Has anyone tried longer .30-30 cases with cast?

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09-07-2021, 03:14 AM
Wilderness

Has anyone tried longer .30-30 cases with cast?

My Marlin 336A Rippletop .30-30 has a chamber length of 2.153". My Savage 99 (including some spare headspace) measures 2.121". Others I have measured run all the way up from 2.060" (a commemorative M94 Musket). This leaves quite a gap for gas to get around the base of the bullet as it enters the rifling. With bullets seated on to the rifling, my 336A for instance will have between .100" and .125" of the bullet base, depending on case length, exposed to the hot gases at the end of the chamber on the final part of the bullet's passage into the barrel proper. [Note: .30-30 cases start life at about 2.025" or less]

This is analogous to seating the bullet base below the shoulder of the case, except the gas is likely to be hotter further down the chamber and the pressure higher.

I measure chamber length with a fully resized case from which half the neck has been trimmed. Inserted in the neck is a brass plunger with a flange on the forward end equal in diameter to the mouth of a fired case. The device is chambered with plunger extended, and the action closed. The end of the neck portion of the chamber pushes in the plunger. The device is removed from the rifle and chamber length (i.e. the device) measured with a vernier.

Excessive chamber length relative to case length seems to me to be a possible cause of accuracy loss, at least with the heavier hunting loads. A long time ago I tried to test the idea in the M99, blowing out some WRACo .32-40 cases to make long .30-30s. I did not prove anything, though this was with iron sights, loads that were not all that good to begin with, and case necks that by then were thinner than regular .30-30s. The modern day solution would be to size down some Starline 2.125" .38-55 cases, although the necks might still be a little thin.

What I would like to know is whether anyone out there has run tests and can offer observations on case length relative to chamber length as it affects grouping with heavier loads.

Incidentally, I see repeated reference to .32-40 cases made out of .30-30s being "too short". In reality their shortness is not much worse than what we experience with regular .30-30 ammo and chambers. Discussion of .30-30 case length could apply equally to .32-40 brass made from .30-30.

With thanks for any contributions.
09-07-2021, 04:07 AM
Wilderness

Shortly after posting, I found this from the CBA - Frank Marshall claims 1/3 reduction in group size with full length necks in .32 Special and .30-30.

https://www.google.com/search?client...h+cast+bullets
09-07-2021, 08:24 AM
1006

The extra chamber space for the neck exists in a lot of my rifles. Trimming is rarely required for safety in my guns. Trimming is only needed for crimp length uniformity in these guns with a long necked chamber.

In line with what you are saying, I have found that my 30-06 produces some of its best accuracy with brass that measures slightly longer than SAMMI. Resized 270 brass gives me good accuracy with a slightly longer case neck.
09-07-2021, 08:19 PM
Hick

I never trim my 30-30, 30-06 and 32WS cases-- unless they are just too long to chamber. With 30-30 and 32WS, especially, since they headspace on the rim, the only downside to longer cases is inconsistent crimp. If you do not crimp loads (as I do not) there really is no downside to longer cases and it may improve accuracy.
09-07-2021, 09:39 PM
Wilderness

Quote:

Originally Posted by Hick

I never trim my 30-30, 30-06 and 32WS cases-- unless they are just too long to chamber. With 30-30 and 32WS, especially, since they headspace on the rim, the only downside to longer cases is inconsistent crimp. If you do not crimp loads (as I do not) there really is no downside to longer cases and it may improve accuracy.

Hick - I don't trim .30-30 either, except if something gets a bit uneven on the mouth. Cases destroy themselves well before they reach chamber length, typically after about 2.060" case length.

More recently I have been following a couple of batches of .30-30 brass to see just how much they do stretch with each shot. Over the batches, sub 2000 fps stretch about .0005" (half a thou) per shot, while the full power hunting loads go closer to .005" (five thou). Nor does the stretch progress evenly. For the heavy loads it may be as little as .001" for one shot and as much as .012" for the next. All of this however does not achieve the case length I am looking for, since the cases fail before they get there. This is with partial sizing in the FLS die

Nor do I crimp - never had the need with .30-30, .32 Special or .32-40. The crimpers at my range destroy lots of cases with mouth splits, which I never see with my uncrimped cases.
09-07-2021, 10:10 PM
Outpost75

I fooled with this for CBA competition, but unless your rifle and load is capable of ten-shot, minute of angle groups, the effort is simply mental masturbation.
09-07-2021, 11:52 PM
Wilderness

Quote:

Originally Posted by Outpost75

I fooled with this for CBA competition, but unless your rifle and load is capable of ten-shot, minute of angle groups, the effort is simply mental masturbation.

OP75: Definitely not in that league, but how much "spare" chamber length are we talking in your case? I'm looking at about .100" for my 336A, which I suspect you would not tolerate in CBA competition. I consider an acceptable five shot group at 50 meters to be 1" to 1.5", iron sights, preferably the former. This is for LAS.
09-08-2021, 07:14 AM
barrabruce

I have some starline long 38-55 cases I use in my 30-30 single shot.
Forget how much length difference there is.
I was getting better accuracy with paper patched bullets at factory speeds using max length cases.
Seated into the lands with pb lower velocity loads it doesn’t make much difference.
The starline are thinner in the necks so I have to neck size for fixed pb loads.
Leaving some blow by on the necks sometimes.
Federal cases are shorter , but I can just finger seat pb bullets in the fired case.
So accuracy sort of evens out.

If I breach seat my bullets I use a case that is to max length and not tampered with and get the best accuracy.
I’m also lazy and I may clean my case once in a while.

I load at the bench and shoot.
I don’t size my bullets.
I finger lube with a soft lube.
I haven’t had great success with gc bullets.

I get between 1 and 1 1/2" at 100 yards.

Gc or Pp bullets seated seated out will easily get 1 -1 /2 " at 50 yards with out much fuss at 17-1800 fps with either brass.

A bullet that fits the throat that doesn’t have to jump into the rifling will be your friend.
Make sure you can ejected the shell if you need too with a dirty barrel as well.
I don’t crimp cos I don’t need to.

I do a chamber cast and measure that up.
I have something to look at and make a drawing up.
Tells you a lot of what your chamber and leade really are and what you are working with.
09-10-2021, 02:50 AM
Wilderness

Thanks for the response BB. You have given me food for thought.

I too have found the lower velocity (subsonic) rounds, with bullets seated into the rifling, have not been a problem. My interest is in making the higher velocity/pressure gas check loads perform better.

And I wondered about the thinner .38-55 case necks. I have had quite good results from my Savage with .3125" bullets, with minimal neck clearance, so thinner necks may be a negative.

Now here's a thought on gas getting at the shank of the bullet: A rifle with a 2.085" chamber, and a case length of 2.025", has a gap of .060" where gas can get at the bullet. The Hornady gas checks on my bullets have shanks a little over .080". This suggests that the gas will be on the shank of the gas check rather than on the shank of the bullet as the latter clears the case. Likewise with a 2.040" case and a 2.120" chamber (as in my Savage 99), the gas will all be on the shank of the gas check, though only just. Change to the 336A with 2.150"+ chamber, and a case length of 2.070" is required to get the bullet shank out of the way of the gas. My .30-30 cases are well and truly had it before they get to that length.

Is this why the Savage shoots the heavy stuff rather better than the Marlin? And would a longer case, with suitable neck thickness, even if it is not full chamber length, bring the Marlin up to speed?
09-10-2021, 09:26 AM
barrabruce

If the marlin has microgroove rifling then fatter and maybe harder bullets are supposed to work better.

I haven’t used gc much as I found paper patching to be more forgiving with softer alloys.
No magic mix needed.
I just can’t seem to get them on square and tight.

Now if theory ,
being right then the bullet will try and expand to fill the gap in the chamber when emerging from the case mouth then slug down in the end of the 45*neck area.

O.k. Liquid being a non compressible medium then if you left enough lube or dip lubed the seated bullet then it would fill the gap in the short case to the end of the chamber and provide a some support for the bullet emerging out the case neck.
Get blown out buy the rest of the powder combustion in the bore.

If you are shaving lead or getting a build in the chamber end/throat/lead area, it will not shoot well to you clean it out.

I was getting paper rings because of short cases.
Full length brass fixed that.

Hope it helps.

If you can get a seal with your bullet then there will be no gas cutting.

One must find what the gun likes.
A column of unburnt powder of the slower kind makes a good wad apparently.
09-10-2021, 10:54 AM
Outpost75

Quote:

Originally Posted by Wilderness

OP75: Definitely not in that league, but how much "spare" chamber length are we talking in your case? I'm looking at about .100" for my 336A, which I suspect you would not tolerate in CBA competition. I consider an acceptable five shot group at 50 meters to be 1" to 1.5", iron sights, preferably the former. This is for LAS.

The your .30-30 chamber dimensions are really extreme, far exceeding SAAMI maximums, then I suppose filling a 1/10" gap would give a useful improvement...
09-10-2021, 06:30 PM
Wilderness

Quote:

Originally Posted by barrabruce

If the marlin has microgroove rifling then fatter and maybe harder bullets are supposed to work better.

......

A column of unburnt powder of the slower kind makes a good wad apparently.

BB: Marlin is 1949 Rippletop 336A with four groove cut rifling, twist 1:10". Bullets are hard - about 10% non-lead - and .3125".

I've considered the filler angle but not tried it in the Marlin. I did try it in my Savage with full loads - 2 gns Precision Spherical Buffer was all I could get in on top of a 2208/Varget hunting charge. That rifle was shooting well (five shots under 2" at 100 m with scope), but when I compared the two sets of groups, with and without filler, there was nothing in it. That's not to say that it would not work on the Marlin LAS loads, where the need is greater, and the space is more (about 4 gns less powder). Unfortunately I've used all my PSB and don't have a replacement. The old time filler in the bush was horse manure, used to economise on black powder in the likes of .25-20 and .32-20.