Home Forums Reloading Big Game Rifles Flat base vs boat tail

I have been trying to dial in a 150 gn blacktail hunting load for a new savage 30 06 I got last year. So far my most accurate load is a 150 gn nosler ballistic tip traveling at about 2910 fps. With 1" groups at 100-200 yards. I am happy with the load and will probably ended up hunting with it this year.

I am sitting on a pretty good hoard of 150 and 180 gn Hornady interlocks BTSP. Only problem is the rifle does not like them very much. I have tested different powder charges and OAL and the groups are still not to my liking. My question is do y'all think it would be worth it to test out some flat base bullets with the rifle?

My understanding is flat base bullets are usually more accurate under 300 - 400 yards. Also some rifles with less then perfect bores tend to shoot flat base bullets better. Is this true?

I was thinking about testing some 150gn grand slams, hot cor or flat base interlocks just to see if a flat base bullets helps tighten up my groups. I hate throwing primers away on load development just to find myself back at the loading bench trying to figure out why my groups are the size of Montana.

Like I said the ballistic tips shoot great from the rifle but they are kind of expensive and I would also like to have a accurate load with a tougher cup and core style bullet that's not as explosive as the ballistic tip.

I'm loading with RamShot Big Game, Fed #210 primers and Win, F.C. and Hornady brass.

Thank you.

Several years ago, a Hornady technician told me that the flat base interlock, in their testing, was slightly more accurate than a boat tail out to about 300 yards.
After 300 yards, the boat tail would beat the flat base by staying more stable at increasing yardage coupled with decreasing speed.

He emphasized that the difference in accuracy out to 300 yards was very little, so it didn't make a difference, as far as he was concerned.

If I have a choice between flat base and boat tail, for example the Sierra .22 cal. 52 BT & 53 FB match bullets and the now discontinued .30 cal. 180 FB soft point vs. the 180 BTSP, I'll always try the flat base version first as they have been slightly more accurate in my guns. I doubt I'd ever shoot at anything beyond several hundred yards so can't see an advantage for the boat tail unless it should group smaller than the flat base. Many times there is no choice between the two as only a boat tail is offered in a particular bullet weight. The BT is certainly more popular these days and they often shoot just fine.

I'd be inclined to do more load work if primers weren't so scarce right now, but I've had a tough time getting the 180 BTSP to shoot well in the 308 and 30-06 that I have on hand at the moment. The flat-base Interlock is much more accurate.


Okie John

I would totally agree with that except sometimes there might be a bit more than a little difference but still not dramatic. Maybe because boat tail bullets seem to be a little harder to get the perfect tuning in on.

If you are getting 1" groups at 200 yards with a deer hunting rifle, I see no reason to try anything else.

I have also heard that generally flat base bullets are more accurate out to 300 yards, and beyond that is where boat tail bullets may be more accurate. I also believe that some barrels like flat base bullets better than boat tails, and the opposite is also true.

In my 50+ years of reloading I have accumulated dozens of full and partially full boxes of bullets in different weights, shapes, and brands that I have tried to reload but didn't get the results that I wanted, so they just sit on a shelf and maybe someday I will try them in a different gun or with different powder.

IMO a 150 grain from a .30-06 is a great deer load, and back when my only rifle was a .30-06 I had no problem killing several elk with them.

Thanks for the input guys. Maybe I'll pick up a box of 150 flat base interlocks and test them out. Or maybe I'll just keep shooting the ballistic tips. The price difference for the two is what's hanging me up.

Unless I draw my pronghorn or muledeer tag for central/eastern Oregon I'll be hunting the thick and nasty National forests of western Oregon where long shots are few and far between.

On a side note I just loaded up a few of those 150 interlock BTSP with 47.0 gn of IMR 4895. I know it's a M1 Garand load but maybe it will do the trick for my savage.

150 gr Interlock, 51-52 gr IMR-4064

That is exactly right. I'm suspect of the OP's rifle and loading practices though. I've never had an issue getting an interlock of any flavor (fb or BTSP) to shoot accurately. Sub 1" pretty much the norm.. And no, I would not try Speers of any flavor. I'd try a 165 flat base Horandy or BTSP if you really have to. The 165 was made for the 30-06.. Save the 150's for the 308.

Mule Deer once posted an article flat base / Boattail bullets on the hows and whys ,maybe someone can repost that post ?

Welcome to the fire, neighbor. I used to live out in Thurston, off 67th.

150 grain Partitions are available right now through Shooters Pro Shop, $37/50 plus $12 to ship.

I’m a big fan of the Partition.




P

In some chambers especially .308, the lands are so far away that you can't use 150 grain boat-tails and get close to the lands as you run out of grip on the bullet. The 150 flat base bullets allow you to seat out further closer to the lands and often get better accuracy. All I'm saying is check how far from the lands you are with the 150 boat-tails and if there is a huge jump, that may be the problem.

150 grn Sierra flatbase, 52.5 grns IMR 4064 (bullets and powder from the 70's)... Shoots about 1/2 moa in 2 rifles... Sako finnbear and baco win 70 Super Grade...

Steve,

I didn't post it here, but wrote it for RIFLE magazine.

The reason flat-based bullets are more accurate out to around 300 yards is their base tends to block off expanding gas as they exit the muzzle. Thus they remain more stable right from the get-go.

Boat-tails allow more more gas blow-by as the exit the muzzle, which "de-stabilizes" them slightly. They settle down pretty soon, but in the meantime they're been started slightly off-line.

Even so, beyond about 300 yards they group better because they drift less in the wind that flat-bases. And even a very mild breeze can cause this, because wind-drift doesn't increase at the same rate as range, but at about twice the rate of range. In other words, if a bullet drifts 1" in a certain wind at 100 yards, it won't drift 2" at 200 yards in the same wind, but around 4 inches. (It takes a pretty stout wind to make a typical big game bullet drift an inch at 100 yards.)

Your BT's have boattails too, so that's not the issue. The seating depth is probably more the cause, and BT's are just flat more accurate that Hornady Interlocks to start with. The Sierra 150gr SBT Gameking is very accurate, and tolerant of jump. If you can find them.

I keep trying (the very definition of insanity) but Grand Slams have never gotten best results for me...still, a fine hunting bullet...and down here, Blacktails don't require moa shooting...even if I was capable.

I found a box of Sierra 150 gn SBT Gamekings at my lgs recently... Any advice on where to start for an accurate load would be much appreciated...

52gr of IMR 4064 is the standard accurate load in the '06 with 150gr bullets. That being said, I have one that prefers 51gr and will put 3 SBTs in a 1/2" when I'm having a good day.

Sorry I dont have Big Game load suggestions. IMR with 59gr works well too.

I used them in a .308, so I don't have a load for .30-06.

https://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/3216390/1

You might find a few good loads here.