Chamber Pressure 45-70 using Unique

[mikeh3]

Can anyone calculate the chamber pressure using 13.5 grains of Unique with a 500 grain cast lead bullet. I hope it is 28K or below. Maybe someone has a software program or another way to calculate pressure. I have a Sharps reproduction 45-70 with a 32" barrel. Another person told me this is an accurate load but I don't want to blow up my gun if the pressure is to high.

[Gunlaker]

Can anyone calculate the chamber pressure using 13.5 grains of Unique with a 500 grain cast lead bullet. I hope it is 28K or below. Maybe someone has a software program or another way to calculate pressure. I have a Sharps reproduction 45-70 with a 32" barrel. Another person told me this is an accurate load but I don't want to blow up my gun if the pressure is to high.

None of my books have data for that combination, but be aware that there are a number of 500gr bullets available for the .45-70, and each will have different pressures with that load, due to seating depth differences. For instance a 500gr RCBS flat nose bullet sits way deeper in the case than their 500gr black powder silhouette bullet. With a fast powder like Unique, the pressure difference between these bullets is likely large. Personally I'd use a powder like SR-4759 instead if you have that option.

Chris.

[mikeh3]

Thanks for your reply.

I have 5744 but I like Unique better and would like to use it if possible.
I use Unique with a 405 bullet with great results.
I may have to give up on using Unique if I can't confirm its ok with the 500.

[Gunlaker]

Thanks for your reply.

I have 5744 but I like Unique better and would like to use it if possible.
I use Unique with a 405 bullet with great results.
I may have to give up on using Unique if I can't confirm its ok with the 500.

OK, I just realized there was one manual I missed. It's the "Loadbooks" manual which is really a bunch of published data photocopied and put into one book.

The data is for the 457125 500gr bullet. But unfortunately the loads are for a Ruger #1 and thus ****NOT***** likely safe in your Sharps.

Just for curiosity they run from 10.0gr to 14.8gr at a max pressure of 33,700 cup.

Chris.

[mikeh3]

Thanks Chris for the data.
It looks like 13.5 grains of Unique would be too much for my gun at that pressure.
Thanks again for nailing this down for me.
Mike

[Gunlaker]

I'd wait a bit longer for more replies. There are lots of people who use unique for various loads in .45-70. I'm sure one of 'em will chime in soon. With data that's appropriate for a Sharps repro.

Chris.

[NHlever]

I did some software poking about, and it looks like your pressures would run 30,000-35,000 psi. with 13.5 grains of Unique using a 500-535 grain boolit. A bit high perhaps, especially since the pressures I came up with are derived from formulas, and not from actual guns.

[Freightman]

Lyman list a 464 gr boolit not a 500 10gr 888fps min 14,100CUP and 14.8 gr max 1153 fps 33,700CUP this will give you a rough idea.
450gr is listed at 11 gr 950 fps 17100CUP and 15,2gr 1209fps and 40,000CUP

[mikeh3]

Thanks again for everyone's input.

[45-70 Chevroner]

I'm a little late on this one. I shoot a Lee 500 Gr. #459-500 3R over 13 Gr. Unique. I'm getting about 1150 to 1200 FPS. I shoot that load in my Pedesorli Roller and my 1853 original black powder action converted to center fire Sharps. Both are 45-70 and that load shoots great in both of them. I'm not sure what the cup is but I have no extractions problems or flattened primers or any signs of pressure. I would just drop down 1/2 gr. from the 13 1/2 and shoot it.

[delt167502]

try the realoder's nest.they have 1 load for unique with a 400 gr boolit also steve's reloading data pages has a loading using unique.

[Okie2]

What do you guys use to fill up the vacant space left after the small quantity of powder & how do you do it? Thanks, Scott

[GOPHER SLAYER]

Mikeh3, I have been using 15 grains of unique with a small cottn wad pushing a 405 grain bullet in my Pedersoli for 16 years without a problem. As I recall it gives me abot 1375 fps. You must remember the falling block design, whether it be Sharpes, Winchester, Ruger#1,Stevens or whatever is far stronger than a bolt action. You have much more locking lug area. For decades Dupont used a Winchester highwall as a proofing test base for working up loads for their various powders. I am sure that there will be some who disagree with me but I have an article, or at least I did have showing the hiwall action they used. They used a stick to knock out the fired cases. After Dupont went to another method to teast pressure they gave the action to an employee. The article was in The Single Shot Journal and there were pictures of the action. Here is something James Grant, the author of Single Shot Rifles didn't know. Model 1885 Winchesters have turned up chambered for high pressure rounds like 30.06 30.40 Krag and 7mm. When I referred to bolt actions, I of course did not mean actions like the .50 cal Barret. Lyman cast bullet handbook lists 20 grains of unique behind the 500 grn bullet as maximum and suggested 15 grns. for 1350 fps. Mikeh3, a copy of Paul Mathews book, Forty Years With the 45-70 would serve you well. I believe he said if I could only have one powder, it would be unque. Of course he prefferd powders such as 3031 and 4759. Hope I haven't stirred up a hornets nest.

[John Taylor]

Lyman cast book shows a 420 grain cast bullet with 13.5 grains of Unique, 1163 FPS and 27,200 C.U.P.
A word of caution, if your getting stuck cases or flat primers in a 45-70 it is loaded way to hot.

[mikeh3]

Thanks to everyone for the continued replies.

[Okie2]

So...how do you take up the extra space left in the case from a light load of powder....new tech. to me. Scott

[JSH]

So...how do you take up the extra space left in the case from a light load of powder....new tech. to me. Scott

With the unique load it is more of, keep the powder back toward the primer. So the powder is in more of a column, rather than laying on the case wall from one ened to the other.
However, there are some powders and loads that prefer no air space.

Unique loads in the 45-70, I use a paper or styrafoam wad cut from a plate to hold the powder back against the primer. I do not pack it though. I position the wad after a bit of measuring with a gauge I made up. It did help at the target doing this.
jeff

[delt167502]

when a person is using a filler you need to remember that the filler cuts the case volume dn. it dosen't matter unless you are load max. loads. I use unique in my 45-70 contender with 340 gr. bullet.it makes a nice light load. I have tried filler and without ,have tipped the gun barrel dn.befor firing & tipped the butt dn. to get the powder over the primer hole. can tell no diff.in the shot grouping.

[Tom-ADC]

Thanks for your reply.

I have 5744 but I like Unique better and would like to use it if possible.
I use Unique with a 405 bullet with great results.
I may have to give up on using Unique if I can't confirm its ok with the 500.

My old Lyman cast bullet handbook shows 482 gr bullet shows 12.0 to 16.0 grs of Unique BUT also states not safe for our rifles. I've shot 11.0 grs with a 405 gr bullet absolute tack driver. I'd stay away from the 13.0 & 500 gr bullet asking for trouble. There are 4 rounds inside the 10 ring, zero recoil.
http://pic20.picturetrail.com/VOL174/1021972/18168454/384269415.jpg

[Tom-ADC]

Okay I find a Lyman load using bullet #457125 starting gr is 10.0 888 fps 14,100 cup max of 14.8 grs 1153 fps 33,700 cup all loads use 1/2 gr of polyester filler OAL of 2.878
I'm thinking you'd be at or over 29,000 cup which is max for most Sharps.

[NHlever]

Quickload says that 13.5 grains of Unique behind the Lyman 457125 500 gr boolit at an overall length of 2.550 will generate just under 30,000 psi. With the variables involved, I would try a different powder for that velocity level.

[DLCTEX]

I'd still suggest trying SR 4759. It's has enough bulk that no filler is needed and is more recoil friendly.

[35remington]

2.550" overall length is rather short for the long 500 grain bullet, as this length is intended for lever action rifles and such an OAL means a very deeply seated bullet. Should the bullet be seated out considerably further than this, this will lower pressure and velocity.

The 45-70 with heavy bullets and fast powder like Unique responds just like a 40 or 9mm pistol......the deeper seated the bullet, the more pressure it makes and the faster it goes.

Look at data with similar overall length to what you'll be using so you're not comparing apples and oranges regarding pressures and loading density.

[excavman]

I have been using 12 gr of Unique with a 405 gr boolit for a long time, it is a nice light easy on the rifle (and me) load and it also shoots good. Here's a three shot 50 yrd group.http://www.castboolits.gunloads.com/picture.php?albumid=315&pictureid=2183