Grain and rifle twist.

[XPR15 SR]

Hi all, am new to the forum, and to rifles. Just purchased my first and it is an XPR15 SR by Head Down Products. It has a 1:9 twist in a 16" barrel. I have been doing some research on bullet grains and ballistics for PD. Came across some info that said that the heavier the grain, the tighter the twist needed to be to stabilize it.
So I decided to do a google search for M4 Forums and found this one and thought 'who would know better than the guys and gals on a forum whose name is the type of rifle I have?':smile: Anyway, I was looking at purchasing the TAP-FPD 75gr until I saw the statement about tighter twist and am now looking at the 65gr instead. So what is the story here?
All info will be greatly appreciated.

[Artos]

bbls can be funny but expect 69gr the heaviest you can go in general...most 75-77gr prefer the 1/7. You just gotta get some lead down range amigo.

welcome to the forum!!

[XPR15 SR]

You just gotta get some lead down range amigo.
Tell me about it. I have a Taurus 24/7 but this is my first rifle. Problem is, there aren't any 100 yard outdoor ranges close to me. I need to sight it in and what not.


welcome to the forum!!
Thank you.

[chadbag]

Technically, I believe, it is not the weight, but the length of the bullet that makes a certain twist a "requirement." (Things like temperature, humidity, altitude, etc can affect it so that a bullet that works in one location does not in another). With most bullets, the length goes up with the weight so we use weight as a proxy. But some bullet construction messes that up.

[XPR15 SR]

Technically, I believe, it is not the weight, but the length of the bullet that makes a certain twist a "requirement." (Things like temperature, humidity, altitude, etc can affect it so that a bullet that works in one location does not in another). With most bullets, the length goes up with the weight so we use weight as a proxy. But some bullet construction messes that up.
It looks like what I need to do is go with the 60gr and then find a place to take it out for its maiden voyage. Appreciate your responses.

[Belmont31R]

The vast majority of 1/9 barrels will shoot 68 and 69 grain bullets. Depending on the specifics a few (very few) can shoot some in the 70's.


Yes it is length but most bullet's length is dictated by the weight since they are of very similar construction. Tracer rounds are very long, and why the mil uses 1/7. Its actually only recently, relatively speaking, that 70+ grains have become popular.

[XPR15 SR]

Does anyone here have experience with the TAP-FPD 60gr? I am looking at mainly Per. Def. use, but am curious how they might perform down range. Distance/accuracy?

[uscbigdawg]

For all around ammo, look at Black Hills, Corbon or Atlanta Arms.

As a side note, being in Canton, you can shoot at either Cherokee Gun Club in Gainesville, GA (about 1.5 hours) or South River Gun Club (about 1.5 hours). That's what I found in a quick search.

Rich

[Safetyhit]

I have a Taurus 24/7...



We can help you with this issue next.


:)

[XPR15 SR]

We can help you with this issue next.


:)

And what issue might that be?