Range Report Bullet drop question?

[KeithR41]

Ok, time for another stupid question.

I shoot a .308 with an 18" barrel and YHM .30 Suppressor. I'm an active LE Sniper so I developed my load to run the same as my duty load (Fed. 168 GMM.) My load: 41.5 IMR 4895, 168 MK, CCI LR primer, Fed match brass, OAL 2.8. I'm getting 2586 FPS from this load.

Anyway, I've only recently started to get interested in long range, we pretty much train for 100yds and closer at work, so I don't have alot of experience. From studying some charts I saw the the Fed load should drop 31" at 400.

I'm planning on entering some LR comps next year and am going to build a rifle for that purpose. However, I may have to shoot my .308 until I can afford to finish the new build.

I went out today to get my 400 yd dope. I dialed in 7.75 MOA (31") and shot 2 minutes low so I dialed in to 9.75 MOA and was right on. Here's the question. I know the factory velocity's were probably taken from a 26" barrel. Is my 18" barrel causing my bullet to drop so much? And...If I do have to shoot my .308 to 1000yds, am I going to be able to hit that far?

Like I said, dumb question. Thanks. Keithr41

 

[McCrazy]

Re: Bullet drop question?

168 gr bullets are not ideal for 1000 yard shooting, and start to lose their velocity quickly after 600 yards. The 155gr Lapua Scenars and 175 gr SMKs would do much better for the long range shooting, although that would put a damper on your efforts to resemble your issued 168gr FGMM bullets.

Launching the 168 grs at sub-2600 fps velocities is definitely not going to help with either long range shooting or simulating your FGMM trajectories either. From what I can tell, FGMM is usually somewhere on the high side of 2650 fps so you may want to try adding some more powder or changing powders to get a higher muzzle velocity.

 

[KeithR41]

Re: Bullet drop question?

My 100yd zero with both loads in nuts on. I don't have to change a thing to switch between loads. Since 99% of my shooting is 100yds and closer I don't want to change anything. I guess I'll just have to get my .260 done quicker.

 

[McCrazy]

Re: Bullet drop question?

Being dead on at short range doesn't mean much if the rest of the ranges don't match up also. 100 yards just isn't letting you see how big a difference there really is between your load and the FGMM out of your duty rifle.

You looked up the drop for 168 FGMM at 400 yards and it was supposed to be 31". However when you shot your own load with that data you were 2 moa low which is a full 8 inches. That is about a 25% error already and probably not acceptable for your desired purposes.

The fact that your 18" rifle with your load matches POI with your 18" rifle with FGMM doesn't account for much. I would recommend working up a faster load that in your 18" rifle matches the ballistics of the FGMM out of your service rifle. Do whatever makes you happy though.

 

[MitchAlsup]

Re: Bullet drop question?

Something is not right, here.

I dialed in 168 SMK (Litz) and 2586 fps. This gives 8.5 MoA to 400 yards not 9.75.

I have to dial in 2450 fps to match you 9.75 MoA. At this rate you are going to need 50.7 MoA to 1000 yards.