I've been shooting Magnus 4-Blade 140 Grain Glue on broadheads and haven't had any problems. This year I wanted to give the Magnus 4-Blade 150 grain broadheads a try as they give a little larger cutting diameter.

Anyway, I've been haveing problems with the 150's. They seem to keep flying to the left. I'm using wood arrows all spined alike and weigh close to the same, but I keep having this problem. When I shoot the 140's they are hitting on the mark.

It seems like it's about the last five yards that they veer to the left. At closer ranges, it doesn't seem as noticable.

I've tried to keep a clean release and I've checked the alignment. Everything seems good.

Any ideas or suggestions (other than to go back to the 140's)?

Thanks!

Aroows may be a little weak, with the smaller broadhead the feathers can correct it.  The larger width cannot be corrected by the feathers.

If you have room, back up another 10 - 15 yards and see if it gets worse.   If they are ONLY going left, I agree, check your spine.  

Sometimes a little change breaks the camels back and as above, the extra "wings" keep the fletch from correcting.  Used to be back in the day, many folks had problems with the wider heads planing.  I believe most of that was due to improper spine and improper alignment of the heads.

at least... that's MY opinion.
ChuckC

I've been shooting these heads since day one and agree wholeheartedly with Chuck and L82hunt.

Odds are it's a tune issue and moving up to the next spine group stiffer should fix it.
 

or if you have any room to cut the arrow shorter you could try that... it could tell you a lot.

Hood:
Do you shoot right or left handed? For a right handed shooter left indicates too stiff spine, however for a lefty it would be too weak. I'm guessing you shoot left handed!!
Bob

Thanks very much for all the advice!

They actually "were" shooting a little low and to the left. It was almost like they "corkscrewed" at the last 15 feet.

A little more info: I shoot right handed. I bought two dozen of these raw shafts. I made up a dozen arrows last year with self nocks, the 140 grain broadheads, and a few with field points.

This year, my father made up the rest for me with plastic nocks, the 150 broadheads, and a few with field points.

The arrows I made all seem to shoot great. When I got the ones from my father, the ones with the field points shot just as well. The only problem seems to be with the 150 broadheads.

I noticed that the nock point seemed to be a little off. This is from the plastic nocks being smaller than the self nocks. So I've been playing around with that trying to get it set just right.

I checked the brace height and it was set at 7", which is the highest recommended from the bowyer. I upped it another 1/2" and it seems to take care of the problem. They are still shooting a little low, but I think the nock point still needs adjusted. It was real windy out this evening, so I just finished up and will try again tomorrow.

I can't cut the arrow down as they are pretty much cut to exact draw length and really don't have any extra money to buy new ones this year.

I've been shooting for a long time and don't ever recall having this problem before.

Thanks again for all the help and advice. If you have any other thoughts, please let me know.

Listen to Charlie...he knows his Magnus Mag I's very well.

Try turning a couple of them 90 degrees and see if things change; Horizontal can help with marginally spined arrows.  Also check to make sure the broadheads are mounted perfectly straight.

Bob is right though, if you are a righty and they hit left that means too stiff, unless they are super weak and you would get an opposite result, but 10 grains should not make a difference, the wider head may be changing your sight picture. Shawn