Why gas checks on 10mm WNFP?

[Aloxite]

Hello everyone.

One of the favorite hunting bullets for the 10mm pistol seems to be a hard cast, wide nose, flat point with a gas check. Double Tap sells a 200 grain and a 230 grain version. Buffalo Bore sells a 220 grain version.

My biggest question is in regards to the gas check. Does it provide any benefit for this cartridge? From what I have been reading a gas check is only needed if you have high velocity and high pressure. Max pressure for 10mm is 37,500 psi IIRC. You might be able to get around 1350 FPS with the 200 grain out of a 6" barrel, maybe a bit more. It doesn't seem like the velocity really is high enough to require a gas check.

Another thought is that there is some benefit with regards to polygonal barrels since many 10mm shooters use Glocks. It doesn't seem like a gas check would make any difference since most of the bearing surface is still hard cast lead.

I'm thinking that the real reason is likely marketing. People are reluctant to try lead bullets. I guess it doesn't matter if there is a real benefit to the gas check. If the customers are more likely to buy it if it has a gas check, that is benefit enough for a cartridge manufacturer.

So I'd like to hear your thoughts on the issue. I'd also be curious where I could find a mold. I'm thinking something around 200 grains and a meplat of around .32".

[ku4hx]

Some people like 'em, some people don't and some people believe they are necessary in certain loadings. Those trying to sell are going to try and reach the largest market they can so they push certain styles with gas checks. The marginal cost of cutting a mold for GC use must be worth it.

I've used GCs in the past but in 40+ years of casting, loading and shooting I've found no significant difference between those with and those without checks. Your mileage may vary.

[mpmarty]

I have several 10mm pistols and they all shoot 170gr tltc boolist without checks just fine thank you. Gas checks seem to me to be a solution looking for a problem.

[Ole]

Maybe they use a gas check for "help" with leading issues in the GlocK G20 pistols?

Just a thought.

[Bret4207]

Aloxite, I think you're more or less right about the marketing end. Look at it this way, and your post references this- A non-cast educated reloader wants to save some bucks and goes to his local shop or online sales page. His choices are jacketed at $25.00 a hundred, PB FN at 10.00 a hundred or SUPER HARDCAST GAS CHECKED DOUBLE TAP WFN @ $15.00 per hundred. The guy wants to save bucks but he's leery of cast in the first place since "cast leads your gun up". So he sees PB boolits that are cheap but then there are those HARDCAST WFNs and they have a GAS CHECK!!! They are still far less expensive than jacketed and they are GAS CHECKED! and HARDCAST!!! They HAVE to be better, right? That's the marketing part.

The other end of it is that a GC in many guns does make getting good results easier, in a few guns it's a Godsend. Plus it covers up flaws in the base, protects the base edges in shipping (one of the chief reasons for the whole HARDCAST idea in the first place IMO) and it simply makes the boolits look "cooler". The fact is that ambiguous terms like HARDCAST have steered shooters entirely away from looking towards the real issues in cast shooting and brought forth the belief that Bhn is THE ANSWER to all cast shooting issues. Your OP is full of the hardcast hype for instance. Bhn is like #17 on the list of what makes cast work. Fit is King.

A GC very, very seldom hurts anything other than your wallet. But n some cases it's a big help. There's nothing wrong with using them and higher pressure rounds like the 10mm in full house loads may need them in some guns. And it's not just velocity that brings us to the desire for GC's, but pressure. A small capacity cartridge moving a heavy for the caliber boolit fast simply will need to produce more pressure to get there. So don't think just in terms of FPS when you ponder all this stuff.

My 2 cents and worth just what ya paid for it.

[white eagle]

I agree with Bret
its funny though some a leary of shooting cast
but when the manufactures call for a hard hitting
deep penetrating bear defense boolet what do you normally see???

[Aloxite]

These are typically loaded very hot since people mostly buy them for hunting or bear defense. Not that the 10mm is a good bear defense weapon. But if you are carrying to defend yourself from two legged as well a four legged vermin it might be a good compromise.

These aren't very cheap. Double Tap sells 100 boolits for $22. I can get XTPs for cheaper than that. But they fill a niche for people that want a deep penetrating round that will smash though bone. It seems like they are better suited for hunting than a FMJ flat point due to the wide meplat.

At some point I'd like to cast something similar. I've bought some Tin and 30% Antinomy/70% lead from Roto to mix up some hard alloy. I think I'd probably want to stick with the gas check if for no other reason than to keep with what is known to work in the 10mm.

Anyone know of someone that makes a mold for this?

[sqlbullet]

I shoot this boolit out of my 10mm's.

http://fellingfamily.net/images/MM_205_FRN.jpg

205 gr Mountain Mold. I got it in trade from a guy locally who also visits this forum from time to time. He believes in crimp grooves and gas checks on 10mm and this only had one. And the crimp groove leaves them too long for about any 10mm I am aware of.

But, treat it like a shallow lube groove and the bullet feeds and shoots great. Only problem with the mold is that it is only a 2 cavity, and it takes too long to make a pile of bullets. Next big purchase in a mold will probably be an Accurate Mold 40-200C.

I see no reason for a gas check on 10mm at the velocities you can safely push a 200 gr bullet.

Accurate Molds 40-200B is a 200 gr gas check design RFN. Or you could have mountain molds cut you one.

[Aloxite]

sqlbullet,

I'm trying to get a handle on matching the bullet alloy with the pressure/velocities that it seals well at. Could you please tell me what alloy you are using, what velocity you run it at, and the barrel length of the pistol?

ETA - I wonder if the crimp groove on that mold is designed for a 610 revolver?

[Bret4207]

Okay, I see I wasted my time entirely. Good luck with the whole hardcast thing. Don't worry about fit at all, that's just nonsense, make 'em HARDCAST!!! That's the answer.

[Ranch Dog]

Okay, I see I wasted my time entirely. Good luck with the whole hardcast thing. Don't worry about fit at all, that's just nonsense, make 'em HARDCAST!!! That's the answer.

Heck, I loved your answer and believe it is spot on. The 10mm is a high pressure cartridge, it derives its performance from its ability to generate and withstand quite a bit of pressure, a Maximum Average Pressure of 37.5K PSI and a Maximum Probable Sample Mean of 40.5K PSI. If you want a bullet to survive that, it is probably going to need to be gas checked. At anything less, you are not really shooting a 10mm.

Outfits like Buffalo Bore put quite a bit of research into their products as they know they will be held to the task on all fronts.

I shoot gas checked 9mm Luger bullets. Why, same reason. it is a 35.0K/37.8K PSI standard performance and 38.5/41.5K PSI at +P. I shoot both but load to +P for personal protection. I feel if you are not going to take advantage of the performance the firearm was designed to operate at, you might as shoot something else that matches your performance expectations.

[Aloxite]

Okay, I see I wasted my time entirely. Good luck with the whole hardcast thing. Don't worry about fit at all, that's just nonsense, make 'em HARDCAST!!! That's the answer.

No, not at all. I should point out that my lead stockpile is all pure lead, dead soft. So I've got to alloy it for anything I do for a 10mm. I guess I shouldn't have said 'hard.' I certainly see that I don't need (and probably don't want) the brinell 21 or so that Double Tap is using. I just am trying to get a feel for what hardness will obturate the best at 10mm pressures. Also, I'm trying to get a feel for how a gas check will affect the relationship between alloy and pressure.

[Aloxite]

Another point to think about is maybe the hard 21 brinell bullet is too hard for the pressure so it doesn't seal as well and a waste of antinomy. But if it provides more penetration because it doesn't deform it might be worth the trade offs to hunters. I'm just thinking out loud.

Looking at Accurate Bullets site it becomes pretty obvious that you need to know approximately what alloy you are going to use when you order the mold. I will need to do a bit more reading on how much various alloys shrink.

[sqlbullet]

So much to say.

First, think less, try more. Much of the book of what works is based on your gun. The knowledge helps shorten the time it takes to figure out what to change when something is not what you want. But knowledge alone will not tell you what you need. You have to shoot your gun and pay attention to those results. The gun is the variable that only you can quantify. That is why no one here with much experience ever says "Blah, blah, blah will work perfect for you" We all know what works for us.

I have three 10mm guns. Two are EAA Witness; standard full-size with a 4.5" barrel, and an Elite Match with the 4.75" barrel. The third is a Para P16-40 converted to 10mm by a barrel ream, 22lb recoil spring, 25 lb mainspring and a flat bottom firing pin stop. This gun has a 5" barrel.

The two EAA guns will eat 175 SWC seated COL 1.260" all day long without any problem. The Para jams every 3-4 shots if the COL is over 1.250" with that bullet.

The Elite Match and the Para will run the 205 grain heavy loads without and jams at all. Put the same load and same magazine (the elite and full size share magazines) in the full size and it jams at least one each mag.

You asked about my alloy. It is isotope lead sweetened with about two ounces of tin per 20 lb pot. This is not the dead soft iodine shielding, but the alloy from cores like Muddy Creek Sam sells.

When I started casting I only had the full size Witness. I water dropped boolits and had them rock hard (BHN of 22-24). I loaded light loads of Blue Dot and had leading. Not terrible, but some. I knew very little, despite having been lurking here for several months before I cast my first boolit.

I switched to Unique for a similar velocity, which was a mid-high Unique load. No more leading. It dawned on me that what had changed is I had pushed the initial pressure up to the plastic range of the lead, and it was obturating and sealing the bore.

I tried air-cooled boolits with the blue dot load that had previously leaded. No leading. This reinforced my theory.

Then I finally slugged my bore. It was over .400. Almost .401, but not quite. So, I honed out my sizing die. No leading at all since then.

So, as Bret4207 says, fit is king. If the bullet fits and you have a decent lube, you probably won't have any issues. Now, there are lots of things to check if you do have issues, once you KNOW your boolits fit. Notice I shouted "know". You don't know they fit till you measure a bullet pulled from a loaded round. Too many times I have seen threads where the problem ended up being the boolit getting smaller during reloading. Usually either during seating or crimping.

About the mold. The original owner wanted to use it with his 1911 10mm. He had measured the magazine and thought it would work, but they were too long when he got the mold and tried them. He also like gas checks.

I mostly water drop my 10mm boolits, more for convenience than anything. I don't have to worry about burning my hands on them when I sort them right after a casting session. I cast a lot of 30 cal, often running a 40 and 30 mold at the same time, and all my 30 cal rifle boolets get quenched. So it is just easier to dunk them all. I am sure they would do fine air-cooled at a BHN of about 13. Because they fit.

My Para does lead just a little. The lands are shiny smooth, but the grooves are a little rough. I think they will smooth out over time and the leading will be less and less.

One last thing. Order you 10mm mold for WW alloy. It is a good general alloy, and you will never need anything softer in a gun that takes a .401 boolit. Also, given the same mold, lead will be the smallest and heaviest. The less lead in the alloy, the bigger and the lighter the boolit will be. That rule of thumb is almost never wrong.

One last thing. Ranch Dog makes a good case for the 10mm requiring a gas check. John Taffin I think would agree. John certainly thinks 357 and 44 magnum need them.

Elmer Keith didn't think much of gas checks in handguns. Look at his favorite bullet designs. Based on his published load data he certainly was shooting "the real thing" too.

Who is right...Both of them. No hard rights or wrongs here.

Ranch Dog would not be surprised at all by someone that has a load for their gun that doesn't lead at maximum 10mm pressures. And neither of us would be surprised it that exact same load did lead a different gun. There are guys here running rifle velocities with no gas check and no leading, and are certainly over the pressure peaks we have discussed.

But, a gas check eliminates some of the variables that otherwise may cause issues. I am sure my Para would be clean as a whistle if I gas checked. But, the extra 1-2 minutes it takes me with a brass brush is not worth the $30+/1000 gas checks would cost, plus the time to put them on, to me. Others opine differently.

So, advice. Slug the bore. Get a mold, load and shoot and see what you get.

[thegreatdane]

I'd guess commercial gas checks are installed due to bore diameter variations/safety measure for unhappy leaded customers

[Aloxite]

sqlbullet,

Lots of good stuff for me to think about. I appreciate you putting the time into your response. I think I will make crude mold to cast some chunks of lead the right size to slug the bores on the various guns I want cast boolits for.

[Bret4207]

No, not at all. I should point out that my lead stockpile is all pure lead, dead soft. So I've got to alloy it for anything I do for a 10mm. I guess I shouldn't have said 'hard.' I certainly see that I don't need (and probably don't want) the brinell 21 or so that Double Tap is using. I just am trying to get a feel for what hardness will obturate the best at 10mm pressures. Also, I'm trying to get a feel for how a gas check will affect the relationship between alloy and pressure.

Well, okay, but let me throw another piece of the game into the mix for you to think about. You're aiming to tailor your Bhn/alloy to obturate at a given pressure. Instead of trying to get the boolit to form itself into a mass of putty in the hopes it will seal the bore and fit right, why not start off with a boolit that fits in the first place and use your Bhn/alloy to avoid obturation ??? Depending on obturation to fit the boolit to the barrel is basically depending on a big hammer to fit a square peg in a round hole.

[Reload3006]

I cast and Swage a lot of pistol bullets. I bought into the gas check idea myself. and started out swaging gas checks on all my PB bullets because I figured being pure lead around 8BH i needed something to keep from gas cutting. It really sounded reasonable. I confess too that I do not have a 40/10mm and have never cast or swaged for it. But back on point I have 9mm and honestly I can tell no difference in performance Leading with gas checked or non gas checked. I have gotten no leading either way. Also the swaged pills were .355 one would have thought that they should be .356 at least. In 44 harder metal mag velocities with and with out gas checks no difference. Soft lead Leading at mag velocities Gas checked and non gas checked no difference. SO. I believe there are just too many variables to definitively say you need a gas check.

[troy_mclure]

i use noe's 200gr .401 boolit in my 10mm. with my lyman #2 im pushing it at 1100-1200fps. no gas check needed as im not getting a smear of leading.

[Aloxite]

Thanks for all of the input. They more I read the more I am seeing that hardness really isn't what the cast bullet manufacturers are making it out to be. It is the fit that is important. I was surprised to see guys running rifle bullets cast out of 50/50 WW/Pb. I probably won't be buying a 10mm mold quite yet. I've been casting some shotgun slugs. It's probably a better way for me to cut my teeth since it takes a couple of variables out of the equation. Right now I'm just soaking up information so I can make an informed choice when I order molds.

[sqlbullet]

They more I read the more I am seeing that hardness really isn't what the cast bullet manufacturers are making it out to be.

This is it. Fit is king. But, hard to make a good business model on selling .400, .401, .402, .403 bullets in 5 different weights to satisfy just the 10mm/40 S&W crowd. Plus, you would drive away your customers cause the ones that buy boolits want easy answers to a financial challenge.

So, no fault to them they sell hard boolits.

As long as it fits you will probably be fine with any boolit at least a 9-10 bhn.

[Got-R-Did]

I have not shot cast out of my 10" T/C Contender bull barrel yet, but the velocities it is capable of might indeed require a gas check. Hope one day to make it to the woods with her where a good WNFP would come in handy.
Got-R-Did.

[Bret4207]

Thanks for all of the input. They more I read the more I am seeing that hardness really isn't what the cast bullet manufacturers are making it out to be. It is the fit that is important. I was surprised to see guys running rifle bullets cast out of 50/50 WW/Pb. I probably won't be buying a 10mm mold quite yet. I've been casting some shotgun slugs. It's probably a better way for me to cut my teeth since it takes a couple of variables out of the equation. Right now I'm just soaking up information so I can make an informed choice when I order molds.

Bingo! Bhn is just a tool, not the Holy Grail. Consider also that Bhn tells you almost nothing. I can treat the same alloy 3 different ways and get 3 different Bhns. I can take 3 different alloys and get the same Bhn. So what does Bhn tell you? Not a lot. But boy, when you're selling boolits and you advertise HARD CAST!, man the people just eat it up.

Good for you! You just took the first real step in becoming a good castaholic.

[45 2.1]

Heck, I loved your answer and believe it is spot on. The 10mm is a high pressure cartridge, it derives its performance from its ability to generate and withstand quite a bit of pressure, a Maximum Average Pressure of 37.5K PSI and a Maximum Probable Sample Mean of 40.5K PSI. If you want a bullet to survive that, it is probably going to need to be gas checked. At anything less, you are not really shooting a 10mm.

Outfits like Buffalo Bore put quite a bit of research into their products as they know they will be held to the task on all fronts.

I shoot gas checked 9mm Luger bullets. Why, same reason. it is a 35.0K/37.8K PSI standard performance and 38.5/41.5K PSI at +P. I shoot both but load to +P for personal protection. I feel if you are not going to take advantage of the performance the firearm was designed to operate at, you might as shoot something else that matches your performance expectations.

I too liked Brett's answer. The thing almost nobody sees is that "The alloy you pick determines your results" idea. Just going with what someone else uses doesn't actually cut it. Look at the 44 Mag Keith loading.......... a "HARD" 16 or 20 to 1 lead/tin alloy. Yep, Elmer called that hard. About 8 or 9 BHN is hard to him. Its also quite ductile........ and can stand top 44 Mag. (about 38K) pressures. There are other alloys out there that do the same and are quite ductile and have excellent heat treating properties while retaining the ductility and expansion properties of the air cooled version. Its really a matter of what you know versus common knowledge (whether its true or not).

[sqlbullet]

I have not shot cast out of my 10" T/C Contender bull barrel yet, but the velocities it is capable of might indeed require a gas check. Hope one day to make it to the woods with her where a good WNFP would come in handy.
Got-R-Did.

Not velocity that makes leading. Blow by/gas cutting or skidding or plastic deformation are gonna be the culprits in most cases. A longer barrel will maybe require more or different lube. But I bet 10" won't be an.issue.

[Oreo]

Good thread! I'm gearing up to cast 10mm heavies as my debut into cast boolits so this is very applicable to me.

[Aloxite]

There is a group buy discussion thread going for 200 grain WFN 10mm molds.

http://castboolits.gunloads.com/showthread.php?p=1492771#post1492771

[Bret4207]

I too liked Brett's answer. The thing almost nobody sees is that "The alloy you pick determines your results" idea. Just going with what someone else uses doesn't actually cut it. Look at the 44 Mag Keith loading.......... a "HARD" 16 or 20 to 1 lead/tin alloy. Yep, Elmer called that hard. About 8 or 9 BHN is hard to him. Its also quite ductile........ and can stand top 44 Mag. (about 38K) pressures. There are other alloys out there that do the same and are quite ductile and have excellent heat treating properties while retaining the ductility and expansion properties of the air cooled version. Its really a matter of what you know versus common knowledge (whether its true or not).

The alloy determines your results, but t won't be the same in every load and gun. That's the part the noobs have a problem with. Just being softer or harder or whatever isn't the whole package.

[45 2.1]

The alloy determines your results, but t won't be the same in every load and gun. Just being softer or harder or whatever isn't the whole package.

The old timers have a problem with it too and don't see past what they do know. Get the right one and it will really educate you. This works for a large range of pressures. Most alloys used here are to brittle and of low ductility.

[sqlbullet]

Most alloys used here are to brittle and of low ductility.

This is too true as well. We get focused on BHN and forget there are other properties that are as important, maybe more important.

Elmer shot 16:1 which is an 11 BHN. But that material is far more ductile than WW. While WW works fine for most of what we do, there are many times that we would benefit from getting the tin content up to 2% or even more.

And I have been guilty as have many others of preaching more than 2% is a waste. That has to be taken in context of maximizing bullet fillout and ensuring solubility of antimony. You may want more for a better ductility in a finished product.