450Bushmaster.net

First post here but have been lurking for a while. I’ve read a lot of info and I thought I had a good grasp on things. I went to load up my first samples for load development and ran into some issues with the crimp. I know that’s a recurring problem, but here’s what I did.

18” 1:24 barrel (AR)
Hornady once fired brass, Hornady dies
275 TSX
Sized but did not expand the case
Seated to 2.335”, will window the mag soon

When Charging the rifle, the bolt slamming home and sudden stop caused the bullet to creep forward to about 2.345-2.35”. I taper crimped down to about .472” to try to get a little more tension but it seemed to not really affect the amount of creep.

I’m not sure how much this amount of creep will affect accuracy. I plan to work up the load and then delve into any effect that the creeping might have on my groupings. Any thoughts?

Glad to be here!

Welcome aboard OM!

The further out you seat a bullet, the less there is of it inside the case for the wall friction to act upon. Admittedly 70 thousandths isn't a lot but every little bit helps. Was your creep observed when only chambering the round once? I degrease the inside of my necks with a Qtip and trichlorethylene solvent to make sure there's no lubrication from the soot of ignition left in there, after tumbling my cases in a vibratory tumbler. If you wet tumble, its not necessary. IMHO, Hornady would have served the 450b better if they had put a cannelure on the bullet right where it seats at say 2.26. Driving the taper crimp down into a cannelure really gives it something to hold onto. At least one member here bought a cannelure tool but a quality one represents a lot of money to invest. You could try putting some bullet and primer sealant on some bullets and see if it helps. NATO bullets are sealed up that way. Not sure how much adhesive quality there is in the sealant they use.

Aside from those pearls of wisdom, your only other avenue is a modded Lee FCD Die.

Hoot

Welcome to our campfire!

Welcome.

About your only options are a side crimp as Hoot mentioned.

You could also go with the 3 groove 275gr XPB and run your taper crimp just over the top band. That would let you run a std mag vs window, and powder capacity you should still have enough for the AR pressure envelope.

The 450 has .200 of freebore so getting close to lands in a AR is gonna be hard with the Barnes.

Thanks for the welcome!

Hoot, yes I first noticed the creep when I was testing the first round to ensure that it chambered well. Then went back and reseated it and crimped more aggressively. Still crept forward. I was wondering if seating it out a bit further would put the crimp closer to the driving band edge? Or would that be counter productive with less bullet friction inside the case?

These were wet tumbled/ultrasonic so I don’t know about any residue, but will keep that in mind for the future.

I haven’t been able to fire it yet, so I’m not sure if the recoil will bump the rounds in the mag as well. I will be able to go to the range tomorrow, but will likely fire single shot for Consistency.

Once I get a load worked out, I would eventually like to see how much the creeping actually affects things. Probably with 2x 5 round groups with Single shot/riding the bolt forward and tapping it all the way closed vs slamming it and allowing semi-auto loading of subsequent rounds. If there’s a significant effect, then I’ll go down the road of a side/stab crimp.

Thanks for the thoughts and I’ll try to keep things updated here. I’m looking forward to being a part of the group!

PHR87 wrote:Thanks for the welcome!

Hoot, yes I first noticed the creep when I was testing the first round to ensure that it chambered well. Then went back and reseated it and crimped more aggressively. Still crept forward. I was wondering if seating it out a bit further would put the crimp closer to the driving band edge? Or would that be counter productive with less bullet friction inside the case?

These were wet tumbled/ultrasonic so I don’t know about any residue, but will keep that in mind for the future.

I haven’t been able to fire it yet, so I’m not sure if the recoil will bump the rounds in the mag as well. I will be able to go to the range tomorrow, but will likely fire single shot for Consistency.

Once I get a load worked out, I would eventually like to see how much the creeping actually affects things. Probably with 2x 5 round groups with Single shot/riding the bolt forward and tapping it all the way closed vs slamming it and allowing semi-auto loading of subsequent rounds. If there’s a significant effect, then I’ll go down the road of a side/stab crimp.

Thanks for the thoughts and I’ll try to keep things updated here. I’m looking forward to being a part of the group!

,
I was reading what wrote but my mind was for some reason on the Hornady 245gr Interlock bullet that has been gaining popularity here, so I missed the fact that you are actually using the TSX 275. don't grow old whatever you do!

By all means, seat the bullet so that you can catch one of the two driving band grooves. You want the majority of the groove you choose to be mostly buried beneath the mouth with just a little peeking out and then drive the taper crimp down into it. You should not have to crimp any narrower than .474 for a good hold on that bullet. The sharp edges of those grooves provide an excellent gripping point.

Hoot

Wonder if the 450 Lee crimp die would be of any benefit in this scenario??

Hoot, that’s exactly where I have the taper crimp. I’m seating at about 2.335” COAL which puts The groove right at the edge of the case lip and the taper crimps down into the groove. I’m measuring .472” with calipers right at the lip.

I had seen the comment about Hornady bullet but figured it was a lapse. Guess it was more of a lapse than I thought!

Al in Mi wrote:Wonder if the 450 Lee crimp die would be of any benefit in this scenario??

Are you thinking for the regular crimp or for a side/stab crimp?

If I do eventually go to the side crimp, I imagine I'll have to drop my powder charge and redo the load testing?

Thanks

their regular 450 factory crimp die which crimps at the case mouth.

I have one, just never got around to trying it.