I have a 40lb Martin jaguar and I just got some Easton 400 spine fmj. If I left them full length with 125 grain field points and 3 4" feathers would they be spined correctly. If not would it work for a 45lb bear grizzly

You really should be asking how do I tune arrows to my bow!

Hence the old saying, Give a man a fish, feed him for a day, teach a man to fish, feed him for a life time

No and No, too stiff.

QuoteOriginally posted by gonefishing600:
You really should be asking how do I tune arrows to my bow!

Hence the old saying, Give a man a fish, feed him for a day, teach a man to fish, feed him for a life time

For the big picture,  I agree gonefishing....but for this particular instance, he's past that, as he already has the materials.....
The answer is no.   Although you could try 1000 grains up front  (kidding)
yes,   unfortunately the shafting you have is WAY WAY too stiff.

I agree to stiff for the two bows your looking at a 500 spine in a FMJ or 600 would be better in another arrow they don't make a 600 spine FMJ i don't think I would have to look to be positive  on that. And with the 500 I would think you might need more point weight maybe get the brass inserts to break down the 500 and I bet the arrow would shoot great with that weight up front.
Gary

Any way a 300 grain point with a brass insert would work?

Justin I shoot 400 spine shafts cut to 29.5"-30" off of my fifty and fifty-five pound center cut longbows and recurves with 275-300 grains up front to get them to bare shaft. I really don't think you will be able to get the 400s to work for a 45 pound bow. A 500 spine shaft should be the ticket though. Don't trash the 400s though you can still make flu flus with them.

Oh I wasn't going to get rid of them. I actually just bought some 55lb limbs for my Hoyt excel riser I hope they will tune for

They should work great for the 55# limbs.