MW3: A Complete Guide to Weapon XP

This is a breakdown of gun XP for primary weapons in MW3:

Level	XP Required	% Complete	XP to Next Level
1	0	0.00%	500
2	500	0.28%	1100
3	1,600	0.89%	1200
4	2,800	1.56%	1300
5	4,100	2.28%	1400
6	5,500	3.06%	1500
7	7,000	3.90%	1600
8	8,600	4.79%	1700
9	10,300	5.73%	1800
10	12,100	6.74%	1900
11	14,000	7.80%	2000
12	16,000	8.91%	2200
13	18,200	10.13%	2400
14	20,600	11.47%	2600
15	23,200	12.92%	2800
16	26,000	14.48%	3000
17	29,000	16.15%	3200
18	32,200	17.93%	3400
19	35,600	19.82%	3600
20	39,200	21.83%	3800
21	43,000	23.94%	4000
22	47,000	26.17%	4300
23	51,300	28.56%	4600
24	55,900	31.12%	4900
25	60,800	33.85%	5200
26	66,000	36.75%	5500
27	71,500	39.81%	5800
28	77,300	43.04%	6100
29	83,400	46.44%	6400
30	89,800	50.00%	89800
31	179,600	100.00%	--

Secondary weapons include only levels 1-10, so the total amount of weapon XP required to max out secondarys is 14,000.

Kill - 100 xp

Headshot - 50 xp

Accolades (e.g. 1st blood, payback) - 100 xp

Shoot enemy pointstreak reward - 100 xp

If you get the first kill in the game and it's a headshot, that will add 250xp to your weapon.

There are two ways to see exactly how much XP is required to get each weapon to the next level.  One is when you are in a game lobby and you used the gun in question during the previous game, the match summary menu will have the current weapon XP of up to three guns used in that game.

The other is on in the Create-A-Class menu on the Elite website, when you put your cursor over top of one of the guns:

You can see my MP5 is currently level 28 with 80,100 weapon XP, and to get to level 29 I need 83,400 weapon xp.