16 replies to this topic

[Antlerz22]

Heres a link I found researching the subject. I found it interesting and practical as money savings for reloads isnt my aim--its accuracy at all costs. If you lean to the latter and dont crimp---reconsider, an apx 10% gain isnt bad! Also it prevents bullets from being seated deeper from recoil in the magazine or from being dropped etc... http://www.accurater...m/crimping.html

[220swift]

Very interesting Antlerz, in reading through the info I noticed the info had not been updated since 1998. I wonder if the newer powders would affect the results.....

[knapper]

some bottle necked cases need to be crimped and it helps with the pressure that you are using. Most often a crimped round is in a straight wall case and that will very with the powder. I have found some that will not like crimping and others that will be helped. Most military rounds are crimped to make sure that the bullet does not set back in the case when feeding in auto loaders. I have not crimped any cases except 45-70 , 44 mag., and 50 beawulf. IMO each person needs to check that out for there own and each firearm.

[prairiewolf]

Interesting, now I have to start all over.

[youngdon]

knapper, on 20 May 2012 - 01:13 PM, said:

some bottle necked cases need to be crimped and it helps with the pressure that you are using. Most often a crimped round is in a straight wall case and that will very with the powder. I have found some that will not like crimping and others that will be helped. Most military rounds are crimped to make sure that the bullet does not set back in the case when feeding in auto loaders. I have not crimped any cases except 45-70 , 44 mag., and 50 beawulf. IMO each person needs to check that out for there own and each firearm.

I agree Knapper, I only crimp revolver cases with out research, so if the bullet wants to jump I don't end up with a tied up cylinder. I have foung no difference if the ballistics of my .223's or my 243 between crimping and not.

[Antlerz22]

220swift, on 20 May 2012 - 10:41 AM, said:

Very interesting Antlerz, in reading through the info I noticed the info had not been updated since 1998. I wonder if the newer powders would affect the results.....

Its all about the pressure curve being stabilzed in a crimped round by restriction before release vs releasing as the preesure is building before a curve can truly develop. So in that regard pressure buildup by whatever powder remains a constant factor whether fast burning or slow--they all have to reach the release point/pressure point. So in that it becomes something that can be predicted and factored in, and this guys data proves it factors a plus where accuracy is concerned. So when it was published has no bearing on its applications as far as powders are concerned.

[Jonbnks]

Most of my rifles and semi auto pistols need the crimp to cycle correctly. I've found that especially with my AR, the rounds will bump back if not crimped.

[knapper]

Jonbnks, on 20 May 2012 - 08:11 PM, said:

Most of my rifles and semi auto pistols need the crimp to cycle correctly. I've found that especially with my AR, the rounds will bump back if not crimped.

What do you mean by bump back?

[youngdon]

i think he means the bullet gets bumped back in the case. I've never had that problem.

[youngdon]

Antlerz22, on 20 May 2012 - 07:11 PM, said:

Its all about the pressure curve being stabilzed in a crimped round by restriction before release vs releasing as the preesure is building before a curve can truly develop. So in that regard pressure buildup by whatever powder remains a constant factor whether fast burning or slow--they all have to reach the release point/pressure point. So in that it becomes something that can be predicted and factored in, and this guys data proves it factors a plus where accuracy is concerned. So when it was published has no bearing on its applications as far as powders are concerned.

When it was published has no bearing on the results of those exact loads.(also take into consideration that powder formulations DO change....albeit slightly, but they do change) The newer powders may very well change things. Keep imn mind that all powders will give different results as will differing amounts of said powders.If you change one factor they all have the potential to change.

I'd also feel a bit better about the accuracy findings if he'd shot them from a mechanical rest. Also his srtatement about the Standard deviation being smaller is true but not by much and only in the .243. Now look at velocities they are higher in the .223 and the 243 ? Something doesn't seem right to me.

[fr3db3ar]

youngdon, on 20 May 2012 - 08:33 PM, said:

i think he means the bullet gets bumped back in the case. I've never had that problem.

Me either. If I shoot soft points out of the 308 it will flatten the points rather than push them back in the case. I haven't noticed any changes in OAL with either the 223 or 308 AR.

[Antlerz22]

knapper, on 20 May 2012 - 08:15 PM, said:

What do you mean by bump back?

Yea my question also?

[Antlerz22]

youngdon, on 20 May 2012 - 08:38 PM, said:

When it was published has no bearing on the results of those exact loads.(also take into consideration that powder formulations DO change....albeit slightly, but they do change) The newer powders may very well change things. Keep imn mind that all powders will give different results as will differing amounts of said powders.If you change one factor they all have the potential to change.

I'd also feel a bit better about the accuracy findings if he'd shot them from a mechanical rest. Also his srtatement about the Standard deviation being smaller is true but not by much and only in the .243. Now look at velocities they are higher in the .223 and the 243 ? Something doesn't seem right to me.

I did notice the same Don, seemed a bit odd as the .243 was/is faster and more than he showed. The only other thing I can think of, was he was loading a milder round in the .243 vs what he might have been doing with the .223 . Also it appears he put information in the wrong place in the .243 data. Thats why the discrepancy. Also I noticed one shot in the .243 was out a bit, indicating shot manually and not mechanically as you were wondering.

[Antlerz22]

Ok heres some information as why crimping (of course they sell crimpers) but it doesnt change the facts. I will post another link shortly looking for where I also read what Fred mentioned as what bump back is. I read it just trying to find and corroberate what all has been said. It is (what knapper was referring to) a happening in the magazine where the recoil forces the front portion of the magazine into the front of the bullet driving the projectile deeper than it was originally seated--affectiing accuracy and changing internal pressures ever so slightly but enough for a visual impact change on your target. Anyway let me find the article--if I can! LOL
So heres the first link on crimping http://leeprecision....ctory-crimp-die .

[youngdon]

Not to agree or disagree with crimping but that link is a sales ad...And so far the facts are that it will hold your bullet more firmly and it will give you a more even pressure curve. As far as accuracy goes you'll have to give me more data to call it a fact. One mans results do not make it factual. I'm not gonna make it easy on you Ralph LOL

I will say I own several lee factory crimp dies and if you find the need to crimp a particular load they are the way to go IMO. They apply a varied degreee of pressure depending on your wishes that is uniform, and well worth the extra step IMO.

[Antlerz22]

Ok heres the other link---some other opinions where I read about "bump back" as mentioned by knapper. And read all the posts as it was an interesting read. And for the moderators this isnt a forum I'm subscribing to nor advertising for--it just was a link that was offered in my search for " crimping vs uncrimped" articles. http://www.thefirear...ead.php?t=28666

[knapper]

Match shooters who have all of the bells and whisles will seat their bullets at .020 from the lands. If the bullet was changed and set to touch the lands there could be a big pressure jump and it would only show up on the brass and primers. Most folks can set their loads a little farther back and shoot good enough for most of us and not work the edge. You never know when there could be a problem that did not appear before and go over pressure and damage things.