Bevel base designs.. why?

[AlaskanGuy]

I recently received a lee 379-250 which is a beveled base design.... I am trying to understand the logics behind a bevel base... I understand a plain base, and a gc base, but fail to see the advantage of a beveled base....

Teach me something new... :)

AG

[Ben]

I believe that it was an effort to make " production , high volume , reloading " run faster.

It was believed that the bevel made the seating of the bullet go better .

As to accuracy, some say the bevel base doesn't affect accuracy at all, others say that a plain base bullet will out shoot a bevel base on any day.

Ben

[bhn22]

yet many popular wadcutter designs are bevel base. One of my favorite SAECO 45 ACP SWC is bevel based. I haven't gotten good results with the wadcutters, but the SAECO works great for me. Go figger...

[btroj]

They are easy to start in a case.

I don't care for them in particular but they do have some benefits. Those benefits don't outweigh my concerns about imperfect bases.

[Larry Gibson]

BB'd bullets feed through automatic bullet feeders best because the BB slips into the case mouth with minimal alignment needed. They are also easier to seat manually into the case mouths in the narrow confines of earlier progressive machines. Some believe the BB induced the bullet to seat straighter also but that is more of a die and seater function than the base of the bullet.

Many years back I did considerable testing of identical designed .38, .44 and .45 cast bullets with and w/o bevel bases. Testing for accuracy at 50 yards was done with the guns held in a very solidly mounted Ransom Rest. Tests of each bullet were with 3 groups each (twice around the cylinder with revolvers and 3 magazines with the semi-autos). Both bullet styles, BB'd & PB'd were tested with target loads, standard loads and +P or magnum loads. WCs and SWCs were tested at the appropriate levels. While the BB'd bullets shot well there was not a single instance that the same load with the flat PB'd bullet of the same bullet design did not shoot more accurately.

The amount of BB has a direct bearing on this also. When I participated in the above test the bullets had the pronounced BB we see in most all commercial cast bullets such as the BB on Lee's 452-200-SWC and most all commercial cast. Some commercial cast BBs are much larger with greater taper. The very small BB we see on most Lee TL designs does not seem to decrease accuracy as the larger BBs. At least I find the TL314-90-SWC, the TL358-158-SWC, the TL410-175-SWC, the TL210-210-SWC and the TL429-240-SWC to give accuracy comparable to FB' PB's bullet designs with target and mid range level loads. The 356-120-TC also has a very small BB and shoots as accurately as any PB'd cast bullet.

The accuracy of BB'd bullets seems mostly dependent on the size and taper of the BB and load level used at as compared to a similar design cast bullet with a flat PB. Were you to side by side test a 375248 alongside your Lee 379-250-RF you would possibly see a discernible difference between the two dependent on load level. The harder you push them odds are the FB'd 375248 would retain better accuracy, especially as velocity got higher.

Larry Gibson

[DRNurse1]

Mr Gibson:

Did you publish this data?

[detox]

A bevel base will help add better uniformity at base when bullet exits barrel. Square bases shrink a little out of square because that’s the last part of the bullet to solidify. You can help square up flat base bullets in a RCBS lubrasizer using concave sizing stem. You will see a ring all around base of bullet if done correctly. Concave sizer pin also seats gas checks square (avoiding any raised sprue plate cut)

[WallyM3]

I'd like to hear more about this. It's new to me.

Does the entire concavity come into contact with the lead, or is the concave punch for peripheral support only (as appears with the GC)?

[AlaskanGuy]

Thanks guys for the input.... I will have to test in the old ABolt 375 and see how it does for me....

AG

[Larry Gibson]

Mr Gibson:

Did you publish this data?

No, I only assisted (did the loading and helped with the testing) the person who actually conceived of and collected the data. Greer cast bullets in LaGrande, Oregon provided the bullets for the testing, Greer is since out of business some years back. They offered both BB and FB'd bullets of the same design. The article was submitted by the author to several publications but was rejected as "too long" with too much technical data. The loss was ours.

Larry Gibson

[detox]

I'd like to hear more about this. It's new to me.

Does the entire concavity come into contact with the lead, or is the concave punch for peripheral support only (as appears with the GC)?

It is not new...the concave end only contacts outer edge of bullet. Lyman sizers have concave allready ground in stem, but must be deburred.

Read Veral Smiths book. JACKETED PERFORMANCE WITH CAST BULLETS

http://www.lbtmoulds.com/books.shtml

[popper]

Larry's comments make technical sense. Just as a concave base edge gets pushed to the bore, the BB edge gets pushed to the middle. The smaller the BB the less area for the pressure to work on. The BB does make for easier seating and for those of us that use coatings, it prevents a loss of coating on the edge, sharp corners don't have as much coating thickness. The bore sizing base 'fringe' may have less effect on exit for a BB. My last experiment with sans check rifle indicated that at low fps, it may be as good as FB if the rear band is seated at the bottom of the neck. More testing in order, got to rework that lousy 'solo' rest.

[wv109323]

Another variable in the mix is how the cast bullet is pushed through the sizer and how the bullet is seated into the case. With the 200 gn. SWC flat base for the .45 ACP, I use a flat bullet punch and size nose first through a Star sizing die. The reason is that it is easier to start the nose of the bullet in the sizing die ( I feed bullets by hand). Another reason is that the flat punch may "flatten" the base of the bullet. The concave design mentioned above may be more effective.
Another thing I use is a special bullet seater. The seating stem is machined so that the only contact with the bullet is around the rim of the bullet shoulder. This aligns the bullet with the case and gives consistent pressure around the bullet's circumference during seating. If a seater does not match the bullet nose exactly(which factory seater's seldom do) then the bullet can be started misaligned and the bullet base distorted.
Some pistol shooters believe that the base of the bullet (flatness,sprue cut and base shoulder) is the controlling factor in accuracy.

[WallyM3]

It is not new...the concave end only contacts outer edge of bullet. Lyman sizers have concave allready ground in stem, but must be deburred.

Read Veral Smiths book. JACKETED PERFORMANCE WITH CAST BULLETS



http://www.lbtmoulds.com/books.shtml

Thanks for the link, detox. I'm ordering the book tomorrow.