.45-70 OAL Question

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GJeffB

GJeffB

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A little confused about my reloads COAL:
.45-70
Chiappa .45-70 Sharps 1874
Load: Rushmore 300gr .459 Rushmore 300gr.jpg ; 30.0 gr H4198. All load manuals show max OAL at 2.550. My loads measured 2.50. None would allow the falling block to close. OK, I'll check. Snap caps measure OAL 2.498 and chamber.

I re-seated the bullet until I got OAL at 2.471

So ... the question is, if manuals ALL show max oal at 2.550, and the longest oal I can chamber is 2.471 (.079 less), is it projectile configuration (FPRN vs RN) or something else causing the (admittedly) miniscule OAL discrepancy?

As an aside, the first live rounds I've tried to fire, as opposed to the snap caps.

-jb, I'll relate to another thread later
 
It's possible you have a very short throat, which would surprise me. My Pedersoli 1885 has quite a bit of freebore, I seat my bullets waaay out there to help suck up some of that space.

If you can, seat a bullet long in an unprimed and uncharged case... and continue to try to chamber it, seating the bullet deeper and deeper into the case until you get it to chamber fully. That will tell you where you are at.
 
Thanks. 3 almost identical replies, i.e. bumping the rifling, as I suspected.
Charlie: That's basically what did: attempt to chamber, reseat, attempt to chamber, reseat, until I came to the 2.471 overall length. And yes, they were crimped at the groove. I later figured it's not necessary in the single shot. But isn't that a wide discrepancy? or is the crimp the issue?
So ...
Follow up question: would this be considered a normal condition? That is, what might contribute to the short throat? Crimp as suggested?
And further, when I get loaded up to regular 405gr, I'm going to be bound by the minimal COAL, reducing case volume, correct?

Thanks for replies
-jb, more explanation to come after factory loads
 
If you over crimp it can cause a bulge giving you false indications. Test seating depth as you did with no crimp to get error free results. This caliber normally has longer free bore for heavy bullets. 405 is standard and heavier is common.
 
AJC1 said:
If you over crimp it can cause a bulge giving you false indications. Test seating depth as you did with no crimp to get error free results. This caliber normally has longer free bore for heavy bullets. 405 is standard and heavier is common.
Click to expand...

That... ^^^ +1

I know guys shooting Sharps with weights in the 500's, there is something else going on here. AJC understood what I was asking... sometimes a heavy roll crimp will actually bulge the case mouth just a hair... enough to give you problems chambering.

Before you get too excited... I would wait to hear from someone who shoots a Sharps... I don't, just my 1885, which is a bit different. The guys I shoot with that have Sharps, have these levers they use to ram the cartridge home... but that may be on a breech-seated bullet, and they are shoving the case up onto the bullet with the lever. I'm not sure if seating into the rifling is a normal thing with the Sharps.
 
Get a long 3/8" dowel and a pencil.

1. open the action, insert bullet (alone). and hold hard against rifling w/ pencil
2. run dowel down bore to meet bullet, mark at muzzle
3. remove pencil, push bullet out of action w/ dowel, close action.
4. push dowel down bore to meet the action block. Mark at muzzle.

Distance between marks is your max OAL for that bullet in that chamber, for that rifle.


.
 
MEHavey said:
Get a long 3/8" dowel and a pencil.

1. open the action, insert bullet (alone). and hold hard against rifling w/ pencil
2. run dowel down bore to meet bullet, mark at muzzle
3. remove pencil, push bullet out of action w/ dowel, close action.
4. push dowel down bore to meet the action block. Mark at muzzle.

Distance between marks is your max OAL for that bullet in that chamber, for that rifle.


.
Click to expand...
Easy-peasy measuring system! :thumbup:

Stay safe.
 
The more I think about this the more I feel AJC1 and Charlie nailed it. I've reloaded several calibers, but this is my first go round with .45-70
Considering a single shot, there's really no need for anything more than a light crimp, right? It's not like bullet setback or creep is going to create "feeding" issues.

Thanks for talking me through it :thumbup:

-jb, only 20 to pull
 
Considering a single shot, there's really no
need for anything more than a light crimp, right?
Click to expand...
If/when running lighter bullets at less-than-lands-engagement OAL, a firm consistent
crimp does have a "not insignificant" benefit to consistent ignition/velocity
 
Do not over crimp;
Get sufficient tension to maintain consistency;
Understood, I'll stay with moderation in everything. Including moderation ;-) I appreciate the comment, thanks

-jb, like Goldilocks looking for juuust right
 
No problemmo....
(honest) :)

The bullet can be very slightly "stuck" (not jammed) in the lands
and the dowel lightly run up against it. Two hands on dowel/sharp
pencil -- or even single-edge razor -- marks the dowel easily/reliably.
 
GJeffB said:
Considering a single shot, there's really no need for anything more than a light crimp, right? It's not like bullet setback or creep is going to create "feeding" issues.
Click to expand...

There are a few things to look at when considering crimp for a single, and particularly with cast...

First is neck tension. Like any cartridge, you need enough neck tension to hold the bullet. I use a Lyman M-Die to flare my brass prior to bullet seating. The M-die actually uses a mandrel to open the neck of the case up, and slightly flare the case mouth so you can properly seat a cast bullet without shaving lead, or swaging the bullet down (with a too tight case neck.) A die like the M-die can solve a lot of problems when shooting cast.

Like any cartridge where the case mouth is flared, you have to knock the flare back out, or you might have problems chambering the cartridge. You can use the crimp die in the bullet seat to just take out the flare, or more die to actually crimp. As was mentioned, a single-shot doesn't require a crimp, per se, but some loads might benefit from a crimp... as MEHeavey mentioned, light bullets and fast powders. You could also make an argument for a case full of slower powder under a jacketed bullet, a good crimp can promote a good burn to maximize the slower powder... not only in rifle cartridges, but pistol cartridges as well (W296 and IMR4227 as an example.) I will sometimes use a taper crimp die to take out the case flare... it's not quite as sensitive to position as a roll crimp, and I think it's easier on the brass, particularly if all you are doing is knocking out the flare.

The other consideration is... if you are at or into the rifling with the bullet, and for some reason you need to withdraw the cartridge after loading... if you don't have enough neck tension or crimp... the bullet could stick in the rifling as you pull the cartridge, dumping the powder in the action and leaving a bullet stuck in the bore.

But... first things first... you need to see if you are actually sticking the rifling, or you are just seeing some resistance from the freebore portion of the barrel. A borescope would help, or just a good strong light and a decent set of eyes.
 
Charlie, I've heard about the M-Die. However my RCBS die does the same function, I can get the flare for initial bullet seating, then the slight crimp to remove the flare.

Just when I thought I had a solution:
Get a long 3/8" dowel and a pencil.
Click to expand...
I made the measurement with 2 different bullets, 300gr on the left, 405gr on the right
300v405(1).jpg 300v405(2).jpg 300v405(3).jpg
By the above method the maximum OAL for the 300gr is 2.510 and for the 405gr is 2.660. That's not making sense in my mind for the considerably shorter measurement for the lighter/shorter bullet. I ran the exercise multiple times to confirm.

-jb,smh
 
There are differences in ogive shape, as well as length... not unusual. They are not identical bullets forward of the crimp groove.

Did either of the bullets show engraving from engaging the rifling?
 
Charlie/Dennis:
no engraving, and I get the ogive/measurement contributing. BUT I used a heavy, non-moveable object against the pencil. Completely certain the 2 bullets were fully engaged. I'm thinking 2 not mutually exclusive procedures:
1. pull and reload all 20, checking for chambering each one and adjusting until I find the sweet spot;
2. I'm not going to do it, but find a local (*really* small rural area) gunsmith to make a chamber casting that can be measured closely;

-jb, on the Unicorn trail :confused:
 
I really think you are hitting the freebore, not the rifling. The result is the same if you can't chamber a cartridge... so a trip to a smithy is certainly in order.
 
Thanks to all for the information. This particular rifle purchase has been a cluster flock since the day I received it. The long story of the fight with Cimarron and Chiappa is at

https://www.thehighroad.org/index.php?threads/cimarron-true-single-shot.879259/page-2#post-11920484

It's a long read, but hopefully informational.
After the fist fight I received the rifle back May 24. First opportunity to test fire was June 10, when I discovered the failure to chamber. The result is my wonderment at the sudden failure to chamber. As I mentioned to another, I'm pretty suspect due to the initial failure and 5+ months of jerk around. I'll try to resolve with a breakdown and reload of all the cartridges at various OALs and with assorted bullets.

Again, thanks for the collective wisdom. I'm doing my best to eliminate all other variables.

-jb, :thumbup:
 
GJeffB said:
Thanks to all for the information. This particular rifle purchase has been a cluster flock since the day I received it. The long story of the fight with Cimarron and Chiappa is at

https://www.thehighroad.org/index.php?threads/cimarron-true-single-shot.879259/page-2#post-11920484

It's a long read, but hopefully informational.
After the fist fight I received the rifle back May 24. First opportunity to test fire was June 10, when I discovered the failure to chamber. The result is my wonderment at the sudden failure to chamber. As I mentioned to another, I'm pretty suspect due to the initial failure and 5+ months of jerk around. I'll try to resolve with a breakdown and reload of all the cartridges at various OALs and with assorted bullets.

Again, thanks for the collective wisdom. I'm doing my best to eliminate all other variables.

-jb, :thumbup:
Click to expand...
If your looking for a source of material for chamber casting yourself I believe rotometals has it. As a bonus they have a lot of other material you may find useful. I watch for specials on superhard.
 
"... man's got to know his limitations ... "
Thanks. I just have to get another professional unbiased opinion. After the experience I have to know if something is wrong or if I'm to fault. Appreciate the referral.

-jb
 
I must be loosing it ...
I just finished loading 20 rds of 405g Brazos LFPRN. W-W new brass.
405g Reloads.jpg
I made SURE to put a slight flare on the case mouth and a little bit of crimp. Several manuals show maximum OAL as 2.540. I found that anything under 2.539 would chamber like butter. Rather apparently the failure to chamber the 300gr Rushmore FPRN is due to over crimp. I'm going to break em down, re-form the mouths, and rebuild them with a minor crimp.

BTW, the brand new W-W case mouths looks like the brass had been packaged with a front end loader. Way out of round, dings and dents. I had to manually remove the dents on a couple to get em in the expander. OTOH I also have an unopened bag of Starline that doesn't show any of that. Just sayin' ...

Thanks Charlie98 and AJC1 for getting me in the right direction. MEHarvey That OAL length measurement is a nice tip. Pretty sure I flubbed it in operation but I always learn something around here. Clearly experience in straight wall handgun cartridges does not seamlessly transfer to straight wall big bore rifles o_O

-jb, rounding out the learning curve
 
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