Flat vs. Bevel base

[long_arm]

Is there a difference in accuracy between bevel and flat based bullets, all else being equal? Any advantage?

[Dinny]

I haven't noticed an accuracy difference but the BB are easier to seat into a case.

Thanks, Dinny

[Milsurp Junkie]

A bit easier to seat bevel base bullets? I haven't seen a difference really.

[Outpost75]

When cylinder throats are much larger than barrel groove diameter a bevel-base bullet which fits reduces finning or cupping of the bullet base when extruded into the smaller groove diameter barrel and tends to reduce leading in full-charge loads. I prefer them for my Colt New Service revolvers in .455, .45 Colt and .44-40.

[long_arm]

Interesting, thank you.

[megasupermagnum]

Is there a difference in accuracy between bevel and flat based bullets, all else being equal? Any advantage?

It's hard to get a 1:1 comparison. The only bullet I shoot that I could was the H&G #68 in 45 acp. I had two molds that were nearly identical in dimensions, except one BB and one FB. In that instance, flat base was considerably more accurate. You can find that test under a thread named something like "45 acp accuracy test". I don't remember the exact wording. The only other bullet I can think of off the top of my head that you could readily compare 1:1 would be a 158gr SWC 38 caliber.

So in my one single test, yes there was a difference. Does that prove that will always be the outcome? I doubt it. As for advantages, the only real advantage to a BB is that they are much more forgiving when loading on a progressive press.

[long_arm]

MSM,
Well that's what got me thinking about this.. I've seen same or very similar commercial cast bullets for .44 mag offered with one or the other base.
Now I am admittedly a novice, but it would seem odd to me if the difference in bases would have no effect on performance/accuracy. Hence the thread.
Anyway, appreciate your response. Thanks

ETA: single stage loader here

[megasupermagnum]

If you are referring to the various 200 and 240 gr RNFP bullets, none of them shoot that good in 44 magnum. I can't speak for 44 special. Some 240gr designs shoot good, but mostly you will want to look for 250+ gr bullets if you are looking for best accuracy in a 44 magnum. I'd suggest you go right for a Lyman 429421, or an H&G #503, both under the general umbrella of "Keith bullet". You can check back on my threads, but I recall my 45 acp FB shooting 3 1/2" at 50 yards average, and around 6" at 50 yards average. Generally I want even better accuracy from my revolvers for hunting.

Really I can't think of any instance I wished for a bevel base. If you are looking for a mold for your gun, go flat based. There's no downsides at all on a single stage.

[Texas by God]

A timely thread. I'm loading some commercial 240gr SWCBB in the 44-40 because they were just sitting there. If they don't shoot as well as the 200gr FN- I'll melt them into something else.

Sent from my SM-A716U using Tapatalk

[dverna]

In general, FB bullets will be more accurate but not if you shave lead off the base seating them. LOL I believe Larry Gibson did testing using a Ransom rest that confirmed that.

BB bullets are easier to seat, and seem to release better out of molds.

Your needs will drive your decision. The vast majority of my cast pistol bullets are used for plinking and I load on progressive presses, so BB is what I use. If I was working on a cast load for a rifle @ 1400 fps, I would select a FB. My plinking load in .38 runs just over 1” at 30 yards out of a scoped carbine using a BB bullet. Not outstanding but good enough.

[MT Gianni]

Might be better posted in our town. Not much of a difference in hunting. I would much rather lube fb than bb, pc doesn't really matter.

[Larry Gibson]

Yes, in general, a flat based cast bullet will prove more accurate than a bevel based bullet all else being equal.

Many years back i had access to a very well mounted Ransom rest. A local commercial castor produced as close to identical bullets with FB and BB being the only difference. They were of various caliber and for revolver and semi auto. I tested them, as best recalled, with Colt, S&W and Ruger handguns in 38/357, 41 Magnum, 44 SPL & Magnum, 45 ACP in S&W M25 and M1817 revolvers and Colt M1911 S70s and 45 Colt in Colt New service and Ruger BH revolvers.

The flat based bullets always proved more accurate at 50 yards than the bevel based bullets. However, probably 99% of shooters won't notice any difference and more than like could not utilize the difference. If match shooting then use the FB bullets as they may save you a point or two. If silhouete shooting also use the FB bullets as they may save you a target or two. If hunting, plinking, shooting steel, shooting SASS events etc. take your pick......

[popper]

Several yrs ago I deliberately nicked the base of same 40 sw FB and shot IIRC 7 yds. Got a nice circular pattern about 2-3" dia. Had trouble with BB in the other 40 mould. Decided to try an idea, remove most of gc shank from a rifle mould. Idea was to get a flat base with well defines edge. Works fine. Kinda self aligning for seating and shoots great. Do all my rifle PB molds this way. Got nearly MOA @ 100 & 145gr @ 2k fps from BO carbine and two 2 shot touching groups about 1" apart, just a front bag, from 336 30/30 145gr @ 50 & ~1500 fps - unique load. Easy to see a 'fudged' bases - BB, not so easy.

[dverna]

Yes, in general, a flat based cast bullet will prove more accurate than a bevel based bullet all else being equal.

Many years back i had access to a very well mounted Ransom rest. A local commercial castor produced as close to identical bullets with FB and BB being the only difference. They were of various caliber and for revolver and semi auto. I tested them, as best recalled, with Colt, S&W and Ruger handguns in 38/357, 41 Magnum, 44 SPL & Magnum, 45 ACP in S&W M25 and M1817 revolvers and Colt M1911 S70s and 45 Colt in Colt New service and Ruger BH revolvers.

The flat based bullets always proved more accurate at 50 yards than the bevel based bullets. However, probably 99% of shooters won't notice any difference and more than like could not utilize the difference. If match shooting then use the FB bullets as they may save you a point or two. If silhouete shooting also use the FB bullets as they may save you a target or two. If hunting, plinking, shooting steel, shooting SASS events etc. take your pick......

Glad you posted. Sometimes my old pea brain gets screwed up, but I thought I remembered you posting about this in the past.

To the OP, It takes time to know who to trust. Mr Gibson and Outpost75 are two members who have earned a lot of respect on this forum. There are others as well, but when those two guys post something it is worth heeding.

Good luck.

[long_arm]

Thank you, Don.

Larry was kind enough to answer a question or two for me via PM.

I'm very impressed with this forum. As I mentioned elsewhere, I sure wish I had started this pursuit 20 or 30 or 40 years ago. In any case, the willingness of you gentlemen in-the-know to share what you have learned over the years is genuinely appreciated by me.

[243winxb]

45 acp, Lyman 200 gr BB most accurate. https://www.thehighroad.org/index.php?media/casting-bullets-for-over-50-years.3532/full

[Jedman]

I have found that shooting bevel based cast bollits in pistol cartridge rifles are less accurate.
Flat based and gas checked boolit seem to always edge out BB at 100 yards, Why ?
Out of semi auto pistols I don’t notice much difference but that’s mostly at 25 yards so not much of a test.

Jedman

[45workhorse]

In my very un-scientific and limited knowledge flat base boolits have always shot better for me. I don't own a bevel base mold, so I can't comment on that, but they do load easier on any press, (store bought)!

[gunther]

20 years ago, bought a couple thousand .429 250 wheel weight swc's with a bevel base. Then measured the throats (Oops) .433. S&W 629-3. They leaded all the way down the barrel. But, they shot pretty well. Seven grains of Unique kept the pop cans jumping out to 50 yards. After 50 rounds, it was 20 minutes of barrel scrubbing.
Finally found a Cramer flat based Keith design that casts at almost .432. Shoots good, slight leading in the forcing cone, with a .431 sizer. Bought a .432 custom sizer from Buffalo Arms; it'll do the next batch.

[CWME]

Dave Corbin has a write up on his theory when dealing with boat tail VS flat base rifle bullets on his web site. His hybrid rebated boat tail is supposed to be a compromise between the two. Theory is the gas on a flat base bullet gets spread out evenly and doesn't flow past the bullet creating as much turbulence. A boat tail or in this context bevel base would have the gas flow around the bullet on exit from the muzzle creating turbulence that the bullet has to fly through.

[popper]

A boat tail or in this context bevel base would have the gas flow around the bullet on exit from the muzzle creating turbulence that the bullet has to fly through.
Some what theoretically correct. But consider the supersonic gas ejected from the barrel before the bullet exit - turbulent gas is there already. I say SS as the pressure wave (increased density) decreased SS. Consider with a 'perfect' crown, at instant of exit, FB gas must exit at a high angle, BB angle is less, BT angle is even less. However the pressure wave is still primarily on the base. The expanding velocity of the exit would be SS for a while, faster at base edges. It's minor imperfections at the base (no matter which kind) that cause the problem.