RC tested my receiver... your opinions...

I tested my receiver at work today. If I remember correctly ORF stated that the correct RC was 45? The RC range on this receiver was 41-42.

As I posted in one of the other threads, any heat treated piece SHOULD have a consistent heat treat throughout the piece. It should NOT matter where you test, as the RC should not vary.

A range of +1 or -1 is not bad... in fact it is fairly good. A range of + or - 5 I consider to be quite broad, though depending on application, may not matter.

I wrote the RC number with a line to the test mark. There was one extraneous test which made the artificially high RC number you see. I am 100% positive that this number is nothing but an error... it in no way affects any of the other numbers or their validity.
http://i43.photobucket.com/albums/e353/falgrunt/IMG_2518.jpg
http://i43.photobucket.com/albums/e353/falgrunt/IMG_2519.jpg

there were no other RC test marks besides the 4 that were made during todays test

Now, the question is... Should I build it... or should I see if ORF will exchange another receiver for it.

-myers

Perhaps 45 is not hard enough for the stresses put on the receiver in the areas in question.What is the hardness of a receiver in a full auto factory gun?td

No idea...

GP? When you see this... :) let us know.

-myers

It is the locking recesses that are in question - and a through harness, not a case-hardening or carborizing.

We also don't know what the spec is supposed to be. Todd claims its 40-45, but he has lied so many times his word is worthless. Also, in his own posts, he claims some receivers were 50. If the spec is 40-45, then 50 is just as defective as 35.


And here is something else to test. Hang your bolt from the locking lugs with the receiver pointing up. the tail of the bolt should lay straight - it is is canted, the locking recesses are out of alignment

rc does vary, one of the biggest reason knife makers are going to sintered steels.
the elements just don't mix well enough to give a uniform hardness in the final alloy.

It is the locking recesses that are in question - and a through harness, not a case-hardening or carborizing.


What does this mean?

Mark, I was hoping you had a IMI or otherwise spec. I'll check the alignment of the bolt to locking recess and report.

Bigwheel, I have to disagree, in a piece of billet steel, using furnace heat treating, there should be little variance in RC. I do not know much about knife making, but I would think that the steel is less uniform than production steel, though again, I could be incorrect. Also, agian, I lack in knife making knowledge, but most heat treating I have seen for knives is either water or oil quenched, after heat is applied visually with either coals/charcoal or a torch. Hardly comparable to a thermostat run heat treat oven. Which... if ORF's heat treater did not use... then they are from the dark ages. The heat treat ovens from where I work are from the 40's or 50's and they can CONSISTENTLY give CONSISTENT heat treat results time and time and time again.

-myers

FAL GRUNT, just curious, what is the serial # of your receiver? I bought some when they went on sale for $250 a few months ago, IIRC my serial numbers are in the 1300 range. Is this an early receiver or a later model "improved" receiver? Are any of them worth building on? As GP pointed out elsewhere, if Todd did make changes/improvements to the receivers, why didn't he help out his customers by listing the serial numbers and the changes he made? Thanks for doing the hardness testing, your research is much appreciated. I am watching all these threads carefully to figure out if it's worth building on one of these receivers.

What does this mean?

Mark, I was hoping you had a IMI or otherwise spec. I'll check the alignment of the bolt to locking recess and report.

Bigwheel, I have to disagree, in a piece of billet steel, using furnace heat treating, there should be little variance in RC. I do not know much about knife making, but I would think that the steel is less uniform than production steel, though again, I could be incorrect. Also, agian, I lack in knife making knowledge, but most heat treating I have seen for knives is either water or oil quenched, after heat is applied visually with either coals/charcoal or a torch. Hardly comparable to a thermostat run heat treat oven. Which... if ORF's heat treater did not use... then they are from the dark ages. The heat treat ovens from where I work are from the 40's or 50's and they can CONSISTENTLY give CONSISTENT heat treat results time and time and time again.

-myers


I'm sure that the IMI and milled AK's are forged using a different steel than 4140. That steel may or may not be in the proper range but Firingline uses 4140 billet with good results. If you want to test a factory milled rifle just use some cut parts from milled kits. There is a guy in Canada selling cut IMI Galil receiver parts. Some are not cut legally for import in to the US and some he has cut just to export to the US. I think he has receivers cut in to 4 (maybe 3) pieces and he has receivers cut down the middle longways in 2 pieces but he won't sell the piece that has the serial number or some odd restriction like that. To just get a working hardness the pieces from the cheap Yugo milled kits should do. Also some Polish milled stubs are around for not much.

The last knife I had made was from bg42, (timken latrobe) I sent it to a heat
treater in Florida that does a lot of aerospace work. It is at a rockwell 64 and
was also cryro'd twice during the process. It still varies from spot to spot. The
knife builder checked it against a test piece he did to see if he could do bg42
in is oven in a stainless pouch with kindling to remove the oxygen. Again it's the
alloy's that don't mix uniformly, not the heat treating that is the problem.

bigwheel, that was not my understanding of 4140... I don't know anything about bg42 as I have never worked with it. We heat treat with the same pouch set up... with paper(kindling) to remove oxygen. How much does your RC vary on your knife?

I think we are arguing semantics... I know the RC will vary on a piece of metal.... but im talking A RC... it should not vary like some of these guys think where the locking recess face could be a totally different number.

If the area below the trigger guard reads 42, the locking recess (if I could get to it) would probably read anywhere from 41-43... but it isn't going to be 32 or 52.

1turboturtle, I don't know what mine is, early? it is in the 600 series. I also have an earlier 600 that is already built, which shows SOME peening of the locking recess.

-myers

FAL, your right on that, it doesn't vary a lot, (with the exception of the unmelted
file or two you run into in chinese steel.) And hard or soft spots are very tiny
and vary random.

bigwheel, that was not my understanding of 4140... I don't know anything about bg42 as I have never worked with it. We heat treat with the same pouch set up... with paper(kindling) to remove oxygen. How much does your RC vary on your knife?

I think we are arguing semantics... I know the RC will vary on a piece of metal.... but im talking A RC... it should not vary like some of these guys think where the locking recess face could be a totally different number.

If the area below the trigger guard reads 42, the locking recess (if I could get to it) would probably read anywhere from 41-43... but it isn't going to be 32 or 52.

1turboturtle, I don't know what mine is, early? it is in the 600 series. I also have an earlier 600 that is already built, which shows SOME peening of the locking recess.

-myers

You are ASSUMING that the company doing the heat treat #1 did not overload the oven #2 did not cut the time in the oven short as a cost saving measure or worse a combination of both conditions, the locking recess are located in a thicker portion of the receiver than the exterior surfaces. in order to get a uniform RC the piece must be heated uniformally in order to accomplish that it must be left in the oven long enough for those heavier areas to come to full temp... likewise if the oven is overloaded the heat is not distributed equally as more time is required to bring all pieces to temp....... you are assuming variables we have no way of knowing so unless ya can actually test the locking recesses themselves then the tests are inconclusive as none of us know if the heat treating company was trying to meet a cut rate by cramming extra receivers into each run..........
Firearms heat treating companies do not do one receiver at a time... they run a bunch in with each run some......... will actually stack up extras ontop of the normal run... this problem resulted in a large number of AK receivers being warped for one major manufacturer awhile back (no it was not NoDak) because the heat treater had been given a fixed rate by the manufacturer that they were willing to pay...... the heat treater was doubling up on each run to meet that rate....... the heat was not distributed evenly as the stacked recievers sheilded those on the bottom as well as those in the center of the oven, there is a reason bakers have baking sheets AND baking pans, heat inside of an oven will vary the more obstacles inside the oven well.... I've screwed up the heat treat of mauser 98 receivers (from when SARCO had all the FNs that just needed to be finished and heat treated) because I tried doing 4 at a time in our oven instead 2 at a time.... the heavier receiver ring... and locking resecces did not heat treat and some side rails warped as a result of overheating while I tried to get all of em equally up to temp... Bob can tell ya about it at breakfast sometime just tell him to relate the story to ya as he was involved at the time if I remember right with that manufacturer ;)

"And here is something else to test. Hang your bolt from the locking lugs with the receiver pointing up. the tail of the bolt should lay straight - it is is canted, the locking recesses are out of alignment"

This was the big problem with mine. No matter the hardness, if you only have one lug contacting, the stress is doubled on the right side locking surface. It distorted on mine after only 20 rounds or so. Lay the bolt in there and see if both lugs seat correctly.

The result is ever growing headspace.....

So is 41-42 RC that bad? According to firingline, their milled receiver rates at 45 RC. I know absolutely nothing about steel and RC values by the way. I have an orf 7.62x38 receiver and have my concerns like everyone else. Anyone ever test an orf vz58 receiver?? I have one and seems to be fine so far...