Determining the length of a powder column in my cva scout conversion.

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redear

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A little while back I stopped using imr 4227 in my scout conversion with the short His breech plug because there is a .542 section of unrifled larger dia. section in front of the breech plug and with my 45 gr. charge being such a short powder column I couldn't be sure that my bullet wasnt hanging down into that unrifled chamber. Another member had incurred some flame cutting damage with this scenario. Well the other day a very experienced sml shooter on another board clued me in on just how to check a certain load to see where exactly the bottom of the bullet lies in relation to that chamber. Yesterday I did what he said and found out that I am safe with my load as the base of my bullet is about 3/16" up into the rifling. I am very happy about this because that powder was getting me good accuracy results. It is a simple operation to check a load.
 

redear

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First off it seems the scenario of having this chamber of 1/2" in front of the breech plug in this case is from having a break action 45-70 conversion cva scout and using a short His breech plug. the chamber area I'm refering to is what is left of the old 45-70 chamber and it is barely larger in dia. than the rifled barrel. those with longer breech plugs may not have this situation. I'm gonna list the steps to check exactly where the bullet lies in a load in relation to this unrifled area.
 

redear

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1. remove the breech plug.
2. find a wood dowel or the butt end of a drill bit or something else that will slide up into the breech until comming to a stop against the front of this unrifled powder chamber area. I used an old aluminum shotgun cleaning rod with duct tape wrapped tightly around the end until I had a tight fit in the unrifled chamber area. I had to lubricate the duct tape wrap slightly and push and twist the rod until it butted against the front of that chamber. I also marked the cleaning rod with a sharpi pen right at the face of the breech of the gun so I could be sure the rod would stay in position.
3.Take your bullet, in my case it was a bullet and wool wad, and push it down the barrel until comming in contact with whatever you used to push up into the breech.
4. then I double checked my breech area rod with the wrapped duct tape had not moved by checking the mark I put on it. you will need to push from the muzzle end and the breech end to be sure the bullet is bottomed out on the breech end rod. and that the breech rod or dowel is in the correct position by checking the sharpie mark.
5.once the bullet is pushed down until it bottoms out on the breech end rod or dowl which the end is at the very front of the powder chamber area, take and mark the ramrod at the muzzle with a sharpie pen or masking tape.
6. now remove breech area dowel etc. push bullet out of the barrel, install breech plug, and load your powder and bullet, or bullet and wad etc. and look at the ramrod mark you just put on the rod. If the mark is further away from the muzzle than it was without the powder in the barrel then the bullets base is up into the rifling and not hanging down into the powder chamber, unrifled area. In my case I found out that my woll wad was 1/8" at least up into the rifled barrel and the bullets base was even further than that, so I surmised that my powder charge column was long enough to keep my bullet up into the rifling.
 

redear

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With the 4198 powders there was no need to check this because the 4198 powder is bulky and creates a long powder column, the problem can happen though when a faster powder is used where less grains is needed and in my case the powder was finer and settled more compact in the breech. I found out through this method that my load was just barely long enough to keep me from incurring barrel damage or unsafe situation due to the position of the bullet.
 

LBAhunter

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Wonder which/whose breech plug would take all/most of the 45-70 chamber?
 

redear

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LBAhunter, I think the ASG plug is longer, but I think the flame path may also be longer, but I am not sure about the flame path being longer. I just checked mine again this evening with a saboted load and the same imr 4227 at 45 gr. load and came up with the same reading. I'm thinking I'm good to go with the His plug and 45 gr. of imr 4227 but I think n110 is where a guy would run into trouble. the breech plug holds a good amount of powder also and I have read where the Dis plug may hold less powder than the His does, if in fact thats true the Dis plug would put the bullet further into the rifling than the His if my brain is thinkin right. I just put this out there because I wanted a way to check this for a couple months and couldnt quite wrap my head around how to do it, and then a guy tells me thats simple, just do this and this and you will know what you have. those guys that shoot the 40's have powder chambers machined in front of the plug many times to reduce the length of the powder column in those narrower bores, so they deal with this all the time.
 

redear

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I do like the short His plug, especially the design of the tungsten bushing, it has a tapered hole.
 

D55

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bdhunter has a longer plug not sure which one maybe he will chime in.
 

BuckDoeHunter

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Both my Apex's have ASG Gen2 LRMP breech plugs. They have very short flame paths with a deep recessed powder pocket.

Black Apex plug measures 1.679 in. long


Deep recess on the powder end runs all the way up to the shelf holding the bushing


The .035 tungsten carbide bushing is inserted on the primer end and held in place by a non-removable insert


When the primer module is inserted into the breech plug, the end of the brass module abuts the face of the bushing which may aid in sealing against blowback but the brass flash channel also swells like a cartridge case making the module difficult to extract by hand but the extractor on the rifle has no trouble doing it.


The flame channel is in the brass module making it very short
 
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redear

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very nice! I bet that plug covers the chamber we are talking about.
 

BuckDoeHunter

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Still some free chamber left, it's threaded up to were the rifling begins. The Camo Apex has .110 free space and the Black Apex has .306. The recess in the breech plug holds around 11 grains of N110.
 

redear

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BDhunter, It's great that you know what you have. Have you checked your bullet position with your n110 load yet?
 

LBAhunter

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Still some free chamber left, it's threaded up to were the rifling begins. The Camo Apex has .110 free space and the Black Apex has .306. The recess in the breech plug holds around 11 grains of N110.
The black Apex must've had a longer throat/dimensions in the 45-70 chambering. If I'm reading it right, the camo Apex has a .110 powder chamber and the black Apex has a .306 powder chamber.
 

BuckDoeHunter

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The black Apex must've had a longer throat/dimensions in the 45-70 chambering. If I'm reading it right, the camo Apex has a .110 powder chamber and the black Apex has a .306 powder chamber.
Yes, those are the numbers I came up with. I was thinking it also may have come from when the breech plug threading was done.

Here's how the Black Apex came out.

Starting on the left, 1st line is the end of the jag and the beginning of the rifling, 2nd line is the base of a 250gr XTP and the beginning of the rifling, 3rd line is 35gr N110 with a wool wad and the XTP


I scared myself after I loaded the Apex, this is the view I had. My brain saw the second orange line disappear and I thought I messed up my measurements :wall: , then I realized the bore guide was blocking my view:drool:
 
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redear

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very good, so the base of your bullet looks to be somewhere around 3/8" into the rifling if I'm looking at it right.
 

LBAhunter

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Yes, those are the numbers I came up with. I was thinking it also may have come from when the breech plug threading was done.

Here's how the Black Apex came out.

Starting on the left, 1st line is the end of the jag and the beginning of the rifling, 2nd line is the base of a 250gr XTP and the beginning of the rifing, 3rd line is 35gr N110 with a wool wad and the XTP


I scared myself after I loaded the Apex, this is the view I had. My brain saw the second orange line disappear and I thought I messed up my measurements :wall: , then I realized the bore guide was blocking my view:drool:

Possible. When I read your post, I started thinking about Luke's Encore barrels, wonder if they have a very small chamber in them due to the breech plug threading? The chamber dimensions shouldn't be an issue with them.
 

redear

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Thanks to everyone who shared their insight on this thread. I was real happy to be able to measure exactly where the base of my bullet was in relation to the beginning of the rifled barrel. It took D55 sharing the situation with his gun, and thanks to him, and also a man on another board who reached out to me with this method in order to check my gun with a certain load that I wanted to shoot but was afraid to.
 

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