Short chamber advantages?

[tmwinds]

Never had a problem with case length. After four or five firings and neck sizing they run 2.035 to 2.038.

Your case length is well within specs for a .243AI.

 

[DaveTooley]

I have 243AI reamers with different neck diameters. I started with STD 243 go gage shortened .004". Per PO Ackley's instructions. The problem is you get a different chamber length with each neck diameter. That violates rule #1. Had to have a 40 degree gage made. So there will be different length chambers out there for any smith using a shortened gage with different neck diameters.

Edit cleaned this up some. Typed it out sitting in a doctors office.

 

[gunsandgunsmithing]

I have 243AI reamers with neck diameters. I started with STD 243 go gage shortened .004". Per PO Ackley's instructions. The problem is you get a different chamber length with each neck diameter. That violated rule #1. Had to have a 40 degree gage made. So there will be different length chambers out for any smith using a shortened gage.

A feller that understands! Wanna discuss a 280AI?

 

[DLCrocket]

So I have a Savage 12FV in .243 AI barrel by E.R. Shaw. After several firings on my brass, I couldn't close the bolt on several of them. Using a Redding full length die with 40° shoulder, it had no effect on the brass shoulder. Had a machinist take 0.010" off the die face and still no shoulder bump. Called Redding and they said I must have a shorter version of chamber. Is there any advantage to having a short vs longer chamber?

Barrel was rechambered. After fire forming and several firings brass measures 1.698 to datum line using Hornady heads space comparator. My Redding full length sizing die doesn't bump the shoulder at all. I'm using a Forster

So I have a Savage 12FV in .243 AI barrel by E.R. Shaw. After several firings on my brass, I couldn't close the bolt on several of them. Using a Redding full length die with 40° shoulder, it had no effect on the brass shoulder. Had a machinist take 0.010" off the die face and still no shoulder bump. Called Redding and they said I must have a shorter version of chamber. Is there any advantage to having a short vs longer chamber?

Barrel was rechambered. After fire forming and several firings brass measures 1.698 to datum line using Hornady head space comparator. My Redding full length sizing die doesn't bump the shoulder at all. I'm using a Forster Co-ax press so no using different shell holders. I've already had a machinist remove 0.010" from the die. I'm going to have him remove more, but trying to figure out a good way to measure exactly how much more to remove so I don't take too much off. Any ideas how to get a measurement? I really appreciate all the good advice on this forum!

 

[6.5 forever]

Maybe the next smith will be of help and I strongly suggest fl sizing after every firing. You only need to bump them a couple of thou.
Anymore, "bolt won't close" has a broad definition to different people. It used to mean it wouldn't close with normal cycling of the bolt...something obvious. Nowadays, if some people feel the slightest resistance, that may be their definition of the bolt not closing. It has become more subjective than ever before. Internet is great for creating something to argue about when it should be simple and clear.

Not sure about the op in this case but unfortunately, a better mental image of the issue might be of help...or not. Hard to believe it went several firings and the problem just appeared though. Maybe I'm misinterpreting something too.

Good thing about the Internet is we get to tap into knowledge from people like you. I always follow your insight. Thank you?

 

[ggshoots]

Sounds to me like you are possibly running a 243 Win Imp. 40deg sizing die. It is different than a true Ackley type taper. The Win Improved die oversizes the brass at the shoulder reducing it by about .004 more than what it should be which in turn lengthens the brass. Ackley chambers are not SAAMI so that is where you can have the issue.

I run 223AI, 22-250AI, 243AI, 7mm-08AI and 2 custom AI's I built. 243AI is the only one I have seen this with. Look at your die box, does it say 243 Ackley Improved 40deg or 243 Win Improved 40deg as ER Shaw sells. I went through the same thing. I chambered my 243AI barrel, had 243WIn Improved 40 deg dies which it does not say anywhere on the box That it is "Ackley" but is always in the description on the website. Could not get the shoulder to bump back yet noticed hard sizing and oversizing the shoulder. Instead of sizing the shoulder to .456" it takes it to about .452". As I said this causes the length to increase then, the brass has to go somewhere. I found very hard sizing, could not bump the shoulder back and case length growth. Measure your shoulders.

Some people will argue you should still be able to move the shoulder back but if you have built wildcats or worked with a 40deg shoulder you will find it is not as easy to move as a 23 or 30 deg shoulder. Of course this is all my personal opinion based upon my experiences and equipment.

RCBS dies work great, the Redding dies are the culprit for me. Now I will say as my memory is coming back to me after looking at the die boxes. The Redding set has the Neck sizer and body sizer separate but body dimensions are what you are having issues with.

 

[dellet]

First thing I would do is to blacken a case and confirm where in the chamber it’s contacting, no sense in chasing a length problem, if it’s actually diameter.

If you size a case and the shoulder is not being touched, it should show on the neck, much like when neck sizing only. More or less like an external doughnut. If you remove the sizing ball it will show even more.

The other thing that will likely happen if the shoulder is not being touched, is that the case body will grow after sizing. The shoulder will actually move forward. Measuring before and offer will confirm this.

One other thing to try is chambering a case after full length sizing without the expanding ball.

The amount that the neck is not being sized would be a good starting point.

Or have a chamber cast done.

Edit to add
Just read your other thread about brass that won’t fire form. If this is the same brass, anneal it, or junk it. Maybe try different brass first, but shoulders that won’t blow out at 50,000 psi, are going to be hard to reset with a die.

 

[ggshoots]

I just went back and reread your opening post. A short chamber is something that should be able to be corrected by adjusting your die. A chamber with different wall taper cant be overcome by adjusting your die. One is basically the same chamber at a different length the other is really a different chamber. Your die dimensions and chamber reamer dimensions need to match up and that is the problem with Wildcats which PO Ackley cartridges really are except for the 280AI which has been SAAMI standardized. That's my take.

 

[cb186]

First time reading this thread....
My first thought is, is this a barrel nut or shouldered barrel? If barrel nut, I would have checked headspace as the first step.
Now, it sounds like your new barrel(headspace not done by your buddy), is also having the same problem? If so, then I'd look at what @ggshoots is saying.

 

[fkimble@charter.net]

To get a good idea of excessive headspace, take a used primer and and seat it about have way in the primer pocket. Then chamber it and close the bolt. Now remove the case and measure how high the primer is sitting out of the case. That is the distance of the case head from the boltface, also know as headspace.

Frank

 

[D the D]

Do not use tape on a case to check headspace. Use the proper gauges. The datum line on a brass case is variable. You adjust your brass to the chamber, not measure the chamber with your brass.

 

[DLCrocket]

Sounds to me like you are possibly running a 243 Win Imp. 40deg sizing die. It is different than a true Ackley type taper. The Win Improved die oversizes the brass at the shoulder reducing it by about .004 more than what it should be which in turn lengthens the brass. Ackley chambers are not SAAMI so that is where you can have the issue.

I run 223AI, 22-250AI, 243AI, 7mm-08AI and 2 custom AI's I built. 243AI is the only one I have seen this with. Look at your die box, does it say 243 Ackley Improved 40deg or 243 Win Improved 40deg as ER Shaw sells. I went through the same thing. I chambered my 243AI barrel, had 243WIn Improved 40 deg dies which it does not say anywhere on the box That it is "Ackley" but is always in the description on the website. Could not get the shoulder to bump back yet noticed hard sizing and oversizing the shoulder. Instead of sizing the shoulder to .456" it takes it to about .452". As I said this causes the length to increase then, the brass has to go somewhere. I found very hard sizing, could not bump the shoulder back and case length growth. Measure your shoulders.

Some people will argue you should still be able to move the shoulder back but if you have built wildcats or worked with a 40deg shoulder you will find it is not as easy to move as a 23 or 30 deg shoulder. Of course this is all my personal opinion based upon my experiences and equipment.

RCBS dies work great, the Redding dies are the culprit for me. Now I will say as my memory is coming back to me after looking at the die boxes. The Redding set has the Neck sizer and body sizer separate but body dimensions are what you are having issues with.

View attachment 1609385

Thanks for the input. I have the Redding Win Imp 40° dies. Customer service at Redding told me two things: 1) they are the same as Ackley improved and 2) no one sells actual AI dies. You are the second person to tell me Win Imp is not the same as AI. I can't find actual AI dies anywhere. RCBS doesn't have them on their website. So I just ran three Winchester cases that had been fired and resized several times through the Redding FLS die. They measure 0.456 - 0.457. So what your saying makes sense. On another note, when I started to weigh the starline brass I was disappointed in the large spread, so I decided to "bite the bullet" and bought Lapua brass and built an annealer. Lapua is incredibly standard in both weight and OAL.

 

[DLCrocket]

To get a good idea of excessive headspace, take a used primer and and seat it about have way in the primer pocket. Then chamber it and close the bolt. Now remove the case and measure how high the primer is sitting out of the case. That is the distance of the case head from the boltface, also know as headspace.

Frank

Hadn't heard that method before. I'll try it. Thanks.

 

[ggshoots]

I went through the same thing. Watch Ebay for an actual set of 243Ackley dies like the ones in my pic previously. Your problem may very well go away. 243 Ackley is the only one I had this problem with.

 

[DLCrocket]

First thing I would do is to blacken a case and confirm where in the chamber it’s contacting, no sense in chasing a length problem, if it’s actually diameter.

If you size a case and the shoulder is not being touched, it should show on the neck, much like when neck sizing only. More or less like an external doughnut. If you remove the sizing ball it will show even more.

The other thing that will likely happen if the shoulder is not being touched, is that the case body will grow after sizing. The shoulder will actually move forward. Measuring before and offer will confirm this.

One other thing to try is chambering a case after full length sizing without the expanding ball.

The amount that the neck is not being sized would be a good starting point.

Or have a chamber cast done.

Edit to add
Just read your other thread about brass that won’t fire form. If this is the same brass, anneal it, or junk it. Maybe try different brass first, but shoulders that won’t blow out at 50,000 psi, are going to be hard to reset with a die.

Thanks for the advice. What works good to blacken a case that will rub off on contact?

 

[SEM]

I went through the same thing. Watch Ebay for an actual set of 243Ackley dies like the ones in my pic previously. Your problem may very well go away. 243 Ackley is the only one I had this problem with.

I prefer to shoot real odd ball wildcats I dont think they are but have been told that a time or 2, I have gone through this many times 2 to 4 sets of the the proper nomenclature until I get one just right. The majority of the time the right one seems to be made by RCBS to bad they stopped making them as regular inventory. I have or had double sets of most every cartridge I shoot some made just a few years apart they defently are not identical

 

[dellet]

Thanks for the advice. What works good to blacken a case that will rub off on contact?

Soot from a candle. More common and easier ink from Sharpie type pen. The softer the coloring, the easier it leaves a mark. Just color the whole case body.

 

[searcher]

Thinking about this - if your die was "incapable" of bumping the shoulder the first few times you loaded ammo for this rifle, I'd be interested to see what the comparator measurements are on your new, unfired brass (if you have any left) and that of one of the cases that won't load. I'd use that "primer half-seated" method to give you an idea of how far your shoulder is away from the die.

Here is what is interesting. Your brass fired through the gun a few times without issue (assuming the shoulders were not bumped at all). Then the brass wouldn't bump when the shoulders seemingly needed it as the die was not bumping all along. You shaved .010" off the die. Still won't bump. If the chamber was short enough to not be affected by shoulder blow-out and that .010" shaved off the die, that is making me wonder how the brass fit in the chamber to start with - seeing how you weren't able to bump those virgin shoulders. I'm not familiar with the caliber you have, nor the caliber of dies you are using - but I'd guess those dies might have something to do with it, as noted by those who may know better than I. If you rule out expanded bases of the brass, trim length and a possible expander ball that is "pulling" your shoulders back out on the upstroke, it pretty much has to be your dies or headspace in the rifle itself.

To your original question - you were curious as to any advantages of having a "short" chamber, versus a long one. There are pros and cons to each. I actually prefer a chamber to be cut a "bit short" to accommodate a particular brand (or brands) of brass. This enables me to bump the shoulder to exactly where I want it before the first firing. Otherwise, it can take several firings to get the shoulders blown forward unless I jam the bullets, etc.. The longer the chamber is, the more of a chore that can be. The downside of a short chamber is the slight reduction of powder capacity and the possibility that some factory ammo might not chamber. If it is a SAAMI chambering, you can't go shorter than the minimum length as called for - or you have what you are encountering - a die that won't bump. For example (even though this refers to a rimfire rifle, it still provides for thought). I had a .17 Hornady Hornet barrel chambered specifically to fit snug to Hornady V-Max ammo which I provided. I got a perfect bolt almost-down crush on the case. I had already bought a lot big enough to wear the barrel out. Then I decided to run some Hornady lead-free ammo after a while and it was a bit too snug, as the brass for that production run was slightly different. Naturally, when handloading, we can fix those things. But when it comes to firing factory ammo - considerations must be given.

 

[DLCrocket]

Sounds to me like you are possibly running a 243 Win Imp. 40deg sizing die. It is different than a true Ackley type taper. The Win Improved die oversizes the brass at the shoulder reducing it by about .004 more than what it should be which in turn lengthens the brass. Ackley chambers are not SAAMI so that is where you can have the issue.

I run 223AI, 22-250AI, 243AI, 7mm-08AI and 2 custom AI's I built. 243AI is the only one I have seen this with. Look at your die box, does it say 243 Ackley Improved 40deg or 243 Win Improved 40deg as ER Shaw sells. I went through the same thing. I chambered my 243AI barrel, had 243WIn Improved 40 deg dies which it does not say anywhere on the box That it is "Ackley" but is always in the description on the website. Could not get the shoulder to bump back yet noticed hard sizing and oversizing the shoulder. Instead of sizing the shoulder to .456" it takes it to about .452". As I said this causes the length to increase then, the brass has to go somewhere. I found very hard sizing, could not bump the shoulder back and case length growth. Measure your shoulders.

Some people will argue you should still be able to move the shoulder back but if you have built wildcats or worked with a 40deg shoulder you will find it is not as easy to move as a 23 or 30 deg shoulder. Of course this is all my personal opinion based upon my experiences and equipment.

RCBS dies work great, the Redding dies are the culprit for me. Now I will say as my memory is coming back to me after looking at the die boxes. The Redding set has the Neck sizer and body sizer separate but body dimensions are what you are having issues with.

View attachment 1609385

ggshoots, did a little more work on this after re-reading your post a couple times. I removed the firing pin from my 243 AI bolt so that it would "fall" closed. Next I sorted through my old Winchester brass that had been fired and reloaded several times, and found three that the bold would close on but were pretty snug. They measured 1.698" at the ogive. Next I took a new Redding S bushing 243 Win Imp full length sizing die and removed the bushing and rod with expander and decapping pin. I adjusted the die in my press so it was just touching the shell holder. I lubed the case and ran it through the die, pausing a few seconds before removing it. I wiped off the lube and measured with Hornady headspace comparator. The case grew to 1.701 and the shoulder measured 0.458. Next I set up my other Win Imp die that I had taken 0.010 off and ran the case through it. No bump on the shoulder. Then I dug out Redding 243 Win Imp body only sizing die I had bought years ago. Once again no shoulder bump. Then I took a sharpie and blackened the case and closed the bolt on it, very snug. The case showed rubbing only on the shoulder between neck and body. Even though my shoulder was not as small as your example of 0.452 I have to conclude that the Win Imp die is the problem. Until I can find a real Ackley improved die, all I can think to do is have some more metal removed from the die until I can get to 1.698.

 

[danny]

That’s the first indication of the problem.

If he had his brother-in-law do it, it might have been .020" short. lol

Danny