Modified case for Hornady head space tool

[PaddyD]

I'm wanting to make my own case vs spending 10 bucks for every modified case from Hornady. Does anyone know the tap size and TPI I will need?

[mike21]

4182

5/16 X 36 Taper. Had a hard time getting the new threads straight, but everyone is a better machinist than me.:rolleyes:

[PaddyD]

4182

5/16 X 36 Taper. Had a hard time getting the new threads straight, but everyone is a better machinist than me.:rolleyes:

Thanks. I've been wondering how I can keep the hole true as I don't have a lathe to do it. All I have is a drill press. Good think I have lots of brass to practice on..
What was your method for expanding the neck after you sized the case?

[geargrinder]

I drilled a piece of 2x4 just as big as about the middle of the case. I used that to hold the brass under the drill press. Not the most elegant solution, but it worked good enough.

I used a fired case without sizing it.

[PaddyD]

I drilled a piece of 2x4 just as big as about the middle of the case. I used that to hold the brass under the drill press. Not the most elegant solution, but it worked good enough.

I used a fired case without sizing it.

Good idea. I'll try the 2x4..
As for using the fired case I don't think it will work for me. When I size my cases for loading I like to set the shoulders back .002" from what the fire formed case measures coming out of the chamber. So unless my modified case has the same dimensions as the case with the .002" set back the measurements won't jive.

[Burr]

If you trim necks, use the same expander mandrel. If you fl resize with a die that has a button, remove the button when you set the shoulder back. Or use a body die to set the shoulder back. Or, just realize the store bought modified case is probably to SAAMI specs and farther off than your once fired brass.

[PaddyD]

If you trim necks, use the same expander mandrel. If you fl resize with a die that has a button, remove the button when you set the shoulder back. Or use a body die to set the shoulder back. Or, just realize the store bought modified case is probably to SAAMI specs and farther off than your once fired brass.

Yes, I'm sure the store bought Hornady case is SAAMI spec in dimensions. When I fire a case in my chamber and then use a comparator to measure the datum on the shoulder to the Hornady case it is always about .002"- .003 longer. This depends on how much the brass has been work hardened and how much spring back it has. In my particular case I only want to let my brass have to stretch any more than it has to. So I set the shoulder back just until it will let the bolt close with no effort. Setting the shoulder back to SAAMI specs means the brass gets worked more than it needs to. So that's why I take a fired case then size it down just enough, which is between .001 and .002". If I just used a fired case screwed on the tool that has not been bumped I won't be able to get the same measurements for throat length using the tool when I start seating bullets for jump with my sized cases with the shoulder setback. Am I correct in this? Sometimes I have a hard time putting my thoughts into words. LOL

[Zero333]

I don't mind spending a few bucks for the Hornady modified case because it's got the same exact dimensions as a go-gauge. Therefore it saves me money not having to buy a separate go-gauge !

[PaddyD]

I don't mind spending a few bucks for the Hornady modified case because it's got the same exact dimensions as a go-gauge. Therefore it saves me money not having to buy a separate go-gauge !

You make a great point there. I once read an article about a guy taking a full length sized case and filling it with devcon epoxy and using it for a go gauge. He filled it with epoxy so it wouldn't be able to squeeze down while he screwed his barrel down on it. I wouldn't trust a case like the modified Hornady because you just never know how exact it is. They say it is the same, but how would you check?

[Robinhood]

You may...or may not find this usefull.

Sharpening a drill to cut brass. (http://www.savageshooters.com/showthread.php?55636-DIY-Hornady-Lock-N-Load-Overall-Length-Gauge-Modified-Cases&highlight=drill)

[OLEJOE]

I know for a fact that my modified case for 6.5 Creedmoor is NOT the same distance from base to datum point on the shoulder as my Go Gauge. I've measured both. Measure the difference between the modified case and your sized case and add the difference. I use a fireformed case myself. If you are bumping the shoulder back.002 then I think it will work either way. Some bullets vary .002 or more in base to ogive. I don't think 2 thousandths is going to make much difference unless they are jammed.

[Robinhood]

I know for a fact that my modified case for 6.5 Creedmoor is NOT the same distance from base to datum point on the shoulder as my Go Gauge. I've measured both. Measure the difference between the modified case and your sized case and add the difference. I use a fireformed case myself.


Yup

[Zero333]

You make a great point there. I once read an article about a guy taking a full length sized case and filling it with devcon epoxy and using it for a go gauge. He filled it with epoxy so it wouldn't be able to squeeze down while he screwed his barrel down on it. I wouldn't trust a case like the modified Hornady because you just never know how exact it is. They say it is the same, but how would you check?

The go-gauges I have measure exactly the same as their corresponding Hornady modified cases. All you need is a headspace comparator or a headspace micrometer to measure them.
The most important measurement is from base to shoulder datum. In this they measure EXACTLY the same. Rest of the dimensions are the same as well.

I don't think a piece of brass will conform when being pushed by a barrel that's being screwed on. I've checked HS on rifles with the modified cases, and when attaching masking tape to their head (to turn them into a no-go gauge) they give a very positive feel of hitting a wall when attempting to close the bolt.

[OLEJOE]

My modified case measures.004 less than my go gauge. That’s more difference than the difference between go and no go gauges. The modified case I have measures the same as new unfired Hornady brass. My fire formed brass measures .0015 longer than the go gauge and that’s over .005 longer than the modified case.

[Zero333]

My modified case measures.004 less than my go gauge. That’s more difference than the difference between go and no go gauges. The modified case I have measures the same as new unfired Hornady brass. My fire formed brass measures .0015 longer than the go gauge and that’s over .005 longer than the modified case.

I guess I got lucky !.

My 223 and 308 go-gauges measure exactly the same as the modified cases. I use the Hornady Headspace comparator to measure.

I suppose it's true when folks say, it's always best to use a real go-gauge.

[OLEJOE]

I use the Hornady Headspace Comparator also. That’s the reason I have only listed differences instead of final measurements. I also use the same tool with different inserts to measure Base To Ogive distances. But it is still a comparator. Can only compare 2 barrels or rifles if using the same gauge.

[PaddyD]

The issue with using the go gauge to compare modified cases with is that not all rifles use the Savage head space system where you can simply screw the barrel down on a go gauge , then lock it down and be done with a perfectly head spaced chamber.. Rifles like M70's, Rem 700's and my 1903A3 are usually short chambered when the barrel is screwed in then finish reamed . Sometimes they are reamed to slightly more than optimal depending how good the smith was doing the finish chamber reaming. Especially the older surplus military rifles that may have passed inspection with a field gauge. This is why I want to take a fire formed case formed in MY chamber, then size it setting the shoulder back between .001 and .002" then drill and thread that case which is exactly to the same dimensions as the cases I will be loading.. The Hornady threaded cases are to spec, but not necessarily to MY chamber. I hope I make sense with this. Maybe I'm not.

[OLEJOE]

I think your method is probably the best since it has a better fit to the chamber. What we need is a tool to measure from the datum point on the shoulder to the ogive on the bullet.

[Artpro]

Hi. You'll need a 5/16-36 TPI tap. It is not very common.

[PaddyD]

Hi. You'll need a 5/16-36 TPI tap. It is not very common.

Thank you. Yes, I found that out after hitting every auto parts and hardware store in the area and finding nothing. My tap arrived yesterday for $6.99 shipped from Amazon.com Today I will be fashioning a jig to hold the case while I drill it