PB vs GC bullets. Why are same profiles offered in both?

[Lead Zeppelin]

I noticed that Noe offers their K31 bullet molds (311-195-RF) in both plain base and gas checked versions .

I understand the reasons for gas checks but why would the plain base version be desirable (other than saving a couple cents on the GC)?

Is the PB version speed limited vs the GC? And if so what would that likely be?

Here are the two bullet diagrams. Identical but for the base.

318412

318413

[TurnipEaterDown]

Gas checks are an additional part, and introduce additional variability into the bullet as a whole.

They protect the base from hot gas impingement, they help seal the bore, they act as a scraper. All true, and have value.

They do however then create an additional concentricity variable, and will come off once the combustion pressure and/or bullet speed is high enough to cause the lube pressure to jack the GC off the base, or deform the base under the GC and cause a compromising of the crimp.

PB doesn't have these issues, and if prepared properly 1600+ fps is acceptable w/ a PB bullet.


For insight into GC crimp loss, look at the Corbin site and comments about Base Guard attachment loss, and the shadowed holes on targets.

Then get your rifle and start making 5 shots groups of ever increasing powder charges and watch the targets at 50 yds. You will see (most likely) shadowed bullet holes just before dramatic group size increase -- this is an indication of GC crimp integrity loss, and detachment from the base due to impact shock wave. Just after this, the groups go to poo because the process started even earlier in flight of the bullet losing integrity and the GC winging off somewhere on way to target.
Use slow & fast powders in different incremental loadings, and you can see how the fast powders will do this at lower muzzle velocity. They attain equal expansion pressure at lower MV than slow burners.

If you can push a bullet fast enough w/o a GC, you are better off from time, money and consistency perspective.

[centershot]

If you can push a bullet fast enough w/o a GC, you are better off from time, money and consistency perspective.

Yes, Amen to that! I use a lot of the Lyman 311041 and Lee 309-170, both are gas check designs. But, I am so thankful that I bought a Group Buy special from Lee many years ago, honcho'd by Junior1942, may he rest in peace. That bullet is a PB copy of the Lyman 311041, but .312" diameter, created for the Micro-groove Marlin 30-30's, Junior knew what he was doing!, It works in all my 30's with proper sizing and is usable in my MN M-44 in light loads. It's a superb small game bullet, loaded to 1000 fps or thereabouts. I shoot it in my 30-30 over 5 grains of Bullseye for small game and in my '06 loaded over 10 grains of 700-X for range fun. GC or PB, these bullets have their place.

[Winger Ed.]

This idea was around before that fad about powder coating came along.:bigsmyl2:

It just gives ya more options for the same boolit.
Several designs that are well proven are like that.
I had the 405 for my .45-70 in both versions.

If you're OK at lower speeds, like the 158 for .38Special, use the plain base.
Or, you can use the same design for .357 and bump the speed on up with a gas check.
You could use the GC one and lube it in the sizer, but it gets sort of messy.

[Larry Gibson]

"They do however then create an additional concentricity variable, and will come off once the combustion pressure and/or bullet speed is high enough to cause the lube pressure to jack the GC off the base, or deform the base under the GC and cause a compromising of the crimp."


I have shot several different cast bullets with Hornady GCs just seated and crimped with the Lyman GC tool in a 450 lubrasizer at velocities from 800 fps upwards of 3000+ such bullets at 2900- 3000 fps at 50m000+ psi (measured psi not guessed at) and have never found this to occur. GCs do come off sometimes when the bullet is pushed above 3000 fps. Other than a couple of us here using slower twist barrels how many actually push their cast bullets that fast.

"PB doesn't have these issues, and if prepared properly 1600+ fps is acceptable w/ a PB bullet."

PB bullet, depending on alloy, can have numerous such problems well below "1600+ fps". Try pushing a very soft 38 WC much above 800 fps. Put a GC on a similar cast bullet of the same alloy and you can push it to 1200 fps with excellent results.


"For insight into GC crimp loss, look at the Corbin site and comments about Base Guard attachment loss, and the shadowed holes on targets.

Then get your rifle and start making 5 shots groups of ever increasing powder charges and watch the targets at 50 yds. You will see (most likely) shadowed bullet holes just before dramatic group size increase -- this is an indication of GC crimp integrity loss, and detachment from the base due to impact shock wave. Just after this, the groups go to poo because the process started even earlier in flight of the bullet losing integrity and the GC winging off somewhere on way to target.
Use slow & fast powders in different incremental loadings, and you can see how the fast powders will do this at lower muzzle velocity. They attain equal expansion pressure at lower MV than slow burners."

When I first read that some years back I wondered why I hadn't observed any such thing after years of shooting cast bullets both PB'd and GC'd. What I find interesting is I have recovered GC'd bullets shot into wet pack at 300 yards that started out at 2900+ fps with a load giving 50,000+ psi and they still retained the GC. Appears, perhaps, someone just is making an assumption?

"If you can push a bullet fast enough w/o a GC, you are better off from time, money and consistency perspective."

This would depend on the type of firearm and shooting that is being done.

[gwpercle]

A lot of boolit shooters suffer from a dis-order called Gascheckophobia ... the extreme and irrational fear of placing a small copper cup on the base of a boolit . This act just disturbs and upsets them to no end ... they will rail against anything but a plain base , rant about any and all reasons why gas checks should not be used and look down on those of us who like to use the gas check in or reloading .
I think it's a fear you are born with like a fear of Spiders ... Arachnophobia ...
Once you have Gascheckophobia there are no cures .

There was one writer , back in the day , who liked the 357 Magnum , used the gas checked Lyman #358156, which has two crimping grooves , to load 357 magnum loads in 38 Special brass , seating the boolit in the lower crimp groove and taking advantage of the gas check to get some +1000 fps loads that didn't lead your barrel ... this was in a time before 38+P and easily available 357 magnum brass...
Thank You Skeeter Skelton :drinks:
Gary

[Harter66]

I just had " I cast to have cheap bullets and I don't want to spend 2 primers in a loaded cartridge" syndrome. As a result of that I learned paper patch .

Things I do and have done with plain base bullets ;
Max jacketed loads in 357 , 9mm , and 40 .
Of course three 45s , and 38 Special.
Full jacketed speeds in 30-30 and 32 Rem.
A 2000 fps MV 45-70 255 gr .
All of these under 3" at 25 yd off hand pistols and 100 yd field position rifle.

Things I've done with a check ;
222 Rem 62gr 2640 fps MV, middle of jacketed data for a 62 gr.
223 to 2100 fps MV, 62 gr hobbled by the 1-8 twist I think .
25-06' 4" is all I seem to be able to get out of 125 gr 260-120 but it's doing it with every powder I've dumped in the case under it from Unique to 4831 .... I guess I need to just shoot the 105 gr 258312 .
24-2500 fps MV
130 gr 6.8 2200 fps MV.
2100 fps MV with a 35-250 from a 358 Win.
Excluding the 25-06 all of these did <2" at 100 .

Paper patched no check on check stepped bullets ;
7×6.8 140 27-130 FP did 2" @100 2400 fps . I don't know what the pressure is here but the next step only did 2200 fps and opened up the LRP to .220 with no primer parts found .
2300 fps 180 gr in a 308 Win.
I guess about 2400 fps from a 6.5×50 Japanese with a 266469 patched .272 .
Not terribly impressive for speed a 200 gr X39 at 16&1800 fps .

I can't see where a check swagged on to a base with 0-mach 2 acceleration in .0075 seconds with 30-51 kpsi behind it can be knocked off by wind forces .......but im just a wrench bender so .....

I'm also not much of a Marksman.
I don't have any really expensive or exotic guns .
I do have a couple of customs and they are very good but a Santa Barbara 98 with a 24" A&B barrel can only give what it can . What do you want from a Remington assembled from Marlin parts in Illion 1895G ?

If we pay attention to fit , tweek alloy a little, pay attention to loading details and casting habits, well I'm walking proof most any fool can do what I have since 2007 .

[TurnipEaterDown]

"They do however then create an additional concentricity variable, and will come off once the combustion pressure and/or bullet speed is high enough to cause the lube pressure to jack the GC off the base, or deform the base under the GC and cause a compromising of the crimp."


I have shot several different cast bullets with Hornady GCs just seated and crimped with the Lyman GC tool in a 450 lubrasizer at velocities from 800 fps upwards of 3000+ such bullets at 2900- 3000 fps at 50m000+ psi (measured psi not guessed at) and have never found this to occur. GCs do come off sometimes when the bullet is pushed above 3000 fps. Other than a couple of us here using slower twist barrels how many actually push their cast bullets that fast.

"PB doesn't have these issues, and if prepared properly 1600+ fps is acceptable w/ a PB bullet."

PB bullet, depending on alloy, can have numerous such problems well below "1600+ fps". Try pushing a very soft 38 WC much above 800 fps. Put a GC on a similar cast bullet of the same alloy and you can push it to 1200 fps with excellent results.


"For insight into GC crimp loss, look at the Corbin site and comments about Base Guard attachment loss, and the shadowed holes on targets.

Then get your rifle and start making 5 shots groups of ever increasing powder charges and watch the targets at 50 yds. You will see (most likely) shadowed bullet holes just before dramatic group size increase -- this is an indication of GC crimp integrity loss, and detachment from the base due to impact shock wave. Just after this, the groups go to poo because the process started even earlier in flight of the bullet losing integrity and the GC winging off somewhere on way to target.
Use slow & fast powders in different incremental loadings, and you can see how the fast powders will do this at lower muzzle velocity. They attain equal expansion pressure at lower MV than slow burners."

When I first read that some years back I wondered why I hadn't observed any such thing after years of shooting cast bullets both PB'd and GC'd. What I find interesting is I have recovered GC'd bullets shot into wet pack at 300 yards that started out at 2900+ fps with a load giving 50,000+ psi and they still retained the GC. Appears, perhaps, someone just is making an assumption?

"If you can push a bullet fast enough w/o a GC, you are better off from time, money and consistency perspective."

This would depend on the type of firearm and shooting that is being done.



Larry,
What I was getting at in the several statements may not have been very well written, and not convey the point well, so will hope to clarify.



"They do however then create an additional concentricity variable..." (My prior comment)
Fact. It is another part. Adding parts creates variability. They also add to potential for bases not square to bullet axis from attachment issues. Why use it if you don't have to?

"if prepared properly 1600+ fps is acceptable w/ a PB bullet." (My prior comment)
"PB bullet, depending on alloy, can have numerous such problems well below "1600+ fps". Try pushing a very soft 38 WC much above 800 fps." (Comment by Larry)

That 38 WC application in my terms would not be "prepared properly". The alloy must be a good match for the intended use.
No dispute at all that pure lead at excessive pressure will be a failure.
Other improper preparations also would be a lack of lube, undersized bullet, poorly designed bullet, etc.



"GCs do come off sometimes when the bullet is pushed above 3000 fps." (Comment by Larry)

They will come off below that in some circumstances. See attached target photo of one such shadowed hole. This I believe is from GC detaching. I will explain why I believe this, and will note that it can't be Proven OR Disproved at this point from my experience.
14 twist, 35 Whelen, 260 NEI, 2100 fps. 318448
Respectfully, this isn't at the "RPM threshold".

I have also had GCs hit my chrono screens, and I don't shoot cast to 3000 fps. More like 2200 fps max. How else do you explain the chrono screen getting hit while still getting a hole in the target? Has happened to me (and I am sure others), and when it happened it me the shot would invariably be out of the normal dispersion for group. If not the GC coming off, what was it? Two impacts (Skyscreen & Target) from 1 bullet with 2 parts. No other reasonable explanation.

These speeds are just max of what I shoot cast for. Not a judgement. I have seen the excellent results you get. You get performance and group size, it is admirable. However, the main point is GCs will come off below 3000 fps.


Here is what happened to groups with notes on "abnormal impact holes" in this short test I ran. Note that I never pushed these bullets nearly to these speeds from this gun previously, and Never had any targets show these abnormal holes when using cast in this gun at 1600-1700 fps.

4350 Reclaim
53 gr 2145 fps ** 50 yd ** -- 1.5" (5/5), 1.5" (4), 1.25 (3)
One of these groups (54-56 gr) had a GC hit chrono diffuser.
54 gr 2186 fps ** 50 yd ** -- 3.25" (5/5), 2.0" (4), 1.375 (3) -- furthest hole out of group was a double, "Shadowed" hole, small ragged w/ 35 cal clean cut. GC disengaging at target, as decribed by Corbin under base guard discussion? Group size doubled compared to 53 gr.
55 gr 2245 fps ** 50 yd ** -- 12.5" (5/5), 5.0" (4), 4.375 (3) -- 2nd furthest hole out of group was a double, "Shadowed" hole, small ragged w/ 35 cal clean cut. GC disengaging at target, as decribed by Corbin under base guard discussion? Group size increased 8x compared to 53 gr.
56 gr 2286 fps ** 50 yd ** -- (?)" (5/5), 6.0" (4), 3.875 (3) -- furthest hole out of group (on paper) was a double, "Shadowed" hole, small ragged w/ 35 cal clean cut. GC disengaging at target, as decribed by Corbin under base guard discussion? Group size indeterminate compared to 53 gr, 5th bullet completely missed target paper.

FSP 759 Stick
50.5 gr 1978 fps ** 50 yd ** -- 1.125" (5/5), 0.625" (4), 0.3125 (3)
51.5 gr 2055 fps ** 50 yd ** -- 1.8125" (5/5), 1.625" (4), 0.875 (3)
52.5 gr 2101 fps ** 50 yd ** -- 4.625" (5/5), 3.25" (4), 1.625 (3) -- 3rd closest hole in group was a double, "Shadowed" hole, small ragged w/ 35 cal clean cut. GC disengaging at target, as decribed by Corbin under base guard discussion? Group size tripled compared to 50.5 gr.
53.5 gr 2166 fps ** 50 yd ** -- (Shot only 4) 3.25" (4/4), 1.875 (3) -- furthest hole out of group was a double, "Shadowed" hole, small ragged w/ 35 cal clean cut. GC disengaging at target, as decribed by Corbin under base guard discussion?


"...will come off once the combustion pressure and/or bullet speed is high enough to cause the lube pressure to jack the GC off the base, or deform the base under the GC and cause a compromising of the crimp."
[/COLOR] (My prior comment)

"I have shot several different cast bullets with Hornady GCs just seated and crimped with the Lyman GC tool in a 450 lubrasizer at velocities from 800 fps upwards of 3000+ such bullets at 2900- 3000 fps at 50m000+ psi (measured psi not guessed at) and have never found this to occur. GCs do come off sometimes when the bullet is pushed above 3000 fps." (Comment by Larry)

Yes, The Mechanism I suggest for the GC coming off Is a hypothesis. Hypothesis is not just speculation however.
Lubricated Sliding interfaces such as the bullet in the bore can be modeled as a rotating bearing w/ lubrication. The motion itself, in the presence of sufficient lubricant film, will create pressure at the interface. The pressure scales with relative velocity and lubricant viscosity.
(In a rotating bearing the pump pressure to get the lube there is Not the dynamic wedge pressure - easy to understand as no splash lube bearing would ever work if that were not true, and splash lube babbit bearings are used frequently.)

Again, yes, Hypothesis on mechanism.
I can't "see" inside the bore during bullet travel, nor teardown and measure bullets after they have been shot and 'do funny things' to the target paper, but there are few reasons that pushing the same bullet faster suddenly makes it start cutting two holes in target paper. I never had these bullets do this in the ~ 1000 I shot out of just this rifle before.

Me, I think it is primarily velocity related in what I have seen, but bullets also pump lube into the interface because high pressures of combustion can (and do) cause a foreshortening of the bullet body column inside the lube groove, and the lube has to go somewhere - it is nearly incompressible. (this bit is teh reasoning for my "and/or" statement.) Since it goes Somewhere it is Possible that it can force it's way into the interface between the bullet and GC. That isn't what I would call a "gapless" interface. The GC will spring back more than the bullet shank when installing the GC. Sure it's tight, there is now a groove indented into the shank, but it isn't in intimate contact, and since the GC slipped over the shank in the first place, same for the GC-shank interface lower down.



"If you can push a bullet fast enough w/o a GC, you are better off from time, money and consistency perspective." (My prior comment)

"This would depend on the type of firearm and shooting that is being done." (Comment by Larry)

Precisely what I meant -- if you can get it to serve it's purpose w/o a GC (accuracy, trajectory, residual fouling, etc.) then you are better off w/o the GC.

[Larry Gibson]

What GCs are you using and how are they fixed to the GC shank of the bullets asdon't mention the specifics? Also, what lube?

[TurnipEaterDown]

Hornady checks, and LBT blue on the NEI 35 Cal.
30 BHN on my LBT tester.

I cast these 15 or so years ago out of a Very hard alloy (made 25 years ago before I knew I didn't need to use up so much antimony I made up a 25 lb pot of this for high pressure loads w/o GC in full charge 475 Linebaugh & LL PB loads -- 50 Kpsi) - 4 lbs indoor pellet / 22 RF range scrap, 1 lb 60/40 Antimony / Tin (my memory, LETS Metals I think) and 1 lb high arsenic shot, water quenched.

0.359" sizer didn't quite touch. Basically, just crimped and lubed.

[DougGuy]

I can't speak about your rifle boolit, but I shoot some very soft Lee C430-310-RF out of a SBH at 1200fps with Felix lube and never need to clean the barrel. Accuracy is very good at handgun distances (shhh don't tell that to Elmer!) so I am a fan of the GC. Never seen evidence of one getting stripped off by the pressure of the lube.

I don't think I can get that big fat boolit to 1600fps in the SBH, the case is very full of H110 to reach 1200fps. Recoil is very noticeable.

[TurnipEaterDown]

A picture of the NEI described above, all lubed, etc.

318449

Don't get me wrong, I am not a GC Hater. Just that if something will do the job w/o, why not save all the Potential issues?
I don't like cleaning lead from barrels at all. Fairly pragmatic that way.

I use my 280 PB (Accurate 43-280G, "mine" because I designed it, not because I use it) out of my SBH at 1450 fps, no leading.
It also doesn't lead at 1600 fps in my TC Contender.

I use the LEE 310gr 44 too, but it doesn't shoot as well for me as my 280, costs more, and takes longer to produce a finished bullet.
I have a more than a coffee can still around though, so they will get used.
I wouldn't expect that LEE to shed a GC either at 1200-ish, and have shot them 1600 fps out of a Marlin 1894.
Not saying the LEE is bad. Not at all.

Again, not a GC hater, I have multiple GC molds.
It's just that I read over many years that PB are fine in many/most pistols, and initially had issue myself, but just said "...there is something I don't know here...", so I kept learning, and guess what? I don't need a GC in my pistols up to 1600 fps. Makes my life simpler.

[reddog81]

I shoot the PB version of the K31 bullet in the OP in 300 Blackout and it works great. Out of half a dozen molds I have that one is best for subsonic loads. It works perfectly in that application without a gas check.

[gwpercle]

I like Sage's Crimp-On Copper Gas Checks Best .
When crimped on the boolit base with a Lyman 450 tool ...
... They Do Not come off .
:popcorn:
Gary

[Bigslug]

I think reddog81 pretty well nails it with "What else can this bullet be loaded in besides a K31?" His .300 Blackout is a perfect home for it.

I'm a big fan of avoiding gas checks where they can be avoided, but given that all of the bottleneck, smokeless, .26 to .32 caliber military rounds were conceived to shoot jacketed ABOVE 2,000 fps, buying a PB mold to shoot them @1,600 or less seems a poor choice.

Too bad we don't have much in the way of rimmed, straightwall .30's, as such could be a lot of fun.