Some background. My GM is fantastic. He has built a fun and fascinating world. He tries to give each player their time to shine. For the most part, we are having a great time.

However... I have told him from session zero forward that I was planning a grappling build. Barbarian for advantage on strength checks, high strength, Skill Expert feat for expertise in Athletics. The usual stuff.

I go to grapple my first critter, and there is immediate conflict. He doesn't seem to know the rules of grappling, and he's making some spot rulings that seem off, complaining about how ridiculous it is that I can grapple a large creature, etc.. So, not the end of the world. Between sessions I ask him politely if he can brush up on grappling, and to make some rulings on ambiguous stuff like moving an opponent, third parties entering the grapple, etc.

He sent me this email, and my initial thinking is that this is a rather big nerf.

Target up to your carrying capacity (15x STR) = may move them at 1/2 your speed. Target up to your push/drag/lift limits (30x STR) = may move at 5' only. However, tiny targets = totally unencumbered = full speed.

 

Pivot = for every 5' of movement burned, you may pivot your grappled opponent one facing (see tiny targets above).

 

May only grapple one creature at a time, unless both targets are one or more size categories smaller than you (i.e., halflings, gnomes).

 

Starting on their first turn after being grappled, the target may counter-grapple. They automatically succeed at this for as long as you maintain your own grapple. Your speed, since you are also grappled, becomes zero. You may oppose the counter-grapple by using a free action to release the target.

 

If you are grappling and a third party moves to grapple you in turn, the third party automatically succeeds in grappling you unless you release your grapple as a free action. This permits you to attempt to oppose the new grapple.

 

All other grappling RAW.

The movement rules seem overly restrictive seeing as how one of the points of grappling is to drag the opponent into an area of effect spell. But I guess I can work with that. Having to know the weight of creatures just seems silly.

Mostly I have a problem with this. It doesn't seem fair to have invested in class and strength and a feat only to be automatically grappled by my opponent.

Starting on their first turn after being grappled, the target may counter-grapple. They automatically succeed at this for as long as you maintain your own grapple. Your speed, since you are also grappled, becomes zero. You may oppose the counter-grapple by using a free action to release the target.

Am I overreacting, or is it reasonable to ask him to reconsider?

He went way way out of his way to make up stuff that there are already rules for. 

Sidenote, Ask if you can change your Feat to Fighting Initiate - Unarmed Fighting or Grappler.

Or forget it. Just ask to make a new character. I know you're set on this build, but if your GM is giving you a really hard time, forget it. The made up stuff destroys the build and is completely unreasonable.

The auto-win counter grapple is ridiculous. If I were the argumentative type I'd ask if I can have an auto-hit attack when an enemy hits me, since they get to do it with grappling. 

But I'm not argumentative, and this is meant to be a game that everyone plays together rather than against each other. I'd just tell the DM straight up that their homebrew rules make grappling not fun, and I'd want to change character if they intend to keep it. 

I understand homebrewing additions to the game, but changing the rules just to remove power from a build you KNOW your player is doing irks me. 

While your DM can make up the rules he want, i must say he heavily houseruled rather straightforward Grappling rules. I can understand any hard feelings, especially after knowingly building a grappler with RAW in mind only to see your DM rule against it at first occasion when it could have been cleared up during session 0. Hopefully you guys can discuss it and come to satisfying terms, or be allowed to make or modify your character. 

Thank you for the responses, everyone. It helps knowing I'm not alone in thinking this is silly.

My inclination is to try once more to reason with him. If it doesn't work I'm torn. I can swap out my skill expertise easily enough. Take Stealth instead of Athletics I suppose (I also have a high Dex). Why not have a Ninja Barbarian? ;-) Or, maybe I'll just be satisfied with the Grapple/Shove combo. I'm not sure.

He should probably list the various possibilities with respect to creature sizes instead of creature weight as the rules have clearly chosen to do it that way for simplicity.  I think that being reduced to 5 feet when dragging a creature that is a larger size than you is a reasonable house rule.  That's a nerf but it sort of makes sense and vaguely aligns with the push/drag restrictions for a given strength score.

The pivot option is actually in the player's (or more generally, grappler's) favor as there is no written option to be able to do this at all with your grapple.  This opens up possibilities such as maneuvering a creature off of a cliff which you typically can't do with a grapple, and you would normally have to use the Shove mechanic instead to achieve this.

I think that imposing a limitation that you cannot grapple more than one larger creature is unnecessary -- perhaps it would be better to house rule a size limitation on being able to drag both creatures at once.  Grappling more than one creature is already a tradeoff since you then typically won't have any additional free hands to actually make attacks.

Unfortunately, his last two house rules are ridiculous and should be reconsidered.  These are deal breakers that should result in you switching to a totally different character at best.  Allowing the grappled creature to auto-succeed on their own attempt to grapple you misses the whole point of the mechanic.  You now allow a creature with a very weak strength score to succeed on a strength contest without a roll.  Resisting a grapple doesn't require any free hands, it's just an ability score contest.  This goes for the "counter-grapple" and also the third-party grapple.  There is no logical reason for him to add this restriction and it seems to show a misunderstanding of why the grapple option exists in the first place.  In addition, he is getting in the way of the fun.  Let the players have their fun!

Quote from up2ng >>

The pivot option is actually in the player's (or more generally, grappler's) favor as there is no written option to be able to do this at all with your grapple.  This opens up possibilities such as maneuvering a creature off of a cliff which you typically can't do with a grapple, and you would normally have to use the Shove mechanic instead to achieve this.

 Yes, I agree with this point. Although I have seen the "drag" rule interpreted more liberally, I think this is just fine.

For anyone interested, my GM and I were able to come to an acceptable understanding. Thank you for your advice. 

I do think that someone attacking a grappler should have advantage on their attacks against him. The grappler does have his whole body occupied in holding onto his opponent.

Quote from TheGnome5786 >>

I do think that someone attacking a grappler should have advantage on their attacks against him. The grappler does have his whole body occupied in holding onto his opponent.

 RAW, Grappling is weak already.  It doesn't need nerfs.

I wasn't thinking of nerfing it.

I was more going along the lines or realistic. No one grapples in combat. They would be immediately attacked by enemies all around them. Trying to grapple in combat is nerfing yourself.

You grapple to subdue someone for some reason. And you would only do that if you knew there were no other enemies around to attack you while you did it.

Or you grapple in a sporting event.

Quote from TheGnome5786 >>

I wasn't thinking of nerfing it.

 

I was more going along the lines or realistic. No one grapples in combat. They would be immediately attacked by enemies all around them. Trying to grapple in combat is nerfing yourself.

You grapple to subdue someone for some reason. And you would only do that if you knew there were no other enemies around to attack you while you did it.

Or you grapple in a sporting event.

 Your "realistic fix" amounts to a nerf by adding additional penalties to someone who attempts to grapple.

Quote from TheGnome5786 >>

I wasn't thinking of nerfing it.

 

I was more going along the lines or realistic. No one grapples in combat. They would be immediately attacked by enemies all around them. Trying to grapple in combat is nerfing yourself.

You grapple to subdue someone for some reason. And you would only do that if you knew there were no other enemies around to attack you while you did it.

Or you grapple in a sporting event.

 Real world reference to the word grapple is NOT the same thing as D&D rules grapple.

What penalties do they normally have while trying to or actually grappling?

Quote from TheGnome5786 >>

What penalties do they normally have while trying to or actually grappling?

 There are not necessarily penalties as such. Trying to grapple is a combat option. Unlike other combat options where there is a single to-hit roll or saving throw, grappling is a contested roll where the attacker makes a roll and the defender makes a roll. I suppose that could be penalty.

You give up your chance to do damage with a standard attack or spell. After that, your opponent is reduced to 0 speed until the grapple is broken. They can still attack you with no problem.

So a grapple attack bypasses all armor benefits.
That sounds like a pretty good benefit.

The only listed disadvantage a grappler gets is if they pin the opponent and then both have the restrained condition. Until then he has full abilities against anyone else attacking him. Full movement and defensive bonuses.

In fact if he gets initiative against the target he actually removes all armor bonuses during his initial grapple attack skill check and in fact gets advantage on other attacks against the target.

Quote from TheGnome5786 >>

So a grapple attack bypasses all armor benefits.
That sounds like a pretty good benefit.

I am not understanding your point. Every attack (fair certain) in the game needs 1 roll (or none) in order to succeed. Grapple needs two rolls in order to succeed. A successful grapple only reduces the movement of the target. 

Quote from TheGnome5786 >>

The only listed disadvantage a grappler gets is if they pin the opponent and then both have the restrained condition. Until then he has full abilities against anyone else attacking him. Full movement and defensive bonuses.

In fact if he gets initiative against the target he actually removes all armor bonuses during his initial grapple attack skill check and in fact gets advantage on other attacks against the target.

Where are you getting this from?  There is nothing about the restrained condition in the rules for grappling.  And yes, the grappler can fully defend himself against attacks.  Why shouldn't he?  He is the one restricting someone else, not the other way around.  But there are some small differences in his situation.  He now has a free hand occupied, so perhaps now he is unable to cast a Shield spell while maintaining the grapple, etc.  Plus, as already mentioned, you've had to use up your Attack Action to even attempt this and this attempt could fail -- that's a pretty big opportunity cost tradeoff.

Also, the grappler doesn't have "full movement".  If he wants to maintain the grapple, movement is usually halved.

What is this about removing all armor bonuses?  The grapple attempt just doesn't interact with AC because it's not an attempt to cause damage.  It's a different mechanic.  But that grappled creature still continues to have AC even if he is grappled.

Why do you think he gets advantage on other attacks against the target?  That is not in the rules for grappling or in the rules for the Grappled Condition.  And what does any of that have to do with winning the initiative?  That's unrelated to how grappling works.

EDIT:

Also, you mentioned above:

"The grappler does have his whole body occupied in holding onto his opponent."

This is also inconsistent with the rules for grappling.  Grappling only requires one hand.  You reach out and grab onto someone to prevent them from moving -- that's it.

Read the grapple feat

Ah, that must be the confusion.  This discussion has nothing to do with the Grappler Feat.  The rules for grappling are found in Chapter 9 of the PHB.  No feat required.