1873 rifle headspace measurement

Ghostdevilguy · February 21, 2024, 05:10:38 PM

Hi all! First post here, I've been wanting to get into CAS for years, my big hold up was getting a rifle, they were always out if my budget. However at the start of February we were on a trip to Tuscon and I found an Cimarron 1873 trapper used for a price I couldn't pass up. I've been going through it and learning about it, from what I can tell it's already had a lot of work done to it for CAS, it has an aluminum carrier, extended firing pin, a super short stroke kit (I think), and a mag tube with the right internal diameter for 357/38 shells, as well has some nice engraving on the receiver.

I took it to the range and it was deadly accurate at 100 yards with 357 loads, however when going to resize the brass I discovered that some of the brass had a bulge. After doing research, I now believe the headspace is too long. It had zero issues functioning, but it's something I'd like to fix or make sure it's correct for the longevity of the rifle.

With a case in the chamber I can fit a .025 feeler guage between the bolt face and cartridge, without calipers to measure the rim, and knowing that the average 357 rim is .060, my headspace would be ~ .085 correct?

Now where I need help, is I can't find anything that states what the headapace is when it's correct. It could be my fault for not searching correctly. Any advice, input, or information would be greatly appreciated!

Abilene · February 21, 2024, 10:13:12 PM

Hi Guy, welcome aboard. I am not a gunsmith, but I think that is pretty excessive. I'm thinking that gap should be less than 0.010"

If the gun has some of those go-fast parts you mentioned, then it likely has a short stroke it. Open the lever all the way and if it goes a little past 90 degrees then it is stock. If it is less than 90, it's a short stroke (some are shorter than others). Most of those consist of a new set of toggle links, usually a new lifter arm, maybe more, but most that's it. Now, putting one of those kits in can change headspace. Depends on the kit and what your gun was like to start with. When it gives a headspace problem, most of the kit makers have other links available that are longer or shorter to correct it. So, it's a possibility that a shortstroke kit is the culprit. You might be able to get a replacement kit with longer links, or possibly returning it to stock would correct it. If you have to do that, parts should be cheap or free because many have them laying around after putting in SS kits. But if you are planning to use it for CAS, you might like to keep is short. Anyway, good luck!

Coffinmaker · February 22, 2024, 08:51:45 AM

Ghostdevelguy

Optimum Head Space for a Toggle Link Rifle is .004 Depending on who make the Short Stroke kit, you can measure your head space and the manufacturer of the links can usually provide extended links to correct the head space. Pictures of the links and Carrier Block Arm would help identify who made it.

Ghostdevilguy · February 22, 2024, 09:09:50 AM

I'll get some pictures of the links, carrier block arm, carrier block, of how far the lever opens up, and just general pictures of the rifle later on today. If I can find a set if factory links I'll put it back in factory condition to fix the headspace so I can shoot it for now, and then get another short stroke kit for it later.

Abilene · February 22, 2024, 09:16:10 AM

When you take the side plate off, look at the links with the lever closed. They should be in a straight line. Another possibility for the issue might be that someone had an OOB, out-of-battery firing, which is more common these days with people trying to go so fast, and that can bend some things, like the lever or lifter arm. I'm not positive if that would affect headspace or not (Coffinmaker?), but something to check.

Coffinmaker · February 22, 2024, 04:28:04 PM

An OOB discharge usually has no effect on Head Space. Bending the lever, yes. But a bent lever is easy to spot as the lever won't close all the way although the bolt closes up. Carrier Block Arm also won't affect Head Space. Head Space is determined by the Links. Very very difficult to "bend" links.

If the rifle has poor Head Space to begin with, a "Cut and Weld" shorty stroke usually makes it worse. Short Stroke with link sets can usually correct bad Head Space so long as the manufacturer is known and it is known how far out of spec the Head Space is.

Head Space is measured between the Cartridge Head and the Bolt Face. Measured with the Bolt closed up in Battery. Best measuring tool is a tapered set of feeler gages (Auto Parts Store). Both Cowboys and Indian Store and Pioneer can provide longer length links. Don't try to do it by eMail. Best with a Phone call so questions can be answered.

Most forgot. You can "get by" with Head Space of .006 - .008. Once past .008 your flirting with light primer strike and fail to fire.

Ghostdevilguy · February 22, 2024, 04:45:23 PM

Ghostdevilguy · February 22, 2024, 04:48:46 PM

So I failed to mention, the main reason I believe it has an extended firing pin is because of how deep the primer strike was on the 357, and it worked 100% reliably. But I was also aware enough to notice the brass and look farther into the issues. I know a .025 headspace isn't right, now it's just a matter of getting her back into spec. Thanks for the help so far! Also, let me know if there are any more pictures needed

Coffinmaker · February 23, 2024, 09:54:25 AM

Ghostdevelguy

Nice Rifle!! Your links appear to be from Pioneer Gunworks. I'd suggest giving them a call and ask if they can make you a longer set of links. It also appears the Carrier Block Arm isn't lifting the Carrier Block all the way up.

Ghostdevilguy · February 24, 2024, 01:41:23 PM

Thanks for the info Coffenmaker!

I will give Pioneer gunworks a call and probably get an new short stroke kit with lifter. After observing the action it also appears that the lifter starts to later than it should. It starts moving after the bolt is done moving, and from what I'm seeing it should just miss the bolt