What size difference for proper neck tension for .38-55?

[BCRider]

I'm getting ready to load up my third batch of ammo for my rolling block and the new Uberti. Up to know I just assumed that the die companies know what they are doing. But while just trying to make up a dummy sizing round I'm finding that there is a fair amount of bulge where the base of the bullet ends. And this is on partialy sized brass, not full length sized which, due to the taper on this cartridge, results in a too sloppy fit in the chamber.

So all this got me to measuring the internal sizing plug to see just how much tension I'm working with. The sizing plug measures at .372 while the bullets measure between .376 to .377.

This seems like a lot so I went searching for an idea of how much of a press fit we should be using. But there is precious little hard information with numbers out there. Or here on Cast Boolits for that matter.

I do know that from the slight amount of hard number information I found that it appears that the .004 to .005 interference fit is too tight. I'm guessing that I'll get some spring back from the brass so it's likely more like .005 to .006 interference. And that seems VERY tight. Like tight enough I might be swaging the bullets to a smaller diameter during seating.

Luckily I've got a lathe and some drill rod so I can make up a new hardened and tempered back expander plug. But I'd love to hear some suggestions for how much tension there should be for a single shot .38-55 round.

[EDG]

Here is my data for .375 Win and .38-55 Win reloading dies.
I have posted it here before but the search engines do not find stuff for me so I am pretty sure they do not find my stuff for someone else.

I find the .38-55 can be a 3 part problem when it comes to dies. Somewhere along the line the die manufacturers forgot that the 38-55 is a .38 and not a .375.

1. The sizing dies may size the case way more than necessary because they were set up for a .375 bullet.
2. The expander plug may be way too small because it was set up for a .375 bullet.
3. The seating die may not be large enough inside if you have a .380 to .382 groove diameter original rifle that needs .381 to .383 grease groove bullets.

I have a lot more experience shooting other BPCR type rifles. Mostly it is .40-65 and .45-70 and they are all single shots.
The following comments may not apply to lever action tube fed rifles because the magazine and recoil may push bullets down into a case.

For jay bullets I long ago determined that I could get by most of the time with only .001 undersize on an expander. I am sure I have a few that are .0015 to .002 undersize but then again these are not BPCRs they are magazine rifles for bottle necked rounds.
For cast bullets (in single shots) I like .001 interference maximum and .0005 is better. When I have a plug that is exactly the same size as the bullet I have used them with success in single shots. The plug expands the brass but the springback may cause the brass to shrink back to .0002 to .0003 undersize. This small interference does not damage 20-1 lead tin plain base bullets.

You need to take this information with a big grain of salt because the condition of the brass counts too.
Annealed brass will often expand right to the size of the expander. Work hardened brass will spring back a lot more than .0005. You have control of the annealing so keep an eye on what your brass is doing.

.	.	RCBS	.	Die	.	Sizer	.	Sizer Inside	.	Seater Bullet	.	Comments
Die Set	.	Date Code	.	Brand	.	Type	.	Diameter	.	Guide Dia.	.
.	.	.	.	.	.	.	.	.	.	.	.
.375 Win	.	78	.	RCBS	.	FL	.	.3890	.	.378	.	.3735 expander
.375 Win	.	79	.	RCBS	.	FL	.	.3900	.	.380	.	.3734 expander
.38-55 Win	.	UNK	.	RCBS CBY	.	FL	.	.3870	.	.381	.	.3742 and .3773 expanders.
.38-55 Win/Ballard	.	84	.	RCBS	.	FL	.	.3850	.	.380	.	.3735 expander
.38-55	.	UNK	.	LEE	.	FL	.	.383/.385	.	.376	.	Short .373 expander tapers to .385.
.38-55		G 56		RCBS		TRIM		.3940		NA		Not a die set

[Doc Highwall]

For my Remington 40X chambered in 7.62 NATO I did my first tests with a bullet sized to .3100" and a expander that was .3090" and I got great results. Then I purchased other sizing dies for my lubersizer so now I have bullets sized .3095",.3100", .3105", and .3110". The next thing I did was make more expanders in the following sizes, .3080", .3085", .3090", .3095", .3100", .3105", and .3110".

Having both the bullet and expander sized in .0005" increments will allow me to make a more scientific test with my shooting. Example shooting a .3100" bullet using a .3090" expander gives me .001" neck tension (not counting case neck spring back) and if I was to try a .3105" bullet with the .3090" expander I would have two variables, a bullet that is .0005" larger and neck tension that is .0015", which one made the difference.

Now when I do a test I can change the bullet size and keep the same neck tension finding what size the gun likes with a particular alloy then play with neck tension for further tests.

Now to the answer to your question try .0010" to .0020" neck tension.

I just finished machining my set of expanders in .0005" increments and now I am looking at having them coated to reduce friction before starting a new test.

My record five shot group at 100 yards is .305" and at 300 yards is 1.610" with 30:1 alloy.

[BCRider]

Thanks guys for those hard numbers. Your recommendations are certainly aiming in the same direction as my other findings.

It was near midnight last night when I was doing the initial setup so I forgot to include the finding for the flared internal size of the casings. I checked two of them just now and it looks like I'm getting roughly .0005 worth of spring back so the cases are coming out at .3715'ish from the flaring plug size of .3720.

In any event it's clear now that I need to make up a new flaring plug. And I really like the idea of a set of them in .001 increments over the sort of size range I really need to use instead of what I've got now.

EDG, in my case with the single shots the bores follow the early sizing of .376'ish for the groove diameter. So the Lee dies I've got are a better fit for me than they would be for someone shooting a lever rifle with the later .379 to .380 standard. So I can certainly understand your dismay from the expander plug sizes I see in the table you posted. It also shows that I likely bought the worst possible die set for my .38-55 loading.

I've still got my Cerrosafe chamber cast put away. I'm going to dig it out today and measure the sizes that correspond to the case and use your table to find out what dies I'm going to buy to get a better fit. In the meantime thankfully .38-55 is a slightly tapered cartridge so I can set up a travel limit on the ram to only partially size the brass to get a closer fit to the bullet size.

I love the .38-55 for the more mild recoil that can allow me to shoot a lot more in a session. But WOW! is it ever a "red headed step child" as far as size standards go! You'd think that the die makers would recognize this and produce one set for the early single shot standard of around .376'sh and a generally bigger set that better matches the .380'ish standard for the lever rifles.

Clearly the RCBS Cowboy set comes closer than the rest with the two larger expander/flaring plugs. But it still looks like it misses the mark on the full length sizer still being the "one size fits all" size. Which leaves us again relying on the tapered nature of the round to let us work with less than full length sizing as our only option.

Why is it that I always seem to pick the difficult ones to like?

[EDG]

BCR I could not help but laugh at your post.
My .38-55 is one of the H&R single shots and the groove diameter is .380. To check the land diameter I was able to push a Hornady .375 H&H jay type bullet through the barrel with about 10 lbs force. The mouth of my chamber is .394 so I cannot chamber a .380 bullet using WW brass.
If this PDF works you can look at the SAAMI standard for the .38-55.
Notice that the maximum bullet diameter is .377 but the maximum groove diameter is .379.
If you try to load a .380 or .381 bullet to match up with the .379 groove diameter the outside diameter of the loaded round can exceed the size of the chamber.
The max cartridge case mouth can be .394 and you can see the dies other than the trim die size way more than that.
If you wind up with interference or want to reduce the sizing amount Starline 38-55 is a little thinner than WW. Starline 38-55 is .0075 thick and WW is .009 thick - at least the brass that I own is. One of my near term projects is to try the RCBS trim die as a FL sizer with .381 bullets.

You might also notice that the .375 Win FL die is closer to the size of the RCBS Cowboy FL die.

Finally you may be in luck with your Lee dies in some ways.
Track of the Wolf and maybe some others make custom size expander plugs that fit the Lee expander die body. The TOW expanders are not very expensive though you may need to polish them down a little to fit a .375 or .376 bullet. That might fix the expander. To fix a sizer you would lap it out with a barrel lap. It is not a big deal if you have a problem. A new Lee die body is only $14.

38-55 Winchester.pdf

[BCRider]

I've got a bit of a mixed bag I'm working with. My first .38-55 is a converted rolling block that uses a Swedish receiver with a Shiloh Sharps barrel. But the chamber is cut a little oversize like it's the one intended for the more "modern" lever gun size of a proper .380. But the bore slugs out at a .376 groove diameter. Between the oversize chamber cut and the bore size my first loads using .379 size bullets and the Starline brass were so loose a fit that the large bullet squeezing into the small bore actually resulted in particles of lead washing back and being smear/glued to the OUTSIDE of the brass. I can't say for sure but I think what happened is that the peeled off lead from one round washed back between the casing and chamber. Then the next round ended up with lead dust on the chamber wall being pressed onto the brass when it snapped out during firing. All in all it was a mess. The lead was fairly easily scraped off the brass but it wasn't pretty and obviously not right

The second batch of test ammo I tried something different. I put a fairly heavy flare on the mouth to aid in holding the bullet more in line with the chamber's leade. And the hope was that it would also give a better fit and result in less lead dust being glued to the outside of the brass. It did work a little but it still wasn't great. I suspect that most of the reduction in lead on the outside of the brass was due to a better bullet fit as this second batch used some .376-.377 gas checked bullets I found to try. So a better transfer through the leade with less peeled off lead was likely more the reason for less deposit on the brass.

A while back I tried a third small batch of ammo with a new tact. I got myself some .375 Winchester brass that has a .003'ish thicker wall. This brass is a trifle shorter of course. But for a single shot rifle that's not a big deal. What the extra wall does for my mixed up rolling block is fill more of the chamber and better center the bullet in the throat and leade. With some .377 plain base lead bullets I found this has worked out the best so far.

The fact that all three of these test batches of ammo proved that the gun can shoot well has kept me going at it. I think this thing will shoot far better than me once I iron out the little things. Even my first rough batches of ammo were producing a roughly 5 inch group at 200 yards. And this was with me really not understanding what it takes to shoot well from a rest. I'm getting better at that too with my .22. So once I iron out the ammo issues I think the rifle and I will be able to do fairly well.

After all these trials and tribulations working with my Perdersoli barreled Uberti 1885 should be a snap.... It slugs out to within a half thou the same as my Shiloh barrel on the rolling block but the chamber is the right size for the thin wall Starline brass I've got. All I need now is a nice mold that drops good looking .376 to 377 size boollets.

[EDG]

The joys of the .38-55

You can wear out a calculator working on dies, brass and bullets.

[Nobade]

Or just load it like it's meant to be, with black powder and soft lead bullets. Then none of this matters at all and it shoots great.

-Nobade

[BCRider]

Or just load it like it's meant to be, with black powder and soft lead bullets. Then none of this matters at all and it shoots great.

-Nobade

I'm working towards that. But I've got to figure out the chamber fit and neck tension thing first regardless of which powder I put in it.

I'm lucky enough to have a lathe and to have had metal working as a more or less life long hobby. So to me making up some neatly made expanders from drill rod which I'll also harden, temper and then finish lap and polish isn't all that big a deal. And I'll have them in my hand in far less time than ordering and waiting to arrive.

[EDG]

Dimensionsal issues that prevent chambering a loaded round or prematurely wear out brass due to excessive sizing ALWAYS count.

Or just load it like it's meant to be, with black powder and soft lead bullets. Then none of this matters at all and it shoots great.

-Nobade

[Nobade]

It's not hard - use a bullet that is a slip fit in a fired case, and size that case more or less to produce the desired neck tension. The case is tapered, so you only have to run it into the sizer die as much as you need. The only reason to need an expander die is if you oversize the case to start with, and there is no need for that.

My own 38-55 H&R has a .372" X .381" barrel, and will not chamber a round with a bullet in it bigger than .377". I either shoot grease groove bullets sized to .376" or paper patched bullets that are .372". All chamber easily, and all shoot very accurately.

The normal 38-55 chamber is very difficult to deal with when trying to use smokeless powder, but a piece of cake with black. Using it like it is made to be used avoids a great deal of grief, and either not sizing cases at all or just barely touching them makes them essentially last forever.

-Nobade

[BCRider]

On my rolling block only the first batch of brass actually needed the expander. I soon learned it was best to fire form the brass and then size down only as much as needed just like you're saying. The second and third test batches were done that way where the expander was only used to get a little flare on the mouth.

But even with that the Starline brass is still a very sloppy fit. I've been too busy to dig out the chamber cast but I seem to recall that there was something like a .01'ish difference in size between the loaded ammo and the front end of the chamber. Hence the buying of some thicker walled .375Win brass.

...My own 38-55 H&R has a .372" X .381" barrel, and will not chamber a round with a bullet in it bigger than .377". I either shoot grease groove bullets sized to .376" or paper patched bullets that are .372". All chamber easily, and all shoot very accurately.

Looking at those numbers indicates to me that you've got the opposite problem. You should have the chamber on my rolling block and I should have your chamber for my barrel. You can't chamber anything bigger than a .377 while mine swallows a .379 bullet slipped into the Starline brass in the chamber with room left over. Like I mean it positively rattles around in there! Even your bore is set up for the larger "standard" while mine is bored and rifled for the smaller size "standard". IT'S NOT FAIR! ! ! ! Seriously though from your numbers compared to mine we're both backwards for chamber to bore dimensions.

The truly telling point in all this is that when I went looking around for chamber reamers I did find that there's a small and large size for .38-55. I'm actually thinking that somewhere along the line I'd like to set back the breech by a thread or maybe two and extend the chambering using the smaller finish reamer so I get something more like the dimensions to the chamber you've currently got.

[seaboltm]

As mentioned, 38-55 dimensions are all over the place. Old 38-55 could indeed be .379-.380. Mine is a JES rebore and is .375. So with a variation of .005 or more, what is a die maker to do? I use Lee dies, and I have never measured the expander, BUT, I can say you can see the clear outline of the seated boolit, telling me my .377 sized boolits are in there tight. I have to expand the case mouth a good deal to get the boolit started without scraping off the lube. Custom dies would help, but hey, this is a plinker for me, so it does what I need it to do.

[EDG]

Here is some data that I ginned up for sizing brass in a RCBS trim die with a .394 ID.

			Neck thickness		Sized in		Case		Bullet
					.38-55 Trim		ID		Fit
38-55	Win brass		.0090		.3940		.3760		.3770
			2x = >>		.0180				.3780
									.3790
.375 Win	Win brass		.0100		.3940		.3740		.3750
			2x = >>		.0200				.3760
									.3770
									.3780
.38-55	Starline		.0075		.3940		.3790		.3800
			2x = >>		.0150				.3810
									.3820

This is data that shows the ID of the brass sized in all of the dies that I own that are either .375 Win or .38-55.
You can see that some of the combinations produce brass that is sized just right and does not need an expander.

	Sizer Inside		Sized Case ID
			.009 case wall
	.3840		.366
	.3850		.367
	.3870		.369
	.3890		.371
	.3900		.372
	.3940		.376
			.010 case wall
	.3840		.364
	.3850		.365
	.3870		.367
	.3890		.369
	.3900		.370
	.3940		.374
			.0075 case wall
	.3840		.369
	.3850		.370
	.3870		.372
	.3890		.374
	.3900		.375
	.3940		.379

[ascast]

I have really enjoyed following this thread. Now that we have all these numbers, I suggest you try neck sizing with 38-56 dies. You can get a much better result.
LEE and Redding will vary. Don't ask me how I know this

more numbers

more numbers

[BCRider]

I got busy over the last few days so I didn't have time to follow up with this thread. However I did find time to make up a .374 and .3755 size longer expanders and loaded up some test rounds. There's a picture below showing the stock expander and the two I made.

I tried both and went with the .3755 to use with the .376-.377 size bullets shown as well in the picture. Yeah, I know I don't need the gas check but that's how these come and it's the only option I have at the moment. I do have a line on a supply of .377 cast plain base bullets but I would not be able to get them soon enough for the testing and the match coming up in a month. So I'll stick with these GC'ed .376's for now.

As you can see from the picture below I made the new expanders longer to better reach down and form the casing deeper to fit the length of the bullet. In use this is of questionable need given the tapered nature of the casing. But it was easy to do and it's there if I should require it for particularly tight brass.

Ascat, I like the idea of that .38-56 as a neck sizing die.

[Doc Highwall]

BCRider, I cannot tell if you have a second step on your expander to open the case mouth like a Lyman M-Die.

The expanders I designed have the part that expands the case neck are as long as the bullet seating depth +.025" to .050" longer before the 2nd larger step enters the case mouth and is approximately .002" to .0025" larger then the largest bullet that I will seat in that gun.

[GOPHER SLAYER]

The joys of the .38-55

You can wear out a calculator working on dies, brass and bullets.

AMEN! I am trying to resolve these same issues with my two 38-55s. Both have .380 bores. One is a Winchester Hi-Wall and the other is a Uberti Hi-Wall. The Winchester was rebarreled and the chamber is more like the 375 Winchester round. It will easily chamber a modern 38-55 round with a 250 grain bullet but there is no way you can load a .cast .380 bullet in the same case and chamber it. The Uberti chamber is a little larger and you can chamber said round with some strong thumb pressure. I wish both rifles had .375 bores. It would make life easier. The only way I see to solve the problem enlarge the chamber with a bigger reamer. The question is , which one.

[BCRider]

The expanders I made don't have a two stage sizing like it sounds like yours do. But they do have a flaring taper over the last .05 inch to give the mouth a slight flaring to aid in guiding the bullet.

[EDG]

Just add 2 case wall thicknesses, the maximum bullet diameter and your desired neck clearance.
For .009 Win brass
.018 (2 case wall thicknesses) + .381 bullet + .003 = .402

For .0075 Starline

.015 (2 case wall thicknesses) + .380 bullet + .003 = .398

.015 + .381 bullet + .003 = .399

AMEN! I am trying to resolve these same issues with my two 38-55s. Both have .380 bores. One is a Winchester Hi-Wall and the other is a Uberti Hi-Wall. The Winchester was rebarreled and the chamber is more like the 375 Winchester round. It will easily chamber a modern 38-55 round with a 250 grain bullet but there is no way you can load a .cast .380 bullet in the same case and chamber it. The Uberti chamber is a little larger and you can chamber said round with some strong thumb pressure. I wish both rifles had .375 bores. It would make life easier. The only way I see to solve the problem enlarge the chamber with a bigger reamer. The question is , which one.