Another thread about barrel length: How short can one go and still hit 1000 yards?

[GrendelNub]

[tdbru]

GN,
there are several ballistic calculators (JBM, Hornady website , the one on Berger site, etc) that you can feed in the bullet you're interested in and the velocity and look at the results.
then look at all the reloading data you can find (you did pick up the 2 volume book from this site, right?) and see if you see any loads with the bullet of choice reaching the velocity needed and note the barrel length. different bullets handle the transonic region differently in terms of dispersion. and bullets make a difference due to BC of course. a 130gr. ELDM and a 130gr. TMK will each have slightly different BCs which will affect the distance at which the bullet starts to hit the transonic region. that's about as close an answer that i can give that makes sense, to me.
have fun
-tdbru

[Bjorn]

I used to think that a long barrel was required for long range shooting. A proper predator rifle had to be 22" or longer and that sort of thing. Then I started reading about LaRue winning long range competitions with 16" barrels. I believe those were 7.62x51. So, I eventually came around to the idea that a short barrel can be accurate at distance. What I don't know without researching is what velocity you could get out of 16" barrel with a Grendel. Like tdbru says, you would have to do some homework. I will note that when LaRue was building a Grendel, it was with an 18" barrel. Alexander Arms offers a 16" tactical rifle, but I would not think that version is meant as a long range shooter. AA's other versions have 18" and 20" barrels. 18" to 20" may be the sweet spot for Grendel barrel length, at least according to what presumably knowledgeable builders are offering to the public.

There are a few here that know that development of the Grendel very well. Some of them might chime in and let you know what they are using at 1,000 yards.

[Klem]

GN,

I would focus on when the bullet slows to the transonic threshold as this is where the wobbles start. Up until then everything is fairly predictable although the slower the bullet and lower the BC, the more wind will affect it at all ranges to the target.

This figure from the PRBlog is a good one for visualising when this happens and for how long until the bullet has transitioned back into calm flight. By then, in all liklihood the group size has blown out wider than the linear cone it was before reaching transonic.


Obviously, atmospheric conditions and bullet shape will vary that velocity of 1,340fps, but not by much.

In 1,000yd shooting our 223 bullets would start the wobbles at around 800-900yds. The cross section of group size heading downrange is like a trumpet, blowing out towards the end. Once transonic is reached it becomes more difficult to drive bullets on a target and you get the feeling you have lost some control. They will still hit the target but with less predictability and like they are drunk. In other words your expectations need to be a little more forgiving.

Shooting long range with a Grendel alongside someone with a bigger 6.5 calibre and you are competing with a velocity handicap. You then need them or their equipment to be less capable, or unlucky with wind to even the field. If you are shooting against other Grendels then it's a fairer fight. Barrel length increases velocity so the shorter you go the earlier you are going to reach transonic and the bigger the group will be by the time bullets reach the target. The laws of physics affects Mark Larue the same as everyone else. Shooting is also a game of statistical averages; sometimes you shoot well and other times you don't. Perhaps LaRue was shooting well on that day, or perhaps there something else we don't know about. My point is, if long range is your intention and it has to be Grendel then you don't want to be handicapping yourself any further than the calibre already does, by shortening the barrel and lowering the velocity even further. So, with this in mind there has got to be a more compelling reason to shorten a long-range barrel; like having a compact rifle, or lowering the weight for carry, or wanting it more maneuverable for hunting.

[lazyengineer]

At near sea level a 20" barrel is still not long enough to make a warm 107 SMK supersonic enough to trigger a ShotMarker target. I was hitting the target, but it was just too slow to activate the supersonic required system to work.

For gongs, and if you don't care if subsonic at impact, you can go quite a bit shorter. Just be aware you'll be going through transition, as Klem mentions. For gongs, you may not even notice it, if they are big enough. The 1000 yard bullseye match I did was an eye-opener. A 6.5 Creedmoor shoots great, without really even trying that hard. But the 6.5 Grendel that I was sure would score also well, didn't even get out of the gate.