Do any of you who reload for your DRs find that the cases stretch after 5 reloads?? I found that above a load that gives me 2300 fps with a 350 gr bullet in my 45-100 DR the cases start to stretch about .005" per firing, so that the case separation ring is showing after 5-6 reloads. Gun is still tight to the face, so it must be springing slightly. Headspace is tight.

quote:

Originally posted by Lanny from NY:
Do any of you who reload for your DRs find that the cases stretch after 5 reloads?? I found that above a load that gives me 2300 fps with a 350 gr bullet in my 45-100 DR the cases start to stretch about .005" per firing, so that the case separation ring is showing after 5-6 reloads. Gun is still tight to the face, so it must be springing slightly. Headspace is tight.

Lanny, First let me say 2300 fps with a 350 gr bullet in a 45-100 seems a little "hot"! The average for that cartridge is around 1900 to 2000 fps.

When the ring first developes, is it more on one side that the other of the case? Also if you rotate the case is it easier to close the rifle than it is with the case turned the opposite way?
You can roll the case on a glass surface after fireing the first loading. does the case's rim seems to wobble? If the answer to any of these question is "YES" then the action is springing with that load!

This causes the case to be bent not stretched. It is just in most cases the case is put in the chamber in a different rotation than the times before and over the five reloads the case is bent in different ways every time the rifle is fired with that case, so the ring developes all the way around the case head.

This is quite common with most older double rifles, or cheap new ones. They may seem tight and on face if they are bending cases, NOT necessarily stretching them then the on face condition is begining to open up! One reason this happens is the lumps under the barrels are not contacting the sides of the recess they fall into when the rifle is closed, letting the the barrels move away from the standing breech on the side being fired.

One more question! What make brass are you using?

..................................................................

Starline cases. The stretch ring seems to be even around the case, but I'll try putting a dial indicator around the base on a vblock, to get a better reading on the uneven stretch idea. The load is NOT for the 45-100 black powder rifles, but a 30,000 psi quickload calculated load. The action is a 1970s Merkel 12 ga, which is supposed to be proofed at 30,000 psi with a 12 ga, with much more thrust than the 45-100 base.

quote:

which is supposed to be proofed at 30,000 psi with a 12 ga,

Sounds high to me for a shotgun. Where did you get that info?

I think it was from Ellis Browns' book on Building DRs on Shotgun Actions. My question is, do other DR's exhibit a few thou stretch in the case??

NO!

What type of shotty did you ise for this conversion project?

He used a 1970s Merkel, which should take 30K psi no problem with a rifle case head. I shoot 28K psi loads all the time from my 45-70 and it is on a cheap Baikal action. Your loads should put about the same back thrust on the frame as a 12 ga shotshell does. Starline brass is usually very thick and if you are stretching it, perhaps your chambers are cut with too much headspace? The answer to your question is, no you should not be experiencing stretching at these pressures; none of my DRs stretch brass at all. Maybe you have a lot of soft brass; try another brand. And are you sure you are at 30K psi? The brass alone will sometimes hold that much pressure (read P.O. Ackley tests).

Whoops I missed that.

Most of the causes of "case stretch" with strong enough, properly chambered DR's, is hot loads and/or over sizeing the cases.

DM

Did you anneal the cases prior to loading. This can also lead to stretching.

dutch

Failure to anneal, that is.


Dutch

I am not familiar with how annealing the brass can lead to stretching.

Lanny, what load are you using that does this?
This is (assuming that the chambers are cut properly) the next step.

quote:

Originally posted by Lanny from NY:
a 30,000 psi quickload calculated load. The action is a 1970s Merkel 12 ga, which is supposed to be proofed at 30,000 psi

Just a thought, but Lanny said the action was "proofed at 30,000 psi" and he is using loads that generate 30,000 psi. If I remember correctly, a proof load is a load that is intentionally loaded to well above the level that is supposed to be the maximum level to be used in that particular firearm in order to verify that it is safe to use. It is not intended to be used on a regular basis, just that once to "prove" the firearm. If he is shooting proof loads on a regular basis, he is probably shooting what amounts to a bomb that could go off at any time. If this is the case, Lanny needs to stop shooting these loads immediately and get the gun to a gunsmith to have it checked.

dpcd:
Read my second post.


Dutch

Scojac-read my whole post about proof tests with a 12 ga. The thrust on the action is area X pressure. The 45-100 head is less than half the area of the 12 ga head. The load is 75.5 gr 4064, with a 350 gr RN seated long, and I throated the barrel longer than the standard 45-100. Maybe, it's just a matter of polishing the chamber.
I don't know why, but my login from home is different than from work. Lanny

Not to insult anyones basic reloading ability but hope you are adjusting your resizing die just enough to allow the case to enter the chamber. FL resizing will often speed up case head separations.

Getting 5-6 firings on a piece of brass would be pretty good with full throttle charges. Might get even more, but I would toss them at the very first signs of any separation. My preference is to only use new brass when hunting with a double.

The 75.5 gr load stretches the case just about .002", but the regulation could use another .5 gr, to get the L-R to 1" at 50 yds, instead of 2". Just looking for info if any DR shooters measured case length before and after shooting. And I use a 45-70 die set to just resize the neck, and crimp on the Hornady 350 gr RN rear cannelure. Decap with a tong tool.
Lanny

Let me rephrase the question. Could somebody measure the case length before firing, and then after firing a full load, and post the before and after lengths?? Thanks.

This could be one of those situations where the circle is not properly fit. If there is a gap in the circle, it can give the results you are seeing - stretched cases. One of the symptoms of a poorly fitting circle is that under pressure (while firing the gun) the barrels are allowed to more forward slightly and causes the brass to "setback" and stretch. That is one issue with using a shotgun action for a double rifle - they don't always fit the circle as tightly on shotgun as they do on a double rifle. Usually, there is no problem, but this could be one of those times. Read the chapter, "Jointing & The Circle" in Vic Venters' book "Gun Craft". It gives a very good explanation of this. It also gives a way to fix the problem - fitting a block of steel into the circle on the action.

Ellis

By "the circle" do you mean the hinge pin location on the monoblock/lump? The surface seems to look evenly worn, no bright spots at the top and bottom of the bearing surface.

quote:

By "the circle" do you mean the hinge pin location on the monoblock/lump? The surface seems to look evenly worn, no bright spots at the top and bottom of the bearing surface.

No, the circle is the forward portion of the rear lump. It is curved and should fit against the mating surface in the action. This can be checked by smoking the lump and closing the barrels on the action. If there is good contact, the smoke will be removed from the lump. If there are no marks at all on the lump, this might be your problem. If it looks like this could be an issue, I would highly recommend that you spend the $30 for Venters' book. It shows how (or at least where) a block of steel can be fit into the action to compensate for the poor fit. Baikal double rifles have this block installed from the factory.

One of the other things that Venters points out, is that with a properly fit "circle", it takes a lot of stress off of the hinge pin. Understanding this resolves a lot of issues around trying to install a "beefier" hinge pin. The pin is not where the force should be riding.

Ahh, thank you, Ellis. Some real insight on DR fitting.