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Post by timgunner on Sept 28, 2015 11:08:18 GMT -5
I'm working on designing a .338 smokeless mz and trying to figure out how much volume I should add in the powder chamber... It seems like a .338 win mag case capacity would be a good place to start. From what I've been able to find out the case capacity is 5.6cc I'm not sure if that is to the neck shoulder junction or case mouth... I obviously want to fill the powder chamber so I'm trying to figure out what size of charge to use. The Hodgdon's book lists 71.5gr h100v as a compressed load so it obviously fills the case. My question for you quick loads whiz guys is what pressure am I looking at with a 27" 1-10" twist barrel minus arrowhead plug 1.84" and 1.5"x.5"(4.85cc) powder chamber. And a FF sized 225gr bullet sitting on a charge of 70gr of H100v with CCI mag209 primer.
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Post by edge on Sept 28, 2015 13:43:22 GMT -5
5.6cc looks to be full case including neck.
IMO, you might want to look at this a little differently.
You never want the bullet to be able to enter the powder chamber especially if you might be using a wad so the chamber should either hold less than your MINIMUM load or you need a restriction for the bullet to rest against so it does not enter the chamber OR a ramrod that is shortened to accomplish the same effect.
Unfortunately that is a newer powder than my version of QL so I can't really help you out.
With that said, if Hodgdon shows a compressed load then you will PROBABLY see less in pressure since the bullet is already sized, at least that is what I have observed with other ML traces.
edge.
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Post by timgunner on Sept 28, 2015 13:53:52 GMT -5
I see what your saying about wanting a smaller chamber than the starting load I just haven't been able to figure out how to measure the cc of a starting load of powder I guess I could try to extrapolate from the weight to fill ratio... That's why I went for a 1.5" chamber to get under 5cc
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Post by Savage Shooter on Sept 28, 2015 14:24:00 GMT -5
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Post by edge on Sept 28, 2015 14:53:47 GMT -5
A 338 Federal, a 338-08 both have about 3.7cc of capacity and IMO if you are going to a 338 I doubt you would want less than these cartridges capacity. IMO, and most don't worry about this but I am a belt & suspender person when it comes to pulling the trigger. A centerfire rifle peak pressure is contained inside of a case that is inside of a reamed chamber. Almost all of the MZ designs just have a threaded section that is part of the chamber. Just because a certain caliber is capable of a certain SAAMI pressure does no mean a rifle of the same dimensions would have the same safety factor  When I am pulling the trigger with the chamber inches from my head I generally try to keep the pressure under 50kpsi even though my barrel in theory would be safe at the SAMMI 65kpsi. The nice thing about a ML is you have the ability to add capacity just by putting in more powder ( hopefully of a slower variety ) edge. |
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Post by timgunner on Sept 28, 2015 15:01:22 GMT -5
Edge I agree with you
I definitely plan on using slow burning powder in this one. According to the Lee chart and Hodgdon's load info... The starting load is 67gr which would yield a volume of 4.8cc. Which is just a bout perfect assuming the powder is not compressed too much from seating pressure.
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Post by timgunner on Sept 28, 2015 15:07:56 GMT -5
Thanks to Dave W it looks like 70gr produces about 55kpsi and 2700fps. Not spectacular velocity... But seems like the pressure would be right about max.
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Post by edge on Sept 28, 2015 16:42:53 GMT -5
Edge I agree with you I definitely plan on using slow burning powder in this one. According to the Lee chart and Hodgdon's load info... The starting load is 67gr which would yield a volume of 4.8cc. Which is just a bout perfect assuming the powder is not compressed too much from seating pressure. " assuming the powder is not compressed too much from seating pressure" IMO, that is the Holy Grail...perfect seating pressure and how can you achieve it...not for a second or a minute, but as long as the rifle stays loaded! I hate to say it, but logically, and I do not use it the only answer is zero. A bullet that just sits on top is always just sitting on top. I used to shoot Dead Center bullets which are pure lead inside of a sabot. At the range with load and shoot they always went bang but in the field after being loaded at 3 am they very often went poof at 8 am. If I re rammed them they went bang every time. The powder was problematic so a bit less pressure seems to be the likely culprit. Even though Doug's has been on the wb since 2001 I doubt we have yet to find all of the problems...yet alone all of the answers edge. |
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Post by cuda on Sept 28, 2015 17:08:49 GMT -5
A 338ML would be a nice gun! Me and my buddies were talking just the other day about a 338ML. So I will be watching this one.
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Post by timgunner on Sept 28, 2015 17:22:10 GMT -5
I'm going to post my progress as the build goes along. I've got all the parts and will be doing all the machining one step at a time. I'm also building my own hunter style bolt conversion as well as FullForm die so my plan is to make the bolt nose first, then the Full form die body, then I can just machine the barrel drop to match while it is still on the barrel and not have to mess with the short drop. This will allow me to machine the barrel drop while diled in with the bore of the rifle...
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Post by timgunner on Sept 28, 2015 17:27:09 GMT -5
Edge my comment about seating pressure was more of a question on how much can I expect the powder to compress when ramming the bullet onto the powder.
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Post by cuda on Oct 14, 2015 9:36:44 GMT -5
Any update yet?
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Post by timgunner on Oct 14, 2015 12:30:44 GMT -5
I've been working on it a little bit at a time as i get a chance. Ive made progress on the bolt nose and got the barrel polished but not much else. I've had to make a few lathe/ mill fixtures so I've been busy with that and haven't just made the effort to put it together. i just opened a photo bucket to share pics as i go how do i upload them?
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Post by timgunner on Oct 14, 2015 12:38:42 GMT -5
Okay i think i figured it out. These are the pics of parts and progress building the rifle sorry they are not very good pictures and they are in reverse order. Anyway as you can see from the pics i still need to braze the bolt handle onto the bolt body and modify the firing pin to work with the shorter bolt. I also have had a heck of a time getting any primers to seat in the Arrowhead plug. I hate to ream it out if i just got a box of over-sized primers. I have been using CCI mag primers and they will not fit in the plug. I polished the plug with some 400 grit sand paper for about a hour and continued trying the primer until it finally chambered up to the bolt face. Then i tried a new primer and it didn't go in at all. I guess all i had done was reshape the primer not the plug. If your reading this Luke am i supposed to ream out the breech-plug? s1168.photobucket.com/user/timnterra/slideshow/338%20Smokeless%20MZ |
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Post by edge on Oct 14, 2015 12:45:01 GMT -5
Very nice will be waiting to see your targets edge. PS that looks like some fine machine work! |
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Post by Dave W on Oct 14, 2015 16:57:43 GMT -5
Watching with interest.
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Post by timgunner on Oct 14, 2015 22:48:23 GMT -5
Very nice will be waiting to see your targets edge. PS that looks like some fine machine work! Thanks for the complement. I'm a just hobby gunbuilder for the most part. I am, however, working on getting an FFL so that I can do work for others, but until that gets approved i am only allowed to build guns for myself. Which is okay for now because i get a lot of satisfaction out of building and shooting my own weapons... |
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Post by lwh723 on Oct 15, 2015 8:00:41 GMT -5
This latest bath of plugs has a pretty tight primer pocket. So you don't have an undersized batch of primers. I know the instructions list sandpaper as an option, but it's a pretty time consuming option as you found. I use a dremel bit to grind it open--but go slow with this option. I recently discovered that if you only ream open the top half of the primer pocket with these tight pocket plugs, you get a substantially better fit the CCI and FED without having to really cam the primer home. Hope this helps. |
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Post by timgunner on Oct 17, 2015 22:59:15 GMT -5
Thanks Luke you don't happen to have a measurement of a finished BP primer pocket do you? I'm okay with slowly opening up the primer pocket till I get a good fit, but I'd like to have an idea on where to stop.
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