Advice for load data sml 4570 cva

Changing bullets will only change the witness mark on the ramrod, chamber should not be effected.

Would this be a consistent chamber for a Hankins CVA Scout and his HIS ignition? I would like to go lower also perhaps. 

Also HIS and DI would be different chamber size. These chambers in the Hankins conversion rifles are close to the same but not exact. As stated above check your own to be sure of what your min load is with a given powder. Different powders may change the grain weight amt. due to the bulkiness of the powder.

Hmmm, I will follow the advice, but I don't think the difference between two guns chambered for 45-70 and head spaced correctly for the cartridge and the module can be off by enough to calculate the difference in powder. That is assuming the breech plugs are the same. I don't know why breech plugs would differ if he is turning them out to screw in and create correct head spacing. His modules are not custom made for specific guns so they are not the adjustment for head space. I would like Jeff himself to weigh in on differences from gun to gun and why. IF I was using cutting edge high pressure loads I might, might worry, but the worst you can do is flame cut the throat with reduced loads......everybody's measuring technique is going to produce variances larger then Hankins machining.

Reduced loads are a lot more dangerous than you think! You absolutely can blow up your gun with reduced loads. It all has to do with how the pressure is released when the powder begins to burn. If the bullet resistance is greater than the yield strength of the chamber area your gun will come apart instead of the bullet traveling down the barrel. When you seat a bullet in the barrel you are, in effect, creating an obstruction in the bore. When the trigger is pulled the goal is for that obstruction to become a projectile. Should the resistance in the barrel be greater than the yield strength of the barrel itself, the steel then becomes the projectile.

Loading manuals list a minimum and maximum for a reason.... Most everyone focuses on not exceeding the maximum charge listed forgetting, or unknowing, the dangers of reduced loads.

Oftentimes don't talk much about "minimum" charges with these SML's because max performance is usually the interest. However, guns with a powder chamber, it is absolutely necessary to measure what a minimum safe charge would be for that particular rifle. Stick with the advice and determine what is safe for your rifle. None of us want to see anyone hurt, and I'm sure you would rather not be making a trip to the ER.

Sure sounds like you do !

Before tapping the plug threads the chamber area is bored with a drill bit in a lathe, I believe and they are very close but not exact. Buckeye68 chamber is 53gr with 4227 powder and DI ignition. Mine is 45.5gr. same gun 
with the same powder and plug. He has been there with Hank while more than a few were machined. I'm sure he doesn't mean to be condescending but is brutally honest 😁

Remember safety is our first priority on this board. We are all very passionate about our sport and we want everyone to be safe and successful. We all try to answer questions as they arise with the knowledge we have gained over the years. If you don’t like the answers you are given I would suggest you do like Deputy819 suggest and call Jeff himself. I am sure Jeff will answer all your questions. Let’s keep it friendly.

OK, Jeff is here to answer the questions the best he can. I have read the above threads, and I will hit on as many questions as I can. I will also post a picture of my findings for a visual reference so everyone can better understand the outcome.

First things first. When someone purchases a CVA scout rifle from me or they send me a barrel to be converted I tell them the load of choice is 65 grains of IMR 4198 with a 265-275 grain bullet. This is the MAXIMUM load, and the MINIMUM load is 55 grains of the same powder. If the owner of the rifle wants to go outside these recommendations, that is up to them and the responsibility of making sure what they are doing will be safe is on them as well.

I think one of the biggest questions is why the powder chambers are different from one gun to the next. The answer to that is: they are not different. What is different is the way people measure the powder chamber. Three people can measure the same barrel and you will have three different answers. So, this is why I think most people agree that you should check your own barrel and don't rely on what others tell you.

When I install the HIS break action ignition system into a 45/70 barrel, each barrel gets the same plug design and the same module design. I only use one. There is a second option plug I make, but that is only used when replacing a plug that was installed by another builder and the customer wants to upgrade to the large rifle magnum primer system.

Now each barrel is drilled to the same depth, then tapped to the same depth, (so in reality) each powder chamber will be pretty much exactly the same. The only exception to this is if the customer requests I make the powder chamber a little larger and, in that case, I will go up to a 55-grain chamber.

In the picture below you will see a 45 caliber barrel I machined for the HIS break action ignition system, excuse the rough chamber, as I had to use a drill to mockup the 45/70 chamber and not a precision chamber reamer. Either way the end results are the same. You will see the first line labeled Breech; this is the breech end of the barrel. At line 1 you can see where my tap drill stops, this is a known measurement and I drill all barrels to this depth, line 2 is where the original 45/70 chamber stops and at line 3 is where I would recommend your do not go below mark to be set at approximately .100 above the original 45/70 chamber. This .100 above is a safety net, could you push it down to the nitty gritty and be just .005 above the chamber, yes you can, and if you want to do that, that will be fine, but for me guiding the general masses I must say stay in the safe zone at .100 above the original 45/70 chamber.



OK, so now you all want to know what the minimum amount of powder is you can use. Well in this test barrel using IMR 4198, the amount of powder it took to set the bullet at .100 above the 45/70 chamber was 40 grains using the HIS plug. Now pay close attention to this next sentence....... Using the DIS plug it took 45 grains of IMR 4198 to get the bullet to sit at approximately the same place in the barrel. So there again, it's important for you to know and understand the differences between the two plugs. They both headspace the same, they both have the exact same shape on the outside; however, the inside of the plug is slightly different.

Now I would also like to tell you guys that not all gunsmiths or hobbyists do things the same way as I do. Whether these differences are right or wrong is not for me to say. What I can say is I know other gunsmiths that buy ignition systems from me, and they use different measurements than I do for the install, some drill deeper, some may not drill as deep. I know one smith that grinds off the un-threaded portion of the plug giving more room for a powder chamber. I'm not saying this is wrong, I am saying you need to know this when figuring out your minimum chamber size. You can’t rely on information you read as 100% correct. 95% of the information will get you in the ballpark, but don't trust your life on it.

Most everyone on this board only wants to pass on good information and help others. Each person has a different way of expressing themselves and reading the written word can sometimes be taken the wrong way. I can read a text for the first time and think, “Man what a douche bag”, then I will wait a day and read it again and think this guy didn’t mean it the way I read it, so sometimes before getting mad or taking offence to what people write, just relax a minute, have a beer, or a coke and a smile and re-read it later, or wait for some others to respond to the post and see how they take it.

Any more questions about breech plugs or powder chambers please ask me here as my phone rings off the hook this time of year and I can’t possibly answer every call.

Oh, and one more thing, all this information above goes out the window when you are talking about an Encore smokeless barrel you buy from my website, because they don’t have a 45/70 chamber in them to start with, so the powder chamber will be much less in those barrels.

The center fire barreled rifles I sell will also have completely different powder chambers as I machine them to hold more powder in the chamber for a reason. We want a hot rod muzzle loader; I build them to burn hot rod loads.