PC coming off when crimping

[Tripplebeards]

It to me is not a PC thing but needed a place to post for help. I am loading lee 300gr FN in a 450 bushmaster. I got some help the summer before last over on 450 BM.net with taper crimping for this round. I was told to taper to .474”. That’s what I’ve been doing. I did work up a load that shot a hair over MOA at a 100 yards testing it last year. I took it out the other day and would get a flier once in a while. The fliers would chrony about a 100 FPS lower. I did find out one of my scope base screws were loose which was aiding in the fliers. All of a sudden I’d have a boolit drop four plus inches and have to sight it in again. The scope was sliding back s well. I did notice that when the gun recoiled my lead sled was a little crooked so I ligned my chrony straight with it again and was getting close to the original FPS readings I started with. So it could have been the boolit path going through my chrony in a diagonal path causing the velocity variable and or my optic shifting causing fliers. But I’m still wondering if I’m taper crimping too hard since I have a shiny pd exposed ring around my boolit when I pulled it. It’s obviously cutting onto the boolit. I’m pushing these pretty good (2070fps)so I need to hold them in place.

[Conditor22]

Sounds like you have the crimp set to tight and it's starting to crimp before you've finished seating the boolit

maybe you need to seat and crimp in 2 operations

[Tripplebeards]

I have been. I seat first and crimp with a separate Hornady taper crimp die afterwards.

[Oily]

.474 does not seem to be your magic taper crimp dimension. Back it off a little at a time until it won't chamber reliably. Measure it there and then you will have a baseline from largest to smallest diameter to work with. Just MHO on where to start.

[cwlongshot]

First off, Thats a pretty stout loading. Im sure its a bolt gun as a AR wont take that punishment or pressure. By the issues you can see its knocking things apart.

I dont use this bullet much as its dia requires very deep seating for me to chamber. Im using a Lyman 300g with better results. I load them to a top vel of 1800 & prefer closer to 1700 for accuracy. (My barrel). You powder coat cure could also be a problem. Its def a consern as it shoulbnt be coming off if properly cured.

Whats your technique with PC? Did you chamge powders or buy new batch? Test one of them and see if it flakes off or peels after smooshing it. Sometimes things change with a different
Lot of powder.

Good
Luck

CW

[randyrat]

How does the bullet fit without crimp?
You need a consistent "pullet pull" Could it be mixed brass doing the flyer, at that velocity everything counts

[Tripplebeards]

Heres a article running them above AR velocities.

http://www.gunblast.com/Ruger-AmericanRR450BM.htm

Yes it’s a bolt gun and I believe the hatches have to be baton downed as I would put it since I’ve had the gun rattle apart running the thing up to 40 grains of H110 wither the lee 300 grain FN. IMO everything brobably would have been alright if I removed the factory installed picatinny rail and lock tited it down in the first place. Had two different scopes (with two different rings tried)slide backwards from recoil. I found the rear base screw finger loose the other day.

Here’s my boolit I pulled its AC COWW with smokes PC. It’s bee; a while since I baked them so I don’t remember. My conventional oven is a little off so it was around 350 for 20 min. I’ve pulled boolits out of the dirt shot with WQ COWW, same boolit pushed hard and the pc stays on. Not the PCs fault, it’s getting scraped off when the case neck is cutting into the boolit. All in all the boolit doesn’t look deformed above the lube groove where it contacts the lands now that I look at it other than the little ring cut inside the lube groove. Probably ok for accuracy or should I lighten up on the crimp?






The taper groove is actually folding over into the lube groove so it’s like a roll crimp but without the sides flailing out. If I roll crimp it the boolit wont feed. It’s common practice to taper crimp only with this round. So all in all there’s plenty of neck tension holding the boolit in place...probably too much?


I can crimp a dummy round with the WQ COWW and pull it to see if the pc stays on?


I’m using all the same brass from the same lot...Hornady. All trimmed to the same length after each firing. My boolits are all from the same pour and weigh them within one grain of each other and color pc to identify weight variances . Tumble coated pc.

[Tripplebeards]

I figured out what happened. The purple one was a boolit I over crimped using a roll crimp. The case was buldging because i crimped so hard. I normally taper crimp these rounds and grabbed the wrong crimp die. Here is one I tested this morning with a taper crimp of .474”. As you can see no PC was removed from the boolit but you can see a little indentation when the case tapered into my tan boolit. I pulled a few I forgot I “over”roll crimped by accident and the purple boolit was one of them. I crimped to the point I bulged my case with the purple boolit being I lowered my crimp die too low so there was a way too much crimp applied... So my fault. The grey spots must be crushed up black powder from when my boolit it the bottom of my hammer type boolit puller. Looks like there a little indentation in the top of the lube groove where the neck tapered into my boolit. Is this OK or should I lighten up on the taper crimp?


My dummy round taper crimped at .474”



And the pulled boolit...

[Conditor22]

I hold the cartridge and push the boolit against my bench, if I can't move it I'm happy with it.

You could load and mike a few rounds, shoot half of them and see if the rest moved.

over crimping shortens the life of your brass

[Oily]

Glad you found your problem so quickly. Roll crimp is only for rimmed cartridges.450 Bushmaster headspaces on the case mouth and as such must be tapered or profile crimped with care.

[Lloyd Smale]

yes and no. Theroreticaly it should headspace on the rim but most semi autos actually are headspaced on the extractor or the shoulder of the round. If they didn't they wouldn't run reliably unless every piece of brass was perfectly trimmed. It hurts nothing to roll crimp something like a 450 bushmaster or 458 socom. Same thing with something like the 45acp. Ive shot 45s for 40 years and never trim my brass and have never had a head space problem because in all actuality they are headspacing on the extractor.

Glad you found your problem so quickly. Roll crimp is only for rimmed cartridges.450 Bushmaster headspaces on the case mouth and as such must be tapered or profile crimped with care.

[cwlongshot]

[DougGuy]

Tripplebeards, by the looks of your tan pulled boolit, sounds like you are overthinking something. That boolit looks perfect. It HAS to have enough neck tension and crimp not to move, so it's expected you would see some witness marks on the PC showing that to be the case.

[BK7saum]

Also something to think about, when you pull a bullet the crimp scrapes and digs into the sides of the bullet. When you fire a bullet, the pressure expands/balloons the case. From what I've read, the release of the bullet from the case with even a heavy roll crimp should not deeply score/scratch the sides of the bullet like you would see when a bullet it pulled.

You should have a visible witness mark on the sides of a lead or pc bullet if you are giving it a decent crimp. If just ironing out the case flare, then probably not. I see nothing wrong with the tan bullet you've posted.

[Tripplebeards]

No pc coming off the bottom groove what so ever...that’s black powder residue from scraping along the side of the kenetic puller when the boolit popped out of the case.

I do get a little lead roll over like the red boolit pictured in Cwlongshot’s picture but I scrape mine off with my finger nail it jack knife. Probably doesn’t hurt anything but i want to do everything possible for consistency to achieve the ultimate accuracy with my loads.

Dougguy, I know you know your stuff so I’m glad I’m doing it right! I was second guessing myself because of some of the stuff I’ve read about crimping too hard and distorting the boolit. I know I’m above max (AR) loads so I need a lot of resistance IMO to hold my boolits in place.


Thanks for everyone’s advise...I’ll keep doing what I’m doing then besides bedding my picatinny rail and adding some 3M super 77 adhesive to the inside of my rings to keep everything put when my rifle comes back from Ruger. There maybe no casing pressure signs but the load vibrates everything else loose.

[cwlongshot]

Not sure what happened to my post as there is no text...

But basically what Doug and BK7 said was my meaning.

Some powders are thick, I find many times these thick coatings are not as durable even tho the back proves correct in testing.

CW

[DougGuy]

I know I’m above max (AR) loads so I need a lot of resistance IMO to hold my boolits in place.

Are you using these in a bolt gun with a magazine? You can always fire a round, pull the loaded rounds and mic them, put them back in the mag in the same order, fire another round or two, pull the others and mic them, this will tell you if your crimp is moving under recoil.

I have a mod I do to a collet crimp style Lee FCD that makes a narrow band on the case mouth that is for extremely hard recoiling rounds, it totally does not allow movement, is highly recommended for heavy boolit/high power ammo used in dangerous game conditions. Here is a link to the mod, with photos: http://castboolits.gunloads.com/show...=1#post2239315

This crimp also serves an excellent purpose by holding the boolit against the initial pressure of primer ignition which can and often will cause the boolit to jump towards the crimp and sometimes start to pull the crimp before the body of the powder has begun to ignite. This lowers the ES by holding the boolit back long enough until powder gases build enough pressure to push it forward. It also opens fully and will not strip PC off the boolit under firing. It may pull some PC off if you use a puller, I dunno I haven't ever pulled one of these. I was getting strings within 20fps shot to shot using this crimp on the Lee 310 in a 44 magnum.

[Tripplebeards]

Yes, Ruger American bolt action 16.5” barrel with a factory brake.

[Tripplebeards]

Not sure what happened to my post as there is no text...

But basically what Doug and BK7 said was my meaning.

Some powders are thick, I find many times these thick coatings are not as durable even tho the back proves correct in testing.

CW

Ive read in some of your old posts that you size yours to .454”? What dose your RAR barrel slug at? Mine slugs at .451” and I size my boolits to .452”.

[cwlongshot]

Mine is also maybe a bit bigger. (>005)

I LIKE larger boolits. Always have worked better for me. My 454 sizing is really measuring 453+.


This was my first loading with a .452 250 Keith SWC...



With My Lyman mold 300G



I get this same powder, (diff charge yes)



CW