Need help designing first rifle mold

[Deep Six]

I'm getting ready to order my first rifle bullet mold. The rifle is a Yugo 24/47 in 8mm with a pristine bore that measures .324/.313. The throat has at least 0.200" of freebore based on measurement I took by closing the bolt on an empty case and a .324 jacketed bullet. I've settled on something in the 170-195 gr range, tangential ogive, bore riding, and gas checked. Target velocity is ~2000 fps (basically 30-30 ballistics from a bolt action). I would like some guidance on the following items:

1) What is a good meplat? I was thinking something around 60%.
2) I know long, unsupported noses usually aren't good with cast. What is a general rule for max ogive length?
3) What percentage of total length should be outside the case? Need to balance lube capacity, seating depth, and feeding considerations.
4) Are multiple small bands (0.050-0.060" long) better than fewer large bands (0.090"+) or vice versa?
5) Do I want a crimp groove or not? I know it's a must in revolvers with powders like H110, etc, but how necessary is a strong crimp in a rifle?
6) If anyone knows of a stock design from any of the makers that I should consider, please share. I like the RCBS 175 gr, but frankly I can buy a custom aluminum mold for less than the RCBS at Midway, where it is out of stock anyways.

I want to get this right the first time. Thanks!

[frnkeore]

I'm getting ready to order my first rifle bullet mold. The rifle is a Yugo 24/47 in 8mm with a pristine bore that measures .324/.313. The throat has at least 0.200" of freebore based on measurement I took by closing the bolt on an empty case and a .324 jacketed bullet. I've settled on something in the 170-195 gr range, tangential ogive, bore riding, and gas checked. Target velocity is ~2000 fps (basically 30-30 ballistics from a bolt action). I would like some guidance on the following items:

1) What is a good meplat? I was thinking something around 60%. I would not go over 50%, I shoot bullets that are usually 30% and less
2) I know long, unsupported noses usually aren't good with cast. What is a general rule for max ogive length?[/COLOR]A 1/3 of bullet length ogive will be good, start the ogive at .003 over bore diameter to help support it. If it's a bore rider make it tangent to the bore riding portion at .001 - .0015 over bore.
3) What percentage of total length should be outside the case? Need to balance lube capacity, seating depth, and feeding considerations. In your case, you want the GC to be at the neck/shoulder juction and the bands extending past your freebore by at least 1/8". The 8x57 has a very long throat (about .4 deg).
4) Are multiple small bands (0.050-0.060" long) better than fewer large bands (0.090"+) or vice versa? I like .050 - .075 long bands (no longer) and grooves that are 80 to 100% of the band width.
5) Do I want a crimp groove or not? I know it's a must in revolvers with powders like H110, etc, but how necessary is a strong crimp in a rifle? Don't use a crimp unless the load has high recoil and shot from the magazine. I like neck tensions between .0005 and .001
6) If anyone knows of a stock design from any of the makers that I should consider, please share. I like the RCBS 175 gr, but frankly I can buy a custom aluminum mold for less than the RCBS at Midway, where it is out of stock anyways.

I want to get this right the first time. Thanks!

Though heavier, (210 gr) the NOE 323471 mold is a excellent choice

85087

Frank

[338RemUltraMag]

I would try the Lee 329-205 I am using it in my M48 with great results.

[paul h]

1) What are you using the bullet for? For hunting big game I'd be in the 75%-80% range, closer to 80% since it's a small bore round, for longer range target practice I'd be in the 70-75% range, or split the difference at 75%

2-3) I think you're looking at this backwards. Design the base of the bullet first so that the base is flush with the base of the case neck, and then go about designing the nose of the bullet. Play with the bearing length of the bullet, i.e. the length from the base to the front of the forward most driving band and compare that length to the nose length. Ogive will take care of itself after you figure out the bearing length of the bullet, and the meplat, and the weight.

4) I've cast and shot many bullets of both designs and honestly haven't found either narrower bands or thicker bands to really matter in and of themselves. For a rifle bullet that is relatively long for it's dia I prefer the lube grooves not to be too deep as I think it hinders the mold fillout, and hence would lean towards narrower bands to have a sufficient amount of lube for the bullet. Figure on two lube grooves and the lube groove above the gas check and you should be in the ballpark.

5) No need for a crimp groove

6) I'm with you on having a hard time paying more for an RCBS production mold than a custom aluminum mold, but I do like RCBS molds and prefer the fact that steel and iron molds hold their heat better when casting a bullet that is on the longer/skinnier side.

[Wayne Smith]

1) If it is truly a bore riding nose it is NOT unsupported. That only happens when your nose is undersized

2) Boolit length inside the case is determined by neck length. You don't want the base of the boolit hanging down in the case. This determines how much hangs out of the case. Boolit length depends on your rifling twist. Search the modified Greenhill formula if you don't know what I'm referencing.

3) Yes on the gas check, no on the crimp groove. Unless you are going to use this in a tube magazine you don't need to crimp.

4.) there is a lot of design information on Dan's Mountain Molds website. If you are not using this resource you need to find it and learn to use it.

[Deep Six]

1) If it is truly a bore riding nose it is NOT unsupported. That only happens when your nose is undersized.
I meant the ogive part of the nose past the bore rider section of the nose. How long is too long of an ogive?


2) Boolit length inside the case is determined by neck length. You don't want the base of the boolit hanging down in the case. This determines how much hangs out of the case. Boolit length depends on your rifling twist. Search the modified Greenhill formula if you don't know what I'm referencing.
In this instance, I'm letting my desired weight determine length. The military Mausers all have pretty fast twist (mine is no exception at 1:9.X) but I don't really want a 210+ gr boolit as the Greenhill formula would give me. So I am going to go lighter. I realize I may not be able to drive it as fast without risking stripping the rifling, but I'm really only after 30-30 ballistics here.


3) Yes on the gas check, no on the crimp groove. Unless you are going to use this in a tube magazine you don't need to crimp.
Thanks - good info. That makes it unamimous that a crimp groove is not required.


4.) there is a lot of design information on Dan's Mountain Molds website. If you are not using this resource you need to find it and learn to use it.
I know about Dan's site and have been using it to toy around with different designs. However, if you read his forum, he doesn't like to make bore-rider designs for bolt actions and won't guarantee any tolerance on bore ride diameter. Apparently it's just his personal preference but he prefers to use a short nose and go as deep into the case as necessary to obtain the desired weight. He claims he has "shot 1000s of rounds with the bullet seated well into the powder space with no ill effects". For this reason, I probably won't be placing this order with him. Although a little more $, I'll probably go with Tom at Accurate.