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View Full Version : Spencer CF repro block: Do these need to be hardened?



Tim Lyne
02-10-2011, 09:15 AM
Folks:
I purchased an "in the white" S&S Spencer centerfire block which dropped right in with a minimal amount of work. I've fired less than 50 rounds through the carbine, but I've found some displaced metal where the hammer impacts the striker and I've got the start of a "dimple" around the firing pin hole in the block face. I cleaned off the displacement on the striker, but I don't want to shoot this again until I know for sure that this is just the way it is and it'll settle in, or I do need to send this out to get hardened. It's not the load: 56/50, 350 Lyman bullet, 20gr. 3F

This is NOT a critique of S&S! These guys have been really, really good to me/us for many a year!

Thanks!
Tim Lyne
Knap's Batt.
#2952V

R. McAuley 3014V
02-10-2011, 05:25 PM
Tim,
I asked S&S almost this same question at the Fall national and was assured that the breechblocks were hardened. While shooting my Spencer, the firing pin carrier shattered into four pieces, and I had S&S to remove it for me, then replaced the carrier with a new one (for an additional $25 I might add). They said how they had never seen this happen before with any of their parts? In showing the shattered part to a machinist, he suggested it was evident that the part had been hardened but it was hardened to the point of becoming brittle, and should have latterly been heat-tempered to reduce the brittleness. One significant difference between the S&S breechblock and the one from Buffalo Arms, while the S&S breechblock is supposedly hardened with Casnit, the BA&Co breechblock is color case-hardened. I might add, the BA&Co breechblock was just $9.95 more than S&S, and was $187.50 including USPS Priority Mail shipping. Shall I say which is now in the rifle?

DAVE FRANCE
02-10-2011, 09:18 PM
A COMMENT ON THE SHATTERED BREECHBLOCK.

Case hardening only hardens a few thousandths of an inch deep. Kasnit is case hardening also. I don't see how case hardening could cause cracking.

My knowledge of heat treating is not as good as what you could find from a metallurgist, but my understanding of the problem follows.

If the part was heated to a high temperature and quenching in oil, and then not annealed correctly (or at all) it might crack.

Another problem can be caused by not having the proper alloying elements in the steel. If the right things aren't in the steel, the part can shatter when it is quenched.

How were the original parts made? Rifle companies at around the Civil War time made some parts from steel and made others that were made from iron and then case hardened.

I don't know why the Breechblock would have to be that hard anyway, that it could be overhardened and crack.

Companys, and people who make heat treated or case hardened iron or steel parts usually know what they are doing and don't make parts that crack. To professional metallurgists, all this stuff is easy.

David

R. McAuley 3014V
02-13-2011, 09:36 AM
Companys, and people who make heat treated or case hardened iron or steel parts usually know what they are doing and don't make parts that crack. To professional metallurgists, all this stuff is easy.
You think?

Glad you dropped by David, though you may want to change the text size to a wee larger font to read the small print on the screen because it is not the original CW breechblock itself that shattered but rather S&S Firearm's reproduction breechblock's firing pin carrier. The S&S Spencer centerfire breechblock consists of four pieces: the breechblock, firing pin carrier, firing pin, and a compression spring that holds the firing pin carrier in place and maintains compression of the firing pin (see illustrations below). The firing pin is shown in red, the firing pin carrier in green, and the compression spring in blue.

When assembled in the breechblock, the firing pin carrier has about a tenth of an inch of free play, so for the firing pin carrier to shatter into four pieces, and the point in which it shattered occurring at about its centroid, infers that when it was struck by the hammer and propelled forward until the firing pin struck the primer firing the cartridge, somewhere in this movement (forward and then back), the stress on the firing pin carrier somehow exceeded its allowable compressive strength, at which point (as we are to understand the carrier deformed before it reached its elastic limits) it shattered, perhaps this part simply wasn’t up to the force exerted on it by an 148 year old hammer and mainspring?

The breechblock itself is supposedly hardened for abrasion resistance, but only S&S can inform us to whether Kasenit, Quickcase, or some other metal hardening compound was used? Whatever hardener was used simply left the part as a dull medium gray in color, and did not imbue the part with any such mottled colors like is exhibited with the BA&Co product.

http://i267.photobucket.com/albums/ii305/rmac1023/Spenc1.jpg
http://i267.photobucket.com/albums/ii305/rmac1023/Spenc2.jpg

DAVE FRANCE
02-13-2011, 11:59 AM
Hi,

I knew the discussion was not about original parts, but I asked about them because I was curious. I did mix up the firing pin carrier and the block.

I had a firing pin break in a Henry a couple months ago. I replaced it with a Uberti part and it was too short to fire rounds reliably. I had to buy another pin from another company.

I never dry-fired the Henry without something to soften the blow (a dummy round, or something to between the hammer and firing pin extension.) I think with a round in the chamber the blow to the head of the firing pin when it hits inside the bolt, is reduced. But, it is a little annoying that the firing pin was not made strong enough to withstand normal use. I am just guessing but I think if a better steel had been used and heat-treated correctly the firing pin would not have broken. It is probably a tolerance stack up problem also that caused the pin to break, or the Uberti pin would have worked.

I think it is a similar situation.

David

John Holland
02-13-2011, 02:10 PM
Richard -

Thanks for the really cool CADCAM pic!

John

R. McAuley 3014V
02-17-2011, 10:59 PM
John,

Perhaps when I get access to a Armisport Spencer I can add it's breechblock to this collection of 3D models. On the far left is the Buffalo Arms Co Spencer breechblock, and at right the S&S Firearms breechblock, with the original rimfire shown in the middle. This is not a CADCAM program but simply Bentley's Microstation XM 3D CADD.

http://i267.photobucket.com/albums/ii305/rmac1023/Spenc5.jpg

John Holland
02-17-2011, 11:09 PM
Richard -

I'll gladly stand corrected! And, thanks again for even more great reference.

John

Dana Hayman
02-18-2011, 01:30 AM
Very interesting, I received a Spencer Block from S & S last week, and it looks just like the picture of the BACO with the angle firing pin, I wonder if they are now using the same Block? My friend just got the BACO block, I will see him this weekend, and compare the Blocks if possible.

Dana

AMB
02-18-2011, 08:28 PM
I wonder if the S&S carrier is made of a high carbon steel rather than case hardened mild (low carbon) steel. High carbon (like air or oil hardening tool steel) will harden through and through when heat treated. If you over do it, or don't do a post hardening heat treat, it can turn out brittle and shatter. Low carbon steel hardens on the surface by absorbing carbon from the environment while the part is bright red hot. The core of the part does not pick up any carbon, so stays softer and more flexible. Kasinit, charcoal, leather or a carburizing welding flame will provide enough carbon to defuse into the metal surface. The longer the part stays hot, the deeper the carbon defuses into the metal and the harder (and more brittle) the part gets.

If you are making parts out of drill rod (high carbon tool steel stock), heat treat by getting the part bright red for about 3 minutes, quench in molten lead for about a half hour, then chill. Parts turn out hard, but not brittle. It's a great process for making cones (nipples), which have the same tough life as Spencer firing pin carriers.

If your block is starting to dimple around the firing pin hole, have someone with an Oxi-acetylene torch heat the area with a carbonizing flame (after you take out the firing pin!) Give it about 5 minutes at red heat and quench in motor oil. You should see a ring of black condensed carbon appear around the heated area. Do this outside as there will be a lot of foul smelling, highly flammable smoke when you quench. I have fixed a couple blocks this way. One was so badly dimpled that I had to build up the face with weld and dress it back down flat before hardening. They hold up quite well afterward.