Newbie question on 450 reloading

[Graziano8]

Decided to get into reloading after hitting a 9pt in the shoulder opening day with hornady blacks. after tracking for over an hour found him but had to shoot him again. the next day my brother shot an 8 pt double lung that didn’t bleed a drop in 80 yards but we did find it. So I decided to switch ammo and bought a box of Buffalo bore 275gr xpb and shot the best group of my life well under 1/2 inch at 100 yards. So I went all in on reloading because I will go broke shooting that stuff. my goal is to try to replicate that ammo.

I can not find the xpb 275gr anywhere but did get some hornady 240 xtp mags and barns 250 ttsx to practice with. I loaded some up today using lee dies 3 rounds of each(first time reloading) both 35.5 g of lil gun all case length where between 1.693 and 1.695. C.o.l on xrp was 2.060 and 2.245 on the ttsx. Crimp both to about .475 my question is last shot on but loads jammed my bolt while trying to load. The bolt was all the way forward but would not go down or back out. I had to tap with a rubber mallet to get unstuck I thought it was a fluke but it did it again on last shot of the ttsx too. is there something that I did wrong? any help would be appreciated.

[offrink]

Check the case mouth to see if it is to wide and also the case overall length. Both/either will make it unacceptable. I had the same problem with 50 beowulf.

[Al in Mi]

If the previous reloads of yours fired fine and seeing it was the last rounds with both bullets, leads me to thinking gunk at the end of the chamber is not letting your bolt close.

[Graziano8]

Thanks for the replays. The bottom end of brass was a little to fat(.502) lower my resizing die a 1/4 turn and have not had any problems

[BobbyJ]

Buy a lyman orange ammo checker for the 450BM. If the round fits in that it will chamber in your gun. Thats what I use for my 450BM.

[Hoot]

Case Head Growth can cause the brass to bind in the chamber back by the web. It most often occurs in brass that has multiple reloadings, especially if they were mostly hot loads. Its easy to check. After resizing, try seating each case after resizing, into the chamber without a bullet in them. If they are tight, the problem is not bullet or neck related.

I check my brass after resizing with a micrometer. If the max widest spot, usually down just above the web, has grown to beyond .5017, they're culled, as that's as wide as my rifle's chamber will allow. They usually start out at .5000 or a little less when new. Actually, I cull them at .5015 just to be safe. I hate having to jack out a round. Different chambers will have different tolerances as to what the maximum web width that they will tolerate. No two are exactly the same as a rule of thumb. I once had a barrel (brand withheld) that had an unusually tight chamber and it even had trouble with cases that had grown to .5005. Emphasis upon "used to have".

If this problem occurs with new brass that had been hand loaded then Yes, something is amiss with the bullet/neck relationship.

Hoot

[RBDMTJager]

I check my brass after resizing with a micrometer. If the max widest spot, usually down just above the web, has grown to beyond .5017, they're culled, as that's as wide as my rifle's chamber will allow. They usually start out at .5000 or a little less when new. Actually, I cull them at .5015 just to be safe. I hate having to jack out a round. Different chambers will have different tolerances as to what the maximum web width that they will tolerate. No two are exactly the same as a rule of thumb. I once had a barrel (brand withheld) that had an unusually tight chamber and it even had trouble with cases that had grown to .5005. Emphasis upon "used to have".

Thank you. Excellent advice will do the same.
I have a bunch of new Starline 450BM brass coming. Will measure each round record the data and monitor it after each subsequent reloading and firing.