Remington RB & Contract rifle owners - could use some he

[JBMauser]

I may have a real problem, not sure, coudl use some data from the group.
I got some gas blow back fireing some way to light case forming loads.  Then as I inspected further I find my Danish 1867 RB has a bit of play between the block and the cam edge of the triger.  I only found it when I took the spring tension off the triger and I could pull the block back the thickness of a charge card before it seated on the trigger cam.  Can you tell me how much clearance or play you have with your RB weapons?
With the hammer down she is snug, I never took the spring tension off the trigger to check the action.  I am not sure if I have a problem or if so how big>  Thanks in advance.  JB

[Ray Newman]

First, what do you mean by “gas blow back”?

Was the gas escaping from the breechblock?

Or, was there insufficient pressure to expand the brass case to seal chamber, which resulted in powder/gas discolouration on the case?

[ribbonstone]

Going to make some assumtions here...think you are talking about slack between the breech block and hammer (and you just used "trigger" in place of hammer).  Yes...the way to check is without hammer tenstion against the breech block (better check is with the barrled action stripped of everthing but the breech block and hammer)....but no, it shouldn't have that kind of credit card thickness slack.   You proably wouldn't have noticed it but for the gas blow by in those fire form loads unless you specifically cheacked for it.

One of my rollers is a Dane that an old-old friend converted to sporter back in the late 1950's. He is still around, just too old to shoot. In describing the conversion, he mentioned making new pins and reaming the holes for a new seat...this would be both the holes in the frame and the holes in the breech block and hammer.  IT has no slack at all.  Sounds good, but even after all these years, if a case doesn't quite seat (fouling of the rim recess is all it takes) will often missfire...believe the hammer expends it's energy in pushing the bolck forward and attemting to seat the round before the pin is struck solidly.

The ohter is an un-repaired 50-70 NY Contract. Never been rebuilt, but in good shape...it has about the thickness of a sheet of news paper as slack.  It's proably not to the point of needing repair. The rifle only sees BP loads, but I keep an eye on this constantly...any slack only gets worsem and as it gets worse, the parts that aren't supose to move now have a running start before contact with eachother...kind of accelerates things.

You might be getting angled case heads/rims from that rifle when shot with full charged ammo...case sets back...breech block moves to take up the slack agaist the hammer...as it moves back it rotates on it's pin...case sets back and takes up this angle.

Pesonally, if what I'm assuming is right, would look into having it repaired.  Rather than welding the hammer and cutting a new locking face, would think re-pinning as described is the better fix.

[ribbonstone]

Got to thinking about this after I signed off.  Depends on hwere yu are measureing the slack. At 1/2 cock, there is always going to be some slack.  Using that 50/70, the slack between hammer and breech blck is .007".  At hammer down(but just off fully down, it's .002".  That's from the well worn rifle that's never been rebuilt.

On the rebuilt Dane, it's .003" at 1/2 cock and Zero at hammer almost all the way down.

[38-72]

"I got some gas blow back fireing some way to light case forming loads. "  

You did not say if the primer was backing out or leaking.  So, I’m wondering if your loads are not building enough pressure to expand the case walls far enough to seal the chamber.?

[JBMauser]

That is correct.  I did not load them up sufficient to expand the brass to where I wanted them.  The blow back I got was from undersized brass not expanding to the chamber.  I will use full power loads next.  I have done that before and had a number of case failures, splits as the brass has to grow a bit.  My goal was to open them up in two firings to reduce to the failure rate.  I have to get out and buy a set of feeler guages but using a exacto knife blade I find I have 20 thousandths clearance between the block and  chamberd brass.  JB

[ribbonstone]

Shuld have zeroed in on the lite-load aspect rather than going off on the slack measurement...yep, will blow that gas back at you and filthy up the firing pin channel. Be worth it to remove and clean that pin (which at least on the Danish at hand is an easy removal...that screw through the breech block holds both the pin and the pin retractor).  One of the things to watch out for on a roller is a frozen firing pin...makes things kind of exciting when you close the unlocked breech.  The ones with the pin retractor would PROBABLY just refuse to open if it jammed up

Where are you measuring that 20/1000's?  

Those Danes have a larger than 45-70  diameter chamber, and as with anything of that era, some are worse about that than others.

[JBMauser]

With the block closed and a primed and empty case in the chamber I slipped the exacto blade between the block and the brass with the spring pressure off the hammer so the block could be moved back till it sat on the cam edge of the trigger.  I read where if you can chamber a 45/70 round without having to trim the rim to fit the chamber it had been reamed to 45/70.  Danish cartiridges are .2 in. shorter not longer than the 45/70.  I took a chamber casting of the dane and there is a long leade.  pleanty of room for a long cartridge.

[ribbonstone]

Base diameter of the Danish 11.4X51R round is listed at .514"...the .45-70 is listed at .505". In real life, many of the old Danish chambers are a bit bigger and many 45/70 cases are a bit smaller in diameter.

Length is not be an issue, but that radial expansion might be.  Certainly means a heavier than expected charge is need to get them to blow out...you have to make up your own mind if the .009" (minimum...with chamber specs and undersized .45-70 cases, .011" would be closer to real-world) radial expansion would be a problem.

[JBMauser]

Yes, you are correct, I realized you ment dia. after I launched my reply.  That is why I was trying to expand my brass in stages as they bulge greatly ahead of the web when formed.  I also reference them with a notch or a mark on the head.  Stout loads open them up but I have had a number of split cases on forming in the past and those the came to size in two cycles had no failures.  Sized brass has not given me any blow back in the past.  JB