PC vs lubes affect accuracy, POI?

[Abert Rim]

Okay, say I worked up accurate loads for a .44 Special with the RCBS Keith using a powder coated boolit. If I were to then shoot a group with the same boolit conventionally lubrisized and another group with boolits tumble lubed with Lee Liquid Alox, should I expect the same size group -- and the same point of impact?
Has anyone compared?

[RogerDat]

I haven't done a comparison but I think there might be some difference depending on when you size your projectiles.

Tumble lube you may or may not size your bullet. With Lee TL design not sizing is a benefit.

Lube sizer sizes and lubes so finished diameter is as sized.

PC you might size before you coat, especially if one is using a gas check bullet design. The PC increases the bullet diameter unless you run through a sizer again.

I think one would have to specify bullet diameter as fired is the same with all three lube choices. Or possibly at typical revolver ranges any slight difference in diameter from PC or tumble lube and shooting at as cast size wouldn't make any difference with POI or POA. Load, alloy and bullet might be the primary factors.

Me I'm still working out loads and powders for all the molds I bought in moments of weakness and mostly just picked tumble lube or PC based on velocity being fired at. Although I do both PC and tumble lube pistol rounds for plinking. "Pretty" bullets are fun conversation starter at the range.

Will be interested at hearing what lube process works to create a consistent bullet performance and if that is possible.

[Abert Rim]

That makes sense. I should have specified all bullets of the same finished diameter just to remove another variable.

[Kraschenbirn]

At typical handgun range (25 yards or less), shooting unsupported, I doubt if you'll be able to tell the difference. I've got a Series 70 Gold Cup that I've shot with the same H&G #68 boolit for over 40 years - at first conventional lubed, then tumble-lubed, and currently PC'd - and don't recall any significant change in group size or POI when transitioning from one to another. On the other hand, if you're going 'long range', like IHMSA, that might be a different ball of wax. My .357 Contender actually groups a little better @ 100 yds with PC than tumble lube while, at the same time, the Labradar shows approx 3% higher MV and a lower SD.

Just my nickel's worth.

Bill

[Hick]

The one test I have done (Lyman 452-374 in 45 acp using loads from the Lyman Cast Handbook ed 4) definitely made a difference. The lubed bullets were much worse in accuracy. However, I think the real problem in that case was bullet shape. The 453-374 has a very short base that tends to get swaged down in the case (which reduced it below 0.452). The PC makes it larger in diameter everywhere, so that there is still some 0.452 portion in front of the case.

[THE_ANTIDOTE]

Pineapples and coconuts, unless all internal and external factors are exactly the same...you will never come close to finding the true answer. It's all luck of the day.

[charlie b]

At least close, yes.

I shoot my .308 out to long ranges (500+). The vel of a load changes more from day to day than the difference in lube vs PC. Here is a 100yd test. Same day, same range, same scope elevation, same load, same bullet, sized identical, one with lubesizer, one with PC. Just a slight breeze.



PS note that shot 1 on the left is from a cold and fouled barrel.

[fredj338]

I have some setup to test in a Ransom rest this spring. I'll let you know. I have ALox, a stick lube & PC & HT coated. I dont expect much diff at 25y.

[stubshaft]

Pineapples and coconuts, unless all internal and external factors are exactly the same...you will never come close to finding the true answer. It's all luck of the day.

What he said! I have found POI and group size changes by just changing lube and/or alloys!

[Forrest r]

What he said! I have found POI and group size changes by just changing lube and/or alloys!

That's actually called a clue.

A link well worth reading.
http://www.lasc.us/FryxellCBAlloyObturation.htm

When efficiency increases (higher velocities) that's telling you you're load is sealing better with that alloy/lube combo. Less blowby, flame cutting and shorter durations until full obturation occurs lead to better accuracy/consistency.

[Forrest r]

Several years ago I was playing around with a 308w using the lee 160gr tl bullet. I cast a pile of them using a 14bhn alloy and used a home made al gas check on them. 1/2 of them I traditionally lubed them, the other 1/2 got pc'd. All bullets were sized to .310" in the same sizing die.
[IMG][/IMG]

Made up ladder tests using h335 and went to the range testing them @ 100yds.
[IMG][/IMG]
[IMG][/IMG]

Well, interesting results. Not what I was expecting to say the least. The pc'd bullets were more efficient and it showed on paper with consistent groups.

Thought about the traditional lubed bullets issue with the 37gr load for a couple days. That group really opened up. Decided it was a lube issue or in reality a lack thereof. Always viewed lube a a gasket so I took the same lubed bullets and gave them a coat of tumble lube. Now they had a coat of tumble lube (what the bullet was designed for) along with traditional lube in the small lube grooves. Went to the range and re-tested @ 100yds.
[IMG][/IMG]
A closeup of the 37gr re-test.
[IMG][/IMG]

What this testing told me was that a pc'd bullet is not alloy or pressure dependent. Nor is it the correct lube/amount of lube used fo a specific pressure/load dependent.

While none of the loads were exceptional by any means, there were a couple of different things that influenced my decision making on what to use in these tests. At the time of testing there were threads on this website where casters were pushing the boundaries of what was considered (back then) extreme velocities with cast bullets holding 2" 10-shot groups @ 100yds. The other major influence of my testing was the use of mixed nato brass.

Basically this was my 1st time testing a cast bullet with velocities over 2400fps. I figured I'd fail miserably so I used junk components and a powder that I had jugs of laying around (use it for blammo ammo in the 223/ar's). Figured while I was at it test the pc'd version of the same bullet at the same time.

[Forrest r]

After the 308w testing it got me wondering about pistol/revolver ammo and pc'd bullets. Decided to use a beater s&w 629 as a test bed. Bought that 629 years ago at a gunshow and it spent it's life rolling around in the bottom of a toolbox in a truck. I want to make a blammo ammo load for that revolver that would do minute of golf ball @ 25yds. So I had a bunch of different cast 44cal bullets laying around that I cast using my favorite/go-to alloy. It's nothing more them 8/9bhn alloy made in 100#+ batches out of range scrap that I've used for decades for 99%+ of all my casting needs.

I picked out 5 different bullets and traditionally lubed them with ben's red. I picked out the same bullets and pc'd them. I made ladder tests (1/2gr increments) using 7 different powders with 44mag starting loads up to +/- 25,000spi (middle of the load data). Went to the range and used a simple rest, setup targets @ 25yds and tested 6-shot groups with the test loads. After all the testing was done I ended up with:

3 targets from the traditionally lubed/sized bullets that could hold 1 1/2" or less 6-shot groups @ 25yds (minute of golf ball).
13 targets from the pc'd bullets that could hold 1 1/2" or less 6-shot groups @ 25yds.
[IMG][/IMG]

Same cast bullets/alloy, same sizing die, same reloading dies/powder/mixed brass/revolver/etc. 3 vs 13

At the end of the day accuracy is nothing more than accuracy. A 1 1/2" 6-shot group is just that, both the traditionally lubed and pc'd bullets produced them. The difference was it was a heck of a lot easier to produce 1 1/2" groups with the pc'd bullets.

It was easier because all the lube/gasket/sealer is already in place with a pc'd bullet making them more consistent with different loads.

[fcvan]

My very first PC was for an AR15 using the Lyman 225415 and harbor freight black for .223/5.56. The AR was built by me, first trip to the range. After sighting in, I put 5 under an inch at 100 yards. Then I pulled out the Glock 23 (I was carrying it that day) and put 5 in the black at 50 yards. I noticed a 4" x 4" block of wood on the berm so I shot at it using a Lee 401-175 (Mine weighed 180 grains) over 5 grains of Unique. It took 3 shots to get the hold over, after which I hit the block 8 of 10 shots. I figured that was decent enough accuracy for 200 yards to the berm. I doubt I could do that today as I'm not shooting 1000 rounds a month like i was.

I haven't lube sized in 12 years, PC all the way for pistol and rifle. Trying to get my brother to the range is hit and miss so I need to get back into the habit without him.

[popper]

In several years of shooting pistol/rifle with HiTek/PC/lubed I've not seen enough difference in accuracy that can be attributed to the 'lube'. Powder/alloy/load makes too much difference.

[wv109323]

My testing using a Ransom Rest with a S&W model 14 in .38 Special. There was no significant difference in accuracy or point of impact with PC vs. traditional lube groove bullets. The bullets were 158g. In matter of fact I used an RCBS 158 RN and a NOE 158g. SWC and no difference in those two boolits. All were sized to .3582, PC after coating. Velocities were target loads.