33:21 GMT -5
In my opinion - with the shorter stack, the powder will burn more efficiently. The bullet travel distance is greater as well. I predict 35-40 fps increase in velocity with the big chamber vs no chamber given the same charge and bullet weight.
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mitch
Junior Member
Posts: 90
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Post by mitch on Sept 10, 2023 21:43:34 GMT -5
In my opinion - with the shorter stack, the powder will burn more efficiently. The bullet travel distance is greater as well. I predict 35-40 fps increase in velocity with the big chamber vs no chamber given the same charge and bullet weight. Would it perhaps have less temperature sensitivity as well, shorter fatter powder column letting the flame front propagate laterally not just lengthwise down a long skinny column?
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Post by ballistic on Sept 10, 2023 22:39:59 GMT -5
In my opinion - with the shorter stack, the powder will burn more efficiently. The bullet travel distance is greater as well. I predict 35-40 fps increase in velocity with the big chamber vs no chamber given the same charge and bullet weight. I’m with you 100% Kyle. I also believe lower pressures will be seen on the primers and the barrel will be cleaner. Could be wrong - but that’s what I’ve seen so far with powder chambers.
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Post by hillbill on Sept 11, 2023 8:53:10 GMT -5
I have a good bit of experience with chambers in the .40 cal, they can make the difference between a load working and not. I also know with big loads like 4895 and 325s in a .45 a chamber close to load volume can make the difference between a stuck bullet and a good clean burn. I know not many here have experimented with chambers in the .45 but I'm about to with regular hunting loads to see what happens.
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Post by Richard on Sept 11, 2023 9:10:00 GMT -5
A good test Bill. I also have not dealt with chambers..at least not any given volume I usually run the hole for my threads somewhat deeper just so I have enough clearance to set my headspace. Probably not more than a 1/4" or so.
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Post by buckeye68 on Sept 11, 2023 21:01:53 GMT -5
I’ve seen Benchmark burn clean with no powder chamber.
I guess the $100 question is will it burn clean with a 24” barrel with the ignition you’re using?
The bigger question is will it be reloadable when you’re setting in your tree stand after you’ve just shot it ??
You’ll definitely see an advantage with a power chamber because the bullet will be in the barrel longer. The bigger the chamber the more efficient your burn rate will be.
For a hunting rig I would put a 70 grain powder chamber in it because you’ll have more available powders to pick from vs if you go too big of a powder chamber your powder options are limited.
I personally has seen a barrel pick up 100 fps just by going to a larger powder chamber with the same charge weight, bullet and primer. Also
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Post by hillbill on Sept 12, 2023 7:50:12 GMT -5
I know Benchmark works very well with a 24” barrel Very clean, very accurate I’m just thinking speeds would be better out of the 24” tube May be able to use even a shorter barrel with the same results
If I’m correct on my calculations a 23” with chamber would yield the same speed as the 24 with no chamber.
I really like the idea of a 23” barrel in a hunting rig.
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Post by hillbill on Oct 30, 2023 5:42:59 GMT -5
So as a conclusion to my testing
Tests were from 24” Brux 20 twist barrels, Benchmark powder 303 Pittman hard core bullets, magnum primers Tested with no chamber. 2910-2920 50-55 grain chamber. 2936 avg 72 grain chamber. 2956 avg In conclusion a little less than 1 fps gain per grain of added powder chamber
This is with a specific powder and barrel length, your results will vary with other powders and barrel lengths
In conclusion Is a powder chamber worth the effort in a .45? Only if you want to run a shorter barrel and keep the speeds up
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Post by paleface45 on Nov 13, 2023 23:50:51 GMT -5
What diameter do you make your powder chambers? .460, .500, .525 ?? I have just tried .460 dia.
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Post by hillbill on Nov 14, 2023 8:33:22 GMT -5
My chambers are an extension of the bore for the plug 5/8” plug is I think .587? Don’t remember off the top of my head though
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Post by sew on Nov 16, 2023 7:50:26 GMT -5
Bill, this is a very meaningful test , IMO. It can well, and should be, a factor in construction of smokeless MLers.
As the bore diameter decreases, ie, 45 -> 40, the powder chamber should have even more of a positive effect. Maybe enough to consider a 5/8 over a 9/16 BP for a 40. Though the advantages of a 9/16 may still be greater.
I’m experiencing the disadvantages of a longer barrel using the large suppressor/quick attachment on my 24” barrel’d 40 cal. The suppressor still wins out though.
Of course, for ultra short barrels (17-20+”), the size of the powder chamber may need to be slightly lower to allow the usage of smaller amts of faster powders(to get 100% burn in these shorter barrels).
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Post by Hank on Nov 17, 2023 8:24:01 GMT -5
Bill, this is a very meaningful test , IMO. It can well, and should be, a factor in construction of smokeless MLers. As the bore diameter decreases, ie, 45 -> 40, the powder chamber should have even more of a positive effect. Maybe enough to consider a 5/8 over a 9/16 BP for a 40. Though the advantages of a 9/16 may still be greater. I’m experiencing the disadvantages of a longer barrel using the large suppressor/quick attachment on my 24” barrel’d 40 cal. The suppressor still wins out though. Of course, for ultra short barrels (17-20+”), the size of the powder chamber may need to be slightly lower to allow the usage of smaller amts of faster powders(to get 100% burn in these shorter barrels). All muzzle loaders built with a full shank barrel should be using the 5/8-18 breech plug system. The 9/16-24 plug was designed for break actions and will not hold as much pressure as the 5/8-18 plug will. Especially in a 40 caliber, I would recommend the 5/8-18 plug for sure. This is my opinion, others will vary.
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Post by sew on Nov 17, 2023 8:40:11 GMT -5
That makes sense, to me, with the threads being the weaker point compared to the thickness of the metal over the chamber area.
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Post by sew on Nov 19, 2023 16:31:19 GMT -5
Bill, this is a very meaningful test , IMO. It can well, and should be, a factor in construction of smokeless MLers. As the bore diameter decreases, ie, 45 -> 40, the powder chamber should have even more of a positive effect. Maybe enough to consider a 5/8 over a 9/16 BP for a 40. Though the advantages of a 9/16 may still be greater. I’m experiencing the disadvantages of a longer barrel using the large suppressor/quick attachment on my 24” barrel’d 40 cal. The suppressor still wins out though. Of course, for ultra short barrels (17-20+”), the size of the powder chamber may need to be slightly lower to allow the usage of smaller amts of faster powders(to get 100% burn in these shorter barrels). All muzzle loaders built with a full shank barrel should be using the 5/8-18 breech plug system. The 9/16-24 plug was designed for break actions and will not hold as much pressure as the 5/8-18 plug will. Especially in a 40 caliber, I would recommend the 5/8-18 plug for sure. This is my opinion, others will vary.
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Post by sew on Nov 19, 2023 16:55:34 GMT -5
Hank and others,
I hadn’t fully thought this through. Assumption: when the ignition occurs, pressure goes up in the chamber creating a back pressure on the BP and on the sides of the barrel. Which is the weaker factor? Surely the BP. The threads hold it in. The coarser the threads, the deeper the threads, the greater # of threads all have a positive correlation in the strength of that BP not letting go.
Though the threads on the 9/16 BP are 24 per inch as opposed to 18 for the 5/8 BP, they each have 16 threads since the 5/8” plug is longer such that they each have the same # of threads. Now, do these threads have the same strength? No. Why? Two reasons. One, there is more metal between the coarser threads of the 5/8” plug plus, the diameter is greater resulting in even more metal. So, there is just considerably more metal holding the 5/8” BP than the 9/16” BP.
Hank, you were very gentle with your closing comment.🙂
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mitch
Junior Member
Posts: 90
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Post by mitch on Nov 19, 2023 19:31:20 GMT -5
Hey SEW, I gotta hit you with the classic engineer answer of “it depends” haha. This one’s all about the details. You’re right there’s a rearward force on the breech plug because of the pressure. Pressure exerts a force on every face in contact with it based upon the perpendicular area in contact with the pressure.
For the breech plug, the exposed face sees a rearward reaction force which has to be opposed by the shear area of the threads. The limiting factor will depend on the area of the major diameter and strength of the barrel material, and the area of the minor diameter and material strength of the breech plug. In both cases the area is the diameter multiplied by the thread engagement length.
Of course complicating things is the bolt face and it’s proximity to the module. If headspace is close enough the bolt might start taking load off of the module/threads. I haven’t run any stress analysis numbers on it (nor have I ever seen a barrel failure to try to investigate the root cause) to try and say whether the BP or the barrel is likely the pressure-limiting device. An additional complication is that - as I mentioned before in the barrel pressure thread - the analysis I’m familiar with is for slow rate stresses, not high rate stresses like caused by powder ignition.
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Post by sew on Nov 19, 2023 20:44:02 GMT -5
Mitch, maybe we should next investigate the comparative strengths and pressures against the primer and module against the bolt face verses the primer of the DI.
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mitch
Junior Member
Posts: 90
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Post by mitch on Nov 19, 2023 20:49:00 GMT -5
Mitch, maybe we should next investigate the comparative strengths and pressures against the primer and module against the bolt face verses the primer of the DI. Oh we’ll have to for sure haha. First though I need to do some basic hand calcs for the relative thread strength and pressure-resisting of 5/8 vs 9/16 threads. I have my suspicions the 9/16 might be stronger. Reason why is the force is generated by a square law (area of a circle, pi*r^2) and is opposed by a linear (circumference of a circle, 2*pi*r). But would need to run the numbers to see.
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Post by sew on Nov 19, 2023 22:36:03 GMT -5
Mitch, Do you have the measurements of the total thread length? Easily calculated since each have 16 threads, one 18/“and the other, 24/“. So, length of threaded portions are 8/9” and the other 3/4”.
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