Jump to content
Brian Enos's Forums... Maku mozo!

To popple or not to popple


jetdriver71

Recommended Posts

  • Replies 92
  • Created
  • Last Reply

Top Posters In This Topic

I love all this info, but HATE it when people get rude. :ph34r:

Really no need to do anything but ask questions, or reply

to questions with YOUR experience.

No reason to get personal or rude, IMHO.

Eric has been a member for the past eight years, and has

contributed some excellent ideas in that time - I personally

look forward to his contributions.

And, I've heard some excellent reviews about his comp. :bow:

Lot of personal opinions on this particular subject - no

reason to criticize someone else's opinion.

And, Eric has not become rude in response to rude

postings. :bow: :bow: :bow::cheers: :cheers:

Link to comment
Share on other sites

Somebody mentioned it earlier but comps are only a piece of the puzzle. Load development is huge in Open. Power factor is only a building block in the process. Once you are well clear of 165 it is all about what works your gun and comp the best. I too have shot guns built by other famous makers. Some are great and some......not. Often times though, it could be attributed to 168-172 PF ammo. Some of these guns like to be turned up to really smooth out

Link to comment
Share on other sites

Somebody mentioned it earlier but comps are only a piece of the puzzle. Load development is huge in Open. Power factor is only a building block in the process. Once you are well clear of 165 it is all about what works your gun and comp the best. I too have shot guns built by other famous makers. Some are great and some......not. Often times though, it could be attributed to 168-172 PF ammo. Some of these guns like to be turned up to really smooth out

Comps are but one piece of the puzzle, but what I'll call the efficiency of the comp is a big piece. If you've got a system, and a comp, that works well at 170-172 PF, that's great. If you don't need to go to 175 or higher to have enough gas to make the muzzle rise predictable and controllable, you're well ahead since you also will have less felt recoil. And I can say that there are some (well, at least one) available that work very well at 170-171 PF.

Link to comment
Share on other sites

Nope! Must be the comp! BWahaha. :)

Honestly I would rather shoot an open gun any day compared to a major PF non compensated gun.

And what I was getting at even your comp would seem to suck with wrong load in there. And the uninitiated would sometimes start shopping for a new comp instead of working on load development

Link to comment
Share on other sites

Yeah, it must be my comp. It hasn't figured out how to bend the laws of physics.

I think we'd both rather shoot comp'd vs. non-comp'd pistols. Probably why we're hanging in the Open Pistol forum. Yes, my comp does suck with the wrong load. Run it up to 175-6 or higher, and it is unnecessarily harsh. That's why I went through a lot of powder & bullet combinations, at a range of PF's.

Link to comment
Share on other sites

I have my CFD data I can share about the effect of holes, I've tried to approach this subject with something other than "feel".

Regardless of powder choices, spring tuning and all the other factors, the design of the comp and the use of holes have repeatable results. You have a fixed amount of energy to work with and you get to choose what you are going to do with it - that's just how it works.

- Barrel holes take advantage of the gas at its highest pressure in the system. The comp is in a lower pressure zone, again within the fixed system. So that is one factor.

- Barrel holes only push the gun down, and flatten it out.

- If you use holes you will have less gas left over to use in the comp, which creates the pull forward.

So it's a trade off. If you want to make the gun shoot flatter, but increase pressure in the hand you can add some holes - you are choosing how to use the gas.

How that looks in terms of actual impulse.

WithholesvsWithout.jpg

Effect of the size of the holes.

barrelholesize.jpg

Link to comment
Share on other sites

Ooohhh... science! I like!! Would it be fair then to say from your testing that a pistol that only runs a ported barrel could be made to shoot flatter but would not see a reduction in felt recoil? Is there a minimum amount of gas that needs to be generated for the ports to accomplish this? I've shot heavily ported steel guns shooting minor and while soft I think the dot has more movement than my Open pistol at 175pf. I realize this could be load development but am curious what you think.

Link to comment
Share on other sites

This is for a 38 super comp.

38 gives you more case capacity so you can afford to waste more powder out holes in the barrel although once charge weights get over 10gr, the gun can feel pretty violent.

In my favorite quote from Matt Cheely he said some short guns with holes are very flat, but so violent you can't see the dot lift, it just explodes, then reappears.

I've got a gun or two like that :)

ummm, that description may apply a little to my gun... :blush:

Link to comment
Share on other sites

Neomet, holes will still produce a little reduction in felt recoil because you're bleeding off gas that would normally add to the recoil force if it came out of the end of the barrel with the bullet.

jid2, can you please give us a little guidance on how to read and interpret your graphs? Thanks.

Link to comment
Share on other sites

^^^^ I'm still working on it.

On my graphs:

- The lines that climb up are showing the force pulling the gun forward. Higher values are more force (good).

- The lines that climb down are the force pushing the gun down. More negative or lower values are more downward force (good).

Edited by jid2
Link to comment
Share on other sites

^^^^ I'm still working on it.

On my graphs:

- The lines that climb up are showing the force pulling the gun forward. Higher values are more force (good).

- The lines that climb down are the force pushing the gun down. More negative or lower values are more downward force (good).

Cool stuff, thanks! I do a have a question on the time axis. What is going on at T0 with relation to the bullet. Where does the bullet leave the barrel and/or past the comp? T0?

Thanks,

Chuck

Link to comment
Share on other sites

Good question. The bullet is not in the model at all, we ignore it because you can't model it properly in the CFD software I use. But T0 is basically the gas just starting to leave the barrel so the bullet would be out in that that 1st section of the plot. With that said, the most useful portion of the data is when things stabilize, and the values you get once things settle down, so the section between .00015s and the end of the graph.

Link to comment
Share on other sites

Thanks guys. Didn't realize this question would elicit so many responses. I appreciate it much! For those who care aBrandon preferred VV 3n38 3n37 imr 7625. However I don't see 7625 even offered. I wonder if Hodgdon will offer another powder with similar burn characteristics?

Link to comment
Share on other sites

Good question. The bullet is not in the model at all, we ignore it because you can't model it properly in the CFD software I use. But T0 is basically the gas just starting to leave the barrel so the bullet would be out in that that 1st section of the plot. With that said, the most useful portion of the data is when things stabilize, and the values you get once things settle down, so the section between .00015s and the end of the graph.

Thanks, that explains things. I can visualize this problem with vector algebra with force vectors through the holes if present and off the comp ports. I can see getting equivalent down force as Eric is describing above. What I am unclear about is the time delay in the ported barrel. The ports will start squirting before the gas is available to the comp. This, obviously, is only for a few hundred usec so I am not sure that would mean anything in a system held by a human and observed by a human. It seem that it is just adapting to gas flow from various loads and momentum from various bullets. It would also be interesting to compare the gas flow decay as time goes on. Perhaps we should see if we have any shooters with day jobs at Lawrence Livermore. They have some pretty capable simulation software and a 9 major or 38 super firing is a fairly sluggish event for them ;) In any case, it appears that there is no single "right" answer in terms of force and this thing is probably dominated by all sorts of human factors that are difficult to model at best. Pick a set of venturi and tweak the load so it feels "good". Thanks for you work!

Later,

Chuck

Edited by ChuckS
Link to comment
Share on other sites

I wonder if Hodgdon will offer another powder with similar burn characteristics?

HS6 and CFE Pistol are in the neighborhood

HS-6 is a little slower. Takes me 1 full grain more to match the same velocity as my 7625 load. Same gun, bullet and brass.

I believe Autocomp might be close to 7625 also from what I have heard.

Link to comment
Share on other sites

I have a long comp like 2 & 1/2" long w/ 4 up on the comp and 1 L & 1 R on the tip. The comps frt 2 ports are angled a little back at my face but the back 2 are about at 1/2 again the angle forward. Plus 4-5/32 poppel holes. This gun has a very predicable dot with 124 & 3n38.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



×
×
  • Create New...