Effect of longer barrel on loads

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  • Last Post 15 September 2012
kevo posted this 06 September 2012

I am about to start reloading for a 45-70 Chiappa sharps quigley, with a 34” barrel. I am wanting to use the starting loads put out by ADI/ Hodgden for these older type rifles. I notice that all of the starting loads are for a rifle with a 24” barrel. How would I reduce these loads to be suitable/safe in a 34” barrel?.>

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Ed Harris posted this 06 September 2012

Published starting loads should not be further reduced because they may give erratic ignition. They will work fine in the longer barrel and you will pick up some velocity compared to the shorter one.

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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onondaga posted this 06 September 2012

Kevin,

I suggest selecting the powder by looking at the recommendations from ADI and Hogdon and then comparing them on a burn rate chart so you can determine the powder with the slowest burn rate that is appropriate for the bullet you want to shoot in your 34 inch barrel.

Fast powders peak pressure early in a long barrel length. Slower powders have a flatter pressure curve in a longer barrel. The flatter curve is an internal ballistics advantage particularly with cast bullets that yields lower variance in velocity and a gentler starting push that cast bullets prefer for accuracy.

You mentioned the molds you got in your PM and your .460 sizer for your barrel that slugs .458".  Check the “as cast” diameter on your bullets too! If you can get bullets of .461 - .462 to seat and chamber with partial full sizing of your brass,  that is a big plus for accuracy also. The rifle will size the larger bullets just fine if they chamber easily and will shoot them better because of a better throat fit.

Gary

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CB posted this 07 September 2012

kevo- just start out with the standard loadings, and take it from there. If you're happy with the accuracy, then you're done. There's no need to try juggling loads unless you need to. The powders burning rate doesn't necessarily guarantee accuracy. You can use the powders from the slower burning rates if you need more velocity, but the differences may not be that great in the end. As Ed mentioned, the loads developed in a shorter barrel will simply go a little faster from your longer barrel. The pressures will remain the same. 45-70 is one of the easiest calibers to load for.

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JeffinNZ posted this 07 September 2012

Why do you feel you have to reduce the loads due to a longer barrel?

Cheers from New Zealand

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kevo posted this 07 September 2012

I wasn't sure Jeff, and that's why I asked the question. Gary has explained the importance of flattening out the ballistic curve re accuracy and Ed has pointed out that the extra long barrel will mainly increase velocity. While I have reloaded many smaller calibres for years, this is my first go at 45-70 in a replica rifle. I just want to be safe rather than sorry. Have just loaded up my first lot using 405gr lead bullets and 49 gr of ADI 2206h powder. Hope to get about 1600 fps. If I can hit a 44 gallon drum at 50 yds, that will be a great starting point for me. Have to wait until tomorrow to test as it's raining at about 1000cdh (cats & dogs an hour) at the moment. Thank's to all for the info! Cheers, Kevo.

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onondaga posted this 07 September 2012

Kevin,  Your ADI 2206h puts you in a great burn rate propellant for the 45-70. It is right between H4895 and IMR 4895 and about the same rate as H335. These are all top performing powders with a good range of bullet weight versatility in 45-70.

I have used all 3 of those powders in my .458 Win Mag with bullets 300-405 gr. and have had great results. Of course, I have larger case capacity with the .458 Win Mag and need 12.2 gr BPI Ballistic filler with my load at 57.7 gr H4895 with the 350 gr Ranchdog bullet at 1700 fps. I can shoot that load without the filler in my bigger case, but I have better accuracy with the BPI. That is my current Bear load in .458 Win Mag.

You won't need any filler with your powder in the 45-70 at your load level; you made a good choice.

Gary

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JeffinNZ posted this 07 September 2012

Actually Gary, AR2206H is H4895 so spot on.

Kevo, join the purists and the fill to the top with black powder, compress enough to seat a bullet and let her fly! LOL.

Cheers from New Zealand

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onondaga posted this 07 September 2012

http://www.castbulletassoc.org/view_user.php?id=80>JeffinNZ Quote"Actually Gary, AR2206H is H4895 so spot on.

Kevo, join the purists and the fill to the top with black powder, compress enough to seat a bullet and let her fly! LOL."

Cool, I didn't know that. That makes Kevin spot on with his powder selection.

Gary

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kevo posted this 08 September 2012

Jeff I would love to be able to use black powder in this rifle for some fun, but unfortunately one cannot buy black powder in Tasmania. All powders have to come into Tassie by barge in a specially constructed static proof van, black powder is not permited. Talk about living in the dark ages!! In fact,when I was asking about powders in general at the local gun shop the other day,they informed me that there was almost zero powder of any sort for sale in Tassie until after November. Looks like ” rock chucking ” and “using gings ” will be popular once more!! Some have suggested to take a vehicle on the ferry to the mainland and purchase their needs, but I hate to think of the consequences of getting caught with explosives on board a domestic ferry. No, definately not an option! Perhaps the only legal way to get BP here would be to go to the mainland, reload the bullets, and then travel back with them, as I believe it is OK to bring bullets in. Oh the joys of living “downunder!!"

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Ed Harris posted this 08 September 2012

Difficulty of getting powders makes a strong case for using the least amount of the fastest burning, most economical powder. In the .45-70 Springfield trapdoor rifle I confirmed many years ago that a safe starting load with a 370-420 grain cast bullet was to use one half of the charge listed for a 12-ga. firing 32 grams of shot at 350 meters per second, or a 3 drams-equivalent, 1-1/8 oz. load. That works out to about 10-11 grains for US powders such as Red Dot or 700-X, or 12-14 grs. of slower powders such as PB or Unique, for about 1000-1080 f.p.s. in a Trapdoor with 32 inch barrel. We did much accurate shooting to 200 yards with these loads.

Try this with the shotshell powders available to you.  Use NO wads or fillers, standard rifle primers are fine.

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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.22-10-45 posted this 15 September 2012

Hello, kevo. When I had Lonestar build my rolling block .40-70 B.N., I wanted a 34” barrel. Dave was concerned about the possibility of low muzzle pressure causing a buildup of fouling near end of brl. Before shipping rifle, he did testing to see if there would be a problem..he found none. He did say the .40-70 2 1/4” B.N. case has higher pressure than the .40-70 2 1/2” straight. I had never even thought low pressure at muzzle could be a problem with black powder before this.

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.22-10-45 posted this 15 September 2012

Hello, kevo. When I had Lonestar build my rolling block .40-70 B.N., I wanted a 34” barrel. Dave was concerned about the possibility of low muzzle pressure causing a buildup of fouling near end of brl. Before shipping rifle, he did testing to see if there would be a problem..he found none. He did say the .40-70 2 1/4” B.N. case has higher pressure than the .40-70 2 1/2” straight. I had never even thought low pressure at muzzle could be a problem with black powder before this.

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.22-10-45 posted this 15 September 2012

Hello, kevo. When I had Lonestar build my rolling block .40-70 B.N., I wanted a 34” barrel. Dave was concerned about the possibility of low muzzle pressure causing a buildup of fouling near end of brl. Before shipping rifle, he did testing to see if there would be a problem..he found none. He did say the .40-70 2 1/4” B.N. case has higher pressure than the .40-70 2 1/2” straight. I had never even thought low pressure at muzzle could be a problem with black powder before this.

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.22-10-45 posted this 15 September 2012

Hello, kevo. When I had Lonestar build a BPCR silhouette rifle in .40-70 2 1/4” B.N., I wanted a 34” barrel. Dave was concerned about that long barrel having a low muzzle pressure with black powder..producing excess fouling in last few inches of bore. He said he would..but if there were fouling problems..might have to shorten. After finishing rifle, he did testing..found no problems. The .40-70 B.N. does generate more pressure than the .40-70 2 1/2” straight. Until he had mentioned it, I had never been aware of low muzzle pressure due to longer barrels..and it's effect on black powder fouling.

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Michael K posted this 15 September 2012

Hi Kevin, If you get really desperate, going to the mainland would work. You can carry up to 5Kg of loaded ammo in checked luggage on QF as per IATA regs. Large capacity cases and projectiles, (12ga blanks...) will leave more room for powder. Need to pack ammo in factory or suitable after market boxes. Will need to get authorization for uplift from the dangerous goods compliance office. It is more of an FYI telling them that is ammo in the luggage, packed properly and within weight limits. I have the contact/email for the QF DG person in SYD if it ever came to that. All the best, Michael.

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