Armory said:
New to reloading ... I've heard that cast bullets should not be used in a glock. could someone explain why not?
Since this is THR, let's not spread false information that may not help the OP.
Disclaimer: Like many other pistol manufacturers, Glock does not recommend shooting reloads (including lead reloads), so use reloads in your Glocks at your own risk.
Now that we got the disclaimer out of the way, can you shoot reloads in your Glocks, including lead reloads? I can't speak for other Glock shooters, but I have for about 20 years now (including lead reloads) with some consideration. BTW, what do countless Glock match shooters (including factory Glock team) use for match shooting week after week all around the world? You got it, reloads.
As to shooting jacketed/plated reloads, just like shooting reloads in other brand pistols, consideration should be made on basic safe reloading practices to maintain accurate and consistent powder charges, inspect range brass to cull damaged/questionable cases, maintain dimensions of finished rounds within spec and maintain sufficient neck tension to prevent bullet setback. You can obtain these information from a good reloading manual like Lyman #49, which I would recommend for someone new to reloading.
As to shooting lead reloads in Glock barrels, there are several more considerations. These are considerations for shooting lead bullets in any barrel:
- Commercial lead bullets come in different hardness ranging from softer 10 BHN to harder 24 BHN.
- Lead bullets come sized .001" larger than jacketed bullets and can be obtained sized .002"+ larger.
- Proper hardness/bullet to barrel fit/sufficient powder charge need to be used to properly deform the bullet base to seal the high pressure gas as gas leakage/gas cutting leads to increased leading.
There are issues specific to Glock barrels (see picture above):
- Glock barrels have longer leade (space the bullet jumps from the case neck/chamber to the start of rifling) which increases high pressure gas leakage.
- Glock barrels have very smooth start of rifling with rounded rifling which allow the lead bullet to slide deeper into the barrel before sufficient chamber pressure starts to develop which further increase high pressure gas leakage.
These Glock barrel features allow more high pressure gas leakage around the bullet which results in more of the following:
- High pressure gas leakage around the bullet blows liquefied lube from the bullet and down the barrel which may increase fouling/leading build up, especially near the chamber end of the barrel.
- If high enough powder charge is not used, powder burn may be inefficient and insufficient/inconsistent chamber pressures may not deform the bullet base to allow the bullet to "skid" down the barrel and increase fouling/leading build up.
Unless you use the proper hardness/sizing of lead bullet for the powder/charge used that produce sufficient chamber pressures to minimize fouling/leading build up, it is a good idea to inspect the Glock barrel more frequently for fouling/leading build up. So more careful load development/powder workup may be required. rcmodel usually recommends inspecting the Glock barrel around 200-300 lead rounds and I found this to be a good interval as loads that produce fouling will start to decrease accuracy above 300 round count. If your lead loads produce fouling/leading at lower round count, inspect the barrel more often and clean as necessary. If you develop lead loads that work well with Glock barrels to minimize/prevent fouling/leading, that's great.