Quite a few states have gone to the "straight wall cartridges". The idea is to limit deer hunting fire arms to a certain power and velocity range. My state of Ohio went that way a few years ago and it was seen as progress, as we were limited to shotguns and slugs prior to that.
The usual concept of "straight wall cartridge" means
no bottle neck. It does not mean whether or not the body of the case has a taper.
The DNR of most states will have a list of acceptable calibers posted somewhere. It may be, but I doubt it, that the power level of the 30-30 falls within the power range that is allowed. And I wouldn't count on it, unless I could find it posted somewhere. And I'd carry the list with me while hunting.
The list of acceptable calibers is not consistent for power levels, except that generally, "straight wall cases" do not generate the velocity that bottle neck cases calibers are capable of. This seems to be an effort to limit bullet flight in flat and populous areas. For example...
List of Legal Straight-Wall Cartridges for Ohio Deer Hunting
As of the latest information available up to November 2023, the following straight-walled cartridges are legal for deer hunting in Ohio:
- .357 Magnum
- .357 Maximum
- .38 Special
- .375 Super Magnum
- .375 Winchester
- .38-55 Winchester
- .41 Long Colt
- .41 Magnum
- .44 Special
- .44 Magnum
- .444 Marlin
- .45 ACP
- .45 Long Colt
- .45 Winchester Magnum
- .45 Smith & Wesson
- .454 Casull
- .45-70 Government
- .45-90 Winchester
- .460 Smith & Wesson
- .50 Action Express
- .500 Smith & Wesson
- .450 Bushmaster
- .50 Beowulf
- 10mm Auto
- .350 Legend
- .360 Buckhammer
- .400 Legend
Looking a this list, it would seem that the only magnums allowed are "pistol" calibers that can be used in rifles. Center fire rifle calibers 50 cal and larger are not permitted, i.e. the 50-110 Winchester. And even modest power calibers with a vestigial bottle neck, like the 44-40, are prohibited. Again, this is Ohio's list not Maryland's. Make sure your rifle is legal in the state where you intend to hunt.
I did find this site which has a video that claims to explain "straight wall cartridges" for Maryland. I didn't watch it, so I don't know if it answers your questions.
Straight Wall Cartridges in Maryland
To confuse the issue even further, I found this statement at
Maryland Deer Season 2024: All the Information You Need! - DeerSeason.Org
Can I use rifles to hunt deer in Maryland?
During firearms seasons, deer hunting is permitted statewide in Maryland using straight-walled rifle cartridges. Bottlenecked centerfire rifles, however, may only be used in a few places, mostly in the counties around the western and eastern shores.
According to this, you may need to check with the individual counties you intend to hunt.