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Very Hot Topic (More than 25 Replies) Breech seating a 50-70 or 50-90? (Read 979 times)
martini79
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Breech seating a 50-70 or 50-90?
Aug 22nd, 2017 at 2:49am
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Hi guys I am looking to have a 50 caliber rifle built and am trying to decided between a 50-70 and 50-90.

I want to shoot heavy bullets, mostly for their higher BC. At the moment I am considering a design that will weigh in around 645 grains! The rifle will be heavy around #18, with a 28" barrel.

I never like to take these things by gospel, and value real experience above all theory; but from running Quickload to achieve by desired velocity of between 1300-1450 fps to keep pressure below 20kpsi I need to breech seat with the 50-70.

Whereas with the 50-90 I may be able to reach 1400-1500 fps using fixed ammo and possibly 1600fps with breech seating.

I am not saying that I have to drive them at 1500 fps, but asking if the 50-70 can satisfactorily drive a 645 grain bullet and do well at 300-500 yards or is a 50-90 needed?

I might add that I can only get a 20 twist, which is faster than ideal, but getting a 50 caliber barrel exported is hard out of America and the slowest in Australia I can get is 1:20 though I  think 1:26:would better.

I know that the 50-90 is more versatile, and I may be able to loan a reamer, but the brass is so much less available and so much more expensive than 50-70.

In short I am asking for advise on if the 50-70 is enough case for a large bullet.

Thanks
« Last Edit: Aug 22nd, 2017 at 8:47am by martini79 »  
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Statesrights
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Re: Breech seating a 50-70 or 50-90?
Reply #1 - Aug 22nd, 2017 at 7:15am
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I tried a 600 grain Paul Jones in a DZ .50-70 with no success. Did not try breech seating.
  
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nuclearcricket
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Re: Breech seating a 50-70 or 50-90?
Reply #2 - Aug 22nd, 2017 at 1:08pm
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I am sure you will get some advice here but you may be better served over on the Shiloh rifle board (You need to Login or Register to view media files and links) or (You need to Login or Register to view media files and links)
I know that there are shooters over on those sites that shoot the 50 and may be of more help. Granted most of them will be using black but am sure some have and do use white powder also.
Sam
  
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John Boy
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Re: Breech seating a 50-70 or 50-90?
Reply #3 - Aug 22nd, 2017 at 3:04pm
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Martini - think about the concept of breech seating any paper patch bullet
The bullet would be fully chambered in the leading bore lands all the way to the bullet base.  Accordingly - the paper wraps would be cut before you even pull the trigger
I know of no one in the BPCR community that breech seats PP bullets.  They are loaded in fixed cartridge reloads only with the wrap below  the bullet nose so as to not cut the paper
The choice between a 50-70 or 50-90 is a personal choice
  

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John
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martini79
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Re: Breech seating a 50-70 or 50-90?
Reply #4 - Aug 22nd, 2017 at 3:46pm
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I am confused who said anything about paper patching?
  
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gunlaker
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Re: Breech seating a 50-70 or 50-90?
Reply #5 - Aug 22nd, 2017 at 3:49pm
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John you can definitely get breech seated, bore diameter, paper patched bullets to work very well.

I don't know of anyone who does this in competition, and I do not plan on it, but I have a few rifles that I shoot only in this manner ( with black powder of course ). 

The rifles I shoot in this way are .38's however, not .50's Smiley

Chris.
  

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Re: Breech seating a 50-70 or 50-90?
Reply #6 - Aug 22nd, 2017 at 8:14pm
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Martini,
I have a 50-90 and I have shot 750's, 500's, 450's - they all shoot well loaded within the velocity range you're talking.  The 750's do quite well in the wind and longer ranges but there is a trade off - recoil, especially for that velocity.  My rifle has a 1:20 twist, barrel is 34" long and weighs in at 16.5 pounds- it still punishes the shooter when the velocity goes above 1200.   
A fellow shooter here has a 50-70 but when he tried some of the heavier bullets he couldn't get enough velocity, he hasn't tried BS that I know of, his twist was close to 1:20 but I'm making an assumption:  because of his velocity there wasn't enough spin to stabilize;  his heavier bullets tumbled-  He loaded 450 and 500 grain with good success.
All we were shooting was black in these, I'm assuming you're doing the same? If not, throw my comments out, you can load with smokeless in a 70 to achieve desired velocities and still not have to breech seat.
Greg
  

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martini79
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Re: Breech seating a 50-70 or 50-90?
Reply #7 - Aug 22nd, 2017 at 9:38pm
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Thanks for that useful reply, I must admit that recoil is what has put me off a 50 cal before.

Lets ask the question more simplisticly, with a 1:20 twist have fast do you think a 645 grain bullet needs to be going to do well at 300 yards? Could it do well at 1000?
  
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J Louis
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Re: Breech seating a 50-70 or 50-90?
Reply #8 - Aug 22nd, 2017 at 10:05pm
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If I may ask why are you stuck on such a heavy bullet for only 300yds, increased accuracy, in hopes of beating the wind or just personal preferance while also breech seating to get the most accuracy out of it and counter producitive unless I am missing some thing.

JLouis
  
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martini79
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Re: Breech seating a 50-70 or 50-90?
Reply #9 - Aug 22nd, 2017 at 10:32pm
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Hi are you saying that at 300 yards that the extra BC will be of no advantage? I guess its not like a 1000 yards and a high BC probably isn't necessary.

Are you also saying that breech seating a bullet for higher velocity coupled with extra recoil is detrimental to accuracy? I can't argue with that!

So would your recommended a cartridge more like a 45-70, 40-65 or a 38-55 for breech seating?

I have no real need for a 50 just an itch I guess, my 38-55 does well without breech seating, perhaps I would be better with that or a 38-56!
« Last Edit: Aug 22nd, 2017 at 10:42pm by martini79 »  
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Re: Breech seating a 50-70 or 50-90?
Reply #10 - Aug 22nd, 2017 at 10:41pm
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If you access a ballistics program  spend time working through it, it will give you an idea what velocity is required to stabilize a given bullet in a given twist. (computer simplified versions of Greenhill and Miller) To some of us mediocre computer literate individuals it requires a lot of picking and cussing,  my right hand man, who also happens to be my son, helps me through most of the trouble areas.  Life is about broadening your horizons so dive in.
I don't have a mold in that grain size, only the 750.  I have never shot this one (according to a Chrony) slower than 1380 MV.   Had it on paper at 800, there may have been just a little tipping starting at that point but it may have been from the angle they were coming in at too.  The group wasn't remarkable, 10 shots probably 18" and that could have been mostly me, recoil is easily anticipated...
I have new toys to play with now - doppler radar chronograph, so I may eventually go back to experimenting with this and push it out to 1000, maybe even the mile (my intentions when I started building it) but it's quite a ways down on the list.
Keep me posted on the 645g, what nose design are you thinking?
I shoot the NEI 600g, single grease groove in my 45-90, recoil on that is substantial but if I bear down and focus it shoots 1000 and 1200y better than anything I've ever touched.  It only shoots fair at 600y and less - explain that.
Here's a picture of it centered on the scale, the one in front is the 750g, .513" and in the background is yet another I made a mold for - drops just shy of 1000g.  Haven't shot it yet, not sure I ever will - don't know what twist I'll need and my barrel operations have a ways to go yet. 
G
  

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Re: Breech seating a 50-70 or 50-90?
Reply #11 - Aug 22nd, 2017 at 10:43pm
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My 26 twist 50-90 will do what you want with smokeless or Black, but will punish you with the high velocity loads. the 515 grain RCBS that will weigh in at 540 grains is the one that my rifle likes to 300 yards, going out farther I switch to a 610 bullet with 110 grains of BP, don't know what its running at but it is accurate to the Ram line. I have a buddy that has a pair of 50's and he cant get his 50-70 to keep up with his 50-90.
  
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martini79
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Re: Breech seating a 50-70 or 50-90?
Reply #12 - Aug 23rd, 2017 at 4:57am
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I have not ordered the barrel yet, I am thinking maybe I should move up from 1.55 to 1.75" taking total weight of the rifle to around #22.

GT how is the recoil on 750@1380?
I think a 1:20 twist will just about stablise anything to 800 grains quite easily.

Staterights did you try the 600 grainer with BP or smokeless?

For me the jury is still out on whether to use BP or smokeless, if I want to go BP I think the 50-90 is the go for versatility. If I use smokless and keep pressure in the 15k to 20k range then with smokeless a 645 out of the 50-70 should be able to do 1300 with the right powder and that's probably as fast as it needs to go.

On a slightly different note I found data for a 700gn in a contender with a 1:10 isn't that way too fast and talk about recoil!
  
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Re: Breech seating a 50-70 or 50-90?
Reply #13 - Aug 23rd, 2017 at 6:50am
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bore diameter pp bullets can be breech seated with no problem whatsoever.
generally when the correct airgap is found, accuracy will exceed that of fixed ammo.
if anything, the paper is less cut than with fixed ammo, suggesting that the airgap uses enough energy to reduce the strength of bumpup compared to the bullet directly on the powder as in fixed ammo.
this suggests that confettii is created by the slicing motion of the rifling as the bullet travels forward.
breech seating bore diameter pp bullets became the main act of long range sometime between 1880 and 1900, leaving fixed ammo to the grunts.
keep safe,
bruce.
  

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Re: Breech seating a 50-70 or 50-90?
Reply #14 - Aug 23rd, 2017 at 7:36am
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Below is a chart showing the twist and desired bullet length for that twist. (Dimensions in inches)

Twist      BL 50 cal
20      1.97
21      1.87
22      1.79
23      1.71
24      1.64
25      1.57
26      1.51
Remember a shorter bullet will shoot in a faster twist, to a point.

The question I have is why would anyone want a 50 cal rifle shooting such a heavy bullet. Hasn't anything to do with range, accuracy, etc, but more a waste of lead and powder. I know everyone can do as they wish but the only reason here is bravado. IMHO
  
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