Marlin Firearms Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
38 Posts
Discussion Starter · #1 ·
Hi all -

It's a BIG world so I'm casting a wide net, here.:lol:

Has anyone anecdotal evidence, or know of published data, concerning effects, if any, of - not INCONSISTENT crimp -but rather REGULARLY INCREASING amount of crimp on velocity and accuracy in a given load?

Note that it doesn't have to be any particular cartridge/load/firearm combination.

Thanks.

Curiously,
 

·
Premium Member
Joined
·
2,295 Posts
I shoot a 110 grain bulk Remington JSP originally intended for 30M1 over 30 grains of RL7 in a .30/30. Tested off bags with 5 shot groups at 100 yards. Groups uncrimped were over 6 inches. Groups with light roll crimp were over 3 inches. Groups with a very heavy Lee Factory crimp are 1.3 inches. I never shot the no and roll crimp loads over a chrono, so I can't give you velocity information.
 

·
Registered
Joined
·
38 Posts
Discussion Starter · #3 ·
Hi IS2 - :D

I've "seen" you wanderin' around the place.

That's plenty good for the "data base" right now.
It's the sort of info I'm looking for.

Thanks. :wink:

regards,
 

·
Registered
Joined
·
154 Posts
curmudgeon -

The question you ask, as asked, has a myriad of answers...

Generally, the reason people crimp is twofold - one is to obtain better confinement of the powder during initial ignition, trying to keep the pressure high enough long enough to get a significant amount of the powder started (so that it can generate enough gas, raise the pressure sufficiently, to cause the rest to ignite); and secondly, to control bullet migration under recoil... and if one is using conductive ignition of the powder (most people do) and you're carrying rounds in the mag, then doing such makes sense.

On the otherhand: we tend to avoid crimps whenever possible. Generally if we're target shooting, we'll use convectively ignited loads (a load sufficiently small and easy enough to ignite that the initial heat of the primer will raise the surface temp of each grain above it kindling point and as such light everything all at once), so we don't need the extra confinement to reach ignition. And likewise, in target shooting we're feeding the cartridges one at a time, so we don't have concerns about bullet migration. But over and above that, since we tend to shoot hard cast lead, over time we're learned that hard crimps tend to destroy the structure of the bullet and cause it to shoot less well [a hard cast bullet gets it strength over a lump of lead via its dendritic structure - if you've ever seen the case where a load that shoots well by increasing it slightly becomes a keyholing load, what you're seeing is the gas pressure overwhelming the structure of the bullet and shattering it... one can accomplish the same by crimping the bullet in a press].

What does this mean: if one is shooting w296, h110 etc (hard to ignite, heavily coated magnum powders), in a straight wall case - then one has little choice - one has to crimp to try to keep the heat high enough long enough to get it started. If on the otherhand, one is shooting light loads of Bullseye, then crimping is either a waste of time, or worse, the cause of poorly shooting loads.

Currently we're taking low velocity lead data for the 300 wsm, and just after 4 powders are down to 1.5 moa 10 shot groups, and with the only crimp being one sufficient to unbell the case mouth to allow for reasonable feeding of the cartridge. Last year when we shot in ranch dog's postal match - the cards we turned in were all at or around 1 moa, and all without a crimp.

Bottom line: let your chronograph and your groupsizes be your guide: if the ES/SDs are smaller with a crimp, then you need it; if your group sizes increase with a crimp, then you don't want it.

hope that helps, and do shoot straight,
greg
www.gmdr.com
 

·
Registered
Joined
·
38 Posts
Discussion Starter · #5 ·
Hi Greg - :D

Thanks for your very clear and concise overview of the topic - your comments are welcome and certainly instructional.
You speak primarily to un/lightly crimped target loads, and it would be well to note your experienced observations.

However, my question is intentionally broad-based, as these effects, if there are any of a "regular" nature, should reveal themselves in samples unlimited by particular application.
Uncrimped target loads obviously won't tell us much,agreed?:lol:

In many years of reading on the subject of reloading and load development, among all the variables addressed - and any who engage in reloading will have some sense of that spectrum - I don't recall discussion of THIS variable in any thorough way - ONLY the need or lack thereof for particular applications, such as that to which you've spoken.


So I'll let the question stand as presented, as I am interested in progressively crimped loads.
As to many answers,one either has shot such loads or not. "Nez pah"?:D

regards,
 

·
Registered
Joined
·
154 Posts
curmudgeon -

Just a quick follow up:

1) I think if you look through the early Handloaders (pre-100) you'll find an article showing chrono data as a function of (degree of) crimp - if I remember it was with 4 or 5 degrees of crimp [none, .020, .040"... , all that's possible]... and they showed V and ES or SD and GS as a function of crimp. (if I wasn't working 90hr weeks I'd try to dig it out... but you might try a title search for the word "crimp").

2) Although our norm *now* is to use as little crimp as possible/necessary, but we did begin our handloading with 296 charged 44 mags and of the school "crimp as much as possible", until someone more knowledgable on the topic ask: "Why?"... to which all we could say was: "doesn't everyone do such", to which they replied: No!... after that it became a learning experience, ie, do what produced the tightest groups and smallest SDs, the norm be damned.

do shoot straight,
greg
www.gmdr.com
 

·
Registered
Joined
·
38 Posts
Discussion Starter · #7 ·
Hi Greg -

Y'know, I could easily go overboard with thanks for that reponse! :D

Your pointing to the "Handloader" article is exactly what I had hoped for.

And I am in full agreement with your second comment. After all, I should think that accuracy is, if not THE reason, certainly a very significant one for load development in the first place.

To be perfectly frank, my interest is in nature more technical research - I too ordinarily find what shoots best and am pleased with that result.

Particularly in light of your workload, I offer my sincerest thanks for humoring me.

regards,
 

·
Registered
Joined
·
1,353 Posts
I'm using the following load worked up without the FCD....

WWcases
CCI200 primer
Hornady 350grRN
[email protected] (max is 54)


This load works real well for me. Now, when I get the new press kit (ordering) and begin to re-workup the loads using the FCD will it be expected that there will be an increase in velocity for the given load?

I believe you'd stated the crimp develops more pressure? I want to stay with safe procedures.

Thanx!


Perferator
 

·
Registered
Joined
·
37 Posts
This ia very interesting topic. For what it is worth my son's 243 has very tight groups 3 shots in a dime / 100yds.
This grouping was found as a result of crimping, and has continued to perform.
I as a habit I factory crimp when I think there is high probability the rounds will be loaded in a mag vs single shot.

Single shooting -- no crimping.

Bojon
 

·
Registered
Joined
·
1,353 Posts
Bojon said:
This ia very interesting topic. For what it is worth my son's 243 has very tight groups 3 shots in a dime / 100yds.
This grouping was found as a result of crimping, and has continued to perform.
I as a habit I factory crimp when I think there is high probability the rounds will be loaded in a mag vs single shot.

Single shooting -- no crimping.

Bojon

My first two sessions of handloading did not include the factory crimp die. The buddy that was helping me (his equip) didnt have one, didnt need one for his Ruger #3. So, this past fall I made two shots from the guide gun being fully loaded at 5rds. Two of the remaining rounds in the tube were notably scrunched down. Today I put my equip order in to MidwayUsa, wanna guess if there was a FCD in the order?? :)


Perferator
 

·
Registered
Joined
·
37 Posts
I understand very well what happened, and since I load for my son, and he shoots with a group of guys sometimes after school, I must assume that some of these rounds will be fired by someone I don't know and that that person will stack them in the magazine instead of single shooting.

It's just a safety issue for me. I don't crimp all my loads but those that just may end up as above.

Also, I am very proud of the group my son shoots with. Good bunch of young men.

Bojon
 
1 - 11 of 11 Posts
Top